Northeast Fisheries Science Center Reference Document 01-16
Causes
of Reproductive Failure in North Atlantic Right Whales:
New Avenues of Research
Report of a Workshop Held 26-28 April 2000, Falmouth, Massachusetts
by Randall R. Reeves1,
Rosalind Rolland2, and Phillip J. Clapham3, Editors
1Okapi Wildlife Assoc., 27 Chandler Ln., Hudson, PQ J0P 1H0
2New England Aquarium, Central Wharf, Boston, MA 02110
3National Marine Fisheries Serv., 166 Water St., Woods Hole, MA 02543
Print
publication date November 2001;
web version posted November 26, 2001
Citation: Reeves, R.R.; Rolland, R.; Clapham, P.J., editors. 2001. Causes of reproductive failure in North Atlantic right
whales: new avenues of research. Report of a workshop held 26-28 April 2000, Falmouth, Massachusetts.
Northeast Fish. Sci. Cent. Ref. Doc. 01-16; 46 p.
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EXECUTIVE
SUMMARY
Despite its protected status, the western North Atlantic right
whale (Eubalaena glacialis) population remains critically
endangered, numbering about 300 individuals. This population's
recovery has been hindered by at least three factors: mortality
from ship strikes, mortality from entanglement in fishing gear,
and, in recent years, a significant decline in reproductive success.
A workshop was held in Falmouth, Massachusetts on 26-28 April 2000
to examine the possible causes of reproductive dysfunction in this
population (including survival and recruitment of calves) and to
develop a feasible research strategy to investigate these factors.
An international group of participants attended the workshop, including
35 scientists representing a broad range of disciplines including pathology,
toxicology, reproductive biology, nutrition, reproductive endocrinology,
chemistry, marine biology, large whale biology, genetics and veterinary
medicine. The workshop was designed to be multi-disciplinary, bringing
together a wide range of expertise with experience studying a variety
of taxa to provide a comparative dimension to the discussion.
The workshop focused on five factors as potential contributors to
reproductive dysfunction in North Atlantic right whales: 1) environmental
contaminants/endocrine disruptors; 2) body condition/nutritional
stress; 3) genetics; 4) infectious diseases; and 5) marine biotoxins.
On the
first day of the workshop plenary presentations reviewed the current
status of the population and summarized relevant research and necropsy
data. On day two there was a comparative review of causes of reproductive
failure in mammals in general and a review of reproduction in the
North Atlantic right whale, especially focused on where in the reproductive
cycle impairment or failure might be occurring. Each of the five
factors
was discussed in detail; for each factor, discussions included a
review of the existing knowledge of effects on reproduction (in any
species),
a review of the available data for effects in North Atlantic right
whales, an evaluation of the likelihood that the factor is affecting
right whale reproduction, and development of testable hypotheses.
Consideration was also given to additional factors (such as habitat
alteration or
loss) that could be impacting reproduction. The final day of the
workshop was devoted to designing a prioritized research program to
test the
hypotheses that had been developed and to a discussion of appropriate "control" population(s).
Based upon discussions with participants both at and after the workshop,
a problem-based approach was developed as a framework for the research
program. An alternative hypothesis-driven approach was also developed
by one of the participants subsequent to the workshop. Both approaches
are included in this report.
The workshop concluded that if calf production and recruitment do
not recover from the low levels observed in recent years, the population
of North Atlantic right whales is unlikely to recover, even if known
anthropogenic causes of mortality are reduced to zero. Therefore, the
participants emphasized that it is important to determine the cause(s)
of the reproductive dysfunction as soon as possible, and strongly recommended
implementation of the proposed research program. The workshop concluded
that none of the five factors considered could be eliminated as a possible
contributor to the observed reproductive dysfunction, and that interaction
among two or more factors (possibly over different time scales) is
more likely than a single cause. It was stressed that the research
program should consider all factors and be interactive and multi-disciplinary
in nature, and the workshop recommended development of a steering committee
to provide central coordination of the research. The workshop further
recommended development of a comprehensive database linked for all
whales across all research programs to allow for multivariate analyses
using different data sets. Finally, the workshop recognized the importance
of the long-term right whale research program and the photo-identification
catalogue and recommended full continuing support for these activities.
1.
INTRODUCTORY ITEMS
The Workshop was held in Falmouth, Massachusetts, on 26-28 April 2000.
The Workshop steering committee was chaired by Roz Rolland of the Center
for Conservation Medicine, Tufts University, and included Phil Clapham,
Scott Kraus, Michael Moore, Teri Rowles, Bruce Russell, and Greg Silber.
Participants included scientists from a variety of disciplines such as
pathology, toxicology, nutrition, reproductive endocrinology, chemistry,
marine biology, large whale biology, genetics, and veterinary medicine
(Appendix 1). The expectation was that this
broad range of expertise would provide a useful comparative approach
to the issue.
Michael Sissenwine, Science and Research Director of the Northeast Fisheries
Science Center, welcomed participants to the Woods Hole-Falmouth area
and briefly summarized the main elements of the Northeast Center/Northeast
Region right whale research program. This program focuses on three topics
of particular concern: ship strikes, entanglement in fishing gear, and
reproductive dysfunction. The ship strike issue is being addressed through
a surveillance and early warning effort and by an attempt to develop
an acoustic method for ships to detect (and thus avoid) right whales.
The entanglement problem is being addressed by seeking to develop alternative
fishing gear and methods, and by supporting disentanglement efforts.
The problem of reproductive dysfunction is not yet being addressed in
a systematic way, and Sissenwine expressed hope that the workshop report
would provide guidance in this regard.
Sissenwine acknowledged the financial contributions to the Workshop
from the International Fund for Animal Welfare and the Island Foundation,
as well as from the National Marine Fisheries Service's Recover Protected
Species program. Clapham, the local convenor, acknowledged the hard work
of Sara Wetmore, Cheryl Kitts and Deb Depunte in helping with the Workshop
logistics.
The Workshop was chaired by Peter Best. Randall Reeves acted as rapporteur,
with assistance from Greg Donovan.
1.1.
Objectives of the workshop
The Workshop had been prompted by evidence that reproductive dysfunction
may be a contributory factor to the failure of the western North Atlantic
right whale (Eubalaena glacialis) population to recover (IWC,
in press a; in press b). The Workshop goals were to identify factors
potentially affecting reproduction (including calf survival and recruitment)
and to develop an appropriate and feasible research strategy to investigate
these factors. The strategy was to include: (a) development of testable
hypotheses, (b) drawing a distinction between those factors that can
be studied with existing research techniques and those that require new
techniques, and (c) developing prioritized recommendations for new areas
of research. Prior to the Workshop, five major potential factors had
been identified: (1) environmental contaminants/endocrine disruptors;
(2) body condition/nutritional stress; (3) genetics; (4) pathology/infectious
diseases; and (5) biotoxins. Finally, the Workshop was to consider the
importance of its conclusions and recommendations in the broader context
of the conservation requirements of western North Atlantic right whales.
The North Atlantic right whale population (estimated at around 300 animals,
IWC in press b) has been studied intensively for the past 20 years. Almost
the entire population is believed to be represented in a photo-identification
catalogue maintained at the New England Aquarium in Boston. A large proportion
of the population (over 250 individuals) has been biopsied for studies
of genetics, demographics, and skin and blubber characteristics (including
contaminant levels). Estimates of life history parameters are available
from the observational and photo-identification work, and some material
is available from necropsies of stranded right whales. These extensive
databases provide a powerful framework for examining factors potentially
associated with reproductive dysfunction.
In addition to directed studies of North Atlantic right whales, the
Workshop was to consider the potential for populations of southern right
whales (E. australis) which are increasing in abundance (and
are thus presumably healthy) to act as control populations. Also, the
closely related bowhead whale (Balaena mysticetus) may be a
useful model species because the Bering-Chukchi-Beaufort Seas population
is large and robust, and fresh specimen materials are available from
the Eskimo hunt.
Although the focus of the Workshop was to be on the North Atlantic right
whale population, it was hoped that the results would have relevance
to the conservation of other highly endangered populations as well.
1.2
Adoption of agenda
The agenda developed by the steering committee was adopted with only
minor changes (Appendix 2).
The first day was devoted to invited presentations. Each plenary presentation
was followed by a brief discussion. Summaries of the presentations and
subsequent discussions are included under the appropriate agenda item
in the body of this report.
The second and third days consisted of discussions of each agenda item,
with the afternoon of Day 3 devoted to the development of a research
program outline. Most of the work was conducted in plenary, although
small ad hoc working groups met informally between sessions.
The workshop report was prepared by the rapporteur and a small steering
group (Best, Rolland, Clapham and Donovan) following the meeting. A draft
was circulated to all participants for review, then revised by the rapporteur
in consultation with the steering group, and finalized by the report
editors.
2.
OVERVIEW OF REPRODUCTIVE BIOLOGY AND REPRODUCTIVE FAILURE
2.1
General review of mammalian reproduction and causes of reproductive
failure
Munson provided an overview of mammalian reproduction and noted the
difficulty of determining the precise cause(s) of reproductive failure
or dysfunction in wild animals. There are numerous potential sites, mechanisms
and critical time periods for reproductive problems, including the hypothalamic-pituitary-gonadal
axis, the gonads, the uterus, foetal development, and post-partum survival.
In addition to permanent reproductive failure, animals may experience
reduced reproductive success or temporary reproductive failure. Because
reproductive function is expendable to the individual, it can be suppressed
under many circumstances, e.g. nutritional or environmental stress, systemic
disease.
Loss of integrity of the hypothalamic-pituitary-gonadal axis can result
in (1) absence of or decrease in hormone secretion (GnRH, LH or FSH),
or (2) disruption in the essential timing of hormone release. Gonadal
inactivity or lesions (i.e. abnormalities) can be caused by many factors
including genetic defects, infectious disease, degenerative changes,
neoplasia or aging (senescence). In addition, gonadal problems can be
secondary to other primary problems such as nutritional or environmental
stress, systemic infection, central nervous system disease or toxins.
Abnormal genital tract structure can be the result of developmental defects
(genetic, disease- or toxin-induced) or acquired abnormalities due to
hormone deficiencies or excesses, toxic exposure or infection. Foetal
development or survival can be impaired by genetic defects, nutritional
deficiencies or excesses, toxic exposure or infection. Post-partum neonatal
death can be caused by inherited or congenital defects, poor nutrition,
environmental stress or infectious disease.
Infectious agents can cause reproductive dysfunction through a variety
of mechanisms, including direct effects on the central nervous system,
damage to the genital tract and damage to the foetus. For example, canine
distemper virus and other morbilliviruses can cause systemic problems
and disrupt the hypothalamic-pituitary-gonadal axis, infect the gonads
directly, or cross the placenta and damage the foetus (resulting in abortion).
Neonatal infections can affect the survival of newborns, as occurred
in red wolves (Canis rufus) (Acton et al. 2000).
Toxins and genetic defects can also operate in a number of different
ways to impair reproductive performance. For example, environmental pollutants
can act at the central nervous system, pituitary or gonadal level to
inhibit or over-stimulate (i.e. disrupt) endocrine function (e.g. PCBs)
or cause direct damage to the genital tract (e.g. exogenous progestins
and estrogens) or the foetus. Genetic defects can be manifest by abnormal
genital tract development [e.g. cryptorchidism in Florida panthers (Felis
concolor) (Cunningham et al. 1999)], abnormal germ cell development
[e.g. decreased spermiogenesis in Ngorongoro Crater lions (Panthera
leo) (Munson et al. 1996) and reduced primordial follicles and minimal
folliculogenesis in vaquitas (Phocoena sinus) (Munson, pers.
comm.)], predisposition to the development of genital tract tumours [e.g.
ovarian, endometrial and mammary gland cancers in jaguars (Panthera
onca) (Munson 1994) and ovarian dysgerminomas in maned wolves (Chrysocyon
brachyurus) (Munson and Montali 1991)] or embryo-lethal effects.
