CONTENTS Abstract Introduction Methods Results Discussion Acknowledgements References Cited
NOAA Technical Memorandum NMFS-NE-214
Mortality and Serious Injury Determinations for Baleen Whale Stocks along the United States and Canadian Eastern Seaboards, 2004-2008Allison H. Glass1, Timothy V.N. Cole1, and Mendy Garron2
1NOAA National Marine Fisheries Service, Northeast Fisheries Science Center, 166 Water Street, Woods Hole, MA 02543
2NOAA National Marine Fisheries Service, Northeast Regional Office, 55 Great Republic Dr., Gloucester, MA 01930
Web version posted May 12, 2010Citation: Glass A, Cole TVN, Garron M. 2010. Mortality and Serious Injury Determinations for Baleen Whale Stocks along the United States and Canadian Eastern Seaboards, 2004-2008. NOAA Technical Memorandum NMFS NE 214 19 p. Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026, or online at http://www.nefsc.noaa.gov/nefsc/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.
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) such that within six months of the implementation of the TRP, commercial takes of strategic stocks of marine mammals are reduced to levels below the Potential Biological Removal (PBR) level of the stocks. 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 and serious injury rates, which has been defined as 10% of PBR (69 FR 43338; July 20, 2004).
The most current five years’ average rate of human-caused serious injury and mortality is reported for each species in the annual marine mammal stock assessment reports (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 (Wade and Angliss 1997). The PBR is the product of the following factors:
- The minimum population estimate of the stock;
- One-half the maximum theoretical or estimated net productivity rate of the stock at a small population size; and
- A recovery factor of between 0.1 and 1.0.
This report presents the protocols and determinations for events 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) whale stocks along the US and Canadian eastern seaboards for the period 2004 - 2008.
Members of the US and Canadian national stranding networks, large whale disentanglement teams, the US and Canadian Coast Guard, and civilians recorded and submitted marine mammal strandings and human-induced 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 each event 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 were applied to the 2007 and 2008 events only. Application of the revised criteria to events prior to 2007 will be completed in a separate document.
Confirmation Criteria for Species and Event (listed in order of certainty)
Species/event was considered confirmed if it met one of the following criteria:
Species/event was considered confirmed in the following less certain cases:
- Photographs or video allowed identification;
- Marine mammal expert reported as certain;
- Report by trained observer or member of the disentanglement network 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.
Species/event was considered unconfirmed if:
- Photographs or video allowed probable identification;
- Marine mammal expert reported as possible;
- Inexperienced observer’s report allowed probable identification; or
- Inexperienced observer’s report verified via interview by NMFS, disentanglement or stranding network staff.
- Photographs or video were of insufficient quality to verify;
- Inexperienced observer report lacked photographs or video and/or detail to confirm;
- Incomplete examination for identification; or
- Carcass 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;
- Extensive entanglement evident*;
- 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 lacerations (anywhere on body, as opposed to just dorsally as in Kraus (1990));
- Large areas of subdermal hemorrhaging, hematoma, or edema;
- Extensive skeletal fracturing; or
- A code 2 (fresh dead) carcass was brought in 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;
- Entanglement prevented feeding*;
- Whale was anchored; or
- 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).
Large whale events from Newfoundland and Labrador were included for the first time in this year’s analysis. Since humpbacks from these regions are known to be from a 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, because of the presence of other species not found in US waters, only events identified to species and involving transboundary stocks were included in tallies.
A total of 539 unique events occurred during 2004 - 2008, involving both live and dead whales (Table 1). Of these, 188 entanglement events and 57 ship strike events were confirmed. A total of 330 mortalities were documented, of which 24 were verified to be due to entanglement and 30 were due to ship strike. The cause of death could not be identified for 256 (78%) of the mortalities. Serious injury was caused by entanglement in 18 events and by ship strike in 2 events. There were 79 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), and 33 entanglement events for which the available information was not sufficient to determine if a serious injury had occurred. Fifteen ship strike events occurred which did not result in serious injury, and 6 ship strikes which lacked sufficient evidence to make a determination. Table 2 presents a summary of mortalities attributed to causes other than entanglement or ship strike, confirmed entanglement and ship strike events not resulting in serious injury or mortality, and confirmed events for which insufficient information was available for determination. Annual human-caused mortality and serious injury rates for 2004 - 2008 are presented for each large whale stock in Table 3. Tables 4 - 8 provide details of each confirmed serious injury or mortality event.
Over the 5 year period, North Atlantic right whales had the highest proportion of entanglements and ship strikes relative to the number of events for a species; of 64 events involving right whales, 24 were confirmed entanglements, and 17 were confirmed ship strikes (Table 1). Of the 21 verified right whale mortalities, 3 were due to entanglements, 8 due to ship strikes, 5 due to natural causes, and 5 were undetermined. Serious injury was documented for one entanglement event and two ship strikes (details in Table 4).
Humpbacks were involved in 204 events, were the most commonly observed entangled whale species, and the most commonly observed dead whale (107 confirmed mortalities; Table 1). Of the 81 confirmed entanglements, 5 resulted in mortality, and 11 in serious injury. Ship strikes were relatively uncommon with only 14 verified events, 8 of which were fatal (Table 5). 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 55 fin whale events, 14 were confirmed entanglements; 3 of these were fatal, the highest percentage for any of the whale species (21%), and 3 resulted in serious injury. Thirteen ship strike events were documented, and 10 proved fatal (Table 6).
Mortalities accounted for 10 of the 12 sei whale events. Two of these mortalities were attributed to ship strikes. In one additional ship strike event, it could not be determined whether the strike occurred pre or postmortem. There were 3 confirmed entanglement events, 1 of which resulted in mortality and 2 in serious injury (Table 7).
Minke whales were involved in 128 events, of which 55 were confirmed entanglements. Eleven of the entanglement events were fatal, while 1 resulted in serious injury. There were only 2 verified ship strike events, both of which resulted in mortality (Table 8).
Bryde’s whales had the lowest number of events--1. The sole mortality was attributed to natural causes.
There were no events involving blue whales.
In 75 of the 539 large whale events during 2004 - 2008, positive species identification was not possible. In 9 of the 75 events, the similarity in body shape and size between fin and sei whales prevented us from distinguishing which of these 2 species were involved. In another 14 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 52 events could not be assigned with any certainty. Entanglement was confirmed in 11 of these 75 events. Fifty-one of the 75 events involving unidentified whales were confirmed mortalities (see Table 1).
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 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).
Assessments 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 5 year period, 256 of 330 confirmed mortalities (78%) lacked sufficient evidence to determine cause of death (Table 2). 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 in 33 of 188 confirmed entanglement events (18%) and 6 of 57 ship strike events (11%).
Perhaps of greater concern is the number of animals never observed. Humpback whale scar evidence suggests that only 3-10% of entanglements are witnessed and reported (Robbins and Mattila 2000, 2004). Thus, whales may succumb to entanglement before the event can be detected. 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). The numbers in this report therefore represent the minimum values for human-caused serious injury and mortality to large whale stocks along the US eastern seaboard.
We are especially grateful to the 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, Misty Nelson, Liz Pomfret-Wiley, Amy Whittingham Chase, Brenda Rone, and Misty Niemeyer assisted in verifying records. PCCS and WCNE provided sighting histories and demographic information. Members of the Atlantic Scientific Review Group have provided numerous useful comments on the protocols described here. We also thank the anonymous reviewers of earlier drafts of this report.
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