Northeast Fisheries Science Center Reference Document 07-02
Methodologies of the NOAA National Marine Fisheries
Service
Aerial Survey Program for Right Whales (Eubalaena
glacialis)
in the Northeast U.S., 1998-2006
by Timothy V.N. Cole, Patricia Gerrior, and Richard L. Merrick
National
Marine Fisheries Serv., Woods Hole Lab., 166 Water St., Woods Hole MA
02543-1026
Print
publication date January 2007;
web version posted January 23, 2007
Citation: Cole
TVN, Gerrior P, Merrick RL. 2007. Methodologies of the NOAA National
Marine Fisheries Service aerial survey program for right whales (Eubalaena
glacialis) in the Northeast U.S., 1998-2006. US Dep Commer, Northeast
Fish Sci Cent Ref Doc 07-02; 11 p.
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ABSTRACT:
This document describes methodologies
of the National Oceanic and Atmospheric Administration’s (NOAA) National
Marine Fisheries Service (NMFS) aerial surveys for North Atlantic right whales
(Eubalaena glacialis) in the Northeast U.S. The surveys covered
waters north of 41°20'N and east of 72°50'W out to the Hague Line during
the spring of 1999, 2000, and 2001, and both the spring and fall of 1998, 2002
and 2003. From 2004 through 2006 the surveys were conducted year-round. The
primary objectives of the surveys included: (1) to provide right whale sighting
locations to mariners in near real-time in an effort to mitigate whale/ship
collisions, (2) to sample offshore areas where dedicated survey effort had
been absent since at least 1992, and (3) to photographically identify individual
right whales found in these offshore areas. The program was also charged
with relocating whale carcasses for species identification and providing aerial
support for attempts to disentangle whales from fishing gear. Survey
flights were performed at a speed of 185 km/hr (100 knots) at an altitude of
230-306 meters (750-1000 feet) using high-wing aircraft equipped with bubble
windows. Environmental parameters (e.g., sea state
and cloud cover) affecting the probability of detecting
animals along track lines were logged on all survey flights. The average
flight duration was five hours. Each
flight was categorized as broadscale survey, a systematic survey of the Great
South Channel (South Channel Ocean Productivity Experiment [SCOPEX] lines),
or a haphazard survey. Over the 9-year period, 336 broadscale, 154 SCOPEX,
and 210 haphazard flights were completed, totaling 3614 flight hours.
INTRODUCTION
Ship strikes are a major source of mortality for the highly endangered
North Atlantic right whale (Eubalaena glacialis) (Knowlton and
Kraus 2001; Moore et al. 2004; NMFS 2005; Cole et al. 2005, 2006). To
prevent collisions between ships and right whales, the NOAA National
Marine Fisheries Service’s Northeast Regional Office (NERO) began
the Right Whale Sighting Advisory System in 1997. The system alerted
mariners of reported locations of right whales and requested that caution
be used when transiting areas where the sightings occurred. Reports
were received from a variety of sources including whale watches, Coast
Guard patrols, fishing vessels, commercial ships, and the general public. Alerts
were distributed by email, fax, NOAA Weather Radio, and Coast Guard Broadcast
Notice to Mariners. In 2001, alert distribution was expanded to
include the Mandatory Ship Reporting system (USCG 2001), which relayed
sighting locations to ships that were transiting through, or adjacent
to, right whale critical habitat areas (NMFS 1997).
To augment the sighting reports to the advisory system, in December
1997 the NERO began conducting aerial surveys for right whales in Cape
Cod Bay and along the western side of the Great South Channel with a
NOAA observer aboard U.S. Coast Guard helicopters. In 1998 the
effort was expanded, using a dedicated plane to cover a greater portion
of the Great South Channel where commercial shipping traffic frequently
bisects designated critical habitat for the whales. In the same
year, the NOAA Northeast Fisheries Science Center (NEFSC) began a companion
aerial survey program with a second plane to provide comprehensive right
whale photographic mark-recapture data from the Great South Channel. Despite
this region’s importance to the species (see Kenney et al. 1995),
survey effort had been largely absent there since the early 1990s.