Reproductive dysfunction in captive cheetahs (Acinoynx jubatus)
was long thought to be related to the high incidence of abnormal sperm
produced by the small, degenerative testes in these animals. However,
this dysfunction is now attributed to hypercortisolemia from chronic
stress (Wildt et al. 1993, Munson 1993), with corticoids acting as hormone
disruptors inhibiting gonad function. The etiology of this discovery
included the following observations: (1) normal genital anatomy and responsiveness
to exogenous hormones, (2) suboptimal spermatogenesis and folliculogenesis,
(3) high prevalence of adrenal cortical hyperplasia, and (4) faecal corticoids
approximately four times the levels found in wild cheetahs.
Degenerative changes can occur in the reproductive tract of animals
that are nulliparous or reproductively inactive for long periods of time.
Old female elephants in captivity can become infertile and exhibit leiomyomas
and endometrial hyperplasia. Vaquitas exhibit ovarian calcified bodies
and early senescence.
The North Atlantic right whale is the only baleen whale for which reproductive
dysfunction has been documented (see Item 2.2). Despite
the fact that other mysticete populations (e.g. gray whales (Eschrichtius
robustus ) in the western North Pacific, right whales (Eubalaena
japonica) in the eastern North Pacific, bowheads in the eastern
North Atlantic Arctic, and blue whales (Balaenoptera musculus)
in several areas) have been reduced to equally low (or even lower) abundance
levels, there is no conclusive evidence of reproductive problems in these
populations. This may simply reflect the fact that these stocks have
been less well studied than the North Atlantic right whale population,
or that the lack of recovery in several of these depleted stock is indeed
a striking indication of reproductive impairment. Clapham noted that
there have been no confirmed observations of right whale calves in the
eastern North Pacific for at least 100 years.
DeGuise summarized the situation of white whales (belugas, Delphinapterus
leucas ) in the St. Lawrence River, probably the most familiar
example of an odontocete population thought to be experiencing some
kind of reproductive dysfunction. The evidence was based upon an age-structured
population model using data from stranded animals to determine what
proportion of the living population would have to be immature (gray-colored)
to replace annual mortality (Béland et al. 1988). The results
indicated that the proportion of immature whales was lower than required
to offset mortality and therefore that the population was declining.
DeGuise also reported that per capita calf production in the St. Lawrence
population was less than in the Arctic. However, this conclusion remains
controversial (see Lesage and Kingsley 1998), as does the hypothesis
that the population is declining (see Kingsley 1998).
DeGuise reported that detailed post-mortems carried out on stranded
St. Lawrence white whales did not reveal any reproductive lesions. Stranded
mature males appeared to have normal spermatogenesis, although the lack
of fresh samples of viable sperm precluded examination of sperm morphology
and motility. Although stranded adult females exhibited a short-term
shutdown of ovarian activity, this is expected of ill animals. The St.
Lawrence white whale population lives downstream of a basin heavily contaminated
by industrial pollutants and appears to have an unusually high incidence
of cancer (Martineau et al. 1999).
Oftedal highlighted the differences in reproductive patterns between
mysticetes and odontocetes from a nutritional perspective, and noted
that odontocetes were probably not very good models for right whales.
Female mysticetes store immense quantities of lipids that can be mobilized
and transferred rapidly to their offspring, and in this sense are more
like phocids than odontocetes. Although balaenids have a more protracted
lactation cycle than balaenopterids, they are still probably more like
phocids than like odontocetes (see Oftedal 1997).
Gray remarked that there is nothing unique about either the endocrinology
or reproductive physiology of mysticetes and therefore findings from
other, more easily studied mammals could be used to make inferences about
right whales. In particular, studies of other species living in the same
habitat would be useful.
The difficulty of isolating a causal mechanism for observed reproductive
dysfunction was reiterated. A good example is the mass mortality of striped
dolphins (Stenella coeruleoalba) in the Mediterranean Sea (Aguilar
2000). In addition to the mortality of individuals, the population was
affected by the loss of normal fecundity, manifest in the high number
of abortions and the presence of luteinized ovarian cysts in many adult
females (Munson et al. 1998). The latter could have been caused either
by morbillivirus infection or by high PCB levels (or a combination of
both). If the reproductive disorder was caused by the viral epidemic,
restoration of reproductive function and population recovery would be
expected during the typical period of immunity following the epidemic.
If, however, the primary cause was PCB toxicity, continued reproductive
problems would be likely and this would affect long-term population recovery
(Munson et al. 1998).
2.2.
Review of North Atlantic right whale reproduction, especially indicating
where in the cycle impairment or failure may be occurring, and development
of testable hypotheses
Right whales migrate between feeding grounds in cool northern waters
(summer) and breeding grounds in lower latitudes (winter). Some feeding
occurs in areas between the two ends of the migration, particularly in
Cape Cod Bay and in the Great South Channel during late winter and early
summer. Although the location of one calving ground (southeastern US
coastal waters - December to March) is known, the location of the mating
ground(s) is unknown.
Kraus and Hatch (in press) discuss mating strategies in the western
North Atlantic right whale population, based largely on observations
of surface active groups engaged in what appears to be courtship behavior
(although if a gestation period of approximately 12 months is assumed/accepted,
summer mating would not result in conception, unless a mechanism such
as delayed implantation occurred). Females do not appear to actively
select males but instead create conditions that lead to competition among
males for opportunities to copulate. Sperm competition is also very likely
given the immense size of the testes (Brownell and Ralls 1986).
Appendix 3 summarizes the available information
on North Atlantic right whale reproductive parameters (see Kraus et al.
in press). In the context of this Workshop, the main points are as follows:
(1) Annual calf production per female is highly variable. Since 1990,
the total number of calves observed (believed to reflect the true total
in the population) has been about half what would have been expected
from comparison with Southern Hemisphere females. From 1998-2000, annual
calf production has been lower in absolute terms than in all but one
of the preceding 17 years.
(2) In recent years, calf production has been largely from cows that do not
take their calves to the Bay of Fundy in summer. This 'non-Fundy' component
consists of only about one-third of the 70 'reproductively active' females
(i.e. those older than 9 years that have given birth at least once) in the
population.
(3) Calving interval has increased significantly from the 1980s through the
1990s and now averages more than 5 years. This increase is apparent in cows
of all ages.
(4) The survival rate of calving females shows a significant decline over
time (Caswell et al. 1999).
(5) The survival rate of immature females shows no significant decline.
(6) Age at first reproduction is similar to that in Southern Hemisphere animals.
(7) The rate of population increase is significantly lower than those of
several Southern Hemisphere right whale populations, and it may have been
negative since 1990 (IWC in press a, b).
A number of points were made in the general discussion, mainly concerning
the increase in the mean calving interval. The Workshop agreed that the
assumption previously made (IWC in press b), that the peak in 5-year
intervals (the 'normal' 3 plus 2) was the result of late prenatal or
neonatal mortality, required further consideration before being accepted.
The lengthening of the mean calving interval had been suggested in the
early 1990s (Knowlton et al. 1994) but was only confirmed to be significant
in the mid-1990s. Kraus commented that had data on the apparently complete
cessation of calving by some Fundy females been included in the calving
interval analyses, the average would be much greater than 5 years. The
likelihood model of Cooke and Glinka (1999) takes account of this. However,
while the mean calving interval has increased significantly, individual
calving histories reveal that the intervals have not increased for every
female. Examination of individual calving histories could provide valuable
insight into which factors most affect calving intervals.
From experience with other species, it is clear that reproductive failure
can occur at several stages in the reproductive cycle, as summarized
below:
(1) Failure to ovulate. Ovulation in right whales is assumed
to be spontaneous as in other cetaceans, and conceptions occur primarily
during the winter season, i.e. probably November-February in the Northern
Hemisphere (see Best 1994). While it may be possible to diagnose ovulation
from samples of feces or blowhole exudates, this requires knowledge
of relative hormone levels at various stages in the reproductive cycle
and longitudinal sampling of individual females.
(2) Failure to mate at a time when the female is fertile. Since the
locality of the mating ground(s) is unknown, there is little prospect of
addressing mating failure using courtship observations as an index of sexual
activity. Based on assumptions about the gestation period, Kraus suggested
that the peak mating period should occur between November and the end of
February. Courtship groups ('surface-active groups'), usually comprising
1-10 individuals, are seen on and near the calving grounds in the South Atlantic
(Best and Schaeff, in prep.). However, such groups are not seen off the southeastern
United States in the winter, when most conceptions are thought to occur.
The courtship groups observed on the feeding grounds in the western North
Atlantic are often larger than 10 individuals, but Marx commented that small
courtship groups are seen occasionally in Cape Cod Bay in February and March.
(3) Lack of adequate sperm production. Addressing this possibility
will require reasonably fresh samples, which in practice are available only
from stranded or ship-struck adult males. Munson noted that if right whales
are seasonally polyestrous (like felids), inferior sperm production could
well cause reproductive dysfunction. Munson suggested looking for a point
source of pollution (for example in Cape Cod Bay) which through short-term
exposure to the whales might affect the availability, production or quality
of sperm.
(4) Failure to implant (pregnancy loss). This possibility will be
difficult to study among living animals in the right whale population (see Item
1).
(5) Abortion or neonatal mortality. If caused by infectious disease,
this is not likely to be repetitive in nature because immunity acquired by
the population would lessen the impacts over time. Genetic factors might
also be implicated in abortions (see Item 3.1.1).
Death of the mother is obviously a potential cause of neonatal mortality.
The Workshop agreed that none of the above could be
ruled out, a priori, as not being relevant to the observed reproductive
dysfunction in North Atlantic right whales.
Sampling for gonadal steroid hormone analysis from the free-swimming
population is constrained by field logistics, timing (except for parturient
females, adult whales are available primarily in the northern feeding
areas between spring and fall, i.e. during what is presumed to be the
non-breeding season), and the need to avoid or at least minimize invasive
procedures. Full use needs to be made of opportunities to sample feces
and blowhole exudate (if steroid hormones can be detected in respiratory
excretions), and if possible to obtain time series of samples from individual
females. Relative levels of gonadal steroid hormone metabolites from
feces or blowhole exudate could provide clues to reproductive status.
Unfortunately, at this stage, it does not appear to be feasible to obtain
even minute blood samples with biopsy darts. Rolland suggested that the
bowhead could provide a useful model for testing gonadal steroid hormone
levels in the feces and blowhole exudate of pregnant and non-pregnant
females, as well as males. The assays could be validated in bowhead whales
through the collection of feces, blowhole exudate, serum and urine from
individual dead whales whose reproductive tracts could be examined directly.
Southern mentioned that work was underway in her laboratory to identify
a genetic marker to assess pregnancy in white whales using frozen skin
samples. It was agreed that a skin test for pregnancy
would be a useful tool in studying reproductive dysfunction in right
whales.
