Endangered and Threatened Wildlife and Plants:
Federal Register: November 17, 2010 (Volume 75, Number 221)
Proposed Rules
Page 70169-70187
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
DOCID:fr17no10-32
DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration 50 CFR Part 224
Docket No. 0912161432-0453-02
RIN 0648-XT37
Endangered and Threatened Wildlife and Plants: Proposed
Endangered Status for the Hawaiian Insular False Killer Whale Distinct
Population Segment
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Proposed rule; request for comments.
SUMMARY: We, the NMFS, have completed a comprehensive status review of the Hawaiian insular false killer whale (Pseudorca crassidens) under the Endangered Species Act (ESA) in response to a petition submitted by the Natural Resources Defense Council (NRDC) to list the Hawaiian insular false killer whale as an endangered species. After reviewing the best scientific and commercial information available, we have determined that the Hawaiian insular false killer whale is a distinct population segment (DPS) that qualifies as a species under the ESA.
Moreover, after evaluating threats facing the species, and considering efforts being made to protect the Hawaiian insular DPS, we have determined that the DPS is declining and is in danger of extinction throughout its range. We propose to list it as endangered under the
ESA. Although we are not proposing to designate critical habitat at this time, we are soliciting information to inform the development of the final listing rule and designation of critical habitat in the event the DPS is listed.
DATES: Comments on this proposal must be received by February 15, 2011.
A public hearing will be held on Oahu, Hawaii, on Thursday, January 20, 2011, 6:30 p.m. to 9 p.m., at the McCoy Pavilion at Ala Moana Park, 1201 Ala Moana Blvd., Honolulu, HI 96814. NMFS will consider requests for additional public hearings if any person so requests by January 31, 2011. Notice of the location and time of any such additional hearing will be published in the Federal Register not less than 15 days before the hearing is held.
ADDRESSES: You may submit comments identified by 0648-XT37 by any one of the following methods:
Electronic Submissions: Submit all electronic public comments via the Federal eRulemaking Portal: http:// www.regulations.gov. Follow the instructions for submitting comments.
Mail or hand-delivery: Submit written comments to
Regulatory Branch Chief, Protected Resources Division, National Marine
Fisheries Service, Pacific Islands Regional Office, 1601 Kapiolani
Blvd., Suite 1110, Honolulu, HI 96814, Attn: Hawaiian insular false killer whale proposed listing.
Instructions: All comments received are a part of the public record and will generally be posted to http://www.regulations.gov without change. Comments will be posted for public viewing after the comment period has closed. All Personal Identifying Information (for example, name, address, etc.) voluntarily submitted by the commenter may be publicly accessible. Do not submit Confidential Business Information or otherwise sensitive or protected information. We will accept anonymous comments (enter ``N/A'' in the required fields if you wish to remain anonymous). Attachments to electronic comments will be accepted in
Microsoft Word, Excel, WordPerfect, or Adobe PDF file formats only. The petition, status review report, and other reference materials regarding this determination can be obtained via the NMFS Pacific Islands
Regional Office Web site: http://www.fpir.noaa.gov/PRD/prd_false_ killer_whale.html or by submitting a request to the Regulatory Branch
Chief, Protected Resources Division, National Marine Fisheries Service,
Pacific Islands Regional Office, 1601 Kapiolani Blvd., Suite 1110,
Honolulu, HI 96814, Attn: Hawaiian insular false killer whale proposed listing.
FOR FURTHER INFORMATION CONTACT: Krista Graham, NMFS, Pacific Islands
Regional Office, 808-944-2238; Lance Smith, NMFS, Pacific Islands
Regional Office, 808-944-2258; or Dwayne Meadows, NMFS, Office of
Protected Resources, 301-713-1401.
SUPPLEMENTARY INFORMATION:
Background
On October 1, 2009, we received a petition from the NRDC requesting that we list the insular population of Hawaiian false killer whales as an endangered species under the ESA and designate critical habitat concurrent with listing. According to the draft 2010 Stock Assessment
Report (SAR) (Carretta et al., 2010) (available at http:// www.nmfs.noaa.gov/pr/pdfs/ sars/) that we have completed as required by the Marine Mammal Protection Act (MMPA), false killer whales within the
United States (U.S.) Exclusive Economic Zone (EEZ) around the Hawaiian
Islands are divided into a Hawaii pelagic stock and a Hawaii insular stock. The petition considers the insular population of Hawaiian false killer whales and the Hawaii insular stock of false killer whales to be synonymous. On January 5, 2010, we determined that the petitioned action presented substantial scientific and commercial information indicating that the petitioned action may be warranted, and we requested information to assist with a comprehensive status review of the species to determine if the Hawaiian insular false killer whale warranted listing under the Endangered Species Act of 1973 (ESA) (75 FR 316).