The NOAA surveys also covered other offshore areas that had previously
received little effort but were potentially of secondary importance to
right whales. These areas included several offshore banks and ledges
in the Gulf of Maine, regions around the periphery of Georges Bank, and
the waters south of Massachusetts, Rhode Island, and Long Island NY (Figure
1).
Prior to 2001 the NOAA surveys were often directed by reports of
right whales from other sources (e.g., Coast Guard and private boaters). Many
flights were speculative, searching areas with features frequently associated
with right whales such as 50-fathom contours, strong sea surface temperature
fronts, or reports of high concentrations of late stage Calanus finmarchicus copepodites
(the right whale’s primary prey).
Although right whales were frequently found and photographed during
these flights, such haphazard surveys provided a poor basis for quantifying
right whale distribution. To provide more robust distribution data,
the NEFSC implemented a systematic, broadscale survey of the entire Gulf
of Maine-Georges Bank study area in 2001. In 2002, the NERO and
NEFSC surveys were combined into a single program, and the broadscale
survey effort was expanded.
PLATFORMS AND SURVEY TEAMS
High-wing aircraft were used, primarily DeHavilland Twin Otters, a Grumman
Widgeon, and a Grumman Goose. The planes were equipped with bubble
windows on each side to provide observers a good view both ahead and abeam
of the aircraft. The crew consisted of two pilots, a data recorder,
and two observers (one positioned on either side of the plane). A
Cessna Skymaster 337 without bubble windows was used briefly late in 2002
for monitoring an aggregation of right whales in the vicinity of Jeffreys
Ledge. One pilot, one recorder (in the co-pilot seat), and two observers
were employed during Skymaster flights. A Shrike was used in the
early spring of 1998 and a Rockwell Aero Commander briefly in the fall
of 2004. A Partenavia was used briefly during the winter of 2003-2004. The
Shrike, Aero Commander, and Partenavia were crewed by two pilots and two
observers.
SURVEY DESIGN
All surveys were conducted at a speed of 185 km/hr
(100 knots), and most at an altitude of 230 m (750 ft); the NERO
surveys were flown at 306 m (1000 ft) during the spring of 2001. Geographical
coverage of the surveys varied considerably among years. During
1998-2000, survey lines were positioned either to patrol waters where
right whales and ships were most likely to co-occur or to maximize
the number of individual right whales encountered. Information
used in planning flight routes included previous studies of right
whale distribution, information on areas of high copepod abundance,
and the location of oceanographic features potentially favorable
to right whales. Most of these flights were focused in the
Great South Channel and followed survey lines established in 1984
under a Mineral Management Service contract (Winn et al. 1985, cited
in Kenney et al. 1995). These lines were also used during stratified
random surveys conducted in 1988-1989 (the South Channel Ocean Productivity
Experiment [SCOPEX]; see Kenny et al. 1995). The NERO flew
these lines largely systematically (non-random) multiple times each
week during the spring of 1998-2001. A set of truncated SCOPEX
lines was used to check for right whale presence each month in the
springs of 1999-2005. Stratified random surveys of SCOPEX
lines were flown intermittently throughout the study period.
Starting in 2001, the NEFSC implemented a broadscale,
stratified random survey scheme that encompassed all federal waters
from New York to Maine. The area was partitioned into a series
of 13 polygons, their western edges defined by the coastline and
their eastern edges by the Hague Line. The northern and southern
boundaries of each block were spaced 37km (20 nautical miles) apart
and followed lines of latitude (Figure
1). Each block contained 20 potential
track lines running east-west and spaced 1.85 km (one nautical mile)
apart. The northern-most line in each block was designated
as line 1, and the southern-most as line 20. A track line number
was randomly selected and then flown in all survey blocks, resulting
in a track line spacing of 37 km over the entire study area. Typically
two adjacent blocks were covered in one flight. For example,
a flight would survey eastward from the western end of line 7 to
its end near the Hague Line, then transit 37 km north or south to
the eastern end of line 7 in an adjacent block and survey westward
back to the coast. In 2002, three polygons were added to cover
the coastal waters of northern Maine up to the entrance of the Bay
of Fundy. These blocks were flown in trios, as were the three
blocks in southern New England waters (blocks NOP and ABC respectively;
see Figure
1). The sequence in which block pairs were surveyed
was largely determined by sighting conditions; blocks in areas with
the best anticipated conditions were selected and among these the
blocks with the longest absence of survey effort. Following
this scheme, coverage of the study area was completed in 7 flights
over a period of 2-9 weeks. Subsequent random number generation
occurred without replacement within 2 integers of the track line
identifier of the previous series.