Munson recommended the following two-step, multi-disciplinary approach
to studying reproductive dysfunction in North Atlantic right whales (see Appendix
4 for more details):
A. Conduct pathologic analysis on all available tissues, i.e.:
Collect all genital tracts that become available, regardless of state
of autolysis
Conduct complete gross and histopathologic analyses
Compare lesions between historic and current populations
Compare lesions between Northern and Southern Hemisphere populations
B. Link genital pathology to other data, i.e.:
Other pathologic findings (overall disease in the animal)
Faecal analysis for gonadal and adrenal steroid hormone metabolites
Evidence of breeding or fertility
History of breeding behavior/success
Nutritional status
Environmental contaminant and biotoxin levels
Ovaries of right whales seem to be exceptionally friable, making them
difficult to locate and collect from beach-cast carcasses. There is little
prospect of meaningful comparisons of lesions in the historic and current
populations, as 'historic' specimen materials and information are almost
entirely lacking.
Munson urged that social and behavioral factors should be taken into
account when considering possible reasons for reproductive dysfunction.
The low density of individuals on the mating grounds could mean that
the frequency of contacts is suboptimal for the species, given its reproductive
strategy (cf. the Allee effect). Rowntree noted that females with calves
off Argentina form groups and may derive some kind of selective advantage
from this behavior. The low number of mothers in any one year in the
North Atlantic right whale population probably precludes extensive 'peer
group' interaction.
3.
CONSIDERATION OF POSSIBLE CAUSES OF REPRODUCTIVE FAILURE
3.1.
Genetic factors (e.g. loss of diversity, inbreeding, effective sex
ratio)
3.1.1.
Review of existing knowledge of effects of these factors on reproduction
The possible role of genetic factors in preventing small populations
from recovering has been widely discussed. Low genetic variation can
lead to reduced population fitness, manifest as the expression of deleterious
alleles or the reduction of heterozygosity at loci that confer immuno-competence.
The term 'inbreeding depression' refers to a condition in which a population's
reproduction and recruitment are correlated with inbreeding. This can
be expressed as reduced fertility and fecundity, decreased foetal and
neonate survival, impaired development or lowered disease resistance.
Inbreeding depression is extremely difficult to detect or verify in natural
populations. In one of the few examples involving natural populations,
inbreeding was found to have a significant detrimental effect on the
survivorship of white-footed mice (Peromyscus leucopus noveboracensis)
derived from a wild population and reintroduced into a natural habitat
(Jimenez et al. 1994). In another example, a depleted snake population
in the UK with symptoms of reproductive failure showed improved reproduction
once snakes from an external source were introduced into the inbred population
(Madsen et al. 1999).
Of particular relevance to ongoing genetic studies of North Atlantic
right whales are examples in which traits linked to the Major Histocompatibility
Complex (MHC), or Human Leukocyte Antigen (HLA), have been shown to be
associated with reproduction, growth and development. In humans, increased
embryonic cleavage, neural tube defects, recurrent spontaneous abortions
and unexplained infertility have been associated with the structure of
MHC. Extensive studies of an isolated Hutterite community in South Dakota
have shown that parental sharing of the 16-locus HLA haplotype is associated
with foetal loss (Ober et al. 1998). It is hypothesized that foetuses
that are genetically identical to the mother have a lowered survival
probability. In addition to its implication in reproductive success,
MHC diversity generally provides the body with a better chance of mounting
a successful immune response to antigens.
However, low genetic diversity, including specifically low MHC polymorphism,
does not necessarily indicate an unhealthy population (e.g. the northern
elephant seal, Mirounga angustirostris, which is large and growing).
3.1.2.
Review of data on these factors in North Atlantic right whales
Multi-locus DNA fingerprinting has shown that North Atlantic right whales
have significantly less genetic variation than right whales in the South
Atlantic (Schaeff et al. 1997), and a lower allelic diversity than any
other baleen whale population studied to date. Half-siblings in the South
Atlantic population are equivalent to the most distantly related individuals
in the North Atlantic (White, pers. comm.). This low genetic variation
has elicited concern because of the possibility that the population is
suffering from the effects of inbreeding (Knowlton et al. 1994, Schaeff
et al. 1997). Preliminary analyses of DNA from bone recovered at 16th century
Basque whaling sites in Labrador suggest that the greatest loss of genetic
diversity occurred about four centuries ago. As most deleterious recessive
alleles would have therefore been purged from the population long ago,
the recent decline in reproductive success is unlikely to be solely a
genetic problem.
About 70% of the 94 females in the right whale photo-identification
catalogue are estimated to be older than 9 years, still alive, and have
given birth at least once (IWC in press b). Paternity assignments made
by White and colleagues at McMaster University suggest an unexpectedly
broad mating success rate, with about 70 different males having sired
at least one calf. Effective population size is therefore on the order
of 100-130, and the estimated loss of heterozygosity per generation (1/2Ne)
is approximately 0.5%. Of 221 calves documented to have been born between
1980 and 1999, 214 are believed to still be alive; of these, 121 were
taken by their mothers to the Bay of Fundy in the summer (see Appendix
5). There are 160 known mother-calf pairs (some females are represented
more than once) in the catalogue, and 85 of these pairs have been genotyped
(72 Fundy, 13 non-Fundy). Work is underway to isolate additional microsatellite
loci to better assess population structuring and develop detailed genealogies.
Low observed genetic variation at MHC Class II loci in North Atlantic
right whales has been hypothesized as contributing to a higher-than-normal
incidence of abortion. While this hypothesis cannot explain any of the
recent changes in reproductive parameters, it may indicate (if true)
that the maximum rate of growth of the North Atlantic population is intrinsically
lower than in Southern Hemisphere populations. This, in turn, may partially
explain the lack of recovery of this population despite its long period
of protection.
Rosenbaum and collaborators are also studying changes in the genetic
diversity of right whales in relation to trends in exploitation and abundance.
3.1.3.
Evaluation of likelihood that genetic problems may be affecting
North Atlantic right whale reproduction and development of testable
hypotheses
White explained that his group would continue to investigate the hypothesis
that low genetic variation at MHC Class II loci is leading to MHC haplotype
sharing between parents, which in turn increases the similarity at MHC
loci between mothers and foetuses and increases the probability of spontaneous
abortion. This will be accomplished by assessing whether the transmission
of a given MHC haplotype from father to calf is significantly different
from random. The conclusiveness of the results depends on the exclusionary
power of the microsatellite markers, and thus more of these are being
developed.
The Workshop agreed that it is unlikely that intrinsic
genetic factors alone are responsible for the reproductive dysfunction
in North Atlantic right whales. However, genetic factors could be interacting
with extrinsic factors including poor nutrition and exposure to toxic
chemicals and/or pathogens. Unfortunately, the relationship of MHC to
disease susceptibility is not amenable to a hypothesis-testing approach
as the lack of genetic diversity in the population predisposes it to
the effects of other stressors. Reduced diversity of cellular detoxification
genes could be contributing to an immune response problem, impairing
the ability of the whales to deal with oxidative stress. It was suggested
that one potential approach would be to look for correlations between
DNA profiles of individuals and the presence or absence of lesions, reproductive
success, et cetera.
The Workshop noted that the topic of whether, and how, genetic factors
are affecting reproduction in North Atlantic right whales was to be explored
in greater detail at the proposed International Whaling Commission (IWC)
Workshop on Right Whale Genetics. The Workshop offered its support for
this initiative.
3.2.
Nutrition
3.2.1.
Review of existing knowledge of effects of nutrition on reproduction
The links between good nutrition (in terms of both quality and quantity)
and reproductive success are well known. Nutrition can affect many stages
of the reproductive process in both sexes. In males, it can influence
the age at which an animal attains sexual (and, where pertinent, social)
maturity; sperm production, quality and viability; and the likelihood
of successful copulation with a receptive female. In females, nutrition
plays a role in the age at which sexual maturity is reached; ovulation
and fertility; quality and quantity of milk production; and the time
between offspring. Nutrition affects calf survival and growth, and influences
the time to weaning.
In most animal species, the energetic costs of reproduction are high
(up to 3-5 times the maintenance requirements). In mammals, the lactation
period is especially demanding. This is particularly true for those marine
mammals that undergo long periods of fasting (or very low food intake)
(see Lockyer 1984; Oftedal 1997). In fin whales (Balaenoptera physalus),
for example, the energetic cost of lactation can be double that of gestation
(Lockyer, 1984).
Given the high energetic cost, and that reproduction is a non-essential
activity (at least at the individual level), reproduction is often suppressed
during periods of nutritional stress and resumes only after the return
of more favourable nutritional conditions.
In addition to the more obvious direct effects (e.g. Lockyer, 1987,
found a strong correlation between body fat and reproductive success
in female fin and sei whales, Balaenoptera borealis), poor nutrition
can affect reproduction in other ways. For example, it can make the individual
more susceptible to disease or cause mobilization of fat reserves that
contain high levels of chemical contaminants (see Items
3.5 and 3.3, respectively, below).
3.2.2.
Review of data on nutrition in North Atlantic right whales
As noted under Item 2, right whales feed in
the northern part of their range (Bay of Fundy and the Scotian Shelf)
primarily from June to October, with some feeding in the winter and spring
in Cape Cod Bay, and in the Great South Channel in the late spring and
early summer. Although Calanus finmarchicus is the most commonly
observed prey species, North Atlantic right whales feed on other species
including barnacle larvae. Patch density may be the critical factor in
eliciting feeding behavior. Lack of information on where animals are
when they are not in known feeding or calving grounds makes it difficult
to estimate how long the 'fasting season' lasts but it is probably around
3 months (for those individuals that migrate to lower latitudes in the
winter). In 1993, right whales appeared to abandon the Roseway Basin
habitat for unknown reasons.
There have been a number of studies on right whale feeding requirements
(see Kenney and Wishner, 1995; IWC In press b) and on whether changes
in right whale habitat have led to a shortage of food thereby threatening
the population. Successful right whale feeding depends on the presence
of extremely dense zooplankton patches (Wishner et al., 1995). Simply
measuring the average zooplankton density in an area will not provide
sufficient information to judge whether feeding conditions exist for
right whales. The main factors influencing prey density are physical
( i.e. advection of prey and its concentration along density discontinuities).
Kenney (in press) concluded that the absence of right whales in the Great
South Channel in 1992 was due to a large reduction in Calanus abundance
and a shift in zooplankton dominance induced by hydrographic changes.
Any habitat studies investigating whether nutritional factors (i.e.
prey availability) are involved in reproductive dysfunction in North
Atlantic right whales will need to examine a number of factors including:
availability and abundance of patches of prey of suitable size and density;
the quality of the prey; and the abundance of any competitors for the
prey. These investigations should also take cognizance of ongoing studies
of physical forcing (e.g. the North Atlantic Oscillation). This is discussed
further in the following section.
Studies of blubber thickness of living animals have shown that North
Atlantic right whales have significantly thinner blubber than right whales
off South Africa (Miller and Moore, in prep.). These findings are consistent
with necropsy measurements and observations that North Atlantic right
whales lack the typical post-blowhole fat rolls evident on right whales
in the Southern Hemisphere. A number of possible explanations for these
differences have been advanced including: inadequate sample size, bias
from differences in body length or sex, genetically determined differences
in morphology, adaptation to different habitat temperature regimes, seasonal
difference in sampling periods, and differences in plane of nutrition.
The Workshop agreed that a difference in the nutritive
regime between the two populations was a plausible explanation that merited
further investigation.