ESA Statutory Provisions
The ESA defines ``species'' to include subspecies or a DPS of any vertebrate species which interbreeds when mature (16 U.S.C. 1532(16)).
The U.S. Fish and Wildlife Service (FWS) and NMFS have adopted a joint policy describing what
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constitutes a DPS of a taxonomic species (61 FR 4722). The joint DPS policy identifies two criteria for making DPS determinations: (1) The population must be discrete in relation to the remainder of the taxon
(species or subspecies) to which it belongs; and (2) the population must be significant to the remainder of the taxon to which it belongs.
A population segment of a vertebrate species may be considered discrete if it satisfies either one of the following conditions: (1)
``It is markedly separated from other populations of the same taxon as a consequence of physical, physiological, ecological, or behavioral factors. Quantitative measures of genetic or morphological discontinuity may provide evidence of this separation''; or (2) ``it is delimited by international governmental boundaries within which differences in control of exploitation, management of habitat, conservation status, or regulatory mechanisms exist that are significant in light of section 4(a)(1)(D)'' of the ESA.
If a population segment is found to be discrete under one or both of the above conditions, its biological and ecological significance to the taxon to which it belongs is evaluated. Considerations under the significance criterion may include, but are not limited to: (1)
``Persistence of the discrete population segment in an ecological setting unusual or unique for the taxon; (2) evidence that the loss of the discrete population segment would result in a significant gap in the range of a taxon; (3) evidence that the discrete population segment represents the only surviving natural occurrence of a taxon that may be more abundant elsewhere as an introduced population outside its historic range; and (4) evidence that the discrete population segment differs markedly from other populations of the species in its genetic characteristics.''
The ESA defines an ``endangered species'' as one that is in danger of extinction throughout all or a significant portion of its range, and a ``threatened species'' as one that is likely to become an endangered species in the foreseeable future throughout all or a significant portion of its range (16 U.S.C. 1532 (6) and (20)). The statute requires us to determine whether any species is endangered or threatened because of any of the following factors: (1) The present or threatened destruction, modification, or curtailment of its habitat or range; (2) overexploitation for commercial, recreational, scientific, or educational purposes; (3) disease or predation; (4) the inadequacy of existing regulatory mechanisms; or (5) other natural or manmade factors affecting its continued existence (16 U.S.C. 1533). We are to make this determination based solely on the best available scientific and commercial information after conducting a review of the status of the species and taking into account any efforts being made by states or foreign governments to protect the species.
When evaluating conservation efforts not yet implemented or implemented for only a short period of time to determine whether they are likely to negate the need to list the species, we use the criteria outlined in the joint NMFS and FWS Policy for Evaluating Conservation
Efforts When Making Listing Decisions (PECE policy; 68 FR 15100).
Status Review and Approach of the BRT
To conduct the comprehensive status review of the Hawaiian insular population of the false killer whale, we formed a Biological Review
Team (BRT) comprised of eight federal scientists from our Northwest,
Southwest, Alaska, and Pacific Islands Fisheries Science Centers. We asked the BRT to review the best available scientific and commercial information to determine whether the Hawaiian insular false killer whale warrants delineation into a DPS, using the criteria in the joint
DPS policy. We asked the BRT to then assess the level of extinction risk facing the species at the DPS level, describing its confidence that the DPS is at high risk, medium risk, or low risk of extinction.
The BRT defined the level of risk based on thresholds that have been used to assess other marine mammal species, and consistent with the criteria used by the International Union for the Conservation of Nature
(IUCN) Red List of Threatened Species (IUCN, 2001). In evaluating the extinction risk, we asked the BRT to describe the threats facing the species, according to the statutory factors listed under section 4(a)(1) of the ESA, and qualitatively assess the severity, geographic scope, and level of certainty of each threat (Oleson et al., 2010).
In compiling the best available information, making a DPS determination, and evaluating the status of the DPS, the BRT considered a variety of scientific information from the literature, unpublished documents, and direct communications with researchers working on false killer whales, as well as technical information submitted to NMFS. The
BRT formally reviewed all information not previously peer-reviewed, and only that information found to meet the standard of best available science was considered further. Analyses conducted by individual BRT members were subjected to independent peer review, as required by the
Office of Management and Budget Peer Review and Bulletin and under the 1994 joint NMFS/FWS peer review policy for ESA activities (59 FR 34270), prior to incorporation into the status review report.
