Northeast Fisheries Science Center Reference Document 05-19
Seasonal Management
Area
to Reduce Ship Strikes
of Northern Right Whales
in the Gulf of Maine
by Richard
L. Merrick
National Marine Fisheries Serv.,
Woods Hole Lab.,
166 Water St.,
Woods
Hole, MA 02543
Print
publication date December 2005;
web version posted January 5, 2006
Citation:
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ABSTRACT: Northeast Fisheries Science Center staff evaluated the spatial and temporal
distribution of northern right whales (Eubalena glacialis) within
the Gulf of Maine to develop potential management areas to reduce ship
strikes of these whales. The following management areas coupled
with routing and speed restrictions should decrease the risk of right
whale ship strikes in the Gulf of Maine:
- A Cape Cod Bay Seasonal Management Area (SMA) to be coterminous with
the existing Cape Cod Bay critical habitat (January 1 - May 15).
- A Gulf of Maine SMA extending eastward from Massachusetts Bay (70.50° W)
to the Hague Line, and southward from 42.50° N to the Cape Cod
Bay SMA and the southern edge of the Great South Channel critical habitat
area. Time period for this SMA would be March 1 - July 31. If
further temporal structuring of the SMA is desired then it could be
split as follows:
- A Western Seasonal Management Area extending from Massachusetts
Bay (70.50° W) eastward to 69.40° W, and from 42.50° N
southward to the Cape Cod Bay SMA and Great South Channel critical
habitat areas (March 1 - April 30)
- An Eastern Seasonal Management Area extending from 69.75° W
eastward to the Hague line, and from 42.50° N southward to the
southern edge of the Great South Channel critical habitat area (April
1 - July 31)
- A modified Boston Traffic Separation Scheme (TSS) which includes
moving the existing East-West leg of the lanes further north, and adding
a new North-South TSS as a spur from the existing TSS. Realignment
of the existing Boston TSS has the potential to reduce interactions
between ships and large whales along the northern portion of the TSS
by 50% or more by directing shipping traffic away from seasonal large
whale concentrations within the existing TSS.
INTRODUCTION
NOAA Fisheries has used seasonal and spatial gear restrictions
to reduce interactions between northern right whales (Eubalaena glacialis)
and commercial fixed gear fisheries as part of the Atlantic Large Whale
Take Reduction Plan (ALWTRP; http://www.nero.noaa.gov/whaletrp/ ).
The most recent application of these restrictions was the Seasonal Area
Management (SAM) and Dynamic Area Management (DAM) zones implemented
in March 2002. Design of these zones was based in part on analyses
conducted by the Northeast Fisheries Science Center (Clapham and Pace
2001, Merrick et al. 2001). Based on these analyses, Management
Areas (MAs) were established to regulate fishery gear deployed in the
Northwest Atlantic Ocean in areas occupied seasonally by right whales
(Figure 1).
Since implementation of the MAs to reduce fishing gear interactions
with right whales, a strategy has also been developed to reduce ship
strikes of right whales in the same waters. In theory, MAs to reduce
gear and ship strike interactions could be similar in time and space. Nonetheless,
it would be prudent to review the design of the existing MAs before extending
their application under the ship strike strategy. It may be necessary
to modify the original fishing gear based MAs to meet the needs of ship
strike reduction.
The goal of this paper is to evaluate Seasonal Management Areas for
reducing ship strikes of right whales. The original MAs are updated
with additional data, and then modified to accommodate shipping characteristics. An
initial analysis is also provided of an alternative alignment of the
Boston, MA Traffic Separation Scheme that allows shipping to continue
but provides increased protection to right whales.
METHODS
Datasets
Right whale sightings data were obtained from the North Atlantic Right
Whale database (NARW) curated at the University of Rhode Island (URI),
which includes survey data from a variety of sources back to the 1960s. This
dataset comprises all right whale sighting information from reliable
sources collected on the East Coast of the US since at least the 1960s,
and includes observations from fine- and broad-scale aerial
and vessel surveys conducted in a variety of projects. Major sources
of data for New England waters include the Cetacean and Turtle Assessment
Program (1978-1982), the South Channel Ocean Productivity Experiment
(1988-1989), and recent NOAA surveys (1999-2003). The NARW dataset
is continually updated. The NARW dataset used in this analysis
was distributed in December 2004, and includes sighting records through
fall 2003. Areas surveyed (including track lines) can be
found at http://www.marinegis.org/series1/index.html.
Right whale sighting records from ~1960 through 2003 collected within
Northeast waters between latitude 40° and 45° N, and eastward
of 71° N to the Hague Line were analyzed. Analysis of the
Boston Traffic Separation Scheme also included humpback (Megaptera
novaeangliae) and fin whale (Balaenoptera physalus) sightings.