Based on their analyses of blubber thickness in North Atlantic right
whales, Moore and Miller reported that: (1) there was no significant
difference between males (n=17) and females (n=16); (2) a significant
correlation existed between age and blubber thickness for females (n=16)
but not males (n=17); and (3) blubber thickness in females was significantly
correlated with time since last calving, regardless of age (n=6). The
last of these observations might help explain the recent increase in
calving interval. Miller and Moore noted that a female might lose her
foetus if a certain threshold of maternal body condition was not met
at a critical time during pregnancy.
Although the Workshop agreed that obtaining blubber
thickness data is valuable (particularly when such data are combined
with other biological information from the same individual whales), it
recognized that blubber thickness alone may not be an adequate measure
of body condition. For example, in fasting seals, the type of lipid and
fatty acid in the blubber is more relevant in assessing nutritional condition
than the actual mass of blubber. Moore and Miller indicated that a more
comprehensive index of body condition could be developed for right whales,
which would include (at least) blubber thickness, blubber lipid content,
body length and body girth.
The Workshop also recognized the need to: (1) obtain increased sample
sizes from right whales of various sex, age and reproductive classes
and (2) investigate the significance of taking measurements at various
sites on the body. Studies on dead animals have revealed large differences
in blubber thickness at different body sites.
The Workshop noted the potential value of obtaining time series of blubber
measurements from individual females to track blubber changes in relation
to pregnancy, calving and lactation. A marked change in blubber thickness
(as well as in lipid content) is likely to occur during lactation. Meaningful
estimates of lipid content would probably be very difficult to obtain,
although detailed examination of ultrasound traces may be of some value.
Miller indicated that there is more connective tissue in northern than
southern right whale blubber, implying lower lipid content in the former.
3.2.3.
Evaluation of likelihood that nutritional problems may be affecting
North Atlantic right whale reproduction and development of testable
hypotheses
The Workshop agreed that inadequate nutrition could be a factor in the
poor reproductive performance of the North Atlantic right whale population
in recent years, and recommended several avenues of research be continued
or initiated.
(1) Investigation of food resources and diet
- Review the literature and unpublished data for information on factors
contributing to the formation of dense copepod patches and on the spatial
and temporal distribution of such patches.
- Encourage studies of factors affecting nutritional composition of
right whale prey, including seasonal, geographic, ontogenetic, nutritional
(phytoplankton) and long-term climatic influences.
- Apply new methodologies, including use of isotopes of carbon, nitrogen
and other elements as well as fatty acid protocols. Skin/blubber biopsies
should be evaluated as primary data sources and the effects of seasonal,
geographic, ontogenetic, nutritional (phytoplankton) and other factors
on prey signatures should be investigated.
- Encourage maximal use of traditional sampling protocols (e.g. faecal
sampling, necropsy sampling, observations of behavior) and remote telemetry
(e.g. satellite tags, time-depth recorders, critter cams) in obtaining
date on feeding habits.
(2) Assessment of body condition
Encourage continued development /application of ultrasonic techniques
to measure blubber-depth to evaluate changes in condition of reproductive-aged
females before, during and after reproduction. These efforts should include
evaluation of various body measurement sites, and validation against
necropsy samples (including data from control species such as the bowhead
whale). The research should attempt to: (a) normalize acoustic blubber
data for measurement location using a model of right whale blubber topography
so that single-point in situ measurements form different body
locations can be compared, and (b) determine lipid composition of blubber
using ultrasound.
- Continue development of morphometric and photogrammetric approaches
for estimating body condition (e.g. estimating girth and other body
parameters using stereo videogrammetry), particularly for reproductive-aged
females.
- Evaluate biopsy samples as indicators of lipid stores. Do they reveal
seasonal or reproductive trends and are they correlated to analyses
of blubber from necropsy specimens?
- Analyze necropsy samples for chemical (nutritional) constituents
and biomarkers that may indicate condition. Characterize lipid deposition
and mobilization patterns in blubber.
(3) Indicators of reproductive performance
Analyze variability in the number of right whale births and calving
interval with respect to climatic pattern, fluctuations in food supply,
use of foraging areas and female age/size (especially primiparous individuals).
- Obtain systematic photogrammetric information on calf size, on both
the nursing and feeding grounds, for evaluating growth performance.
- Conduct repeated sampling of blubber depths in relation to the lactational
cycle.
- If a lactating female becomes available for necropsy, collect milk
samples and data on mammary gland mass and anatomy.
The Workshop also identified the role of leptin in right whale body
condition and reproduction as worthy of further research. Leptin is a
hormone produced by adipose tissue and secreted into the bloodstream.
In other mammals, leptin affects feeding behavior, metabolism, reproduction
and immunology, and may regulate overall energy balance. Leptin production
increases as energy stores increase. Leptin alters nutrient partitioning
through metabolic actions on muscle and adipose tissue. It may influence
the onset of puberty through actions in the central nervous system and
in the ovaries, and it may promote development of the immune system.
Leptin expression in dermal biopsies and blubber samples could be analyzed
using immunohistochemical, biochemical and molecular methods. The initial
aims of such analyses should be to: (a) characterize patterns at different
body sites; (b) compare blubber and serum levels; and (c) evaluate leptin
levels and biological information from known animals in the photo-identification
catalogue (including age, sex, reproductive history and habitat use).
If possible, leptin levels should be compared in northern and southern
right whale populations.
3.3.
Chemical contaminants
3.3.1.
Review of existing knowledge of effects of contaminants on reproduction
An extensive body of literature on the effects of contaminants on mammalian
reproduction (including in marine mammals) has recently been reviewed
by O'Shea (1999), O'Shea et al. (1999) and Reijnders et al. (1999). A
great deal of information exists on the traditional suite of elements
and organic compounds found in mammal tissues (with emphasis on persistent
organic pollutants), but little data exist on dose-response effects for
even the better-known contaminants. Although the IWC Scientific Committee
concluded that sufficient data were available on the adverse effects
of pollutants on terrestrial species and non-cetacean marine mammals
to warrant concern for cetaceans, the Committee indicated that significant
fundamental research was needed to adequately assess the effects of pollutants
on cetaceans. To this end, the Committee developed the multi-national
multi-disciplinary research program POLLUTION 2000+ (Reijnders et al.
1999).
Gray provided a concise summary, with a few examples, of mechanistic
studies on laboratory animals. Endocrine-disrupting toxicants (e.g. antiandrogenic
pesticides, xenoestrogens, TCDD, some PCB congeners) affect development,
puberty, sexual differentiation and fecundity in rats (see the extensive
tables on reproductive and endocrine effects on rodents prepared by Gray
and Rolland in O'Shea et al. [1999: their Tables 4-6]). PAHs (of concern
for right whales, see below) are known to affect ovarian function and
DNA synthesis, and potentially cause permanent infertility. In Gray's
view, in vivo or in vitro studies using well-characterized
surrogate species can enhance our understanding of the effects of endocrine
disruptors on species, such as right whales, that will never be amenable
to controlled studies. Notwithstanding this, the Workshop recognized
that extrapolations fro one species to another must be made with caution.
Ross briefly summarized the effects of toxic contaminants on pinnipeds,
and noted that contaminants have been implicated in, or associated with,
impaired reproduction in pinnipeds, as identified via reduced reproduction
rate, reproductive tract pathologies, and complete reproductive failure.
Persistent organicpollutants, notably PCBs and the DDT-type compounds,
have been implicated in the failure of depleted Baltic Sea seal populations
to recover (Helle 1980; Bergman 1999). Uterine lesions were found in
42% of reproductive-aged female ringed seals in the Baltic Sea in the
1970s, suggesting a possible pathogenesis for a toxic effect (Helle 1980).
PCBs are thought to have affected reproductive success in harbour seals
in the Wadden Sea (Reijnders 1980). A captive feeding study in the Netherlands
found that harbour seals fed fish from the more contaminated western
Wadden Sea had greatly reduced reproductive success when compared with
seals fed fish from the less contaminated eastern Wadden Sea (Reijnders
1986). The results of marine mammal studies, all of which have involved
exposure to complex mixtures rather than single contaminants, have been
consistent with mechanistic studies of laboratory animals that document
a range of reproductive effects. DeGuise pointed out that there is much
confusion in the literature regarding contaminant mixtures as the effects
of particular chemicals in combination can be additive, antagonistic
or synergistic.
3.3.2.
Review of data on contaminant levels in North Atlantic right whales
Total PCB fractions in North Atlantic right whale blubber are an order
of magnitude lower than those in seals and odontocetes (Weisbrod et al.
2000). Seasonal trends suggest that lipid-stored organochlorines may
be released during winter when whale food intake is reduced and body
fat becomes depleted. Concentrations of some metabolizable PCBs and trans-chlordane
increase with age in males. Comparisons of organochlorine accumulations
in biopsy tissues and feces with those in prey species have been interpreted
as indicating that right whales consume different prey or forage in different
localities during their annual migration cycle (Weisbrod et al. 2000).
Deshpande and colleagues found very low levels of PCBs in zooplankton
sampled from Cape Cod Bay.
Because right whales occupy a relatively low position in the food chain,
feed at least occasionally in the sea surface microlayer, and inhabit
feeding grounds near regional sources of pollutants, they may be exposed
to certain 'non-traditional' contaminants.
Moore reported a study which measured cytochrome P450 1A (CYP1A) in
the dermal vascular endothelia of right whales, using biopsies obtained
from various locations in the western North Atlantic (Bay of Fundy, Cape
Cod Bay, Georgia/Florida coast) and in the Southern Hemisphere (South
Africa, Argentina, Auckland Islands, South Georgia). CYP1A induction
occurs in response to the presence of Ah receptor agonists, and it is
therefore a sensitive biomarker for potential toxicological impacts from
dioxin-like compounds. Marked differences were detected in CYP1A among
areas, ranging from a mean of 4.0 (SD=2.6) in the Bay of Fundy to 0.8
(SD=1.3) in the Auckland Islands (New Zealand). Within the western North
Atlantic, PAH concentrations in copepods were relatively high in the
Bay of Fundy and Cape Cod Bay (both well-known feeding areas for right
whales), but much lower on Georges Bank where right whales are not known
to congregate to feed. Moore views these findings as suggestive of a
link between exposure to non-persistent and non-bioaccumulated chemicals
and reproductive dysfunction in right whales.
The Workshop recognized the importance of controlling for confounding
variables (e.g. age, sex, reproductive state, et cetera; see Aguilar
et al. 1999) when comparing samples.
Castellini stressed the importance of differentiating between starvation
and fasting as these are separate biochemical events (with different
characteristics relative to energy mobilization). During winter when
right whales reduce their food intake, they are fasting not starving.
Clapham pointed out that there is no evidence of right whales in the
North Atlantic fasting for a full six months and that, except for parturient
females, animals forage at least occasionally throughout winter and spring.
However, females that are simultaneously lactating and fasting may mobilize
and circulate toxic chemicals stored in their blubber during late autumn
when they are at the southern end of their migration.
Southern noted that CYP1A can be induced by stressors other than chemical
contaminants, referencing ice-entrapped white whales and humans with
HIVas examples. Moore responded that even in these cases the induction
may still be due to toxins if the stressors cause fat mobilization, thereby
releasing toxins into circulation.
3.3.3.