The BRT acknowledged that considerable levels of uncertainty are present for all aspects of the Hawaiian insular false killer whale's biology, abundance, trends in abundance, and threats. Such uncertainties are expected for an uncommon species that is primarily found in the open ocean where research is expensive and knowledge is consequently poor. The BRT decided to treat the uncertainty explicitly by defining where it exists and using a point system to weigh various plausible scenarios, taking into account all of the best available data on false killer whales, but also considering information on other similar toothed whales. The BRT's objectives in taking this approach were to make the process of arriving at conclusions detailed in the status review report as transparent as possible and to provide assurance that the BRT was basing its conclusions on a common understanding of the evidence. Details of this approach can be found in
Appendix A of the status review report.
The report of the BRT deliberations (Oleson et al., 2010)
(hereafter ``status review report'') thoroughly describes Hawaiian false killer whale biology, ecology, and habitat, provides input on the
DPS determination, and assesses past, present, and future potential risk factors, and overall extinction risk. The key background information and findings of the status review report are summarized below.
Biology and Life History of False Killer Whales
The following section presents biology and life history information gathered from throughout the range of false killer whales. A later section focuses on information specific to the Hawaiian insular false killer whale.
Description
The false killer whale, Pseudorca crassidens (Owen, 1846) is a member of the family Delphinidae, and no subspecies have been identified. The species is a slender, large delphinid, with maximum reported sizes of 610 cm for males (Leatherwood and Reeves, 1983) and 506 cm for females (Perrin and Reilly, 1984). Length at birth has been reported to range from 160-190 cm, and length at sexual maturity is 334 through 427 cm in females and 396-457
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cm in males (Stacey et al., 1994; Odell and McClune, 1999). Estimated age at sexual maturity is about 8 to 11 years for females, while males may mature 8 to 10 years later (Kasuya, 1986). The maximum reported age has been estimated as 63 years for females and 58 years for males
(Kasuya, 1986), with females becoming reproductively senescent at about age 44 (Ferreira, 2008). Both sexes grow 40 to 50 percent in body length during their first year of life, but males subsequently grow faster than females. Growth ceases between 20 and 30 years of age, and there is evidence of geographic variation in final asymptotic body size. Off the coast of Japan, asymptotic length is 46 cm (females) and 56 cm (males) longer than off the coast of South Africa (Ferreira, 2008). Large individuals may weigh up to 1,400 kg. Coloration of the entire body is black or dark gray, although lighter areas may occur ventrally between the flippers or on the sides of the head. A prominent, falcate dorsal fin is located at about the midpoint of the back, and the tip can be pointed or rounded. The head lacks a distinct beak, and the melon tapers gradually from the area of the blowhole to a rounded tip. In males, the melon extends slightly further forward than in females. The pectoral fins have a unique shape among the cetaceans, with a distinct central hump creating an S-shaped leading edge.
Global Distribution and Density
False killer whales are found in all tropical and warm-temperate oceans, generally in deep offshore waters, but also in some shallower semi-enclosed seas and gulfs (e.g., Sea of Japan, Yellow Sea, Persian
Gulf), and near oceanic islands (e.g., Hawaii, Johnston Atoll,
Galapagos, Guadeloupe, Martinique) (Leatherwood et al., 1989).
Sightings have also been reported as ``common'' in Brazilian shelf waters (IWC, 2007) where animals could be seen from shore from Rio de
Janeiro feeding in an upwelling zone that concentrates prey. There are occasional records in both the northern and southern hemispheres of animals at latitudes as high as about 50 degrees (Stacey and Baird, 1991; Stacey et al., 1994). In the western Pacific off the coast of
Japan, false killer whales appear to move north-south seasonally, presumably related to prey distribution (Kasuya, 1971), but seasonal movements have not been documented elsewhere. Densities in the central and eastern Pacific range from 0.02 to 0.38 animals per 100 km\2\ (Wade and Gerrodette, 1993; Mobley et al., 2000; Ferguson and Barlow, 2003;
Carretta et al., 2007), with the lowest densities reported for waters north of about 15 degrees north off Baja California, Mexico, and within the U.S. EEZ around Hawaii, and highest densities reported in waters surrounding Palmyra Atoll. Unlike other species that can be found both along continental margins and in offshore pelagic waters (e.g., bottlenose dolphins (Tursiops truncatus)), false killer whale densities generally do not appear to increase closer to coastlines.
Although false killer whales are found globally, genetic, morphometric, and life history differences indicate there are distinct regional populations (Kitchener et al., 1990; Mobley et al., 2000;
Chivers et al., 2007; Ferreira, 2008). Within waters of the central
Pacific, four Pacific Islands Region management stocks of false killer whales are currently recognized for management under the U.S. MMPA: The
Hawaii insular stock, the Hawaii pelagic stock, the Palmyra Atoll stock, and the American Samoa stock (Carretta et al., 2010).