Recent NOAA Fisheries Service data
The only recent unbiased, broad-scale survey observations included in
the NARW database are those from NOAA aerial surveys. Directed
surveys for North Atlantic right whales were flown during March-November,
1999-2003 in the area from south of Nantucket, MA northward to the Bay
of Fundy, and from the New England coast eastward to the Hague Line. Surveys
were accomplished using two high-wing, twin-engine fixed wing aircraft. One
was a NOAA DeHaviland Twin Otter, and the other was a chartered amphibious
Grumman Widgeon (1999-2001) or Goose (2002-2003). Surveys were
flown at ca. 230 m (1999-2000) or 310 m (2001-2003) altitude, and 100
kts (185 km/hr) by at least one aircraft on virtually all days when sighting
conditions were Beaufort 3 or better. Flights typically were not
conducted when visibility was obscured (snow, rain, or fog).
During 1999-2000, flights were either flown along tracklines developed
for SCOPEX in the Great South Channel area, or directed towards
areas of reported or suspected right whale concentrations. During
2001-2003, one aircraft flew a monthly series of east-west track lines
over the entire study area, while the second aircraft focused on the
Great South Channel and other offshore areas.
Analysis
Defining Seasonal Management Areas
The MAs developed in Merrick et al (2001) provided the baseline
for the ship strike MAs, and the additional analyses focused on
refining the temporal and spatial extent of the East and West Seasonal
MAs (Figure 1) previously developed for the ALWTRP (Merrick et al. 2001). The
Cape Cod Bay MA was not analyzed further, but was assumed to be coterminous
with the existing Cape Cod Bay critical habitat management area defined
as part of the northern right whale recovery plan and the ALWTRP.
Additional analyses[1] of right whale sightings prompted
a potential spatial adjustment of the western Seasonal MA (Figure
2) to better reflect
recent data on right whale seasonal distribution. This report provides
a further update using the full 2003 dataset.
Analysis of DAM actions during 1999-2003: The predictability
of right whale concentrations distinguish Dynamic from Seasonal MAs. Dynamic
MAs were developed to address unpredictable concentrations (which could
be because of a lack of knowledge or because the whales truly do represent
an unusual aggregation), while seasonal MAs were designed to cover areas
of known right whale concentrations. The Cape Cod Bay and Great
South Channel Management Areas are examples of Seasonal MAs, because
they were drawn based on historical sightings of right whales in these
areas.
Dynamic MAs may be candidates for Seasonal MAs if whales are observed
in the same area during the same season during three or more years; the
area would then be considered to have predictable concentrations of
whales. If, however, whales were observed in 1-2 years or in different
months in different years, then the area would not be considered as a
candidate Seasonal MA. For analysis, this means that Dynamic MAs
needed to be created for each sighting of 2+ whales during each analysis
year, and boundaries drawn around applicable zones for the aggregate
of years. In summary, the process was to:
- Identify right whale sightings which met the trigger criteria (a
sighting with 2+ whales)
- Define 15 nm radius buffer around the core area
- Join, as necessary, the circular buffer zones
Dynamic event were triggered whenever there was a sighting of 2+ right
whales sufficiently close to each other to achieve a density of 0.04
right whales/nm2 (Clapham and Pace 2001). Revised Seasonal
MAs were then drawn to encapsulate all Dynamic areas exhibiting such
whale concentrations during the same season for three or more years.
Analyses focused on sightings during March-July, because this is the
time period when whales move out of Cape Cod Bay into offshore areas.
Gridded Analysis: Ideally, right whale sightings in an
area would be corrected for sightings effort to evaluate spatial and
temporal distributions. However, this is difficult given the varying
levels and quality of the sightings survey efforts; at best, adjusting
for effort would entail a long and complex process that would eliminate
from consideration any sightings without associated effort data. GIS
analyses by New England Aquarium staff (http://www.marinegis.org/series1/index.html)
using only “good survey effort and sightings data” disclosed
only a single sighting of one animal north and west of Cape Cod Bay during
the month of May from 1978 through 1999. In contrast, during this
same time period the URI right whale database contains a total of 19
sightings (mostly from surveys without associated effort data) representing
25 individual animals.
As an alternative, one can grid the data and then normalize the sightings
within each grid cell (dividing by the cell’s area). The
normalized values (“densities”) can then be compared between
cells to evaluate the overall distribution of animals. Comparing
relatively close cells should compensate, to a limited degree, for the
lack of uniform survey effort over the entire Gulf of Maine. This
assumes that sighting effort is relatively consistent for the area. For
this reason, analyses were restricted to the March-July 1999-2003 period,
the time interval when the NEFSC conducted systematic right whale surveys
of the Gulf of Maine complementing the systematic surveys of Cape Cod
Bay conducted by the Provincetown Center for Coastal Studies.
