ABSTRACTS

Shillinger, G.L., D.M. Palacios, H. Bailey, S.J. Bograd, A.M. Swithenbank, P. Gaspar, B.P. Wallace, J.R. Spotila, F.V. Paladino, R. Piedra, S.A. Eckert, and B.A. Block. 2008. Persistent leatherback turtle migrations present opportunities for conservation. PLoS Biology 6(7), e171, doi:10.1371/journal.pbio.0060171.

Effective transboundary conservation of highly migratory marine animals requires international management cooperation as well as clear scientific information about habitat use by these species. Populations of leatherback turtles (Dermochelys coriacea) in the eastern Pacific have declined by 90% during the past two decades, primarily due to unsustainable egg harvest and fisheries bycatch mortality. While research and conservation efforts on nesting beaches are ongoing, relatively little is known about this population of leatherbacks' oceanic habitat use and migration pathways. We present the largest multi-year (2004-2005, 2005-2006, and 2007) satellite tracking dataset (12,095 cumulative satellite tracking days) collected for leatherback turtles. Forty-six females were electronically tagged during three field seasons at Playa Grande, Costa Rica, the largest extant nesting colony in the eastern Pacific. After completing nesting, the turtles headed southward, traversing the dynamic equatorial currents with rapid, directed movements. In contrast to the highly varied dispersal patterns seen in many other sea turtle populations, leatherbacks from Playa Grande traveled within a persistent migration corridor from Costa Rica, past the equator, and into the South Pacific Gyre, a vast, low-energy, low-productivity region. We describe the predictable effects of ocean currents on a leatherback migration corridor and characterize long-distance movements by the turtles in the eastern South Pacific. These data from high seas habitats will also elucidate potential areas for mitigating fisheries bycatch interactions. These findings directly inform existing multinational conservation frameworks and provide immediate regions in the migration corridor where conservation can be implemented. We identify high-seas locations for focusing future conservation efforts within the leatherback dispersal zone in the South Pacific Gyre.

Bograd, S.J., C.G. Castro, E. Di Lorenzo, D.M. Palacios, H. Bailey, W. Gilly, and F.P. Chavez. 2008. Oxygen declines and the shoaling of the hypoxic boundary in the California Current. Geophysical Research Letters 35, L12607, doi:10.1029/2008GL034185.

We use hydrographic data from the California Cooperative Oceanic Fisheries Investigations program to explore the spatial and temporal variability of dissolved oxygen (DO) in the southern California Current System (CCS) over the period 1984-2006. Large declines in DO (up to 2.1 mmol/kg/y) have been observed throughout the domain, with the largest relative DO declines occurring below the thermocline (mean decrease of 21% at 300 m). Linear trends were significant (p < 0.05) at the majority of stations down to 500 m. The hypoxic boundary (60 mmol/kg) has shoaled by up to 90 m within portions of the southern CCS. The observed trends are consistent with advection of low-DO waters into the region, as well as decreased vertical oxygen transport following near-surface warming and increased stratification. Expansion of the oxygen minimum layer could lead to cascading effects on benthic and pelagic ecosystems, including habitat compression and community reorganization.

Bailey, H., G. Shillinger, D. Palacios, S. Bograd, J. Spotila, F. Paladino, and B. Block. 2008. Identifying and comparing phases of movement by leatherback turtles using state-space models. Journal of Experimental Marine Biology and Ecology 356:128-135, doi: 10.1016/j.jembe.2007.12.020.

Leatherback turtles (Dermochelys coriacea) are currently critically endangered and could be on the verge of extinction within the Pacific Ocean. In 2004-7, satellite transmitters were attached to 46 female turtles nesting at Playa Grande, Costa Rica, to further investigate their distribution and movements in the eastern Pacific to improve conservation measures. State-space models (SSM) provide a valuable tool for modelling movement data by simultaneously accounting for measurement error and variability in the movement dynamics. Track simulations and a measure of the uncertainty for each position estimate allowed model performance with large amounts of missing satellite data to be assessed, as this is common for marine animals. A switching SSM was applied to the tracks of the turtles, which also provided an estimate of the behavioural mode at each location. This enabled the internesting period to be objectively defined based on a shift between these two modes. This switch occurred later than the last observed nesting event, indicating turtles did not immediately move offshore and the length of time and area that turtles utilise during internesting could previously have been underestimated. The movement parameters, mean turning angle and autocorrelation in speed and direction, for each mode were similar to those in the Atlantic Ocean, but the foraging phase was more prolonged and widely dispersed suggesting that food patches are less predictable in the Pacific. This may explain the long period between nesting seasons.