Life History
False killer whales are long-lived social odontocetes. Much of what is known about their life history comes either from examination of dead animals originating from drive fisheries in Japan (Kasuya and Marsh, 1984; Kasuya, 1986) or strandings (Purves and Pilleri, 1978; Ferreira, 2008). The social system has been described as matrilineal (Ferreira, 2008). However, this is not consistent with two known characteristics of false killer whales: Males leave their natal group when they begin to become sexually mature; and research showing females within a single group have different haplotypes, indicating that even among females, groups are composed of more than near-relatives (Chivers et al., 2010).
Ferreira (2008) suggested the mating system may be polygynous based on the large testes size of males, but actual understanding of the mating system remains poor.
The only reported data on birth interval, 6.9 years between calves, is from Japan (Kasuya, 1986). However, annual pregnancy rates were reported for Japan as 11.4 percent and 2.2 percent for South Africa
(Ferreira, 2008). A rough interbirth interval can be calculated by taking the inverse of the annual pregnancy rate, which yields intervals of 8.8 and 45 years for Japan and South Africa, respectively. A single stranding group where 1 out of 37 adult females was pregnant was the source of the South African data, which may not be a representative sample and could be insufficient to estimate pregnancy rates in that population.
Comparisons of the life history parameters inferred from the
Japanese drive fishery samples and the South African stranding sample indicated that the whales in Japan attained a larger asymptotic body size and grew faster. Also, a suite of characteristics of the whales in
Japan indicated a higher reproductive rate: The ratio of reproductive to post-reproductive females was higher and the pregnancy rate was higher than in South Africa. Possible reasons given by Ferreira (2008) for the apparently higher reproductive rate in Japan are: The Japan whales are exhibiting a density-dependent response to population reduction as a result of exploitation; the colder waters near Japan are more productive; or differences in food quality. The estimated reproductive rates in both Japan and South Africa are low compared to those of other delphinids and especially to the two species with the most similar life history: Short-finned pilot whales (Globicephala macrorhynchus), and Southern Resident killer whales (Orcinus orca)
(Olesiuk et al., 1990).
Little is known about the breeding behavior of false killer whales in the wild, but some information is available from false killer whales held in oceanaria (Brown et al., 1966). Gestation has been estimated to last 11 to 16 months, (Kasuya, 1986; Odell and McClune, 1999). Females with calves lactate for 18 to 24 months (Perrin and Reilly, 1984). In captive settings, false killer whales have mated with other delphinids, including short-finned pilot whales and bottlenose dolphins. Bottlenose dolphins in captivity have produced viable offspring with false killer whales (Odell and McClune, 1999).
Reproductive senescence is quite rare in cetaceans but has been documented in false killer whales and other social odontocetes. The two primary reasons given for reproductive senescence are increasing survival of offspring as a result of care given by multiple females of multiple generations (grandmothering), and transmission of learning across generations allowing survival in lean periods by remembering alternative feeding areas or strategies (McAuliffe and Whitehead, 2005;
Ferreira, 2008).
Wade and Reeves (2010) argue that odontocetes have delayed recovery as compared to mysticetes when numbers are reduced because of the combination of their life history, which results in exceptionally low maximum population growth rates, and the potential for social disruption. Particularly if older females are lost, it may take decades to rebuild the knowledge required to achieve maximum population growth rates.
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Wade and Reeves (2010) give numerous examples, both from cetaceans
(beluga whales (Delphinapterus leucas), killer whales, and sperm whales
(Physeter macrocephalus) are particularly pertinent) and elephants, which are similarly long-lived social animals with reproductive senescence.
Feeding Ecology
False killer whales are top predators, eating primarily fish and squid, but also occasionally taking marine mammals (see references in
Oleson et al., 2010). These conclusions are based on relatively limited data from various parts of the species' range.The large, widely spread groups in which false killer whales typically occur (Baird et al., 2008a; Baird et al., 2010) and their patchily distributed prey suggest that this species forages cooperatively. Further evidence for the social nature of false killer whale foraging is the observation of prey sharing among individuals in the group (Connor and Norris, 1982; Baird et al., 2008a). False killer whales feed both during the day and at night (Evans and Awbrey, 1986; Baird et al., 2008a).
Diving Behavior
Limited information is available on the diving behavior of false killer whales. Maximum dive depth was estimated at 500 m (Cummings and
Fish, 1971). Time depth recorders have been deployed on four false killer whales (R. Baird, pers. comm., Cascadia Research Collective) totaling approximately 44 hours. The deepest dive recorded during a 22- hour deployment was estimated to have been as deep as 700 m (estimate based on duration past the recorder's 234 m limit and ascent and descent rates). However, only 7 dives were to depths greater than 150 m, all of them accomplished in the daytime. Nighttime dives were all shallow (30-40 m maximum), but relatively lengthy (approximately 6-7 minutes).
