Table of Contents Introduction Methods Results Discussion Acknowledgements References Cited Northeast Fisheries Science Center Reference Document 11-18
Mortality and Serious Injury Determinations for Baleen Whale Stocks along the Gulf of Mexico, United States, and Canadian Eastern Seaboards, 2005-2009
by Allison G. Henry, Timothy V.N. Cole, Mendy Garron, and Lanni Hall
NOAA National Marine Fisheries Service, Northeast Fisheries Science Center, 166 Water Street, Woods Hole, MA 02543
Web version posted October 21, 2011
Citation: Henry AG, Cole TVN, Garron M, Hall L. 2011. Mortality and Serious Injury Determinations for Baleen Whale Stocks along the Gulf of Mexico, United States and Canadian Eastern Seaboards, 2005-2009. US Dept Commer, Northeast Fish Sci Cent Ref Doc. 11-18; 24 p. Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026, or online at http://nefsc.noaa.gov/publications/Information Quality Act Compliance: In accordance with section 515 of Public Law 106-554, the Northeast Fisheries Science Center completed both technical and policy reviews for this report. These predissemination reviews are on file at the NEFSC Editorial Office.
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CORRECTION: In the first edition of this report, published October 21, 2011, Table 4 incorrectly listed the annual entanglement rate (US/CAN waters) for right whales as 1.0 (0.4/0.6). It was corrected to read 1.0 (1.0/0) on January 20, 2012.ABSTRACT
The Northeast Fisheries Science Center (NEFSC) has developed criteria to evaluate reports of human-caused injury and mortality to large whales. The criteria minimize the identification of false positive human-caused mortalities and serious injuries and provide a minimum value of human impact to whale stocks. Serious injury is defined as an injury that is likely to lead to death. This report describes determinations made for reports received from 2005 - 2009 involving North Atlantic right (Eubalaena glacialis), humpback (Megaptera novaeangliae), fin (Balaenoptera physalus), sei (B. borealis), blue (B. musculus), minke (B. acutorostrata), and Bryde's (B. edeni) whales observed along coastal Gulf of Mexico and the eastern seaboard of the United States and adjacent Canadian Maritimes. A total of 496 unique large whale events were verified during the period, of which 252 (51%) involved human interactions, 20 (4%) did not involve a human interaction, and for 224 (45%) of the events it was unknown if a human interaction occurred. Of the events involving human interactions, we confirmed 193 unique entanglements and 63 ship strikes. Four events had evidence of both entanglement and ship strike, and are included in the totals for both these event categories. Eighteen (9%) of the entanglements and 28 (44%) of the ship strikes were fatal. Serious injury was sustained in 22 (11%) of the entanglement events and in 2 (3%) of the confirmed ship strikes. Serious injury was prevented due to disentanglement efforts in 30 (16%) entanglement events. Forty-one (21%) of the entanglements and 11 (17%) of the ship strike events did not have adequate documentation to determine if serious injury occurred. Seventy-eight (40%) of the entanglement events and 18 (29%) of the ship strike events were determined to have not caused serious injury or death. We also confirmed a total of 308 mortalities: 46 (15%) due to human interaction, 16 (5%) due to natural causes and 246 (80%) which lacked sufficient evidence to determine cause of death. Minke whales had the greatest number of entanglement mortalities (n=7); humpback whales had the highest number of serious injury events resulting from entanglements (n=12); fin whales had the greatest number of ship strike mortalities (n=9); and right whales had the only serious injuries (n=2) from ship strikes. These mortality and serious injury numbers are minimum counts because of poor detection probabilities and inadequate documentation for the majority of events. Thus, the true level of human impact to these stocks is assumed to be greater than that reported here; the amount greater is unknown.
INTRODUCTION
As part of the 1994 amendments to the Marine Mammal Protection Act (MMPA), the NOAA National Marine Fisheries Service (NMFS) is mandated to establish monitoring programs to estimate incidental mortality and serious injury of marine mammals taken during commercial fishing operations. The agency is also charged with developing Take Reduction Plans (TRPs) that reduce commercial takes of strategic stocks of marine mammals to levels below their Potential Biological Removal (PBR) level within six months of implementation. The longer-term goal of all the TRPs is to reduce--within 5 years of implementation--commercial takes of marine mammals to insignificant levels approaching zero mortality, which has been defined as 10% of PBR (69 FR 43338; July 20, 2004).
The average rate of human-caused serious injury and mortality for the most recent five years of data is reported for each species in the annual marine mammal stock assessment report (SAR). This rate, when compared to a population's PBR, can be used as an index of the success of a recovery plan. The PBR is defined as the maximum number of animals-- not including natural mortalities--which may be removed from a marine mammal stock while allowing that stock to reach or maintain its optimum sustainable population size (Wade and Angliss 1997).