Branch, T.A., K.M. Stafford, D.M. Palacios, C. Allison, J.L. Bannister, C.L.K. Burton, E. Cabrera, C.A. Carlson, B. Galletti-Vernazzani, P.C. Gill, R. Hucke-Gaete, K.C.S. Jenner, M-N.M. Jenner, K. Matsuoka, Y.A. Mikhalev, T. Miyashita, M.G. Morrice, S. Nishiwaki, V.J. Sturrock, D. Tomorosov, R.C. Anderson, A.N. Baker, P.B. Best, P. Borsa, R.L. Brownell, Jr., S. Childerhouse, K.P. Findlay, T. Gerrodette, A.D. Ilangakoon, M. Joergensen, B. Kahn, D.K. Ljungblad, B. Maughan, R.D. McCauley, S. Mckay, T.F. Norris, Oman Whale And Dolphin Research Group, S. Rankin, F. Samaran, D. Thiele, K. Van Waerebeek and R.M. Warneke. 2007. Past and present distribution, densities and movements of blue whales Balaenoptera musculus in the Southern Hemisphere and northern Indian Ocean. Mammal Review 37:116-175, doi: 10.1111/j.1365-2907.2007.00106.x.

1. Blue whale locations in the Southern Hemisphere and northern Indian Ocean were obtained from catches (303,239), sightings (4,383 records of 8,058 whales), strandings (103), Discovery marks (2,191) and recoveries (95), and acoustic recordings.
2. Sighting surveys included 7,480,450 km of effort plus 14,676 days with unmeasured effort. Groups usually consisted of solitary whales (65.2%) or pairs (24.6%); larger feeding aggregations of unassociated individuals were only rarely observed. Sighting rates (groups per 1,000 km from many platform types) varied by four orders of magnitude and were lowest in the waters of Brazil, South Africa, the eastern tropical Pacific, Antarctica and South Georgia; higher in the Subantarctic and Peru; and highest around Indonesia, Sri Lanka, Chile, southern Australia and south of Madagascar.
3. Blue whales avoid the oligotrophic central gyres of the Indian, Pacific and Atlantic Oceans, but are more common where phytoplankton densities are high, and where there are dynamic oceanographic processes like upwelling and frontal meandering.
4. Compared with historical catches, the Antarctic ('true') subspecies is exceedingly rare and usually concentrated closer to the summer pack ice. In summer they are found throughout the Antarctic; in winter they migrate to southern Africa (although recent sightings there are rare) and to other northerly locations (based on acoustics), although some overwinter in the Antarctic.
5. Pygmy blue whales are found around the Indian Ocean and from southern Australia to New Zealand. At least four groupings are evident: northern Indian Ocean, from Madagascar to the Subantarctic, Indonesia to western and southern Australia, and from New Zealand northwards to the equator. Sighting rates are typically much higher than for Antarctic blue whales.
6. South-east Pacific blue whales have a discrete distribution and high sighting rates compared with the Antarctic. Further work is needed to clarify their subspecific status given their distinctive genetics, acoustics and length frequencies.
7. Antarctic blue whales numbered 1700 (95% Bayesian interval 860-2,900) in 1996 (less than 1% of original levels), but are increasing at 7.3% per annum (95% Bayesian interval 1.4-11.6%). The status of other populations in the Southern Hemisphere and northern Indian Ocean is unknown because few abundance estimates are available, but higher recent sighting rates suggest that they are less depleted than Antarctic blue whales.

Rasmussen, K., D.M. Palacios, J. Calambokidis, M. Saborio, L. Dalla-Rosa, E. Secchi, G. Steiger, J. Allen, and G. Stone. 2007. Southern Hemisphere humpback whales wintering off Central America: insights from water temperature into the longest mammalian migration. Biology Letters 3(3), doi:10.1098/rsbl.2007.0067.