Evaluation of likelihood that chemical contaminants may be affecting
North Atlantic right whale reproduction and development of testable
hypotheses
The Workshop agreed that right whales are routinely
exposed to a wide array of xenobiotic chemicals, some of which generate
toxic effects on mammalian reproductive and immune systems. Thus, even
though most of the fat-soluble persistent compounds usually associated
with reproductive dysfunction and impaired immuno-competence seem to
occur at relatively low levels in right whale tissues, chemical contamination
may be partly responsible for the observed reproductive problems in the
stock.
A number of questions were raised regarding the search for potentially
relevant types of contaminants:
(1) Are there chemicals whose release into the environment is correlated
either spatially or temporally with the decline in reproductive success
of right whales?
(2) What are the levels of xenobiotic substances in right whale prey species?
(3) Are there unique avenues of exposure that might be affecting right whales?
With regard to the last of the three questions, it was noted that the
North Atlantic right whale population forages downstream of a large metropolis
that dumps sewage treatment effluent into nearby waters, creating a high
probability of exposure to estrogenic chemicals and other pharmaceuticals.
The whales also feed in and near major shipping lanes where they may
be exposed to aromatic hydrocarbons (oil leaks and discharges) and organotins
(leaching from hulls). Marx pointed out that the component of the population
that migrates to the calving grounds in the southeastern USA must swim
through paper mill effluent and is in close proximity to military activities.
Since defecation has occasionally been observed in these waters, the
whales may feed opportunistically in this area.
Appendix 6 lists examples of contaminants
of possible concern with regard to North Atlantic right whales. The list
is based on three considerations: (1) likely exposure because of the
right whale's trophic level and prey selection; (2) a recent general
increase in usuage of the chemical concerned; and (3) a regional source
of contaminant supply is known to exist. There are several reasons why
'non-traditional' chemicals are included on this list. Flame retardants
and plasticizers were used extensively during the 1980s and 1990s. Use
of alkylphenols in surfactants (and as additives in many commercial products)
has also increased since the 1980s. Emissions of pharmaceuticals, including
synthetic estrogen, have accelerated, as has the use of anti-fouling
agents. Proliferation of aquaculture since the 1980s has meant the introduction
of antibiotics and pesticides directly into the sea. Finally, inputs
of methyl mercury via atmospheric deposition have increased in both New
England and the Canadian Maritimes in recent years.
Ross summarized the elements of toxic risk assessment as follows:
(1) identifying the chemicals - types, history of production and use,
transport pathways and fates;
(2) characterizing the chemicals - solubility, bioaccumulation pathways,
persistence in the environment and levels in prey species;
(3) pharmacology/toxicology of the chemicals - metabolizable or not, formation
of toxic metabolites and immunological or endocrine effects;
(4) quantification of exposure - feeding locations, prey selection et cetera;
(5) consideration of species sensitivity.
As obtaining direct, conclusive evidence concerning contaminant effects
on right whale reproduction will be difficult, Ross advocated that a
'weight-of-evidence' approach be used to assess the risks of such effects
(see Ross 2000). This would have at least six components, as follows:
(1) characterize and eliminate all possible confounding factors, e.g.
age, sex and condition;
(2) conduct comprehensive, congener-specific contaminant analyses (concentrations
and patterns) using blubber biopsies (Deshpande noted that current biopsies,
which contain considerable amounts of connective tissue, may not represent
the lipid contents deep within the blubber and that therefore deeper biopsy
samples may be necessary);
(3) conduct similar analyses on right whale prey species to help identify
contaminant sources, chemical classes of concern and trophic pathways;
(4) examine biomarkers of exposure and effect (e.g. CYP1A, as discussed above;
petroleum biomarker compounds such as triterpanes and steranes);
(5) explore linkages between toxicological endpoints measured in right whales
and the more comprehensive multi-compartment studies of harbor seals, with
a view to making appropriate inferences about effects in right whales; and,
(6) use all available information to evaluate the risks to right whales.
Ideally such studies should take place in a tiered fashion and follow
the U.S. Environmental Protection Agency's guidelines for ecological
risk assessment. This would involve identifying potential hazards and
exposure pathways, completing a toxicity assessment, and then characterizing
risk, using a weight-of-evidence approach.
Moore emphasized the importance of giving closer attention to non-bioaccumulative
contaminants rather than being fixated on the 'traditional' problem chemicals.
Southern expressed a dissenting view with regard emphasizing the detection
of chemicals rather than impacts (physiological responses). In her opinion,
it is important to investigate the molecular evidence of stress response
in right whales, as well as to catalogue toxin levels.
Muir pointed out that differences in types or levels of contaminants
in tissues can sometimes be used to distinguish populations. He suggested
that a comparison of contaminant profiles in Fundy and non-Fundy right
whales could help establish the location of the non-Fundy 'nursery' area.
3.4.
Biotoxins
3.4.1.
Review of existing knowledge of effects of biotoxins on reproduction
In recent years, the frequency, distribution and diversity of harmful
algal blooms have increased along the east coast of North America, as
well as globally. Five major classes of biotoxins are associated with
these algal blooms : saxitoxins (responsible for paralytic shellfish
poisoning, or PSP), brevetoxins (neurotoxic shellfish poisoning, NSP),
domoic acid (amnesic shellfish poisoning, ASP), okadaic acid and dinophysistoxins
(diarrhetic shellfish poisoning, DSP), and ciguatoxins (ciguatera fish
poisoning, CFP). Four of these classes have been implicated in mortality
events involving marine mammals; saxitoxins and brevetoxins are the two
groups that most often occur in the distributional range of North Atlantic
right whales. Domoic acid (ASP) events also occur off the northeastern
United States, but such events appear to have declined since the late
1980s.
Most toxins of algal origin are neurotoxic. Saxitoxins and domoic acid
are water-soluble compounds that function as sodium channel blockers
and as glutamate agonists, respectively. Brevetoxins are lipid-soluble
and act as sodium channel agonists. The water-soluble toxins, while capable
of attaining high levels during acute exposure, do not biomagnify, but
the lipid-soluble toxins bioaccumulate.
It is unclear how biotoxins affect reproduction, per se. Doucette
noted that mice exposed in utero to domoic acid during the middle
embryonic period experienced severe reorganization of the hippocampus
within three weeks of birth (Dakshinamurti et al. 1993), and that neonatal
rats exhibited a 40-fold increase in sensitivity per body weight to domoic
acid (Xi et al. 1997). Acute exposure of California sea lions (Zalophus
californianus) to toxigenic diatoms (via trophic interactions) produced
seizures and mortality of adult animals, as well as abortions (Scholin
et al. 2000). Brevetoxins are immuno-suppressive in vitro and
may cause hemolytic anemia. A mass mortality of manatees in Florida was
likely due to prolonged respiratory exposure to brevetoxins (Bossart
et al. 1998). Saxitoxins cause loss of equilibrium and respiratory distress,
with possible implications for feeding efficiency. Acute trophic exposure
via contaminated mackerel was associated with a mass mortality of humpback
whales in New England (Geraci et al. 1989). However, very little is known
about the sublethal, chronic effects of exposure to saxitoxins.
3.4.2.
Review of data on biotoxin levels in North Atlantic right whales
The algae producing brevetoxins are most prevalent in warm waters (22-28°C),
and are thus largely outside the southern migratory range of right whales,
which is limited primarily to waters cooler than 18-20°C; Anonymous,
1997). However, direct respiratory exposure of adult females and young
calves to biotoxins in Florida and Georgia nearshore waters during winter
cannot be ruled out.
Exposure to saxitoxins is a concern with regard to North Atlantic right
whales. The dinoflagellate genus Alexandrium, which produces
saxitoxin, overlaps in space and time with right whales, and toxicity
levels generally increase from southern New England northwards, e.g.
to the Bay of Fundy. Peak dinoflagellate blooms typically occur in July
and August, concurrent with the presence of right whales in the Gulf
of Maine/Bay of Fundy region. Exposure of right whales to saxitoxins
most likely occurs via trophic transfer. Laboratory studies indicate
that various copepod species (including Calanus finmarchicus)
largely avoid Alexandrium cells but still ingest enough to acquire
measurable toxicity levels (Turriff et al. 1995). In this regard, Doucette
noted that an ECOHAB regional study in the Gulf of Maine should soon
provide information on biotoxin loading in right whale prey species.
He also cited a recent study in Massachusetts Bay that showed preferential
saxitoxin accumulation in large copepods, including Calanus finmarchicus and Centropages
typicus (Turner et al. in press). Based on the LD50s (i.e. the dose
level at which 50% of treated animals die) of saxitoxin for terrestrial
mammals (200-600g/kg), the estimated daily food consumption of right
whales (ca. 4% of body weight/day) (see Anderson and White,1989), and
typical toxin loads in larger copepods (100-200g STX equiv./g wet weight;
Turner et al. in press), Doucette estimated that right whales could receive
a lethal dose of saxitoxin in a day.
3.4.3.
Evaluation of likelihood that biotoxins may be affecting North
Atlantic right whale reproduction and development of testable hypotheses
If biotoxins impair reproduction of right whales, this likely occurs
via acute toxicity to pregnant females or neonates. The central nervous
system may be affected during foetal or post-natal development, with
consequent long-term effects on regulation of the reproductive system
by the hypothalamic-pituitary axis. However, given rapid renal clearance
rates in right whales for water-soluble saxitoxins, it is unlikely that in
utero exposure represents a high risk to foetuses. Geraci et al.
(1989) suggested that cetacean diving adaptations (which channel blood
into the toxin-sensitive heart and brain and away from the organs responsible
for detoxification (liver and kidney)), could make right whales susceptible
to the neurotoxic effects of biotoxins. Historical data series of biotoxin
activity are available from long-term monitoring efforts of PSP toxicity
in the Gulf of Maine (since 1957) and the Bay of Fundy (since 1944) that
could be compared with temporal trends in right whale calf production.
White (1987) proposed a 18.6 yr cycle in maximum toxicity in the Bay
of Fundy, and his analysis predicted a peak in the late 1990s. Jennifer
Martin (DFO, St. Andrews, New Brunswick), has maintained the data set
initiated by White, thereby allowing comparisons to be made with the
most recent calving data.
Determination of toxin levels in zooplankton size fractions containing C.
finmarchicus or Centropages spp. would be useful (frozen
samples are best for such analyses), as would assays of right whale
feces, body tissues and fluids for biotoxins (particularly saxitoxins).
The Marine Biotoxins Program at the NOAA/NOS Charleston laboratory
is currently diagnosing PSP toxins using dried blood spot cards, and
Doucette suggested that this technique might be useful if blood was
available from biopsies. Brown reported, however, that very little,
if any, blood is present in most biopsy samples. Although exposure
by right whales to brevetoxins on the winter calving grounds in the
southeastern U.S. coast is unlikely, detection of these toxins (most
likely acquired via inhalation of aerosols) may be possible by testing
blowhole exudates.
A key issue is whether a causative link can be established between the
presence of toxins in the feces, body tissues, or fluids of right whales
and the occurrence of acute or subacute toxicity. In this regard, Doucette
pointed out that in bullfrogs a special protein (saxiphilin; Mahar et
al. 1991) is synthesized that binds with saxitoxin with sub-nanomolar
affinity, thereby conferring 'resistance' to the toxin. Based on this,
if right whales have been historically exposed to saxitoxin, they may
have developed a similar detoxification mechanism. Nonetheless, measuring
PSP toxins in both right whales and their primary prey is an important
first step in assessing the potential impact of biotoxins on these mammals.
3.5.
Disease
3.5.1.
Review of existing knowledge of effects of disease on reproduction
Munson provided an overview of how disease can affect reproduction.