Indirect evidence of dive depths by false killer whales can be inferred from prey. Mahimahi has been noted as a prominent prey item
(Baird, 2009). Based on the catch rates of longlines instrumented with depth sensors and capture timers (Boggs, 1992) in the daytime, mahimahi are caught closer to the surface than other longline-caught fish, primarily in the upper 100 m. Other prey species, such as bigeye tuna, typically occur much deeper, from the surface down to at least 400 m
(Boggs, 1992). The deepest dives by the instrumented false killer whales approach the daytime swimming depth limit of swordfish (Xiphias gladius), a prey item, near 700 m (Carey and Robinson, 1981).
Social Behavior
There is quite a bit of variance in estimates of group size of false killer whales. At least some of the variability stems from estimation methods and time spent making the group size estimate. Most group sizes estimated from boats or planes vary from 1 to over 50 animals with an average from 20 to 30, and group size estimates increase with encounter duration up to 2 hours (Baird et al., 2008a).
Group size tends to increase with encounter duration because the species often occurs in small subgroups that are spread over tens of square miles. It is possible that the groups seen on typical boat or plane surveys are only part of a larger group spread over many miles
(see e.g., Baird et al., 2010) that are in acoustic contact with one another. These widespread aggregations of small groups can total hundreds of individuals (Wade and Gerrodette, 1993; Carretta et al., 2007; Baird, 2009; Reeves et al., 2009). Mass strandings of large groups of false killer whales (range 50-835; mean = 180) have been documented in many regions, including New Zealand, Australia, South
Africa, the eastern and western North Atlantic, and Argentina (Ross, 1984). Groups of 2-201 individuals (mean = 99) have also been driven ashore in Japanese drive fisheries (Kasuya, 1986). The social organization of smaller groups has been studied most extensively near the main Hawaiian Islands (Baird et al., 2008a), where individuals are known to form strong long-term bonds. False killer whales are also known to associate with other cetacean species, especially bottlenose dolphins (Leatherwood et al., 1988). Interestingly, records also show false killer whales attacking other cetaceans, including sperm whales and bottlenose dolphins (Palacios and Mate, 1996; Acevedo-Gutierrez et al., 1997).
Biology and Life History of Hawaiian Insular False Killer Whales
Current Distribution
The boundaries of Hawaiian insular false killer whale distribution have been assessed using ship and aerial survey sightings and location data from satellite-linked telemetry tags. Satellite telemetry location data from seven groups of individuals tagged off the islands of Hawaii and Oahu indicate that the whales move widely and quickly among the main Hawaiian Islands and use waters up to at least 112 km offshore
(Baird et al., 2010; Forney et al., 2010). Regular movement throughout the main Hawaiian Islands was also documented by re-sightings of photographically-identified individuals over several years (Baird et al., 2005; Baird, 2009; Baird et al., 2010). Individuals use both windward and leeward waters, moving from the windward to leeward side and back within a day (Baird, 2009; Baird et al., 2010; Forney et al., 2010). Some individual false killer whales tagged off the Island of
Hawaii have remained around that island for extended periods (days to weeks), but individuals from all tagged groups eventually ranged widely throughout the main Hawaiian Islands, including movements to the west of Kauai and Niihau (Baird, 2009; Forney et al., 2010). Based on locations obtained from 20 satellite-tagged insular false killer whales, the minimum convex polygon range for the insular population was estimated to encompass 77,600 km\2\ (M.B. Hanson, unpublished data).
The greatest offshore movements occurred on the leeward sides of the islands, although on average, similar water depths and habitat were utilized on both the windward and leeward sides of all islands (Baird et al., 2010). Individuals utilize habitat overlaying a broad range of water depths, varying from shallow (4,000 m)
(Baird et al., 2010). Tagged insular false killer whales have often demonstrated short- to medium-term residence in individual island areas before ranging widely among islands and adopting another short-term residency pattern. It is likely that movement and residency patterns of the whales vary over time depending on the density and movement patterns of their prey species (Baird, 2009).