Sufficient flight hours were budgeted to complete at least one broadscale
series each month. Additional flight hours were allotted for
the completion of two series in both May and June, corresponding
with peak right whale activity in the study area. Time was
also provided on the majority of flights for finer scale coverage
of a limited area, to verify opportunistic reports of right whale
activity or to investigate oceanographic features potentially attractive
to right whales.
Surveys of Navy ordnance areas were undertaken in 2002 following
the discovery of a right whale calf’s carcass in the vicinity
of the exercises. These surveys followed fixed track lines
30 nautical miles long and following lines of latitude over two exercise
areas.
Beginning in 2003, additional flights were made to verify and monitor
right whale aggregations that triggered Dynamic Area Management zones
(DAMs). Enacted in 2002, this federal regulation (NMFS 2002)
required lobster and gillnet gear to be removed from areas where
no protective measures were in place and three or more right whales
were sighted in densities equal to or greater than 0.04 right whales
per nm2 (Clapham and Pace 2001; NMFS 2002). The
closures encompassed a core area commensurate with the size of the
aggregation plus an additional 27.8 km (15 nautical miles) buffer
extending from the periphery of the core area. The buffer served
to accommodate the whales’ movements over the 2-week life span
of the closure. The closure was extended for an additional
two weeks if whale density still exceeded the threshold during the
closure’s second week. The design of aerial surveys checking
existing DAM areas was typically systematic, but the objective of
these flights was to relocate the whale aggregation and not to provide
uniform coverage of the closure area.
EFFORT AND SIGHTING DATA COLLECTION
Variables recorded during the study period are summarized
in Table
1. Laptop computers with custom data logging programs
were used to collect all effort and sighting variables. The
program “Aersurv,” developed
by Jim Cubage of Cascadia Research, was used from 1998 through
2001. “Tandem,” developed by Phil Lovell of Sea
Mammal Research and Lex Hiby of Conservation Research Ltd., was
used from 2002-2006. The programs automatically collected
GPS data in NMEA 183 format at three to six second intervals. These
data included the aircraft’s position (latitude and longitude
using the WGS 83 grid), speed over ground, and course over ground. These
data were also automatically logged when effort or sighting information
was entered. Sighting condition variables were reported by
the observers, and included sea state (Beaufort scale), cloud cover,
and glare intensity on each side of the plane. Observers
also used a visibility ranking parameter that conformed to the
one used in the North Atlantic Right Whale Consortium Database
(housed at the University of Rhode Island Graduate School of Oceanography),
which indicated whether or not visibility was greater than two
nautical miles. If visibility dropped below two nautical
miles, sighting conditions were recorded as poor or observers were
taken off effort completely. In 1999, the NEFSC
stopped recording visibility and adopted instead a measure of overall
quality of sighting conditions. In 2002, observers began
estimating visibility in nautical miles (e.g., a crisp horizon
was recorded as 35 nautical miles).
Sightings were logged as they passed abeam of the
aircraft. Animals
were identified to species, if possible, and counts made of the
number of individuals present within a group or area. When
time allowed, the swim direction of the animals relative to the
plane’s heading was also noted. In 2003, sighting cues
(visuals that alerted observers to the presence of animals) were
recorded, including blows, an exposed body part, or a splash. Sightings
by other survey crew members clearly missed by primary observers
were recorded after the aircraft had passed the animals.
Starting in 1999, the perpendicular distance of each
sighting from the track line was measured using hatch marks spaced
at equal intervals on the bubble windows. Observers aligned
their eye laterally with the plane’s hull and vertically
using the top hatch mark matched with the horizon. Observers
then interpolated between hatch marks to obtain a declination
angle for each sighting. The sighting distances were calculated
from the hypotenuse angles post-flight.
When right whales were sighted, the plane turned off from the
survey line and circled over the whales to allow observers to record
their exact locations, to estimate more accurately the number of
whales present, and to take photographs of each whale’s callosity
pattern for individual identification (see Whitehead and Payne
1981; Payne et al. 1983; Kraus et al. 1986). Observers also
obtained location data and photographs of any
dead or entangled whales sighted during the surveys, regardless
of species.
