Northeast Fisheries Science Center Reference Document 05-08
Mortality and Serious Injury Determinations
for Large
Whale Stocks Along the Eastern Seaboard
of the United States, 1999-2003 (2nd Edition)
by Timothy V.N. Cole,
Dana L. Hartley, and 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 December 5, 2005
Citation: Cole TVN, Hartley DL, Merrick RL. 2005. Mortality and serious injury determinations
for large whale stocks along the eastern seaboard of the United States, 1999-2003. US Dep
Commer, Northeast Fish Sci Cent Ref Doc. 05-08; 18 p.
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ABSTRACT
As part of the 1994 amendments to the Marine Mammal Protection Act (MMPA),
the NOAA National Marine Fisheries Service (NMFS) was mandated to establish
monitoring programs to obtain statistically reliable estimates of incidental
mortality and serious injury of marine mammals taken during commercial
fishing operations. A serious injury has been defined as “any
injury that will likely result in mortality”. Using guidelines
recommended by NMFS’s 1997 Serious Injury Workshop, the Northeast
Fisheries Science Center developed protocols for determining large whale
serious injuries and human-caused mortalities. We describe the
protocols used and report on the determinations made for right, humpback,
fin, sei, blue, minke and Brydes whale events that occurred from 1999
through 2003 along the eastern seaboard of the United States. A
total of 408 unique large whale events were reported during the period,
including both strandings and sightings at sea. These included
173 entanglement reports and 37 reports of ship strikes. We were
able to verify 146 entanglement events, 25 ship strikes, and 267 mortalities. Entanglements
were identified as the cause of 29 whale deaths and ship strikes the
cause of 18. Entanglements were determined to have caused serious
injury in 18 events. Minke whales had the greatest number of entanglement
mortalities (15). Humpback whales had the highest number of serious
injury events resulting from entanglements (12) and the most incidents
of ship strike mortalities (6). Right whales and fin whales each
had five mortalities from ship strikes. No serious injuries resulting
from ship strikes were confirmed for any species. These human-caused
mortality and serious injury rates represent the minimum levels of impact
to these stocks. Procedures and methods for estimating actual serious
injury and mortality rates have yet to be developed.
INTRODUCTION
As part of the 1994 amendments to the Marine Mammal Protection Act (MMPA),
the NOAA National Marine Fisheries Service (NMFS) was mandated to establish
monitoring programs to obtain statistically reliable estimates of incidental
mortality and serious injury of marine mammals taken during commercial
fishing operations. The Agency was also charged with developing
Take Reduction Plans (TRPs) to reduce commercial takes of strategic stocks
of marine mammals below the Potential Biological Removal (PBR) levels
specified in the TRPs within six months after Plan implementation. The
longer-term goal of all the TRPs is to reduce--within 5 years of implementation--commercial
takes and serious mortality of marine mammals to insignificant levels
approaching zero mortality and serious injury rates.
Mortalities are relatively easy to assess, but assessments of serious
injuries are more problematic. NOAA has defined an ‘injury’ under
50 CFR 229.2 as:
“... a wound or other physical harm. Signs of injury to a marine
mammal include, but are not limited to, visible blood flow, loss
of or damage to an appendage or jaw, inability to use one or more appendages,
asymmetry in the shape of the body or body position, noticeable swelling
or hemorrhage, laceration, puncture or rupture of eyeball, listless
appearance or inability to defend itself, inability to swim or dive
upon release from fishing gear, or signs of equilibrium imbalance.
Any animal that ingests fishing gear, or any animal that is released
with fishing gear entangling, trailing or perforating any part of the
body will be considered injured regardless of the absence of any wound
or other evidence of an injury.”
A serious injury has been defined as “any injury that will likely result
in mortality”.
In April 1997, NMFS convened a Serious Injury Workshop to develop a
consistent set of guidelines for determining what constitutes a serious
injury (Angliss and DeMaster 1998). Although the Workshop
produced a set of recommendations, implementation of a national serious
injury standard has not yet occurred.