Using these datasets, ARCView was used to generate a monthly series
of “density” plots in the SAM West area:
- A rectangular grid was generated for the area between 40° and
45° N latitude from the Hague Line westward to the New England
coast or 73° W longitude. Cells throughout the area were
defined as 0.25 degree longitude and latitude squares.
- Counts of individual right whales sighted in surveys conducted during
1999-2003 were then summed for the March-July period and by month for
each grid cell.
- Of the total 1,994 cells, 983 had no right whale observations during
the 5-year, 5-month period. Four cells had very high right whale
densities (e.g., Cape Cod Bay in March-April) that skewed the distribution. The
remaining cells were all below 100 animals per cell for the entire
period. Cells were grouped binned into six bins based on right
whale densities: 0, 1, 2-4, 5-14, 15-99, and >99 sightings per cell
for the period.
- Using these categories, the data were plotted on a gridded, ARCView
base map of the Gulf of Maine using shaded values to distinguish between
ranges of values.
The resulting monthly plots were then compared to the Seasonal MAs prepared
as part of the DAM analysis to provide an alternative assessment of the
area.
Traffic Separation Scheme (TSS) Analyses
The existing TSS was designed prior to the availability of much of the
data included in the analysis presented in this paper. Nonetheless,
the existing TSS was evaluated, and an alternative configuration provided
that reduces the potential for large whale ship strikes. This configuration
was designed to address two issues: (a) to move the TSS to an area with
the lowest densities of whales, and (b) to design a spur or “cutout” from
the TSS to allow vessels to exit and enter the TSS from the north.
The analysis involved moving the lanes northward until the number of
potential interactions (defined as the number of sightings which fell
within the TSS) was minimized. This is only meant as a preliminary
evaluation of the routing, as alternative evaluations are currently underway
by staff of the Stellwagen Banks National Marine Sanctuary (pers. comm.,
David Wiley, 12 October 2005), and by the US Coast Guard as part of Port
Access Route Study for the Boston area requested by NOAA.
1Memo from Richard
Merrick to Mary Colligan dated 31 October 2003. Avail.
Protected Species Branch, NEFSC, 166 Water Street, Woods Hole, MA 02543.
RESULTS
Seasonal Management Areas
Simulated Dynamic MAs
The URI database includes 7,698 right
whale sighting events (13,118 animals; Figure 3)
recorded during 1960-2003 in Northeast waters. During
March-July 1999-2003, there were 2,396 right whale sighting events in
Northeast U.S. waters, with 1,301 events recorded outside of Cape Cod
Bay. Of these events, there were 155 sightings of groups of 2+
animals observed outside of Cape Cod Bay (Figure 4).
The DAM zones drawn using the five seasons of data are shown in Figure
5. Most of the zones, (particularly the overlapping zones) occur
from Cape Cod Bay eastward across the Great South Channel and on the
northern edge of Georges Bank. Temporally isolated (less
than 3 years) sightings of 2+ animal groups occurred southwest of the
Great South Channel (n = 2), west of the Cape Cod Bay critical habitat
area (n = 3), and north of Wilkinson Basin (n = 2). A cluster of
repeated sightings occurred in the Cashes Ledge area (n = 11); 9 of these
occurred in 2000 and 2 in 2003. Because these sightings do not
suggest a pattern of repeated inter-annual use of the area, they do not
qualify for considerations as a Seasonal MA.
Consolidating the DAMs to produce single zones which included 3 or more
seasons of overlapping buffers resulted in the rectilinear shape shown
in Figure 6. This area encompasses 137 (88%) of the Gulf of Maine
2+ animal sightings during March-June 1999-2003. It also
includes 1,095 (84%) of the 1,301 Gulf of Maine right whale sighting
events outside of Cape Cod Bay for the March-July 1999-2003 period.
The rectilinear Gulf of Maine Seasonal MA includes the existing Great
South Channel right whale critical habitat area. This MA expands
protection for right whales during March-July in two general areas:
- North (Stellwagen Bank) and east (Wilkinson Basin) of the Cape Cod
Bay critical habitat and,
- North and east (northern edge of Georges Bank) of the Great South
Channel MA.
Sighting data were also analyzed for the months of
April through July (Figure 7), the period after
most right whales have moved out of Cape Cod Bay but still remain in
the Gulf of Maine prior to moving to the Bay of Fundy. The analyses
suggest that whales occur throughout the Gulf of Maine Seasonal MA during
this time; alternatively, the zone could be split into a West zone during
March through April (eastward to 69.40° W)
and an East zone during April-July (eastward from 69.75° W).