Sightings of other cetaceans, sea turtles, and large fishes were
also logged. On occasion, fields of basking sharks were encountered;
this forced survey teams to abandon reporting sighting data in
case observers’ ability to detect right whales was compromised.
Sightings of commercial shipping traffic (e.g., tankers, container
ships, barges, etc.) were recorded throughout the study period. NERO
flights during 1998 through 2001 frequently flew over ships to
record the ships’ exact location. During surveys conducted
by the NEFSC, the ships’ distance, bearing, and heading relative
to the plane’s direction of travel was used to calculate
their location and heading.
Fishing gear was recorded during the 1998
surveys conducted by the NEFSC, and during surveys conducted by
the NERO from 1998-2001. After 1998, the NEFSC did not collect fishing gear routinely because of the potential
to distract observers from sighting marine mammals.
These data were not collected routinely
during 2002 and 2003 because of the potential to distract observers
from sighting marine mammals. However, the presence of fishing
gear in the vicinity of right whales was noted. Starting in 2005, fishing gear was collected as gear fields when individual pieces
became too numerous to count.
From 2004-2006
fishing vessels were recorded as a proxy of fishing effort.
From 1999-2003, sea surface temperature (SST) was recorded somewhat
routinely using an MS Visual Basic program to query a Linear Laboratories
MX6 (0-5 VDC) infrared sensor. The program queried the sensor
every two seconds and recorded an average value for each minute. These
SST data were merged with the sighting and effort data by time
using a Statistical Analysis Software© script. From
2004 through 2006 a program written by Ken Prada of Upper Cape
Systems was used; this program simultaneously collected and merged
all GPS, SST, and plane pitch and roll data. Pitch and roll
measurements were recorded from an HL Planartechnik NS-15/E2 dual
axis digital inclinometer.
DATA PROCESSING
Each flight’s effort, sightings, and GPS
data were merged and downloaded into Microsoft Excel spreadsheets. Observers
reviewed each flight’s data for errors and made corrections. The
audited data from each flight were concatenated into a single
database and submitted to the Consortium database at the end
of each survey season. All data were also loaded into an
Oracle database at the NEFSC.
INDIVIDUAL IDENTIFICATION OF RIGHT
WHALES
Prior to fall 2002, slide film was used to collect images
of right whales. The date, time, and latitude and longitude
of each image were written on the slide’s cardboard frame. Beginning
in fall 2002, the teams switched to digital cameras and merged image
file data with GPS files to identify the location of each image. All
images of right whales were submitted to the New England Aquarium (NEAq)
in Boston, Massachusetts, for matching to the North Atlantic Right
Whale Catalog. NEAq staff returned the matching status and identification
of the right whales photographed by the NOAA survey teams upon request.
RESULTS AND DISCUSSION
Table
1 summarizes the NOAA right whale aerial survey effort in the
Northeast U.S. From spring 1998 to the end of 2006, 3614 hours
were logged over 700 flights. The total of right whale counts
from these flights was 4311. These counts include many of the
same individual right whales sighted on different flights. Figure
2 depicts the survey effort and right whale sighting locations
and illustrates the progression from haphazard surveys to more systematic
coverage of the region over the period. Flights two hours or
less in duration were excluded; these short flights were typically
the result of encountering unacceptable sighting conditions offshore.
Totals of right whale counts from each year are not directly comparable
due to differences in survey objectives and recording protocols. The
majority of surveys conducted during 1998-2001 focused on surveying
SCOPEX lines, locating right whales, and surveying areas where right
whales or high densities of copepods had been reported. Comparison
to and between haphazard surveys is further complicated by differences
in the level of pre-flight knowledge of whale presence, which varied
from reliable reports received the day before a flight to historical
accounts of right whale sightings. Any comparison of sightings
per unit effort (SPUE) is unbiased only when systematic survey data
are used, such as those from the SCOPEX and broadscale survey lines.
