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Abstract
Introduction
Methods
Results
Discussion
Acknowledgements
References Cited

Northeast Fisheries Science Center Reference Document 12-11

Mortality and Serious Injury Determinations for Baleen Whale Stocks along the Gulf of Mexico, United States East Coast and Atlantic Canadian Provinces, 2006-2010

by Allison G. Henry1, Timothy V.N. Cole1, Mendy Garron2, Lanni Hall2, Wayne Ledwell3, Andrew Reid4
1NOAA National Marine Fisheries Service, Northeast Fisheries Science Center, 166 Water Street, Woods Hole, MA 02543
2NOAA Northeast Regional Office, 55 Great Republic Dr., Gloucester, MA 01930-2276
3 Whale Release and Strandings Group, 244 Tolt Rd., Portugal Cove-St. Philip's, Newfoundland, CAN A1M 1R2
4Marine Animal Response Society, c/o Nova Scotia Museum, 1747 Summer St., Halifax, Nova Scotia CAN B3H 3A6

Web version posted June 29, 2012

Citation: Henry AG, Cole TVN, Garron M, Hall L, Ledwell W, Reid A. 2012. Mortality and Serious Injury Determinations for Baleen Whale Stocks along the Gulf of Mexico, United States East Coast and Atlantic Canadian Provinces, 2006-2010. US Dept Commer, Northeast Fish Sci Cent Ref Doc. 12-11; 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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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 likelihood of incorrectly assigning whale mortalities and serious injuries to human causes and provide a minimum count of such human-caused incidents. Serious injury is defined as an injury that is likely to lead to death. This report describes determinations made for reports received from 2006 - 2010 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, the eastern seaboard of the United States, and the Atlantic Canadian provinces. A total of 500 unique large whale events were verified during the period, of which 264 (53%) involved human interactions, 16 (3%) did not involve a human interaction, and for 220 (44%) of the events it was unknown if a human interaction occurred. Of the events involving human interactions, we confirmed 206 unique entanglements and 58 vessel strikes. Four events had evidence of both entanglement and vessel strike, and are included in the totals for both these event categories. Twenty-four (12%) of the entanglements and 28 (48%) of the vessel strikes were fatal. Serious injury was sustained in 33 (16%) of the entanglement events and in 1 (2%) of the confirmed vessel strikes. Serious injury was prevented due to disentanglement efforts in 28 (14%) entanglement events. Forty-five (22%) of the entanglements and 9 (16%) of the vessel strike events did not have adequate documentation to determine if serious injury occurred. Seventy-three (35%) of the entanglement events and 17 (29%) of the vessel strike events were determined to have not caused serious injury or death. We also confirmed a total of 313 mortalities: 52 (17%) due to human interaction, 16 (5%) due to natural causes and 245 (78%) which lacked sufficient evidence to determine cause of death. Humpback whales had the greatest number of entanglement mortalities (n=9), the highest number of serious injury events resulting from entanglements (n=20); and the greatest number of vessel strike mortalities (n=10); and right whales had the only serious injury (n=1) from vessel 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 (Federal Register/Vol. 69, No. 138 p. 43338/Tuesday, July 20, 2004[1]).

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 observed 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, the eastern seaboard of the US, and the Atlantic Canadian provinces for the period 2006 - 2010.

Methods

Members of the US and Canadian regional 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. Analysis of entangling gear is conducted by NERO and is included in annual Take Reduction Team (TRT) reports. 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 - 2010 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 at a national level by NMFS (see Andersen et al. 2008).

Some large whale events from Newfoundland and Labrador are included in this analysis. Because some species in these areas are not found in US waters, only events identified to species and involving trans-boundary stocks (i.e., stocks known to enter into US waters) were included in tallies. 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.

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:

1.      Photographs or video allowed identification;

2.      A marine mammal expert reported the event and/or species as certain;

3.      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

4.      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:

1.      Photographs or video allowed probable identification;

2.      A marine mammal expert reported the event and/or species as possible;

3.      An inexperienced observer's report allowed probable identification; or

4.      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:

1.      Photographs or video were of insufficient quality to verify;

2.      An inexperienced observer's report lacked photographs or video and/or detail to confirm;

3.      An incomplete examination did not allow for identification; or

4.      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:

1.      Fishing line constricted any body part, and subdermal hemorrhaging or extensive necrosis was present at point of attachment;

2.      An extensive entanglement was evident*;

3.      An entanglement prevented feeding*; or

4.      A code 2 (fresh dead) whale was pulled up during fishing operations*.

Events were categorized as vessel strike mortalities if one of the following indications was confirmed to be present on a whale carcass:

1.      Large linear laceration(s) was present anywhere on body, as opposed to just dorsally as in Kraus (1990);

2.      Large area(s) of subdermal hemorrhaging, hematoma, or edema was evident;

3.      Extensive skeletal fracturing was evident; or

4.      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:

1.      Fishing line constricted any body part or was likely to become constricting as the whale grew;

2.      It was uncertain if the line was constricting, but appendages near the entanglement's point of attachment were discolored and likely compromised;