When an animal suffers from any chronic (non-infectious) systemic disease,
reproductive activity generally diminishes or shuts down entirely. Infectious
systemic disease in adults can similarly inhibit reproductive activity
although this can be reversible, depending on recovery. Neonates that
contract an infectious systemic disease either die or suffer long-term
developmental damage. Neonatal deaths are frequently observed in marine
mammals but the cause usually remains undiagnosed. If a pregnant female
contracts a reproductive tract infection, e.g. in the uterus, she may
fail to carry the foetus to term. Reproductive diseases can be acutely
lethal (e.g. infection), recurrent (e.g. associated with environmental
conditions that recur on a seasonal basis) or chronic causing permanent
damage (e.g. uterine occlusions in Baltic seals).
Hall provided a broad review of epidemiological principles, highlighting
the need to view disease exposure and susceptibility in an ecosystem
context. Hall noted that it is important to consider interactions between
pathogens, as well as the possible involvement of multiple pathogens,
in a given disease syndrome. In some instances, the ultimate cause of
infection may be an antecedent event, condition or characteristic which
'sets the stage' for the proximate disease occurrence. In other words,
there may be no single cause but rather a series of components which,
acting together, comprise the causal mechanism.
A number of viral, bacterial and protozoal diseases affecting reproduction
have been documented in marine mammals. These include: leptospirosis,
salmonellosis, campylobacteriosis, brucellosis, toxoplasmosis, morbillivirus,
papillomavirus, adenovirus, influenza virus, herpes virus, nasitremosis,
stenurosis and halocerosis. Brucella sp. has been found in marine
mammals but marine species of Brucella have yet to be definitely
linked with abortions in the wild. Rowles, however, called attention
to the fact that a Brucella isolate from a seal in Puget Sound
caused abortions when inoculated into cattle. Morbillivirus has been
implicated in harbor seal abortions.
3.5.2.
Review of data on disease in North Atlantic right whales
Little is known about disease in North Atlantic right whales. Moore
reviewed necropsy data from 25 of the 45 right whales known to have died
in the western North Atlantic since 1970. Trauma, mainly from ship strikes,
was detected in 12 cases. One or more bones were salvaged from 14 carcasses,
and one or more soft-tissue samples from nine. On only eight occasions
were gonads found. Tissue autolysis has generally been a major impediment
in histological investigations of right whales. Munson emphasized that
even when the cause of death is attributable to trauma based on gross
findings, it is important to strive for histological analyses that could
reveal an underlying pathological condition. Southern added that it would
be useful to test grossly normal biopsy tissues for virus antigens.
Marx described three types of skin lesion observed on North Atlantic
right whales: circular, blister or crater, and swath. Skin lesions, mainly
circular, have been detected on more than 100 individuals in the right
whale populationsince 1980, and have significantly increased over time
(p=0.004). During 1980-1996, the average percentage of identified whales
with skin lesions was 5.06% (sd=5.86), with a peak of 24% in 1995. Regressions
for females that should have calved but did not (as determined by calving
history) and for whales with lesions both showed significant increases
(F=23.3, p<0.01 and F=32.6, p<0.01, respectively). The two classes
were themselves significantly correlated (r=0.768, p<0.01). De Guise
noted that the death of an adult female in 1999 (caused by a ship strike)
provided an opportunity for histological examination of the skin lesions.
The lesions on this animal were papilloma-like, exhibiting some acute
and chronic inflammation in the dermis. Electron microscopic studies
did not reveal an etiological agent, but further analyses of the lesions
are underway. Given that skin lesions have increased coincident with
the decline in the whale population's reproductive success, there was
considerable discussion concerning a possible etiological link between
the two trends. It is not clear whether the lesions are primary and thus
limited to the whale's skin, or a secondary manifestation of an underlying
systemic health problem.
Skin lesions of the kind observed on North Atlantic right whales have
not been observed on North Atlantic humpback whales. Rowntree noted that
blister-like lesions are seen on right whales in Argentina but the type
of lesions seen on North Atlantic right whales are generally not observed
on southern right whales.
Ross noted that vitamin A plays an important role in skin maintenance.
He suggested that a possible link involving a lack of vitamin A, or alternatively
a contaminant-induced breakdown in normal circulatory transport of vitamin
A, should be explored as a cause of the skin lesions. Southern pointed
out that a molecular stress response could be involved, as either a cause
or an effect of vitamin A deficiency, and that causation would be difficult
to establish. Munson indicated that skin lesions similiar to those on
right whales had been observed on black rhinoceroses and that vitamin
A involvement had been ruled out as a causative agent. Moore stated that
the only right whale tissue presently available for vitamin A assays
is a frozen sample in the care of Robert Bonde, US Geological Survey,
Sirenia Project, in Florida.
Marx noted that the distribution, abundance, and other characteristics
of cyamids are used as a crude index of a right whale's overall health
status. She and Rowntree explained that orange cyamids (Cyamus erraticus)
occur primarily in body folds or recesses (e.g., in the genital and axillary
regions) but quickly invade and colonize wounds. In debilitated animals,
cyamids also occur in the mouth area and blowholes. The sloughed skin
that cyamids eat, as well as the cyamids themselves, are less likely
to be 'washed off' on whales moving more slowly than normal, leading
to the orange appearance.
3.5.3 Evaluation
of likelihood that disease may be affecting North Atlantic right
whale reproduction and development of testable hypotheses
Workshop participants agreed that skin lesions were a high priority
for further research. It was suggested that individual sighting histories
could be informative if skin lesions could be related to reproductive
events using the photo-identification database. No opportunity should
be missed to obtain biopsy or necropsy samples of skin lesions. Hamilton
explained that lesions tend to be more focal than general, suggested
that photographs or video of the whole bodies of living whales would
be useful in characterizing the lesions. Skin diseases are often classified
according to the distribution of lesions on the body. Brown noted that
permits were being procured for the use of a critter-cam for studying
North Atlantic right whales and that this equipment might be useful in
documenting the distribution of body lesions.
It was generally agreed that obtaining fresh tissue samples as quickly
as possible from carcasses was a high priority. Munson urged that necropsies
examine all organs for lesions and that necropsy reports not be limited
only to diagnosing the cause of death. Moore responded that existing
necropsy reports could be scrutinized further for this kind of ancillary
information.
House and DeGuise cautioned that the presence of a disease agent does
not necessarily indicate a pathologic outcome and should, therefore,
be interpreted in context. Recognizing that sample sizes for North Atlantic
right whales would almost certainly be too small to support meaningful
epidemiological analyses, Hall indicated that case control studies were
suited to small sample sizes and therefore could be useful.
3.6
Other potential factors (e.g. habitat loss/disturbance) and multi-factorial
processes
Right whales no longer occupy their full historic range in the North
Atlantic. This range contraction could mean that formerly occupied areas
are no longer suitable to support right whales, or that the cultural
memory for finding or using those areas has been lost to the population.
Reproduction could be affected if calving habitat has been reduced (e.g.
loss of Delaware Bay) or foraging habitat no longer used (e.g. Gulf of
St. Lawrence, Strait of Belle Isle, the Labrador coast). Stormy Mayo
is said to have data showing a decline since 1987 in the availability
and quality of prey resources in Cape Cod Bay. Participants hoped that
Mayo's analyses of these data would be completed and published soon.
It was also noted that Kenney (in press) provides documentation for a
significant alteration in habitat use over time. Participants discussed
the importance of finding out where breeding (= mating) occurs and where
non-Fundy females take their calves in the summer. It was recognized
that there may not be a single non-Fundy nursery area, or a single breeding
ground. Apart from the use of satellite telemetry to locate the 'missing'
areas, it was suggested that useful insights might be gained from further
analyses of individual sighting histories, particularly those of adult
females seen on or near the Florida/Georgia calving grounds unaccompanied
by calves.
4.
DESIGN OF RESEARCH PROGRAM TO TEST ONE OR MORE OF THE ABOVE HYPOTHESES,
BASED ON RELATIVE LIKELIHOOD OF OCCURRENCE AND FEASIBILITY OF RESEARCH
ACHIEVING STATED OBJECTIVES, INCLUDING DISCUSSION OF APPROPRIATE
'CONTROL' POPULATION(S)
A table of research topics was drafted during the workshop and discussed
during the last hours of the third day. Each research problem - stated
as either a hypothesis, an objective, or a task - was prioritized based
on its relevance and the likelihood of it being successfully addressed.
Requirements for biological specimens and data were also identified,
as was the need for 'control' species or populations. In some instances,
other whale species (e.g. bowhead whales or Southern Hemisphere right
whales ) were identified as appropriate models or surrogates. For various
analytical purposes, it was considered appropriate to subdivide the North
Atlantic right whale population, for example into 'treatment' (e.g. Fundy)
and 'control' (non-Fundy) groups.
Munson offered an alternative framework for organizing the presentation
on a problem-by-problem basis (see Appendix 4).
After the workshop, Rolland took the lead in developing this approach
in consultation with workshop participants. The following research program
outline was developed from the a table of research topics discussed at
the workshop. It should be read in the context of both the main report
text and Appendix 4, the latter being a more
hypothesis-based approach prepared after the workshop by Munson. Priorities
are indicated in brackets for each item listed as a research need.
PROBLEM: DECLINING
CALF PRODUCTION
NEED:
To investigate the incidence of females without calves in the southeastern
US and relate to individual calving histories (HIGH).
To establish baseline information on reproductive physiology using
gonadal and adrenal steroid hormone metabolite levels in feces and
blowhole exudate to monitor reproductive status (HIGH).
To determine if extremely reduced haplotypic and allelic diversity
in the major histocompatibility complex (MHC) has increased the risk
of disease and probability of abortion (HIGH).
To investigate the potential value of molecular analysis of stress
response in right whale skin (including enzyme assays) (LOW TO MODERATE).
ACTION:
Continue collection of photo-identification and sighting histories
of individual whales.
Analyze existing catalogue data on an individual basis to determine
if non-calving females are clustered by age (suggesting development)
or region (suggesting genetics, biotoxins, contaminants, disease or
nutritional stress).
- Compare BOF vs. non-BOF females.
- Conduct geographic and temporal analysis of non-calving vs. calving
females.
- Conduct age-based analysis.
- Include nulliparous females over 9 years.
Continue biopsies for genetic testing and to develop additional genealogies.
- Increase sample coverage of the population.
- Conduct genetics-based analyses of the paternity of calves during
critical and baseline periods to assess if there is regional (BOF
vs. non-BOF) or temporal male infertility.
- Determine which males are breeding and their habitat preferences
through paternity analysis.
- Determine inbreeding coefficients for breeding/non-breeding whales.
Determine MHC class II genetic profile of more females and calves.
- To determine if reduced diversity could increase risk of early
abortion.
Develop assay for gonadal steroid hormone metabolites in feces and
validate with samples from bowhead whales.
- To determine if pregnancy is occurring and being lost.
- To determine if females are cycling.
- To determine if unsuccessful males are producing androgens.
- To determine if an underlying endocrine problem is related to
the reproductive dysfunction.
- To determine if non-breeding whales have elevated levels of glucocorticoid
hormones suppressing reproductive function.
Investigate use of blowhole exudates to assay for gonadal steroid
hormones using samples from bowhead whales (similar to saliva assay).
Investigate analysis of stress proteins in skin to determine if elevated
stress impairs reproductive health.