The broadscale surveys also provide the best indication of relative
vessel collision and entanglement risks within the region. Although
the coarse coverage of the broadscale surveys undoubtedly missed some
areas where whales were present for short periods or dispersed in small
groups, larger aggregations of right whales were more likely to be
detected. Larger groups of whales increase the likelihood of
a whale being at the surface and available for detection, and right
whale aggregations tend to persist within small (18-35 km) geographic
areas for periods of weeks (Clapham and Pace 2001), extending their
availability for detection in time. Collision and entanglement
risk is proportional to the density of whales present and the duration
of their residency; the longer whales remain in an area the more likely
a vessel will transit through the area or a whale will encounter fishing
gear set within it.
Lessons Learned
Surveys were crafted to meet multiple objectives that accumulated
over a nine year period. Data collection became more sophisticated
and comprehensive in efforts to use the aerial platforms to the fullest
extent. Survey protocols changed considerably during the program’s
first four years, which led to a cascade of changes in data audit and
storage methods. In general, refinements to protocols were engineered
to reduce in-flight interpretation of observed events such as re-sightings
of individual right whales or the distribution and size of a right
whale aggregation. Post-flight data processing was increasingly
automated to reduce the potential of human error being introduced. Making
these protocol changes was time-intensive as new terms often required
discussion and refinement before, during, and after incorporation into
the routine. Anyone considering an aerial survey program is encouraged
to adopt these protocols, or those of another well-established survey
program, in their entirety.
Several different airframes were used over the study period. The
DeHavilland Twin Otters alone met the requirements for all operations. In
addition to the Widgeon, Goose, and Otters, the teams occasionally
made use of Skymasters, an Aero Commander and a Partenavia. However,
these smaller airframes could not truly accommodate two pilots and
three science crew; although room could be made in the back where a
recorder might sit, emergency egress would be difficult. These
smaller airframes were used only during periods when larger airframes
were not available, to confirm that right whales were still present
in closure areas. Data recording was greatly simplified on these
flights so that only two science crew members were needed and a two-pilot
safety measure was maintained.
For
track line surveys, the Otters afforded both an unobstructed view perpendicular
to the track line as well as ahead of the plane through 24 x 18” bubble
windows. The Widgeon and Goose were also equipped with bubble
windows, but these were too small to allow a clear view forward. Both
the Skymaster and the Partenavia had flat windows where observers were
stationed, making forward viewing difficult. The Shrike and Aero
Commander had flat windows as well, and an added detraction of engine
nacelles that limited the observers’ view perpendicular to the
track line during flat and level flying.
The
Otters, Goose, and Widgeon were equipped with opening windows aft to
allow the science crew to obtain clear photographs of right whales
for photo identification. The Partenavia had only one opening
window at the co-pilot seat, but the team opted to shoot through a
flat window in the back (with poor results) rather than have the co-pilot
abandon monitoring the flight instrumentation while circling over whales. The
Skymaster had opening windows for the pilots, but concern of any debris
reaching the aft propeller required they stay shut. The back
windows were of decent optical quality and introduced little distortion
to images taken through them. The Aero Commander had only fixed
windows and their properties created too much distortion to obtain
useful photographs.
The Skymaster’s tight circling ability facilitated positioning
for obtaining good photographs of whales. The Shrike and Partenavia
were likely a close second in maneuverability (their pilots didn’t
have whale circling experience), and the Otters a somewhat distant
third. The Widgeon and Goose could not circle tightly, and getting
good whale images was difficult even with their opening windows and
the use of very good camera equipment.
Using
a handheld camera from an open side window was the preferred method
for photographic capture of individual right whales, as photographers
could track a whale through the viewfinder while waiting for it to
surface. Using a 300mm lens to increase the subject whale’s
size within the frame provided greater resolution for photo identification
and scarring rate analyses. Photogrammetric data collection was
conducted following thorough photographic capture of individual right
whales using handheld cameras. A successful capture using the
photogrammetric system depended on the whale surfacing nearly simultaneous
to the plane passing overhead. To increase the likelihood of
capture and avoid lens distortion, an 85mm lens was used, which yielded
a much smaller image of the whale within the frame.