3.      The whale showed a marked decline in appearance following entanglement, including skin discoloration, lesions near the nares, fat loss, or increased cyamid loads;

4.      The entanglement prevented feeding*;

5.      The whale was anchored; or

6.      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 500 unique events were confirmed during 2006 - 2010, involving both live and dead whales (Table 1). Of these, 264 (53%) involved human interactions, 16 (3%) did not involve a human interaction, and for 220 (44%) of the events it was unknown if a human interaction had occurred. Human interaction events were categorized as either entanglement or vessel strikes, with four cases having evidence of both types of interaction. These four events are included in the totals for both entanglement and vessel strike event categories. Of these human interactions, 206 entanglement events were verified, determined to be the cause of death in 24 events and cause of serious injury in 33 events. There were 73 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). Twenty-eight of these events warranted serious injury classification had the animal not been disentangled. Additionally, there were 45 entanglement events for which the available information was not sufficient to determine if a serious injury had occurred (Table 2). The remaining 31 entanglement events were mortalities where cause of death could not be confirmed as entanglement. Of the 58 confirmed vessel strike events, 28 were determined to have been lethal and one caused serious injury. Eighteen vessel strike events occurred which did not result in serious injury and 9 vessel strikes lacked sufficient evidence to make a determination (Table 3). The remaining two events were mortalities where cause of death could not be confirmed as vessel. There were 5 events involving whales entrapped in fishing weirs, all of which occurred in Canadian waters. Three minke and one right whale were successfully released from the weirs and deemed non-seriously injured. One minke did not have adequate documentation to determine if serious injury or mortality occurred. These events are not classified as entanglements as the animals were not wrapped in any of the weirs' lines.

A total of 313 mortalities were documented, of which 52 (17%) were confirmed to be the result of human interactions, 16 (5%) were due to natural causes and 245 (78%) for which there was insufficient evidence to determine cause of death (Table 1). The average annual confirmed human-caused mortality and serious injury rates for 2006 - 2010 are presented for each large whale stock in Table 4. Tables 5 - 10 provide details by stock of each confirmed human interaction event resulting in serious injury or mortality.

Over the 5 year period, North Atlantic right whales were involved in 55 confirmed events, of which 33 were confirmed entanglements and 13 were confirmed vessel strikes (Tables 1-3). Of the 19 verified right whale mortalities, 4 were due to entanglements, 5 due to vessel strikes, 5 due to natural causes, and 5 were from undetermined causes (Table 1). Serious injury was assigned for five entanglement events and one vessel strike (Table 2 and Table3). Detailed records for confirmed human-caused mortality and serious injury are provided in Table 5. For six additional entanglements, serious injury classification would have been warranted if not for intervention of disentanglement teams.

Humpbacks, involved in 208 verified events, were the species most commonly observed entangled (101), hit by vessels (21), and observed dead (119; Table 1-3). Of the 119 confirmed humpback whale mortalities, 9 were due to entanglements, 10 due to vessel strikes, 2 due to natural causes and cause of death was undetermined for the remaining 98 events (Table 1). Of the 101 confirmed entanglements, 9 resulted in mortality and 20 in serious injury (Table 2). An additional 13 events would have resulted in serious injury had disentanglement teams not intervened. Humpbacks were involved in 21 verified vessel strike events, 10 of which were fatal (Table 3). Detailed records for human-caused mortality and serious injury are provided in 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 and are therefore not included in this report.

There were 43 documented fin whale events, 15 of which were confirmed entanglements and 8 of which were confirmed vessel strikes (Tables 1-3). Of the 31 verified fin whale mortalities, 2 were due to entanglement, 6 due to vessel strikes, 4 due to natural causes, and 19 were from undetermined causes (Table 1). Two of the entanglements resulted in serious injury (Table 2). Detailed records for human-caused mortality and serious injury are provided in Table 7.

There were 12 events involving sei whales including 3 confirmed entanglements and 3 vessel strikes (Tables 1-3). Mortalities accounted for 10 of the 12 confirmed events, with 1 attributed to entanglement, 3 due to vessel strikes, and 6 where cause of death was undetermined (Table 1). Two of the entanglement events resulted in serious injury (Table 2). Detailed records for human-caused mortality and serious injury are provided in Table 8.

Minke whales were involved in 112 verified events, of which 48 were confirmed entanglements and 2 were confirmed as vessel strikes (Tables 1-3). Seven of the entanglement events were fatal, while four resulted in serious injury (Table 2). In nine entanglement events, disentanglement teams removed gear that would have warranted a serious injury classification. There were only two verified vessel strike events, both of which resulted in mortality (Table 3). Detailed records for human-caused mortality and serious injury are provided in Table 9.

Bryde's whales' two documented events were both mortalities (Table 1). One was attributed to natural causes while the other mortality was a result of vessel strike (Table 3), the details for which are provided in Table 10.

Blue whales had the lowest number of documented events - one mortality - where cause of death could not be determined (Table 1).