A genetically distinct population of pelagic false killer whales occurs off Hawaii (Chivers et al., 2007). Hawaiian insular false killer whales share a portion of their range with the genetically distinct pelagic population (Forney et al., 2010). Satellite telemetry locations from a single tagged individual from the pelagic population, as well as shipboard and small boat survey sightings, suggest that the ranges of the two populations overlap in the area between 42 km and 112 km from shore (Baird et al., 2010; Forney et al., 2010). Based on this evidence, it is clear that the region from about 40 km to at least 112 km from the main Hawaiian Islands is an overlap zone, in which both insular and pelagic false killer whales can be found. However, a small sample size of satellite-tracked individuals creates some uncertainty in these boundaries. In particular, the offshore boundary of the insular stock is
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likely to be farther than 112 km because their documented offshore extent has increased as sample sizes of satellite-tracked individuals have increased. It is likely that additional deployments in the future will continue to result in greater maximum documented distances for insular false killer whales. Thus, an additional geographic ``buffer'' beyond the present maximum distance of 112 km has been recognized out to 140 km. Moreover, 140 km is approximately 75 nmi which follows the original boundary recommendation of Chivers et al. (2008). Therefore, the draft 2010 SAR for false killer whales recognizes an overlap zone between insular and pelagic false killer whales between 40 km and 140 km from the main Hawaiian Islands based on sighting, telemetry, and genetic data (based on justification in Forney et al., 2010; Carretta et al., 2010). We recognize that boundary for this status review as well.
Life History
There is no information available to assess whether the life history of Hawaiian insular false killer whales differs markedly from other false killer whale populations. However, there is also no evidence to show they are similar. As discussed earlier, false killer whales in Japan were larger and had a higher reproductive output than those in South Africa, and these differences were attributed to one or more of the following: colder more productive waters, response to exploitation, and different food in the two regions (Ferreira, 2008).
It remains uncertain whether Hawaiian insular false killer whales are more like those from Japan or those from South Africa.
Social Structure
Molecular genetic results support the separation of Hawaiian insular false killer whales from the more broadly distributed Hawaiian pelagic false killer whales (Chivers et al., 2007; 2010). Matches from photo-identification of individuals in groups of insular false killer whales also suggests functional isolation of the insular population from the overlapping pelagic population of false killer whales (Baird et al., 2008a). Based on 553 identifications available as of July 2009, with the exception of observations of four small groups (two observed near Kauai and two off the Island of Hawaii), all false killer whales observed within 40 km of the main Hawaiian Islands link to each other through a single large social network that makes up the insular population. A large group of 19 identified individuals of the pelagic population (or presumed to be) seen 42 km from shore and identifications from a number of other sightings of smaller groups do not link into the social network (Baird, 2009).
The social cohesion of insular false killer whales is likely important to maintaining high fecundity and survival as it is in other highly social animals. Although some aspects of the behavior and
``culture'' of Hawaiian insular false killer whales have been investigated or discussed, the mechanisms by which they might influence population growth rates are not well understood. The situation of this population could be analogous to those of other populations of large mammals in which females live well beyond their reproductive life spans
(e.g., elephants, higher primates, and some other toothed cetaceans such as pilot whales) (McComb et al., 2001; Lahdenpera et al., 2004).
The loss of only a few key individuals--such as the older, post- reproductive females--could result in a significant loss of inclusive fitness conveyed by ``grandmothering'' behavior (i.e., assistance in care of the young of other females in the pod). In addition, cultural knowledge (e.g., how to cope with environmental changes occurring on decadal scales) could be lost, leading to reduced survival or fecundity of some or all age classes. Wade and Reeves (2010) document the special vulnerability of social odontocetes giving examples of killer whales, belugas, sperm whales, and dolphins in the eastern tropical Pacific.
Historical Population Size
Historical population size is unknown. BRT members used density estimates from other areas together with the range inferred from telemetry data (see above) to suggest plausible ranges for historical abundance. Using the estimated density of false killer whales around the Palmyra Atoll EEZ, 0.38 animals/100 km\2\, where the highest density of this species has been reported (Barlow and Rankin, 2007), and extrapolating that density out to the 202,000 km\2\ area within 140 km of the main Hawaiian Islands (proposed as a stock boundary for
Hawaiian insular false killer whales in the draft 2010 SAR), a point- estimate, or a plausible historical abundance, for the insular population is around 769. Alternatively, using one standard deviation above the point-estimate of the density around Palmyra Atoll to account for uncertainty in that density estimate, the upper limit of the abundance of Hawaiian insular false killer whales could have reached 1,392 animals. The BRT placed the lower limit of plausible population size in 1989 at 470 based on the estimated number of animals observed in the 1989 aerial surveys (see above).
There are several important caveats. Even though Palmyra has a density that is high relative to other areas, it is unlikely that this represented a pristine population during the 2005 survey on which the estimate is based. Given the depredation tendencies of false killer whales, known long-lining in the Palmyra area, and the fact that false killer whales are known to become seriously injured or die as a result of interactions with longlines, the possibility that current densities are lower than historical densities cannot be discounted. Although
Palmyra is situated in more productive waters than the Hawaiian
Islands, we do not understand enough about the feeding ecology, behavior, and social system(s) of false killer whales to know how or whether productivity might be related to animal density for false killer whales. This caveat is true for all other areas where population density estimates exist for false killer whales. Therefore, we used and view data from Palmyra as a conservative estimate of pristine density.