- Include control groups, e.g. southern hemisphere right whales,
BOF vs. non-BOF right whales.
PROBLEM: APPARENT
DETERIORATION IN BODY CONDITION
NEED:
To determine if variability in calf production is associated with
variations in prey abundance (MODERATE TO HIGH).
To determine if variability in calf production is associated with
variations in the condition of prey organisms (e.g. lipid content)
and in diet quality (HIGH).
To determine if variability in calf production is related to variations
in whale body conditions (HIGH).
To evaluate calf growth rates (MODERATE).
To publish studies of historical prey availability in Cape Cod Bay
(HIGH).
To develop a comprehensive necropsy protocol and rapid response capability
(HIGH).
To establish a centralized necropsy database including all data (not
just cause of death) (HIGH).
ACTION:
Collate and analyze existing data on prey abundance and environmental
variables.
- Review prey patch formation, history of spatial/temporal distribution
and environmental variables (e.g. oceanographic factors, North Atlantic
Oscillation).
- Encourage studies on factors affecting the nutritional composition
of major and minor prey species, including seasonal, geographic,
ontogenetic, nutritional and long-term climatic effects.
Apply new methodologies to the study of North Atlantic right whale
diets.
- Study nutrient composition of prey.
- Apply new techniques, e.g. stable isotopes of carbon and nitrogen,
fatty acids, retinoids.
- Evaluate diet composition and feeding habits using feces and behavioral
observations.
Establish a comprehensive index of right whale body condition, which
includes estimates of blubber thickness, quality and composition, and
estimates of body girth and length.
- Continue collecting acoustic blubber data with amplitude mode ultrasound,
and validate using necropsy samples and controls (e.g. bowheads).
- Develop methods for determining lipid composition of blubber from
ultrasound data and characterize lipid mobilization and deposition
patterns.
- Calibrate blubber measurements with regard to position on body.
- Compare blubber thickness in BOF vs. non-BOF females, calving
vs. non-calving females and Northern vs. Southern Hemisphere right
whales.
- Determine if incidence and type of skin lesions are related to
blubber thickness.
- Determine if whales that are ship-struck are thinner than other
whales.
- Analyze leptin expression in dermal biopsies and necropsy samples
of blubber using immunohistochemical, biochemical and molecular methods.
- Assess biopsy and tissue samples as indicators of lipid stores,
for nutritional constituents and for biomarkers indicating condition.
Analyze photos of calves to determine if growth rates can be deduced
from length and girth measurements.
- Assess need for dedicated photogrammetric program.
- Review available data on calf growth rates from southern hemisphere
right whales, bowheads.
If lactating females are necropsied, collect milk samples and data
on mammary gland mass and anatomy.
Establish a comprehensive necropsy protocol.
- Improve methods for necropsy to acquire more data on population
health.
- Improve tissue harvesting methods and archiving of tissues.
- Develop capability and protocol for sampling right whale carcasses
at sea.
- Conduct pathologic assessment of fertility, collect reproductive
tracts, assess gonadal activity, and perform gross and histopathological
assessment of reproductive tracts.
- Identify and characterize lesions, and their possible causes.
Collate all available pathology information in a central database.
- Further review/examine existing necropsy reports.
PROBLEM: INCREASED
NUMBER OF WHALES WITH SKIN LESIONS
NEED:
To determine if different types of skin lesions affect individual
reproductive success (HIGH).
To determine if different types of skin lesions impair reproductive
success (MODERATE).
To better assess the gross character, distribution and histopathology
of skin lesions (LOW).
ACTION:
Analyze existing photo-identification catalogue data for skin lesions
and reproductive history of individual females and males.
- Determine if occurrence of skin lesions correlates with females
without calves.
- Conduct a temporal and habitat preference analysis of whales with
skin lesions.
Obtain biopsies of skin lesions to determine their cause.
- Conduct histopathology and electron microscopy on all biopsies.
- Conduct viral culture on cetacean cell lines.
- Conduct PCR for pox and herpes viruses using genetic primers.
Integrate the assessment of the distribution of skin lesions in ongoing
studies measuring blubber thickness, body length and girth.
PROBLEM: INCREASED EXPOSURE
TO
BIOTOXINS (PSP) FROM HARMFUL ALGAL BLOOMS MAY BE AFFECTING REPRODUCTION
NEED:
To determine if an association exists between the occcurence/prevalance
of harmful algal blooms (especially saxitoxins) and annual right whale
calf production (MODERATE TO HIGH).
To examine biotoxins in zooplankton (C. finmarchicus and Centropages)
(MODERATE).
To analyze bio-toxins in tissues, fluids and feces from North Atlantic
right whales (MODERATE TO LOW).
ACTION:
Analyze available data (going back to the 1940s) on biotoxin events
in the Bay of Fundy.
Collect zooplankton samples in close proximity to feeding right whales
and analyze samples for biotoxins.
Analyze fresh material (e.g. blood) from stranded whales and feces
from free-swimming and dead whales for presence biotoxins.
Investigate diagnosis of biotoxins using dried blood spot cards.
Develop baseline data on tissue and fluid samples from controls and
measure background toxin levels.
PROBLEM: EXPOSURE
TO CONTAMINANTS MAY BE AFFECTING REPRODUCTION.
NEED:
To review available information on the types and sources of contaminants
in the areas where right whales feed (HIGH).
To analyze dead whales (esp. ship strikes) for a targeted list of
chemicals (HIGH).
To assay right whale prey, sympatric species, and co-predators for
chemicals of concern (based on the preceding two items), possibly using
historical samples (HIGH).
To design a biomarker approach based on exposure data (e.g. CYP1A,
DNA adducts, retinoids, leptins, triterpanes, steranes) (LOW TO MODERATE).
To extract contaminant mixtures from right whale tissues (and/or right
whale prey) for bioassays, in vitro studies or gene expression
assays (HIGH).
ACTION:
Perform literature review on sources and types of chemicals and pharmaceuticals
occurring in right whale habitats (including POPs and non-persistent
chemicals) to develop a targeted list of chemicals that may impact
right whale reproduction (see Appendix 6).
- Review the chemical list from O'Shea et al. (1999).
Use a food-web-based approach to determine exposure.
- Analyze samples of copepods, herring, sandlace, and co-predator
species for chemicals of concern.
- Assess availability of historical samples for comparative analysis.
Analyze tissues from biopsies, stranded whales, and archived samples
for chemicals of concern.
- Relate concentration of persistent chemicals in biopsies to concentrations
in blubber.
Apply and develop suitable biomarkers of effects to determine if there
is a physiological response to the chemicals of concern (e.g. CYP P450,
DNA adducts, retinoids, leptins).
Re-analyze existing contaminant data (e.g. Weisbrod et al. 2000; Westgate
et al. unpublished data; Moore et al. 2000, draft manuscript).
- Compare reproductively successful vs. non-successful whales and
habitat preferences.
- Apply PAH toxic equivalency factors (TEQs) and dioxin TEQs to
assess toxicity in right whales.
Conduct further congener-based analysis of PCBs and other 'dioxin-like'
chemicals and calculation of TEQs.
Compare levels of contaminants of concern in calving and non-calving
females (BOF vs. non-BOF) and successful vs. unsuccessful males.
Investigate the use of chemical 'fingerprints' to assess habitat preference
and reproductive history.
Extrapolate results to better-studied species to assess toxicity thresholds
and potential risk.
Standardize sample collection protocols and inter-laboratory analysis
techniques.
Use a weight-of-evidence approach to assess risk from toxic chemicals
to northern right whale reproduction.
5.
SUMMARY AND CONCLUSIONS IN THE CONTEXT OF THE OVERALL CONSERVATION
REQUIREMENTS OF NORTH ATLANTIC RIGHT WHALES
The most immediate conservation priority for the North Atlantic right
whale population is to reduce anthropogenic mortality to zero (see IWC,
in press b: Report of the Workshop on Status and Trends of Western North
Atlantic Right Whales). However, the Workshop noted that, if calf production
does not increase from the low levels observed during 1998-2000, even
the complete removal of anthropogenic mortality may be insufficient to
allow the population to recover. It is therefore critical that the reasons
for the reproductive dysfunction of the population be established as
soon as possible. To this end, the Workshop recommended that
the research program proposed above be supported to the fullest extent
possible.
The Workshop concluded that genetics, nutrition, contaminants, biotoxins
and disease could each/all cause reproductive dysfunction in North Atlantic
right whales. It is likely that no one factor is entirely responsible,
and that two or more factors could be interacting, possibly over different
time scales. For example, reduction in genetic diversity might have been
caused a loss of population resilience over several centuries, while
in recent decades, exposure by right whales to contaminants, biotoxins,
and/or adverse environmental conditions may have resulted in poor body
conditions and a greater incidence of disease. It is therefore important
that the proposed research program be interactive and multi-disciplinary
in nature and have strong central coordination. As such, the Workshop recommended that
a steering committee be established to develop protocols, review results
and progress, and provide nececessary revisions to the research program
proposed in this report. The steering committee should consist of researchers
possessing expertise in the various topics of concern (e.g. contaminants,
pathology, nutrition et cetera). The steering committee has responsibility
for selecting an appropriate coordinator for the research program, and
this coordinator's position should be fully funded.
The Workshop further recommended the development of
a comprehensive database (coordinated through the North Atlantic Right
Whale Catalogue) linked for all whales across all research programs.
Such a database would allow for multivariate analyses using data from
photo-identification studies, health assessments, genetic studies, pathology
results, contaminant levels and biomarker studies, biotoxin levels, and
blubber thickness/composition studies.
The Workshop noted that the North Atlantic Right Whale catalogue (and
its associated sighting history data base) has provided most of the data
used in determining the status of the right whale population. The catalogue
(and the sightings database) are integral components of the proposed
research program and will be essential for determining reproductive performance
in the future. The Workshop therefore recommended that
the photo-identification program be fully supported on a continuing basis.
The Workshop agreed that the multi-disciplinary nature of the meeting
and the interactive nature of the discussions had been extremely valuable,
and commended the steering group for their efforts in setting up the
meeting.
LITERATURE
CITED
Acton, A.E., Munson, L. and Waddell, W.T. 2000. Survey of necropsy
results in captive red wolves (Canis rufus), 1992-1996. J.
Zoo Wildlife Medicine 31:2-8.
Aguilar, A., Borrell, A and Pastor, T. 1999. Biological factors affecting
variability of persistent pollutant levels in cetaceans. J. Cetacean
Res. Manage. (special issue 1):83-116.
Aguilar, A. 2000. Population biology, conservation threats and status
of Mediterranean striped dolphins (Stenella coeruleoalba) J.
Cet. Res. Manage. 2:17-26.
Anderson, D.M. and White, A.W. (Eds.). 1989. Toxic dinoflagellates
and marine mammal mortalities. Woods Hole Oceanogr. Inst. Tech. Rep.
WHOI-89-36 (CRC-89-6).
Anonymous. 1997. Data report for 1996-1997 aerial surveys for northern
right whales and other listed species in Atlantic waters from Charleston,
SC to Cape Canaveral, FL. Prepared for Department of the Navy, Southern
Division, NFEC, Charleston, by Continental Shelf Associates, Inc., Jupiter,
FL. 43 pp.
Béland, P., Vézina, A. and Martineau, D. 1988. Potential
for growth of the St. Lawrence (Québec, Canada) beluga whale (Delphinapterus
leucas) population based on modelling. J. Cons. Int. Explor.
Mer 45:22-32.