We report on a wintering area off the Pacific coast of Central America for humpback whales (Megaptera novaeangliae) migrating from feeding areas off Antarctica. We document seven individuals, including a mother/calf pair, that made this migration (approx. 8300 km), the longest movement undertaken by any mammal. Whales were observed as far north as 11° N off Costa Rica, in an area also used by a boreal population during the opposite winter season, resulting in unique spatial overlap between Northern and Southern Hemisphere populations. The occurrence of such a northerly wintering area is coincident with the development of an equatorial tongue of cold water in the eastern South Pacific, a pattern that is repeated in the eastern South Atlantic. A survey of location and water temperature at the wintering areas worldwide indicates that they are found in warm waters (21.1-28.3°C), irrespective of latitude. We contend that while availability of suitable reproductive habitat in the wintering areas is important at the fine scale, water temperature influences whale distribution at the basin scale. Calf development in warm water may lead to larger adult size and increased reproductive success, a strategy that supports the energy conservation hypothesis as a reason for migration.

Palacios, D.M., S.J. Bograd, D.G. Foley, and F.B. Schwing. 2006. Oceanographic characteristics of biological hot spots in the North Pacific: A remote sensing perspective. Deep-Sea Research II 53(3-4):250-269, doi:10.1016/j.dsr2.2006.03.004.

Biological hot spots in the ocean are likely created by physical processes and have distinct oceanographic signatures. Marine predators, including large pelagic fish, marine mammals, seabirds, and fishing vessels, recognize that prey organisms congregate at ocean fronts, eddies, and other physical features. Here we use remote sensing observations from multiple satellite platforms to characterize physical oceanographic processes in four regions of the North Pacific Ocean that are recognized as biological hot spots. We use data from the central North Pacific, the northeastern tropical Pacific, the California Current System, and the Galápagos Islands to identify and quantify dynamic features in terms of spatial scale, degree of persistence or recurrence, forcing mechanism, and biological impact. The dominant timescales of these processes vary from interannual (Rossby wave interactions in the central North Pacific) to annual (spring-summer intensification of alongshore winds in the California Current System; winter wind outflow events through mountain gaps into the northeastern tropical Pacific), to intraseasonal (high-frequency equatorial waves at the Galápagos). Satellite oceanographic monitoring, combined with data from large-scale electronic tagging experiments, can be used to conduct a census of biologicalhot spots, to understand behavioral changes and species interactions within hot spots, and to differentiate the preferred pelagic habitats of different species. The identification and monitoring of biological hot spots could constitute an effective approach to marine conservation and resource management.

Palacios, D.M., and S.J. Bograd. 2005. A census of Tehuantepec and Papagayo eddies in the northeastern tropical Pacific. Geophysical Research Letters 32, L23606, doi: 10.1029/2005GL024324.

We use a 12-year (1992-2004) time series of satellite altimetry to characterize long-lived, wind-generated anticyclonic eddies originating in the Gulfs of Tehuantepec and Papagayo in the northeastern tropical Pacific. A total of 42 Tehuantepec and 26 Papagayo eddies were observed. Eddy merging, usually of a Tehuantepec-Papagayo pair, was observed on 16 occasions. On average, the eddy season began in late October and lasted approximately 250 days until early July, with 3.5 Tehuantepec and 2.2 Papagayo eddies formed each year. Minimum average eddy lifespan was 143 days and 84 days for Tehuantepec and Papagayo eddies, respectively. There was considerable interannual variability in eddy activity, with greater (fewer) number of eddies, more intense (weaker) eddies, and a longer (shorter) eddy season during El Niño (La Niña) years. Eddy intensification was consistently observed at the East Pacific Rise.

Mendelssohn, R., S.J. Bograd, F.B. Schwing, and D.M. Palacios. 2005. Teaching old indices new tricks: A state-space analysis of El Niño related climate indices. Geophysical Research Letters 32, L07709, doi:10.1029/2005GL022350.

State-space models were applied to several climate indices associated with the El Niño-Southern Oscillation (ENSO), including the Southern Oscillation Index (SOI) and its component sea level pressure series; the NINO3 sea surface temperature index; and the Northern Oscillation Index (NOI). The best models for each series include a significant long-term nonparametric trend combined with a stochastic stationary cyclic term that clearly delineates the El Niño and La Niña events. There is no evidence that the frequency of ENSO events has changed over the 20th century. The long-term trend, however, has contributed to an apparent increase in the magnitude of recent El Niño events. This trend, potentially related to global warming, has increased the level of each series by an amount equal to 30-50% of the amplitude of their corresponding annual cycle or cyclic ENSO term. Thus, the background sea surface temperature in the eastern equatorial Pacific is more than 0.5°C warmer now than prior to 1950, implying a greater overall impact of El Niño events.

Palacios, D.M., S.K. Salazar, and D. Day. 2004. Cetacean remains and strandings in the Galápagos Islands, 1923–2003. Latin American Journal of Aquatic Mammals 3(2):127-150.