Current Abundance
The draft 2010 SAR for Hawaiian insular false killer whales
(Carretta et al., 2010) gives the best estimate of current population size as 123 individuals (coefficient of variation, or CV = 0.72), citing Baird et al. (2005). Recent reanalysis of photographic data has yielded two new estimates of population size for the 2006-2009 period.
Two estimates are presented because two groups photographed near Kauai have not yet been observed to associate into the social network of false killer whales seen at the other islands. These animals may come from the pelagic population, may come from another undocumented population in the Northwestern Hawaiian Islands, or may represent a portion of the insular population that has not been previously documented photographically. The current best estimates of population size for Hawaiian insular false killer whales are 151 individuals (CV = 0.20) without the animals photographed at Kauai, or 170 individuals (CV
= 0.21) with them. As a comparison, the Hawaiian pelagic population is estimated to be 484 individuals (CV = 0.93) within the U.S. EEZ surrounding Hawaii (Barlow and Rankin, 2007).
Although the absolute abundance of Hawaiian insular false killer whales is small, the core-area (within 40 km) population density (0.12 animals/100 km\2\) is among the highest reported for this species. The high density of the Hawaiian insular population suggests a unique habitat capable of supporting a
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larger population density than nearby oligotrophic waters.
Trends in Abundance
Aerial survey sightings since 1989 suggest that the Hawaiian insular false killer whale population has declined over the last 2 decades. A survey was conducted in June and July 1989 on the leeward sides of Hawaii, Lanai, and Oahu to determine the minimum population size of false killer whales in Hawaiian waters. False killer whales were observed on 14 occasions with 3 large groups (group sizes of 470, 460, and 380) reported close to shore off the Island of Hawaii on 3 different days (Reeves et al., 2009). As described in the Current
Abundance section, the current best estimates of population size for
Hawaiian insular false killer whales are 151 individuals without the animals photographed at Kauai, or 170 with them. Therefore, the largest group seen in 1989 is much larger than the current best estimate of the size of the insular population. Although the animals seen during the 1989 surveys are assumed to come from the insular population based on their sighting location within 55 km of the Island of Hawaii, it is possible that they represent a short-term influx of pelagic animals to waters closer to the islands. Moreover, because photographic or genetic identification of individuals is often required to determine the population identity of false killer whales in Hawaiian waters, we cannot be absolutely certain that sightings from the 1989 or 1993 to 2003 aerial surveys came from the insular population. Similarly, false killer whale bycatch or sightings by observers aboard fishing vessels cannot be attributed to the insular population when no identification photographs or genetic samples are obtained. Nevertheless, because of the location of the sightings and lack of evidence of pelagic animals occurring that close to the islands, it is most likely that this group did consist of insular animals.
With respect to trends in group size, the average group size during the 1989 survey (195 animals) is larger than the typical average group size for the insular population (25 animals for encounters longer than 2 hours) during more recent surveys (Baird et al., 2005). The 1989 average group size is also larger than the more recent average of that observed for the pelagic population (12 animals) (Barlow and Rankin, 2007).
Five additional systematic aerial surveys were conducted between 1993 and 2003 covering both windward and leeward sides of all of the main Hawaiian Islands, including channels between the islands, out to a maximum distance of about 46 km from shore (Mobley et al., 2000;
Mobley, 2004). A regression of sighting rates from these surveys suggests a significant decline in the population size (Baird, 2009).
The large groups sizes observed in 1989, together with the declining encounter rates from 1993 through 2003 suggest that Hawaiian insular false killer whales have declined substantially in recent decades.
It is possible that weather or other survey conditions are at least partially responsible for the decline in sighting rates from 1993 through 2003; however, there was no downward trend in the sighting rates for the four most commonly seen species of small cetaceans
(spinner dolphin (Stenella longirostris), bottlenose dolphin, spotted dolphin (Stenella attenuata), and short-finned pilot whale). These four species represent nearshore and pelagic habitat preferences and span a range of body sizes from smaller to larger than false killer whales. It can be inferred from this evidence that variability in sighting conditions during the survey period did not have a major effect on sighting rates and therefore the sighting rate for insular false killer whales has, in fact, declined.
A number of additional lines of evidence, summarized in Baird
(2009), support a recent decline in Hawaiian insular false killer whale population size. Individual researchers in Hawaii have noted a marked decline in encounter rates since the 1980s and the relative encounter rate of false killer whales during the 1989 aerial survey was much higher than current encounter rates.