Nonetheless, NOAA Fisheries staff and Scientific Review Group (SRG)
members decided to take account of serious injuries in the annual marine
mammal stock assessment reports (SAR). Specifically, the Atlantic
SRG (ASRG) at its April 1999 meeting recommended that
“…the draft serious injury guidelines be followed whenever
possible and applied in all fisheries. Those serious injury observations
should be added to the observed mortalities and extrapolated to the population
for status determination.”
The ASRG was specifically concerned about serious injuries to small
cetaceans in the Atlantic pelagic longline fishery and large cetaceans in Northwest
Atlantic Ocean pot and gillnet gear.
Subsequently, the Northeast (NEFSC) and Southeast Fisheries Science Centers
(SEFSC) prepared serious injury determinations for the SARs and presented these
to the ASRG in autumn 1999. The SEFSC implemented the Serious Injury
Workshop recommendations for small cetaceans taken in the longline fishery,
while the NEFSC implemented the Workshop’s large cetacean recommendations
for right, humpback, fin, sei, blue, minke and Brydes whales interacting with
gillnet and pot gear. At this and subsequent meetings, the ASRG spent
considerable time discussing the protocols in general, and the analyses conducted
for specific species (especially right whales).
Serious injury determinations continue to be prepared annually by the NEFSC
and SEFSC. However, the actual criteria used in these determinations have never
been formalized in manuscript form. In this document, we formally describe
these protocols and report on the determinations made from 1999 through 2003.
METHODS
Marine mammal strandings and human-induced interaction events were recorded
and submitted to the NMFS Northeast Regional Office (NERO) and Southeast
Regional Office (SERO) by members of the National Stranding Network,
large whale disentanglement teams, the U.S. Coast Guard and civilian
sources. The Regional Offices identified and obtained all available
information for each event (photos, necropsy reports, etc.) and placed
these in a central folder for each event. Case files were compiled
for all individually identified whales with injuries. Several NEFSC
and NERO staff were involved in reviewing event records, confirming each
event’s occurrence and the species involved, identifying duplicate
records and consolidating unique information from each source into a
single record for each event. Information from additional sightings
of a previously documented event was added to the original event record. If
an identified whale was involved in a second interaction, a new event
record was assigned. The NEFSC staff then 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 (TVC) reviewed all
determinations each year to ensure consistency within and across years.
Event and Species Confirmation Criteria
Events and the species involved were considered confirmed if they meet
one of the following criteria:
- The event was observed by a trained marine mammal observer who
was certain of the species or event;
- The event was observed by a trained
member of the Disentanglement Network and the species or event was
verified via interview by NMFS, disentanglement or stranding network
staff;
- The observer was inexperienced, but the report was accompanied
by photographs or videotape of sufficient quality to positively verify
the species or event;
- A fisherman reported a whale entangled in his/her
gear or a shipper reported colliding with a whale;
- Gear was retrieved
from a whale.
Events and the species involved were considered confirmed in the following
less certain cases:
- The observer was experienced and was fairly certain, but not positive,
of the species or event;
- The observer was inexperienced, but was interviewed
and the account was descriptive enough that the species or event
was probable but not certain;
- The report was accompanied by poorer
quality photographs or video, and staff reviewing this material assessed
the event as probable but not certain.
Events or the species involved were considered unconfirmed if:
- The observer
was inexperienced and no photographs or video were taken, and the
observer’s
account did not provide sufficient detail to identify the species
or event occurrence;
- The observer was experienced, but did not see
the whale long enough or in good enough conditions to state the species
or event as being probable;
- The event was photographed or video taped,
but staff reviewing the images could not identify species or the event’s
occurrence;
- A carcass was too decomposed to identify species or to show
any indication of human interaction.
Human-Induced Mortality Determinations
Events were categorized as entanglement mortalities if the following indications
were confirmed to be present during gross inspection or necropsy of the carcass:
- Fishing line constricted any body part;
- Subdermal hemorrhaging or extensive
necrosis was present at point of attachment.
Events were categorized as ship strike mortalities if any of the following
indications were confirmed to be present on a 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 any of the following
indications were confirmed on a living whale:
- Fishing line constricted on 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 changed in appearance following entanglement,
including skin discoloration, lesions near the nares, fat loss, or increased
cyamid loads;
- Gear was ingested;
- Whale was anchored.