A compilation of data on cetacean remains and strandings found on the shores of the Galápagos Islands, eastern equatorial Pacific, for the period 1923–2003 is presented. Information is available for 87 records belonging to 13 species. Four species account for 71% of the records: Tursiops truncatus, Globicephala macrorhynchus, Delphinus delphis, and Ziphius cavirostris. Visitor sites and the vicinity of population centers yielded most of the records; no other geographic pattern was evident in the strandings. The stranding record reflects the odontocete communities of nearshore and upwelling environments in the Galápagos. Morphometric and meristic measurements are presented for 17 skulls belonging to T. truncatus, Stenella attenuata, D. delphis, and S. coeruleoalba. The measurements for T. truncatus are consistent with the offshore ecotype, although in the Galápagos the species predominantly occupies the nearshore environment. The stomach contents of a young Z. cavirostris included seven species of cephalopod and two crustaceans. Mass strandings of Z. cavirostris (n = 2) and G. macrorhynchus (n = 2) have been witnessed and documented, while remains of multiple individuals found together on the beach suggest additional mass strandings of Pseudorca crassidens, S. attenuata, T. truncatus, and G. macrorhynchus. Some of the records could be attributed to confirmed or presumed interaction with human activities including industrial-scale fishing, pollution, and loud sound sources.

Palacios, D.M., S.J. Bograd, R. Mendelssohn, and F.B. Schwing. 2004. Long-term and seasonal trends in stratification in the California Current, 1950–1993. Journal of Geophysical Research 109, C10016, doi:10.1029/2004JC002380.

State-space model decomposition of subsurface temperatures from the World Ocean Database is used to detect and characterize changes in thermal stratification in the upper 200 m of the California Current System (CCS) over the period 1950–1993. Model results are analyzed at eight locations representing the meridional and offshore extent of the CCS between 31°N and 40°N. Thermocline strength, depth, and temperature are derived from the mean-level trend term and the seasonal component of the state-space models. Over the 44 years, the mean level of the coastal thermocline strengthened and deepened, while it weakened and shoaled offshore. These tendencies are likely the result of geostrophic adjustment to changes in basin-scale circulation, as well as to a long-term increase in upper ocean heat content of 2-9% throughout the study area. Reduction in nutrient inputs to the surface layer resulting from these climate signals are a likely explanation for the pronounced decline in biological production in CCS ecosystems observed over the same period. Substantial decadal variability superimposed on these linear tendencies may play a role in determining the response of the upper ocean to interannual events such as El Niño. The seasonal component of thermocline depth and strength exhibited a high degree of nonstationarity, with alternating periods of weakened and enhanced annual cycles lasting 3-5 years, along with changes in the phase. This changing seasonality may have implications for marine species whose life cycles are closely tuned to the seasonal cycle.

Palacios, D.M. 2004. Seasonal patterns of sea-surface temperature and ocean color around the Galápagos: regional and local influences. Deep-Sea Research II 51(1-3):43-57, doi: 10.1016/ j.dsr2.2003.08.001.

Monthly climatologies of satellite-derived sea-surface temperature (SST, from AVHRR) and ocean color (from Ocean Color and Temperature Scanner and Sea-viewing Wide-Field-of-view Sensor) around the Galápagos Archipelago are used to estimate the mean seasonal cycle of these properties and their relationship to the equatorial circulation in this oceanographically complex region. Harmonic analysis of the climatological time series indicates a best fit with annual and semi-annual constituents. The annual amplitude is the dominant signal in SST, corresponding to the basin-wide seasonal cycle of warming and cooling associated with the north-south migration of the intertropical convergence zone. Influx of upwelled water from the Panamá Bight into the northeastern part of the study area is also consistent with the annual signal. An empirical orthogonal function decomposition identifies two main spatial patterns with amplitude time series representing out-of-phase annual cycles. The dominant mode corresponds to the strengthening of the Equatorial Front and the South Equatorial Current during the second part of the year. This mode explains 92.2% of the SST variance and 82.9% of the ocean-color variance. The second mode is consistent with the topographically induced upwelling of the Equatorial Undercurrent on the western side of the archipelago, and with influx of upwelled Panamá Bight water on the eastern side, both reaching their peak during the first part of the year. This mode accounts for 6% of the SST variance and 7.7% of the ocean-color variance. The seasonal evolution of water-column temperature and nitrate (from World Ocean Atlas 1998 climatologies) is consistent with the satellite-derived patterns. A slight tilt aligned with the east-west axis of the Galápagos Platform (outlined by the 2000-m isobath) is evident in all property fields, suggesting that the presence of the archipelago introduces a small but noticeable perturbation to the large-scale currents and property gradients of the eastern equatorial Pacific.