This report presents the method and results of a process that calculates the rate of human-caused serious injury and mortality for North Atlantic right (Eubalaena glacialis), humpback (Megaptera novaeangliae), fin (Balaenoptera physalus), sei (B. borealis), blue (B. musculus), minke (B. acutorostrata), and Bryde's (B. edeni) whale stocks along the Gulf of Mexico and the US and Canadian eastern seaboards for the period 2005 - 2009.
METHODS
Members of both US and Canadian stranding networks, large whale disentanglement teams, the US and Canadian Coast Guard, and civilians provided marine mammal stranding and human interaction reports to either the NMFS Northeast Regional Office (NERO), Southeast Regional Office (SERO), or the Northeast Fisheries Science Center (NEFSC). The Regional Offices obtained all available information for each report (photos, necropsy reports, etc.), which was then reviewed by NEFSC and NERO staff members. Confirmed reports were designated "events," and the species involved was verified, duplicate records identified, and relevant information from each source consolidated into a single record. Information from additional sightings of a previously documented event was added to the existing record. If an identified whale was involved in a second interaction, a new event record was assigned. Subsequent sighting and demographic information for injured whales were obtained, where available, from local population monitoring studies. NEFSC staff reviewed each mortality event and assigned a cause of death following the confirmation criteria listed below. Each injury event was similarly examined for indications of cause and identified as a serious injury if it was likely to lead to the whale's death. One staff member reviewed all determinations each year to ensure consistency in the application of determination criteria within and across years. Criteria indicated by an asterisk (*) in the lists below are new and were developed to accommodate events that were not well addressed by existing criteria. The revised criteria were applied to the 2007 - 2009 events only. Application of the revised criteria to events prior to 2007 will be completed in a separate document. These analyses are different from a serious injury determination process currently being developed by NOAA (see Andersen et al. 2008).
Large whale events from Newfoundland and Labrador are included in this analysis. Since humpbacks from these regions are known to be from feeding stocks that are distinct from the Gulf of Maine stock (Palsbøll et al. 2001), humpback events from these regions were not included in tallies. Similarly, due to the presence of other species not found in US waters, only events identified to species and involving trans-boundary stocks were included in tallies.
Also, incidental take data provided by the National Marine Fisheries Service Observer Programs are not included in this report. These data are addressed in NESFC fisheries bycatch technical memoranda and included in separate tables in the relevant SARs.
Confirmation Criteria for Species and Event (listed in order of certainty)
The species and/or event was considered confirmed if it met one of the following criteria:
- Photographs or video allowed identification;
- A marine mammal expert reported as certain;
- The report was made by trained observer or member of the disentanglement network and was then verified via interview by NMFS, disentanglement or stranding network staff; or
- A fisherman reported a whale entangled in gear or a shipper reported colliding with a whale.
The species and/or event was considered confirmed in the following less certain cases:
- Photographs or video allowed probable identification;
- A marine mammal expert reported as possible;
- An inexperienced observer's report allowed probable identification; or
- An inexperienced observer's report was verified via interview by NMFS, disentanglement or stranding network staff.
The species and/or event was considered unconfirmed if:
- Photographs or video were of insufficient quality to verify;
- An inexperienced observer's report lacked photographs or video and/or detail to confirm;
- An incomplete examination did not allow for identification; or
- A carcass was too decomposed to identify.
Human-induced Mortality Determinations
Events were categorized as entanglement mortalities if one of the following indications were confirmed to be present on a whale carcass:
- Fishing line constricted any body part, and subdermal hemorrhaging or extensive necrosis was present at point of attachment;
- An extensive entanglement was evident*;
- An entanglement prevented feeding*; or
- A code 2 (fresh dead) whale was pulled up during fishing operations*.
Events were categorized as ship strike mortalities if one of the following indications was confirmed to be present on a whale carcass:
- Large linear laceration(s) was present anywhere on body, as opposed to just dorsally as in Kraus (1990);
- Large area(s) of subdermal hemorrhaging, hematoma, or edema was evident;
- Extensive skeletal fracturing was evident; or
- A code 2 (fresh dead) carcass was found on the bow of a ship.
Serious Injury Determinations
Events were categorized as entanglement serious injuries if one of the following indications was confirmed on a living whale:
- Fishing line constricted any body part or was likely to become constricting as the whale grew;
- It was uncertain if the line was constricting, but appendages near the entanglement's point of attachment were discolored and likely compromised;
- The whale showed a marked decline in appearance following entanglement, including skin discoloration, lesions near the nares, fat loss, or increased cyamid loads;
- The entanglement prevented feeding*;
- The whale was anchored; or
- The entanglement was extensive*.
A whale was typically not considered seriously injured if all constricting lines were removed or shed.