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 change in skin discoloration, lesions near the nares, fat loss, or
increased cyamid loads.
Injuries that impaired the whale’s locomotion or feeding were not considered
serious injuries unless they were likely to be fatal in the foreseeable future.
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 408 events was reported during 1999-2003, involving both live
and dead whales (Table 1). There were 173 reports of entanglement
and 37 of ship strike. From these, we confirmed 146 entanglement
events and 25 ship strike events. We were able to verify
267 mortalities, and determine that 29 mortalities were due to entanglements
and 18 mortalities were the result of ship strikes. The cause of
death could not be established for the remaining mortalities. Entanglement
was determined to have caused serious injury in 18 events. There
were no records of serious injuries resulting from ship strikes. Annual
human-caused mortality and serious injury rates for 1999-2003 are presented
by stock in Table 2. Tables
3 to 8 provide the details of each
confirmed serious injury or mortality record.
Right whales had the highest proportion of entanglements and ship strikes
relative to the number of reports for a species--of 50 reports involving
right whales, 31 were confirmed entanglements and 8 were confirmed ship
strikes. Over the five-year period, there were 18 verified
right whale mortalities (Table 1). Three of these mortalities
were due to entanglements, and five were due to ship strikes. Serious
injury was documented for five entanglement events involving right whales.
Humpbacks were involved in 169 reported events (Table 1). Of these,
74 of the 82 reported entanglements could be confirmed, as could 10 of
the 14 reported ship strikes. Humpbacks were the most commonly
observed entangled whale species and the most commonly observed dead
whale (92 confirmed mortalities). Entanglements accounted for eight
mortalities and 12 serious injuries. Ship strikes were relatively
uncommon, with only 10 confirmed events, six of which were fatal. Whales
identified as members of the Gulf of Maine stock accounted for five of
the entanglement mortalities, nine of the entanglement serious injuries
and three of the ship strike mortalities (Table 2).
Fin whales had a low proportion of entanglements; of 40 reported events,
only 7 were of entanglements (all confirmed), two of which were fatal
(Table 1). Ten ship strikes were reported, five of which were confirmed
and proved fatal. No serious injury events involving fin whales
were reported.
Only four events were reported for sei whales, all of which were confirmed
mortalities. Two of the mortalities were determined to have resulted
from ship strikes.
Minke whales were reported in 82 events. Entanglements accounted
for 35 of these events, but only 27 could be confirmed (Table 1). Fifteen
of the confirmed entanglement events were fatal, the highest percentage
for any of the whale species. One additional entanglement event
was determined to have caused serious injury. There were only two
ship strike reports, but neither of these could be confirmed.
Blue whales and Brydes whales appeared in only one reported event each. The
blue whale report was a confirmed entanglement in the St. Lawrence River,
Canada, but there was not sufficient information available to confirm
if a serious injury was sustained. The Brydes whale report was
a confirmed entanglement in the Gulf of Mexico, which resulted in the
death of the whale.
In 61 of the 408 large whale events reported during 1999-2003, positive
species identification was not possible (Table 1). In five stranding
events, the similarity in body shape and size between fin and sei whales
prevented positive species identification. In another 14 strandings,
the whales could only be identified as balaenopteriids based on the presence
of ventral pleats. In 42 other events, the taxonomic identity
of the whales could not be assigned with certainty. Entanglement
was reported in 12 of these cases, five of which were considered confirmed. Twenty
eight of the 42 reported events involving unidentified whales were confirmed
mortalities.
DISCUSSION
Sufficient experience with serious injury determinations has been gained
since 1999 to now comment on the efficacy of the recommendations from
the 1997 Workshop for assessing large whale serious injuries.
First and foremost, determinations of human-caused mortality and serious
injury must be made on a case-by-case basis. The guidelines provided
in the Workshop report tend to be overly general, so it is important
that individual users clearly define a priori how the guidelines
are to be used and then apply them in a consistent fashion. The
process might best be conducted using the same personnel to ensure consistency. All
available data should be carefully examined before determinations are
made. Frequently determinations are made in a rush in response
to decision makers’ requests, when in fact a measured approach
will likely provide a more accurate evaluation. The serious injury
determinations for Northwest Atlantic baleen whales are performed annually,
immediately prior to completion of the draft Stock Assessment Report
for the next year (i.e., determinations for animals observed in
2003 were made in late summer 2004 for the 2005 SAR).