Palacios, D.M. 2002. Factors influencing the island-mass effect of the Galápagos Islands. Geophysical Research Letters 29(23), 2134, doi: 10.1029/2002GL016232.

Enhanced phytoplankton biomass in the wake of the Galápagos Islands is thought to result from an island-mass effect (IME) fueled by upwelling of the Equatorial Undercurrent (EUC) and by natural iron enrichment from the island platform. Annual means of five variables describing the thermocline, the pycnocline, and the availability of nitrate at the surface were derived from the World Ocean Atlas 1998 (WOA98). The first principal component of these variables explained 55.8% of the variance, corroborating that the Galápagos IME is associated with features of the EUC, mainly a shallow thermocline/pycnocline and its vertical spreading in the vicinity of the Galápagos. Regression analysis of SeaWiFS-derived chlorophyll-a (chl) on the WOA98 variables indicated that the depth of the thermocline and nitrate availability explain 91.9% of the chl variance. A secondary IME of enhanced chl levels associated with the wind-sheltered area north of Isabela Island was evident in the residual variability.

Capella, J.J., L. Flórez-González, P. Falk-Fernández and D.M. Palacios. 2002. Regular appearance of otariid pinnipeds along the Colombian Pacific coast. Aquatic Mammals 28(1):67-72.

A compilation of 34 records of otariid pinnipeds along the Pacific coast of Colombia for the period 1970–2001 is presented. The species involved are the South American sea lion (Otaria flavescens), the Galápagos Sea lion (Zalophus wollebaeki), the Galápagos fur seal (Arctocephalus galapagoensis), and the South American fur seal (A. australis). The observations suggest that vagrant individuals of these species make regular excursions into the tropical waters of the Colombian Pacific, traveling distances of 900-2400 km from their normal geographic range. These apparently unusual occurrences could be related to environmental variability resulting from of El Niño or other climatic events.

Palacios, D.M. 1999. Blue whale (Balaenoptera musculus) occurrence off the Galápagos Islands, 1978–1995. Journal of Cetacean Research and Management 1(1):41-51.

Twenty-three blue whale (Balaenoptera musculus) sightings made in the vicinity of the Galápagos Islands (~00°S, 90°W) between 1978–1995 are analysed. Blue whales occurred seasonally in the austral winter/spring months. A significant proportion of the sightings (13 or 56.5%) had a tendency to occur on the same day or on consecutive days in a given year. Five (21.7%) of the sightings were of groups of three or more individuals. Distribution was to the west and southwest of the Galápagos archipelago, where a plume of cool, upwelling-enriched surface water with high planktonic biomass develops during this season. Blue whales were observed feeding on surface swarms of the euphausiid Nyctiphanes simplex in 1993. Defecation was commonly seen. The external appearance of these whales suggests they were true blue whales (B. m. intermedia). Much of the evidence from this study suggests a Southern Hemisphere stock feeding west of the Galápagos during the austral winter/spring months. Alternatively, they may belong to a presumed eastern tropical Pacific stock of blue whales which exploits the productive habitats of the Costa Rica Dome and the Peruvian/Ecuadorian coast.

ADMINISTRATIVE REPORTS ABSTRACTS

Gerrodette, T., and D.M. Palacios. 1996. Estimates of cetacean abundance in EEZ waters of the eastern tropical Pacific. Southwest Fisheries Science Center Administrative Report LJ-96-10. 28 pp. (with Spanish translation)

Seven study areas were defined based on the Exclusive Economic Zone Pacific waters of Mexico, Guatemala, El Salvador, Honduras, Nicaragua, Costa Rica, Panama, Colombia and Ecuador. Abundances of the most common cetaceans within these jurisdictional waters were estimated using line-transect methods based on ship surveys that took place from July to December between 1986 and 1993. In general, during the months of the surveys cetaceans were most abundant and diverse at the northwest range of the study areas (Mexican Pacific and Gulf of California). Abundance and diversity decreased toward the southeast, reaching lowest values off Ecuador. The composition of the cetacean fauna by body size showed broad patterns of similarity among countries. Numbers of dolphins of the genera Stenella, Delphinus, and Tursiops ranged from tens to hundreds of thousands. The short-beaked common dolphin (D. delphis) was the most abundant cetacean in each country except Colombia. Estimates of abundance for small whales, such as short-finned pilot whales (Globicephala macrorhynchus) and beaked whales of the genera Ziphius and Mesoplodon, were in the thousands, while estimates for rorquals (Balaenoptera edeni, B. physalus and B. musculus) were in the tens to hundreds of animals. Sperm whale (Physeter macrocephalus) estimates ranged from 300 to 3,000, and were an order of magnitude greater than the estimated numbers of rorquals.