Events were categorized as ship-strike serious injuries if, following the appearance of a linear laceration or large gouge, a living whale exhibited a marked decline in appearance, including skin discoloration, lesions near the nares, fat loss, or increased cyamid loads.
No forecasts were made as to how an entanglement or injury might increase the whale's susceptibility to further injury (e.g., from additional entanglements or collisions with vessels).
RESULTS
A total of 496 unique events were confirmed during 2005 - 2009, involving both live and dead whales (Table 1). Of these, 252 (51%) involved human interactions, 20 (4%) did not involve a human interaction, and for 224 (45%) of the events it was unknown if a human interaction had occurred. Human interaction events were categorized as either entanglement or ship strikes, with four cases having evidence of both types of interaction. Of these human interactions, 193 entanglement events were verified and determined to be the cause of death in 18 events and cause of serious injury in 22 events. There were 78 entanglement events which did not result in serious injuries (this includes cases where the animal was freed by a disentanglement team or shed gear on its own). Thirty of these events warranted serious injury classification had the animal not been disentangled. Additionally, there were 41 entanglement events for which the available information was not sufficient to determine if a serious injury had occurred (Table 2). The remaining 34 entanglement events were comprised of 31 mortalities where cause of death could not be confirmed as entanglement, two that were confirmed as ship strike mortalities, and one that was assigned as serious-injury due to unknown cause. Of the 63 confirmed ship strike events, 28 were determined to have been lethal and two caused serious injury. Eighteen ship strike events occurred which did not result in serious injury, and 11 ship strikes lacked sufficient evidence to make a determination (Table 3). The remaining four events comprised of two mortalities where cause of death could not be confirmed as ship strike, one that was a confirmed entanglement mortality, and one that was assigned as serious-injury due to unknown cause. There were 5 events involving whales entrapped in fishing weirs - 4 minke and 1 right whale. All of these occurred in Canadian waters and all animals were successfully released and deemed non-seriously injured. These events are not classified as entanglements as the animals were free-swimming within the weirs.
A total of 308 mortalities were documented, of which 46 (15%) were confirmed to be the result of human interactions, 16 (5%) were due to natural causes and 246 (80%) for which there was insufficient evidence to determine cause of death (Table 1). Annual human-caused mortality and serious injury rates for 2005 - 2009 are presented for each large whale stock in Table 4. Tables 5-10 provide details of each confirmed human interaction event resulting in serious injury or mortality.
Over the 5 year period, there were 60 confirmed events involving North Atlantic right whales, of which 29 were confirmed entanglements and 17 were confirmed ship strikes (Tables 1-3). Of the 20 verified right whale mortalities, 2 were due to entanglements, 6 due to ship strikes, 5 due to natural causes, and 7 were from undetermined causes (Table 1). Serious injury was assigned for three entanglement events and two ship strikes (details in Table 5). Serious injury classification was warranted in six additional entanglements, but was prevented by the intervention of disentanglement teams. There was an additional event which warrants noting: one right whale was documented with evidence of both entanglement and vessel collision and exhibited signs of extreme health decline. However, the precise cause of the decline could not be determined. Therefore that animal is tallied as both an entanglement and ship strike event, but is considered a serious-injury due to unknown cause.
Humpbacks, involved in 202 verified events, were the most commonly observed entangled whale species, and the most commonly observed dead whale (115 confirmed mortalities; Table 1). Of the 94 confirmed entanglements, 6 resulted in mortality and 12 in serious injury. An additional 16 events would have resulted in serious injury had disentanglement teams not intervened. Humpbacks were involved in 18 verified ship strike events, 7 of which were fatal (Table 6). We assumed all humpback events occurring in or near US and southeast Canadian waters involved the Gulf of Maine stock unless a whale was confirmed to be from another stock. Humpback events from Labrador and Newfoundland were assumed to not involve the Gulf of Maine stock.
Of 46 documented fin whale events, 14 were confirmed entanglements. Two of these resulted in fatalities--yielding the highest percentage for any of the whale species (14%)--and two resulted in serious injury. Twelve ship strike events were documented, 9 of which were fatal (Table 7).
Mortalities accounted for 10 of the 12 confirmed sei whale events. Three of these mortalities were attributed to ship strikes. There were 3 confirmed entanglement events, one of which resulted in mortality and two in serious injury (Table 8).
Minke whales were involved in 110 verified events, of which 48 were confirmed entanglements. Seven of the entanglement events were fatal, while three resulted in serious injury. In eight entanglement events, disentanglement teams removed gear that would have warranted a serious injury classification. There were only two verified ship strike events, both of which resulted in mortality (Table 9).
Bryde's whales had the lowest number of documented events - two mortalities. One was attributed to natural causes while the other mortality was a result of ship strike (Table 10).
There were no reported events involving blue whales.