Secondly, for dead animals, it is essential that the carcass be recovered
and necropsied by a competent biologist with an attending veterinarian
or pathologist present. Differentiating causal injuries from pre-existing
ones or post-mortem damage is problematic, but can be accomplished through
examination of necropsy data. Necropsies frequently identify subdermal
hemorrhaging or hematomas, indicating that blood was still circulating
at the time of injury. McLellan et al. (2004) have provided
an excellent right whale necropsy protocol that should be followed.
In our determinations, fishing line constrictions were considered circumstantial
evidence of pre-mortem entanglement, as these constrictions were likely
the result of force applied by an active animal. Large lacerations
were considered an indication of a pre-mortem vessel collision since
only whales at depth would be exposed to the propellers of a ship.
Events involving constricting entanglements with evidence of the whale’s
deteriorating health were considered confirmed serious injuries. Removal
of constricting gear was generally considered to prevent serious injury. A
whale’s physiological response to tissue damage includes increased
secretion of glucocorticoids, which suppresses lymphocytes and if sustained
(due to chronic destruction of tissue by gear) compromises the ability
of an animal to fight other infections. Therefore, the removal
of gear frees a whale’s immune system resources to combat resident
disease or infection that might otherwise lead to the whale’s death. Loosely
wrapped gear did not appear to elicit as much stress (some whales carried
loose wraps for years), and were not considered serious injuries even
if they impaired the locomotion or feeding of an animal. We also
made no attempt to predict how an entanglement or injury might increase
a whale’s susceptibility to further injury; however, further research
on the fate of individual entangled/injured/impaired animals might provide
information to improve such predictions. Fishing gear interactions may
also generate non-lethal effects, such as impacts to reproduction that
may negatively affect population recovery (Robbins and Mattila 2001a;
Robbins et al. 2004); however, such impacts require further investigation.
However, our greatest concern in our serious injury work was the number
of animals we never saw! Scar-based studies suggest that interactions
between whales and fishing gear are common, and that many whales survive
those encounters. Hamilton et al. (1998) examined photographs
of 357 individual right whales and found that 62% (n = 220) had scars
from entanglement, and 124 had been entangled more than once. Approximately
half (48-65%) of Gulf of Maine humpback whales have been entangled at
least once in their life time, while 8-25% sustain new injuries each
year (Mattila and Robbins 1998; Robbins and Mattila 1999, 2000, 2001a,
2001b, 2003, 2004). But scar studies generally only provide information
on non-lethal encounter rates. Any interaction between a whale
and fishing gear has the potential to be fatal if a constricting entanglement
occurs. There is currently no reliable method for estimating the
number of large whales that die each year from entanglements, although
recovered carcasses provide minimum values. 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. Right whales
may also become negatively buoyant if an injury precludes effective feeding
for an extended period (Moore et al. 2004).
Vessel collisions frequently lack external evidence, and may not be
detected unless a necropsy is conducted. Knowlton and Kraus (2001)
reported on 45 right whale mortalities from 1970-1999. Of these, 16 (36%)
were attributed to ship strikes, 13 (29%) to natural causes, 13 were
from unknown causes, and 3 (7%) were the result of entanglements. Of
15 right whales identified as ship strike mortalities, four (27%) showed
no outward appearance of a strike (Hamilton et al. 1998). Wiley
et al. (1995) reported a similar lack of external evidence of vessel
collisions; of 20 large whale carcasses examined from the Carolina, Virginia
and New Jersey coasts, 6 (30%) had major injuries potentially attributable
to ship strikes and two of these showed no external signs of trauma. Carcasses
floating at sea often cannot be examined sufficiently for either internal
or external indications, and generate false negatives if they are not
towed ashore and necropsied. Of the 30 right whales necropsied
during 1970 through 2002, 13 (43%) were confirmed as ship strike mortalities,
four (13%) were confirmed to be the result of entanglement, and one was
due to natural causes (Moore et al. 2004). The causes of
death were not identified for the remaining cases, however, one was possibly
the result of a ship strike. An additional 24 mortalities were
reported during the period, but no internal examination was conducted
(Moore et al. 2004).