Palacios, D.M., and T. Gerrodette. 1996. Potential impact of artisanal gillnet fisheries on small cetacean populations in the eastern tropical Pacific. Southwest Fisheries Science Center Administrative Report LJ-96-11. 16pp. (with Spanish translation).

Numbers of small cetaceans killed in artisanal gillnet fisheries were estimated for the Exclusive Economic Zones of Ecuador, Costa Rica and Panama, based on limited available information on numbers of fishing boats, intensity of fishing effort, net sizes and small cetacean capture rates. The estimated mortality in Ecuador was 6,377 small cetaceans in 1993, based on information collected in a previous study. If the gillnet capture rate of small cetaceans in other areas is similar to that in Ecuador, annual mortality would be approximately 16,600 animals in Costa Rica and 3,600 in Panama. Annual mortality rates were estimated to be 4.3-9.5% of population size for all small cetaceans combined, but the impact on individual species may be higher. These rates are unlikely to be sustainable based on current knowledge of small cetacean population growth rates. Although they provide a first approach to the assessment of the impact on the populations, our mortality estimates are compromised by the paucity of detailed data and therefore should be treated with caution. To determine the actual extent and impact of small cetacean mortality in gillnet fisheries in the eastern tropical Pacific, additional data are needed on fishing effort, bycatch rates, and bycatch composition. Management of fisheries harmful to small cetaceans should take into account the socio-economics of the region and offer alternatives to the fishermen and their communities.

ABSTRACTS OF CONFERENCE PRESENTATIONS

Schramm, Y., S.L. Mesnick, J. de la Rosa, J. Hyde, D. Palacios, H.M. Snell, and A.E. Dizon. 2001. Genetic structure of California and Galápagos sea lions. Page 190 in Book of Abstracts, 14th Biennial Conference on the Biology of Marine Mammals, 28 November – 3 December 2001, Vancouver, B.C., Canada.

California sea lions are capable of travelling long distances (~2000 km) and show different levels of dispersion along their range. A defined migration pattern, however, is not known and therefore the population structure is difficult to determine. Most recently, Rice (1998) divides the eastern North Pacific sea lions into two species, the California sea lion (Zalophus californianus) and the Galápagos sea lion (Z. wollebaeki). The present study seeks to determine the genetic structure of sea lions within the eastern North Pacific and to re-examine the divergence between Z. californianus and Z. wollebaeki. 197 skin samples from pups were collected at 11 rookeries along the Baja California peninsula and 2 rookeries on the Channel islands, off the coast of California. An additional 34 skin samples were collected from animals at the Galápagos Islands. A fragment of approximately 315 base pairs from the hypervariable region I of the control region of the mitochondrial DNA was sequenced. We found, (1) two distinct clades, corresponding to Z . californianus and Z. wollebaeki, (2) a strong phylogeographic signal within Z. californianus corresponding to the Gulf of California (particularly the central and upper portions) and to the Pacific; some haploytpes from the southern Gulf of California were found in the portion of the tree comprised predominantly of Pacific haplotypes, (3) haplotypes from the Galápagos are connected to haployptes from the California sea lion through haploytpes found in the upper Gulf of California, (4) there are a number of unique haplotypes found in the upper Gulf of California, each separated by a few base pairs. These data support the separation of Z. californianus and Z. wollebaeki as distinct species and indicate the existence of population structure within Z. californianus, with a higher degree of isolation and antiquity in the upper Gulf of California.

Palacios, D.M. 2001. Cetacean abundance off the Galápagos Islands for the line-transect survey GalCet2K, 5–19 April 2000. Page 167 in Book of Abstracts, 14th Biennial Conference on the Biology of Marine Mammals, 28 November – 3 December 2001, Vancouver, B.C., Canada.