Bergman, A. 1999. Prevalence of lesions associated with a disease complex
in the Baltic gray seal (Halichoerus grypus), during 1977-1996.
pp. 139-43 in O'Shea, T.J., Reeves, R.R. and Long, A.K. (eds.). 1999. Marine
mammals and persistent ocean contaminants: proceedings of the Marine
Mammal Commission workshop, Keystone, Colorado, 12-15 October 1998.
Marine Mammal Commission, Washington, D.C.
Best, P.B. 1994. Seasonality of reproduction and the length of
gestation in southern right whales Eubalaena australis. J.
Zool., Lond. 232:175-89.
Bossart, G.D., Baden, D.G., Ewing, R.Y., Roberts, B. and Wright, S.D.
1998. Brevetoxicosis in manatees (Trichechus manatus latirostris)
from the 1996 epizootic: gross, histologic, and immuno-histochemical
features. Toxicological Pathology 26:276-82.
Brownell, R.L. Jr. and Ralls, K. 1986. Potential for sperm competition
in baleen whales. Rep. int. Whal. Commn (Spec. Iss. 8):97-112.
Caswell, Fujiwara, M. and Brault, S. 1999. Declining survival probability
threatens the North Atlantic right whale. Proc. Natl Acad. Sci.
USA 96:3308-13.
Cooke, J. and Glinka, S. 1999. A comparative analysis of the demography
of the Southwest Atlantic and Northwest Atlantic right whale populations
from photo-identification of females with calves. Paper SC/O99/RW1 submitted
to Woods Hole right whale meeting, October 1999.
Cunningham, M.W., Dunbar, M.R., Buergelt, C.D., Homer, B.L., Roelke-Parker,
M.E., Taylor, S.K., King, R. Citino, S.B. and Glass, C. 1999. Atrial
septal defects in Florida panthers. J. Wildl. Dis. 35:519-530.
Dakshinamurti, K., Sharma, S.K., Sundaram, M. and Watanabe, T. 1993.
Hippocampal changes in developing postnatal mice following intrauterine
exposure to domoic acid. J. Neurosci. 13:4486-95.
Geraci, J.R., Anderson, D.M., Timperi, R.J., St. Aubin, D.J., Early,
G.A., Prescott, J.H. and Mayo, C.A. 1989. Humpback whales (Megaptera
novaeangliae) fatally poisoned by dinoflagellate toxin. Can.
J. Fish. Aquat. Sci. 46:1895-98.
Helle, E. 1980. Lowered reproductive capacity in female ringed seals
(Pusa hispida) in the Bothnian Bay, northern Baltic Sea, with
special reference to uterine occlusions. Ann. Zool. Fennici 17:147-58.
IWC. 2001 a. Report of the workshop on the comprehensive assessment
of right whales: a worldwide comparison. J. Cetacean Res. Manage.,
Spec. Iss. 2 (in press).
IWC. 2001 b. Report of the workshop on the status and trends of western
North Atlantic right whales. J. Cetacean Res. Manage., Spec.
Iss. 2 (in press).
Jiminez, J.A., Hughes, K.A., Alaks, G., Graham, L and Lacy, R.C. 1994.
An experimental study of inbreeding depression in a natural habitat. Science 266:271-73.
Kenney, R.D. 2001. Anomalous 1992 Spring and summer right whale (Eubalaena
glacialis) distribution in the Gulf of Maine. J. Cetacean
Res. Manage. Spec. Iss. 2 (in press).
Kenney, R.D. and Wishner, K.F. 1995. The Great South Channel Ocean
Productivity Experiment. Cont. Shelf Res. 15:373-384.
Kingsley, M.C.S. 1998. Population index estimates
for the St. Lawrence belugas, 1973-1995. Mar. Mamm. Sci. 14:508-30.
Knowlton, A.R., Kraus, S.D. and Kenney, R.D. 1994. Reproduction in
North Atlantic right whales. Can. J. Zool. 72:1297-1305.
Kraus, S.D., Hamilton, P.K., Kenney, R.D., Knowlton, A. and Slay, C.K.
2001. Reproductive parameters of the North Atlantic right whale. J.
Cetacean Res. Manage., Spec. Iss. 2 (in press).
Kraus, S.D. and Hatch, J.J. 2001. Mating strategies in the North Atlantic
right whale (Eubalaena glacialis). J. Cetacean Res. Manage.,
Spec. Iss. 2. (in press).
Lesage, V. and Kingsley, M.C.S. 1998. Updated status of the St. Lawerence
River population of the beluga, Delphinapterus leucas. Can.
Field-Nat.112:98-114.
Lockyer, C. 1984. Review of baleen whale (Mysticeti) reproduction and
implications for management. Rep. Int. Whal. Commn (Spec. Iss.
6):27-50.
Lockyer, C. 1987. Evaluation of the role of fat reserves in relation
to the ecology of North Atlantic fin and sei whales. Pp. 183-203 in A.C.
Huntley, D.P. Costa, G.A.J. Worthy, and M.A. Castellini (eds), Approaches
to Marine Mammal Energetics. Society for Marine Mammalogy, Spec.
Publ. No. 1.
Madsen, T., Shine, R., Olsson, M. and Wittzell, H. 1999. Restoration
of an inbred adder population. Nature 402:34-35.
Mahar, J., Lukacs, G.L., Li, Y., Hall, S. and Moczydlowski, E. 1991.
Pharmacological and biochemical properties of saxiphilin, a soluble saxitoxin-binding
protein from the bullfrog (Rana catesbeiana). Toxicon 29:53-71.
Martineau, D., Lair, S., DeGuise, S., Lipscomb, T.P. and Béland,
P. 1999. Cancer in beluga whales from the St Lawrence Estuary, Quebec,
Canada: a potential biomarker of environmental contamination. J.
Cetacean Res. Manage. (Spec. Iss. 1):249-65.
Munson, L. 1993. Diseases of captive cheetahs (Acinonyx jubatus):
results of the Cheetah Research Council pathology survey 1989-1992. Zoo
Biol. 12:105-24.
Munson, L. 1994. A high prevalence of ovarian papillary cystadenocarcinomas
in jaguars (Panthera onca). Vet. Pathol. 31:604.
Munson, L., Brown, J.L., Bush, M., Packer, C., Janssen, D., Reiziss,
S.M. and Wildt, D.E. 1996. Genetic diversity affects testicular
morphology in free-ranging lions (Panthera leo) of the Serengeti
Plains and Ngorongoro Crater. J. Reprod. Fert. 108:11-15.
Munson, L., Calzada, N., Kennedy, S. and Sorensen, T.B. 1998.
Luteinized ovarian cysts in Mediterranean striped dolphins. J. Wildl.
Diseases 34:656-60.
Munson, L. and Montali, R.J. 1991. High prevalence of ovarian
tumors in maned wolves (Chrysocyon brachyurus) at the National
Zoological Park. J. Zoo Wildlife Med. 22:125-29.
Ober, C., Hyslop, T., Elias, S., Weitkamp, L.R. and Hauck, W.W. 1998. Human
leukocyte antigen matching and fetal loss: results of a 10 year prospective
study. Human Reprod. 13:33-38.
Oftedal, O.T. 1997. Lactation in whales and dolphins: evidence of divergence
between baleen- and toothed-species. J. Mammary Gland Biol. Neoplasia 2:205-30.
O'Shea, T.J. 1999. Environmental contaminants and marine mammals. pp.
485-563 in J.E. Reynolds, III, and S.A. Rommel (eds), Biology of
marine mammals. Smithsonian Institution Press, Washington, D.C.
O'Shea, T.J. and Brownell, R.L. Jr. 1994. Organochlorine and metal
contaminants in baleen whales: a review and evaluation of conservation
implications. The Science of the Total Environment 154:179-200.
O'Shea, T.J., Reeves, R.R. and Long, A.K. (eds.). 1999. Marine
mammals and persistent ocean contaminants: proceedings of the Marine
Mammal Commission workshop, Keystone, Colorado, 12-15 October 1998.
Marine Mammal Commission, Washington, D.C.
Reijnders, P.J.H. 1980. Organochlorine and heavy metal residues
in harbour seals from the Wadden Sea and their possible effects on reproduction. Netherlands
J. Sea Res. 14:30-65.
Reijnders, P.J.H. 1986. Reproductive failure in common seals feeding
on fish from polluted coastal waters. Nature 324:456-57.
Reijnders, P.J.H., Aguilar, A. and Donovan, G.P. (eds.). 1999. Chemical
pollutants and cetaceans. J. Cetacean Res. Manage., Spec.
Iss. 1. International Whaling Commission, Cambridge, U.K.
Ross, P.S. 2000. Marine mammals as sentinels in ecological risk assessment. Human
Ecol. Risk Assess. 6(1):29-46.
Schaeff, C.M., Kraus, S.D., Brown, M.W., Perkins, J.S., Payne, R. and
White, B.N. 1997. Comparison of genetic variability of North and South
Atlantic right whales (Eubalaena), using DNA fingerprinting. Can.
J. Zool. 75:1073-80.
Scholin, C.A., Gulland, F., and Doucette, G.J. 2000. Mortality of sea
lions along the central California coast linked to a toxic diatom bloom. Nature 403:80-84.
Turner, J.T., Doucette, G.J., Powell, C.L., Kulis, D.M., Keafer, B.A.
and Anderson, D.M. Accumulation of red tide toxins in larger size fractions
of zooplankton assemblages from Massachusetts Bay, USA. Mar. Ecol.
Prog. Ser. (in press).
Turriff, N., Runge, J.A. and Cembella, A.D. 1995. Toxin accumulation
and feeding behaviour of the planktonic copepod Calanus finmarchicus exposed
to the red-tide dinoflagellate Alexandrium excavatum. Mar.
Biol. 123:55-64.
Weisbrod, A.V., Shea, D., Moore, M.J. and Stegeman, J.J. 2000. Organochlorine
exposure and bioaccumulation in the endangered northwest Atlantic right
whale (Eubalaena glacialis) population. Environ. Tox. Chem. 19:654-66.
White, A.W. 1987. Relationships of environmental factors to toxic dinoflagellate
blooms in the Bay of Fundy. Rapp. P.-v. Reun. Cons. int. Explor.
Mer 187:38-46.
Wildt, D.E., Brown, J.L., Bush, M., Barone, M.A., Cooper, K.A., Grisham,
J. and Howard, J.G. 1993. Reproductive status of cheetahs, Acinonyx
jubatus in North American zoos, the benefits of physiological surveys
for strategic planning. Zoo Biol. 12:45-80.
Wishner, K.F., Schoenherr, J.R., Beardsley, R. and Chen, C.S. 1995.
Abundance, distribution and population structure of the copepod Calanus
Finmarchicus in a springtime right whale feeding area in the southwestern
Gulf of Maine. Cont. Shelf Res. 15:475-507.
Xi, D., Peng, Y.-G. and Ramsdell, J.S. 1997. Domoic acid is a potent
neurotoxin to neonatal rats. Nat. Toxins 5:74-79.
APPENDICES
Appendix 1: Participant list
Appendix 2: Plenary presentations and workshop
agenda
Appendix 3: Summary of available information
on North Atlantic right whale reproduction
Appendix 4: Proposed research program to address
declining calf production in North Atlantic right whales
Appendix 5: Assessment of current reproductive
data for the western North Atlantic right whale
Appendix 6: Examples of contaminants of possible
concern with regard to North Atlantic right whales