In 67 of the 500 confirmed unique large whale events during 2006 - 2010, positive species identification was not possible (Table 1). In four of the 67 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 nine 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 54 events could not be assigned with any certainty. Entanglement was confirmed in 6 and vessel strike was confirmed in 10 of these 67 events (Table 2 and Table 3). Fifty-two of the 67 events involving unidentified whales were confirmed mortalities, one of which was attributed to entanglement and one to vessel strike. The cause of death could not be determined for the remaining fifty mortalities (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 likelihood of incorrectly assigning whale mortalities and serious injuries to human causes. The resulting values provide a minimum count of such human-caused incidents. Despite minimum values, the mean annual observed human-caused mortality and serious injury rate exceeds PBR for four of the seven stocks examined, including North Atlantic right, humpback, sei, and Bryde's whales (Table 4).

Differentiating injuries that cause mortalities from preexisting injuries or postmortem damage is problematic but can be accomplished through necropsy or, in many cases, 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 exhibit these signs of declining health over time. 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 have carried loose wraps for years.

Over the five year period, 245 of 313 confirmed mortalities (78%) lacked sufficient evidence to determine cause of death (Table 1). Of those 245 mortalities, evidence of entanglement was confirmed in 31 and vessel strike in 2 events, but could not be confirmed as the cause of death. Likewise, insufficient documentation precluded determination of fate in 45 of 206 confirmed entanglement events (22%) and 8 of 58 vessel strike events (14%). Carcasses floating at sea often cannot be examined sufficiently for either internal or external indications if they are not towed ashore and necropsied.

Perhaps of greater concern is the number of injured animals that are 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 vessel 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 vessel strike serious injuries and mortalities are not observed and that the serious injury and mortality criteria applied here are designed to minimize the likelihood of incorrectly assigning whale mortalities and serious injuries to human causes, 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, the US east coast, and the Atlantic Canadian provinces.

Acknowledgements

We are especially grateful to the Gulf of Mexico, US, and Canadian Maritime Provinces and Newfoundland stranding and entanglement networks, whose members searched for and examined whales both live and dead. It is a difficult, dirty and ceaseless 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, New Brunswick Museum, Atlantic Veterinary College , Grand Manan Whale and Seabird Research Station, 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

Andersen MS, Forney KA, Cole TVN, Eagle T, Angliss RP, Long K, Barre L, Van Atta L, Borggaard D, Rowles T, Norberg B, Whaley J, Engleby L. 2008. Differentiating serious and non-serious injury of marine mammals: report of the Serious Injury Technical Workshop, 10-13 September 2007, Seattle, Washington. Silver Spring (MD): NMFS Office of Protected Resources. US Dep Commer, NOAA Tech. Memo. NMFS-OPR-39.

Angliss RP, DeMaster DP. 1998. Differentiating serious and non-serious injury of marine mammals taken incidental to commercial fishing operations: Report of the Serious Injury Workshop, 1-2 April 1997, Silver Spring, Maryland. Silver Spring (MD): NMFS Office of Protected Resources. US Dep Commer, NOAA Tech Memo NMFS-OPR-13.

Knowlton AR, Korsmeyer FT, Kerwin JE, Wu H, Hynes B. 1995. The hydrodynamic effects of large vessels on right whales. Boston (MA): New England Aquarium. Final report to NOAA Fisheries for Contract No. 40EANFF400534.

Kraus SD. 1990. Rates and potential causes of mortality in North Atlantic right whales (Eubalaena glacialis). Mar Mamm Sci. 6(4):278-291.

Moore MJ, Knowlton AR, Kraus SD, McLellan WA, Bonde RK. 2004. Morphometry, gross morphology and available histopathology in North Atlantic right whale (Eubalaena glacialis) mortalities (1970-2002). J Cetacean Res Manage. 6(3):199-214.

Palsbøll PJ, Allen J, Anderson TH, Bérubé M, Clapham PJ, Feddersen TP, Friday N, Hammond P, Jørgensen H, Katona SK, Larsen AH, Larsen F, Lien J, Mattila DK, Nygaard FB, Robbins J, Sponer R, Sears R, Sigurjónsson J, Smith TD, Stevick PT, Vikingsson G, Øien N. 2001. Stock structure and composition of the North Atlantic humpback whale, Megaptera novaeangliae. Cambridge (UK): International Whaling Commission. Presented to International Whaling Commission Scientific Committee. SC/53/NAH11.

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.

Robbins, J. 2010. Scar based inference into Gulf of Maine humpback whale entanglement: 2008. Provincetown (MA): Provincetown Center for Coastal Studies. Report to the National Marine Fisheries Service. Order number EA133F09CN0253

Wade PR, Angliss RP. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS Workshop, April 3-5, 1996, Seattle, Washington. Seattle (WA): NMFS Alaska Fisheries Science Center. US Dept of Commer, NOAA Tech. Memo, NMFS-OPR-12.

Waring GT, Josephson E, Maze-Foley K, Rosel, PE, editors. 2011. U.S. Atlantic and Gulf of Mexico Marine Mammal Stock Assessments -- 2010. NOAA Tech Memo NMFS NE 219; 598 p. Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026, or online at http://nefsc.noaa.gov/publications/



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