Cetacean abundance is assessed from line-transect data collected during GalCet2K, a 15-day cruise that investigated the influence of mesoscale oceanographic conditions on cetacean occurrence. The area surveyed was a 72,400-km^2 box located on the downstream (western) side of the Galápagos Islands, eastern equatorial Pacific, within a region where environmental gradients are strong. The R/V Odyssey, a 28-m ketch, was used as the research platform. Distance-sampling methods are used to estimate abundance in terms of density and encounter rates. Approximately 1,770 km of trackline were surveyed and 176 cetacean sightings (involving 12 species and two genera) were collected during the on-effort segments of the trackline. Estimates are reported for nine species. Additionally, sightings of identified and unidentified whales in the family Ziphiidae are combined to produce a single estimate of beaked whale abundance. Four species of small dolphins were numerically dominant. Density estimates (in animals km^-2) and coefficients of variation (in parenthesis) are: 2.886 (0.22) short-beaked common dolphin, Delphinus delphis; 0.248 (0.46) pantropical spotted dolphins, Stenella attenuata; 0.235 (0.34) striped dolphins, S. coeruleoalba; and 0.067 (0.41) spinner dolphins, S. longirostris. Medium-sized cetaceans had intermediate densities: 0.040 (0.62) short-finned pilot whales, Globicephala macrorynchus; 0.025 (0.67) bottlenose dolphins, Tursiops truncatus; and 0.007 (0.39) beaked whales. Large cetaceans occurred at low densities: 0.0014 (0.37) Bryde's whales, Balaenoptera edeni, and 0.0009 (1.01) sperm whales, Physeter macrocephalus. Dwarf sperm whales, Kogia sima, had the lowest density: 0.0005 (0.69). Maps of group encounter rates for common and striped dolphins, the two most frequently encountered species, show different scales of patchiness and suggest spatial segregation between these two species within the study area. Comparisons of abundance and distribution are made with data from other studies around the Galápagos, the eastern tropical Pacific, and other regions.

PhD THESIS ABSTRACTS

Palacios, D.M. 2003. Oceanographic Conditions Around the Galápagos Archipelago and Their Influence on Cetacean Community Structure. Ph.D. Thesis, Oregon State University, Corvallis, Oregon. 178 pp.

The objectives of this dissertation were to describe the complex oceanographic conditions around the Galápagos Archipelago (eastern equatorial Pacific), their seasonal variability, and their effects on patterns of cetacean occurrence. The physical and ecological factors leading to a plume of high phytoplankton biomass in the wake of the Galápagos were investigated with principal component and regression analyses of water-column climatologies and satellite-derived ocean color. The results supported the notion that this "island-mass effect" is fueled by upwelling of the Equatorial Undercurrent (EUC) combined with natural iron enrichment from the island platform. Seasonal variability in long-term monthly fields of satellite-derived seasurface temperature and ocean color was studied through harmonic analysis and empirical orthogonal function decomposition. Two annual cycles were identified in both variables. The intensification of the Equatorial Front and the South Equatorial Current in the second part of the year was the dominant signal in the data. A secondary cycle reaching its peak in the first part of the year was associated with the topographically induced upwelling of the EUC on the western side of the archipelago, and with advection of upwelled Panamá Bight water on the eastern side. The occurrence of nine cetacean species (including seven small and medium-sized delphinids, the sperm whale, and the Bryde’s whale) in relation to environmental variability around the archipelago was described. Seasonally persistent sectors of the archipelago characterized by the presence of distinct species assemblages of stratified, upwelling, and nearshore environments were identified through cluster and indicator species analysis. The dominant pattern in species distribution, as extracted by a nonmetric multidimensional scaling procedure, was well correlated with the main environmental gradient (described by the degree of water-column stratification, chlorophyll-a concentration, and distance from the islands). The collective results of this study indicate that the ocean environment surrounding the Galápagos Archipelago is strongly influenced by equatorial flows. However, the archipelago also introduces a disturbance to these flows, creating localized and persistent conditions that favor the establishment of distinct biological communities around the islands.

Chapter 4: Cetacean Community Structure Around the Galápagos in Relation to Environmental Heterogeneity and Seasonal Change. Pages 84-157.