The Marine Mammal Commission has indicated that serious injury and mortality
estimates based only on confirmed reports are not precautionary because
these estimates are negatively biased. That is, not all injured
or dead animals are accounted for. Given the low sighting probability
and apparently high rate of interaction of whales with fishing gear and
ships, we concur that any estimate based on observed dead or seriously
injured animals is a very conservative lower bound. Thus, if the observed
mortality and serious injury estimate developed from stranding/floater/
entanglement data is near but below a threshold value (e.g., PBR
for a marine mammal stock), it is reasonable to assume that the true
mortality/serious injury value exceeds the threshold.
ACKNOWLEDGMENTS
We are especially grateful to the East Coast stranding and entanglement
networks, whose members searched for and examined whales both live and
dead. It is a difficult and seemingly thankless job that deserves special
recognition. We are also grateful to the staff of the Center for Coastal
Studies and New England Aquarium, NOAA aerial survey teams, Wildlife
Trust, the States of Florida/Georgia and many others for providing the
sightings that have allowed this work to be conducted. Liz Pomfret-Wiley,
Amy Whittingham Chase, Brenda Rone, Mendy Garron and Misty Niemeyer verified
records. 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.
LITERATURE
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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.U.S. Dep. Commer., NOAA Tech Memo. NMFS-OPR-13, 48 p.
Barco, S.G., W.A. McLellan, J.M. Allen, R.A. Asmutis-Silvia, R. Mallon-Day,
E.M. Meagher, D.A. Pabst, J. Robbins, R.E. Seton, W.M. Swingle, M.T.
Weinrich, and P.J. Clapham. 2002. Population identity of humpback whales
(Megaptera novaeangliae) in the waters of the US mid-Atlantic
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Hamilton, P.K., M.K. Marx, and S.D. Kraus. 1998. Scarification analysis
of North Atlantic right whales (Eubalaena glacialis) as a method
of assessing human impacts. Paper SC/M98/RW28 presented to the IWC Special
Meeting of the Scientific Committee towards a Comprehensive Assessment
of Right Whales Worldwide, 16-25 March 1998, Cape Town, South Africa.
Knowlton, A.R., and S.D. Kraus. 2001. Mortality and serious injury of
northern right whales (Eubalaena glacialis) in the western North
Atlantic Ocean. Journal of Cetacean Research and Management (Special
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Kraus, S.D. 1990. Rates and potential causes of mortality in North Atlantic
right whales (Eubalaena glacialis). Marine Mammal Science 6(4):278-291.
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on the caudal peduncle of humpback whales in Gulf of Maine. Center for
Coastal Studies. Order number 40EMNF700232 pp.
McLellan, W.A., Rommel, S.A., Moore, M., Pabst, D.A. 2004. Right whale
necropsy protocol. Final report to NOAA Fisheries for contract #40AANF11252551pp.
Moore, M.J., A.R. Knowlton, S.D. Kraus, W.A. McLellan, R.K. Bonde. 2004.
Morphometry, gross morphology and available histopathology in North Atlantic
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the caudal peduncle of Gulf of Maine humpback whales: 1997-1999. Center
for Coastal Studies. Order number 40ENNF900253. 24 p.
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scar monitoring results, 2000. Center for Coastal Studies. Order number
40ENNF030121.
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Service. Order number 40ENNF030121.
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novaeangliae) entanglement rates on the basis of scar evidence.
Report to the National Marine Fisheries Service.Order number 43ENNF030121,
22 pp.
Robbins, J.D., W. McKay, and M.L. Sheridan. 2004. Gulf of Maine humpback
whale, Megaptera novaeangliae, vital rates inferred from blubber
progesterone concentrations. Report to the National Marine Fisheries
Service, Order number EA133F03SE0293, 25 pp.
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