In 64 of the 496 confirmed unique large whale events during 2005 - 2009, positive species identification was not possible. In six of the 64 events, the similarity in body shape and size between fin and sei whales prevented us from distinguishing which of these two species were involved. In another eight events, the whales could only be identified as balaenopteridae based on the presence of ventral pleats. The taxonomic identity of the whales involved in the remaining 50 events could not be assigned with any certainty. Entanglement was confirmed in five of these 64 events. Forty-five of the 64 events involving unidentified whales were confirmed mortalities (see Table 1).
DISCUSSION
The criteria employed in this report evolved from recommendations of serious injury workshops (Andersen et al. 2008; Angliss and DeMaster 1998) and our experience examining large whale reports collected since 1990. The criteria attempt to encompass all event scenarios and minimize the identification of false positive human-caused mortalities and serious injuries. The resulting values provide a minimum value of confirmed human impact to whale stocks.
Differentiating causal injuries from preexisting ones or postmortem damage is problematic but can be accomplished through examination of necropsy data or parsimonious evaluation of available evidence. In our determinations, fishing line constrictions were considered circumstantial evidence of premortem entanglement, as these constrictions were likely the result of force applied by an active animal. Vessel collisions frequently lack external evidence and may not be detected unless a necropsy is conducted; necropsies frequently identified subdermal hemorrhaging or hematomas, indicating that blood was still circulating at the time of injury. Large lacerations were considered an indication of a premortem vessel collision since only whales at depth would be exposed to the propellers of a ship; floating carcasses would be pushed aside by the ship's bow wave (Knowlton et al. 1995).
Assessment of serious injury was guided by regulation 50 CFR 229.2, which defines serious injury as "any injury that will likely result in mortality." Evidence of the whale's deteriorating health was used as confirmation of serious injury. A whale's physiological response to tissue damage includes increased secretion of glucocorticoids, which suppresses lymphocytes, and if sustained (because of chronic destruction of tissue by gear or hydrodynamic forces) compromises the ability of an animal to fight other infections. External indications of poor health, including skin discoloration, lesions near the nares, fat loss, or increased cyamid loads, are part of a cascade of immunological disorders. Cases of constricting entanglements invariably follow this sequence. Removal of constricting gear typically reversed the decline in appearance, and disentanglement was generally considered to prevent serious injury. Whales only loosely entangled in line typically did not have external indications of poor health; some whales carried loose wraps for years.
Over the five year period, 246 of 308 confirmed mortalities (80%) lacked sufficient evidence to determine cause of death (Table 1). Carcasses floating at sea often cannot be examined sufficiently for either internal or external indications, and they generate false negatives if they are not towed ashore and necropsied. Likewise, insufficient documentation precluded determination of fate in 41 of 193 confirmed entanglement events (21%) and 11 of 63 ship strike events (17%).
Perhaps of greater concern is the number of animals never observed. Humpback whale scar evidence suggests that only 6-12% of entanglements are witnessed and reported (Robbins 2009, 2010). Thus, whales may succumb to entanglement before the event can be detected. It is also likely that some number of ship strikes are not detected or reported. Negatively buoyant species are less likely to be detected after death, and positively buoyant species, such as North Atlantic right whales, may become negatively buoyant if an injury precludes effective feeding for an extended period (Moore et al. 2004). Given the likelihood that some number of entanglement and ship strike serious injuries and mortalities are not observed and that the serious injury and mortality criteria are designed to minimize the identification of false positive human-caused mortalities and serious injuries, the numbers in this report represent the minimum values for human-caused serious injury and mortality to large whale stocks along the Gulf of Mexico and US and Canadian eastern seaboard.
ACKNOWLEDGEMENTS
We are especially grateful to the Gulf of Mexico, US, and Canadian East Coast stranding and entanglement networks, whose members searched for and examined whales both live and dead. It is a difficult and dirty job that deserves special recognition. The United States Coast Guard was instrumental in conveying sightings reported by mariners, investigating carcasses at sea, and assisting in disentanglement efforts. We are also grateful to the staff of the Provincetown Center for Coastal Studies (PCCS), New England Aquarium, Whale Center of New England (WCNE), NOAA aerial survey teams, Wildlife Trust, the states of Florida and Georgia, Northeast Fisheries Observer Program, Marine Animal Response Society, Whale Release and Stranding, and many others for providing the sightings that have allowed this work to be conducted. Betty Lentell and Misty Nelson assisted in verifying records. PCCS and WCNE provided sighting histories and demographic information. Members of the Atlantic Scientific Review Group have provided numerous helpful comments on the protocols described here. We also thank the anonymous reviewers of earlier drafts of this report.
REFERENCES CITED
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Robbins, J. 2009. Scar based inference into Gulf of Maine humpback whale entanglement: 2003-2006. Provincetown (MA): Provincetown Center for Coastal Studies. Report to the National Marine Fisheries Service. Order Number EA133F04SE0998.
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