Gridded Data
The gridded results for the March-July
(n = 2,396 sightings; Figure
8) suggest that the Cape Cod Bay and Gulf of Maine Seasonal Management
Areas encompass most of the animals sighted. The only obvious discrepancy
is to the north in the central Gulf of Maine where right whale sightings
occurred in June 2000 and 2003 (Figure 9). Otherwise,
the distributional patterns generally follow the known seasonal movements
of right whales through the Gulf of Maine. During March, animals
are located at relatively high densities only within Cape Cod Bay, though
scattered sightings exist outside the Bay. Animals begin moving
out of the Bay in April, with densities still high there but also moderately
high to the north of the Bay, and in isolated areas of the Great South
Channel. By
May, most of the activity has shifted out of the Bay and into the Great
South Channel. Densities remain high there through June (Figure
9), and then in July animals depart the Bay, reaching temporarily high
densities north of Cape Cod Bay in July, before animals move to the Bay
of Fundy.
Traffic Separation Scheme (TSS) Analyses
The current or
original TSS has the unfortunate property of routing vessels through
high whale density areas north of Race Point, MA (Figure 7 and Figure 10). However,
by moving the East-West portion of the TSS somewhat north, it is possible
to avoid many of these animals (Figure
11). Analyses
of the sighting data available through 2003 from the URI dataset suggest
that encounter rates could be decreased by 46%, 58%, and 66% for right,
humpback and fin whales, respectively (Table 1),
by such a move. Also
shown in Table 1 and Figure 11 is an alternative alignment of the East-West
portion of the TSS proposed by the Stellwagen Bank National Marine Sanctuary
(“NOS alternative”). Both alignments show the potential
for significant reduction of ship strike risk for large whales.
DISCUSSION
Extension of the existing gear management areas (Cape Cod Bay, SAM West,
SAM East, and the Great South Channel) in time and space would provide
greater protection for right whales. Such an extension would also
protect the concentrations of right whales observed in the Gulf of Maine
during spring-summer in recent years. This includes groups of animals
observed on Stellwagen Bank in April, Wilkinson Basin in April-May, and
in the northern Great South Channel in April-May. Right whale concentrations
to the north of SAM East appear to be less predictable, but occur in
areas with a lower likelihood of gear interactions due to the limited
fishing there.
The simulated DAM and gridded density results both suggested that SAM
West (Figure 1) should be expanded to the west and south to provide greater
protection for right whales. The SAM East’s southern boundary
should also be modified to better encompass the known distribution of
right whales on Georges Bank (e.g., Figure 8). The seasonal division
on May 1 between the original SAM East and West zones is a significant
problem in that aggregations of right whales have been repeatedly sighted
in the eastern part of SAM West (Wilkinson Basin), after it has been
reopened. This problem could be remedied by extending the SAM West
Area to the end of May, or by extending the western boundary of SAM East
to 69.75°W.
Finally, the existing Boston Traffic Separation Scheme could be realigned
to pass through areas with lower concentrations of right, humpback and
fin whales (Figure 11). Such a realignment would significantly
reduce the likelihood of ship strikes in the area. Additional analyses
being conducted cooperatively between Stellwagen Bank National Marine
Sanctuary and NEFSC staff, and by the US Coast Guard as part of a current
Boston Port Access Route Study, will further refine this alignment.
LITERATURE
CITED
Clapham, P. J., and R. M. Pace, III. 2001. Defining Triggers
for Temporary Area Closures to Protect Right Whales from Entanglements:
Issues and Options. Northeast Fish. Sci. Cent. Ref. Doc. 01-06; 28 p.
Available from: National Marine Fisheries Service, 166 Water Street,
Woods Hole, MA 02543-1026.
Merrick, R. L., P. J. Clapham, T. V. N. Cole, P. Gerrior, and R. M.
Pace, III. 2001. Identification of Seasonal Area Management
Zones for North Atlantic Right Whale Conservation. Northeast Fish. Sci.
Cent. Ref. Doc. 01-14; 18 p. Available from: National Marine Fisheries
Service, 166 Water Street, Woods Hole, MA 02543-1026.
ACKNOWLEDGMENTS
The efforts of the survey teams and pilots (NOAA, Provincetown Center
for Coastal studies, and commercial pilots) are gratefully acknowledged.
Without their efforts over the past three years this report would not
have been possible to produce. Recent surveys by NOAA were authorized
under MMPA/ESA permit 775-1600. I would also like to thank Dr.
Fred Serchuk, Dr. Greg Silber, David Wiley, and David Gouveia for reviews
of earlier versions of this report.