Flights
to relocate carcasses were typically flown at an altitude of 457 m
(1500 ft) to increase observers’ oblique visual range for oil
slicks generated by whale carcasses. Setting up search patterns
for whale carcasses perpendicular to the wind was considered because
a windblown slick becomes more detectable when its greatest extent
is parallel, rather than perpendicular, to an observer’s line
of sight. However, the team felt it was more important to have
a means of easily tracking the area covered to avoid duplicating effort,
as carcasses often drifted tens of miles over a 24-hour period. An
expanding box following lines of latitude and longitude was the easiest
search pattern logistically, but expanding arcs were also used with
one or two reference points to maintain spacing between survey lines. Various
drift models were used to help direct carcass relocation efforts.
Relocating active whales entangled in line or netting was much more
difficult. Flights to relocate whales for disentanglement attempts
were typically unsuccessful. Even if located, observers usually
lost track of an entangled whale within a few hours, and once lost
they were rarely resighted the same day. It was extremely difficult
to successfully hand off an entangled whale to a disentanglement team
if their vessel was more than 40 miles away. Tracking an entangled whale was
most often successful if it had a telemetry beacon attached to the trailing gear.
The directional antenna system installed in the Otters that could detect VHF
signals at distances of greater than 20 nautical miles was vital to several disentanglement
attempts. The VHF beacons, coupled with satellite position beacons, allowed rescuers
to pick when and where a disentanglement attempt might be made successfully.
Aerial support provided the assurance that the whale would be found once the
disentanglement team was positioned nearby.
The
most valuable asset to this survey effort was experienced aerial observers. The
pace of data collection during aerial surveys and the distance at which
whales were observed required a keen ability to both detect whales
and identify them to species. Observers with only boat-based
survey experience required a few flights with sightings of various
whale species to develop the search images to effectively identify
whales from the plane. Familiarity with wildlife photography
and whale behavior (and a strong stomach) were especially important
for photographic capture of individual right whales, disentanglement
support and photo documentation of carcasses.
ACKNOWLEDGMENTS
We are indebted to the observers who spent many hours over the water
and many more in the office double checking the data, including Cynthia
Christman, Lisa Conger, Rob DiGiovanni, Peter Duley, Holly Fearnbach,
Allison Glass, Brett Hayward, Kelly Houle, Brendan Hurley, Amy Knowlton,
Brenna Kraus, Keri Lodge, Regina Campbell-Malone, Marilyn Marx, Misty
Nelson, Misty Niemeyer, Liz Pomfret, Cathy Quinn, Sara Quinn, Amy Renner,
Brenda Rone, Cheryl Ryder, Kent Smedbol, Alison Stimpert, Christopher
Tremblay, Peter Trull, Fred Wenzel, and Monica Zani. We also
had the observer services of Jon Alberts, Allison Chaillet, G. Childreth,
Jason Conner, A. Farak, Tom Fetherston, Andrea Hallett, Brian Hopper,
Nate Johnson, Juliette Finzi, Glenn Mitchell, Mia Morete, Dave Potter,
Janeen Quintal, Marjorie Rossman, Owen Nichols, Rebecca Scott, Amber
Sobrosky, Rob Stephenson, Jonathan Wendland, and Dave Wiley. Expert
piloting was provided by Nancy Ash, Chris Barton, Eric Berkowitz, John
Bidwell, Nicole Cabana, Bill Clark, B. Cooper, Adam Dunbar, Phil Eastman,
Brad Fritzler, Jeff Hagan, Phil Hall, T. Hinds, Nickie Lambert, Gregg
LaMontagne, Doug MacIntyre, Jason Mansour, Cathy Martin, Kirk McQuown,
Mark Moran, Mark B. Nelson, Jon Neuhaus, Carl Newman, Wally Pierce,
Scott Sandorf, Charlie Smith, Tom Strong, Mark Sweeney, Brian Taggart,
Bob Thistle, Nick Toth, Kristie Twining, Bob Wallace, Fred Weir, and
James Wortham. Thanks
also to Richard Pace for providing biometric oversight on survey design
and valuable input on this manuscript, Debra Palka for sharing her
survey and programming expertise, and Phil Clapham. We are especially
indebted to the U.S. Coast Guard Air Station on Cape Cod for the use
of their facilities and airframes, as well as their whale sighting
and weather reports.
This work was funded in part by the US Coast Guard under a Memorandum
of Agreement (NEC 2003-021), and was conducted using MMPA/ESA Permits
775-1600, 1295, and 917.
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