A cetacean community consisting of seven small and medium-sized delphinids (Stenella attenuata, S. longirostris, S. coeruleoalba, Delphinus delphis, Tursiops truncatus, Grampus griseus, and Globicephala macrorhynchus), the sperm whale (Physeter macrocephalus), and the Bryde’s whale (Balaenoptera edeni) was studied in relation to environmental conditions around the Galápagos Archipelago, using a compilation of sighting for the period 1973–2000. Sightings were gridded at a resolution of 0.25 degrees and seasonal composites were formed for analysis. Three major groups of sample units were obtained with cluster and indicator species analyses. The spatial distribution of two of the groups and their species composition showed a good correspondence with the main habitats found around the archipelago in all seasons. Areas of strong water-column stratification were characterized by presence of S. attenuata and S. longirostris, while upwelling and nearshore areas were characterized by presence D. delphis, T. truncatus, B. edeni, G. griseus, and G. macrorhynchus. The third group, characterized by presence of S. coeruleoalba and P. macrocephalus, was spatially incoherent. Ordination of the sample units via nonmetric multidimensional scaling yielded two axes, which represented 86% and 4.2%, respectively, of the information in the data set. The dominant environmental gradient in the study area (from cold, upwelling, and phytoplankton-rich conditions close to the islands to warm, stratified, and phytoplankton-poor conditions away from the islands) explained 27–35% of the variance in community structure along the first axis. Structure along the second axis was independent of the environmental variables considered.

Chapter 5: General Conclusion. Page 158.

The areal extent and seasonal variability of the different environments around the Galápagos Islands was illustrated by the satellite fields. Emphasis was placed on describing the ecological processes associated with the island-mass effect (IME) of this archipelago, which is fueled by the topographic upwelling of the Equatorial Undercurrent (EUC) combined with a local input of iron. The year-round persistence of the Galápagos IME underscores its importance as an "oasis" for marine biota, exploited by all trophic levels from primary producers to apex predators. This biological response exemplifies Margalef’s (1978) model of upwelling as a deformation of the local ecological fields. Variability in the depth, strength, and nutrient content of the EUC upstream probably have a large impact on the extent of the upwelling ecosystem (cf. Barber and Smith, 1981; Steger et al., 1998). However, the supply of iron from a local source is probably crucial for the development of this habitat. Therefore, a question that should be addressed by future studies is which is the source of iron: hydrothermal fluxes or resuspension of iron-rich sediments? The possibility that secondary IMEs develop in the lee of the tallest volcanoes on Isla Isabela should also be explored. Finally, the patterns of cetacean distribution indicated strong habitat differences that probably have trophic preferences as the underlying cause. However, the local trophic ecology is largely unknown, and efforts should be placed on a comprehensive description of the stocks and the roles of mesopelagic and epipelagic zooplankton (crustacean and gelatinous) and nekton (squid and fishes).

BSc THESIS ABSTRACT

Palacios, D.M. 1994. Population Status and Notes on the Breeding Ecology of the Pelecaniform Seabirds of the "Corales del Rosario" National Park, Colombian Caribbean. B.Sc. Thesis, Universidad de Bogotá Jorge Tadeo Lozano, Bogotá, Colombia. 68 pp.

A colony of Pelecaniform seabirds was surveyed between February-May and August-December 1992, on Isla Skandia, in the "Corales del Rosario" National Park. Censuses and observations were carried out from a kayak on a weekly basis. The mean colony size was 110 birds. Magnificent frigatebirds (Fregata magnificens) accounted for 80% of the population; the remainder consisted of brown pelicans (Pelecanus occidentalis) (10%), and brown (or yellow-footed) boobies (Sula leucogaster) (9%). The size of the colony is highly variable in the short term (i.e., days), stable in the medium term (a breeding cycle or one year), and declining in the long term (years). The size of the colony has decreased by more than 50% since 1979, when the birds occupied a nearby mangrove islet known as Pajarales. This islet gradually disappeared owing to human and natural causes. F. magnificens and P. occidentalis seem to breed annually, in overlapping seasons. The breeding cycle probably starts with displays by the males in August-September, just before the maximum peak of rainfall (October). However, the hatching of the chicks and their first months of development are probably synchronized with the dry season (December-April). S. leucogaster apparently does not breed in the area; instead using the colony as a roosting-loafing site. The annual nesting activity of F. magnificens in this colony suggests that Isla Skandia might be a breeding site for the adults of a population distributed over several non-breeding aggregations along the Caribbean coast of Colombia. The size of the Pelecaniform aggregations along this coast appears to be comparatively small, due to a probable limitation in food supply. Habitat degradation (mangrove harvesting) and human disturbances threaten the colony. Strong conservation measures should be enforced to protect fully the colony, as it is the only reported nesting site for F. magnificens on the Caribbean coast of Colombia. Long-term censusing, a marking and banding program, and a study of the breeding and feeding biology of the species are recommended.