Population Structure
Chivers et al. (2007) delineated false killer whales around Hawaii into two separate populations: Hawaiian insular and Hawaiian pelagic.
That work has recently been extended with new samples, the addition of nuclear markers, and an analysis with a broader interpretation of the data (Chivers et al., 2010). The new analysis examined mitochondrial
DNA (mtDNA) using sequences of 947 base pairs from the d-loop and nuclear DNA (nDNA) using eight microsatellites. These additional samples help confirm the delineation of these two populations.
Three stratifications of the mtDNA data examined genetic differentiation at different spatial scales (Chivers et al., 2010). The broad-scale stratification recognized three groups: Hawaiian insular, central North Pacific, and eastern North Pacific. In the fine-scale stratification, five strata were recognized: Hawaiian insular, Hawaiian pelagic, Mexico, Panama, and American Samoa. The finest-scale stratification recognized each of the main Hawaiian Islands as strata.
All but one Hawaiian insular false killer whale had one of two closely related haplotypes that have not been found elsewhere. The presence of two distinct, closely related haplotypes in Hawaiian insular false killer whales is consistent with Hawaiian insular false killer whales having little gene flow from other areas. This pattern differs from those of Hawaiian stocks of bottlenose, spinner, and spotted dolphins that all have evidence suggesting multiple successful immigration events. The pattern of primarily closely related haplotypes shown in Hawaiian insular false killer whales is consistent with a strong social system or strong habitat specialization that makes survival of immigrants or their offspring unlikely. One single individual, a male, was found in among Hawaiian insular false killer whales with a different haplotype. Although there is no photograph of that male to connect it directly to Hawaiian insular false killer whales, it was sampled within a group with such strong connections that assignment tests could not exclude that it belongs to the insular group. Given the low power of the current assignment test (with few microsatellite markers), the possibility of immigration (permanent membership with Hawaiian insular false killer whales but with an origin outside the group) cannot be ruled out. Likewise, the possibility that this individual was a temporary visitor (i.e., not a true immigrant) from the pelagic population cannot be excluded. The rare haplotype is sufficiently distantly related that it seems most plausible that this resulted from a separate immigration event (i.e., that immigrants are accepted on rare occasions).
The mtDNA data also show strong differentiation between Hawaiian insular false killer whales (n = 81) and both broad-scale strata
(central North Pacific (n = 13) and eastern North Pacific (n = 39)) and fine-scale strata (Hawaiian pelagic (n = 9), Mexico (n = 19), Panama (n
= 15), and American Samoa (n = 6)). Genetic divergence between the
Hawaiian insular false killer whales and other strata examined showed magnitudes of differentiation that were all consistent with less than one migrant per generation. No significant differences were found among the main Hawaiian Islands with sufficient data for statistical analysis
(Hawaii, Oahu, and Maui).
Nuclear DNA results also showed highly significant differentiation among
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the broad and fine strata (Hawaiian insular (n = 69), central North
Pacific (n = 13), eastern North Pacific (n = 36), Hawaiian pelagic (n = 9), Mexico (n = 19), Panama (n = 12), and American Samoa (n = 6)). The estimates of divergence between the Hawaiian insular strata and other strata demonstrate that the magnitude of differentiation was less for nDNA than for mtDNA, indicating the potential for some male-mediated gene flow. Tests for differences between currently living males and females in level of differentiation were not significant for either mtDNA or nDNA. However, this test has no ability to detect differences in male versus female gene flow in the past. Chivers et al. (2010) give a number of hypotheses for the apparently different magnitude of signals between mtDNA and nDNA: (1) There is a low level of male- mediated gene flow that was not apparent because of insufficient sampling of nearby groups of false killer whales and/or the test for male-mediated gene flow can only detect first-generation male migrants;
(2) the magnitude of nDNA differentiation is underestimated because of the high mutation rate of microsatellites; or (3) the magnitude of differentiation is not inconsistent with cases where selection has been shown to be strong enough for local adaptation.
The aforementioned uncertainties will best be resolved with additional sampling of nearby pelagic waters. Although the sample distribution is improved since the 2007 analysis, it remains poor in pelagic areas. The only full-scale cetacean survey of Hawaiian pelagic waters resulted in only two sightings of false killer whales in four months of effort, and the weather was too poor to obtain any high- quality identification photographs or biopsies (J. Barlow, pers. comm.,
NMFS SWFSC). Fisheries observers are trained to obtain identification photographs and biopsy samples; however, conditions during disentanglement usually result in photographs difficult to identify due to darkness, and prevent successful biopsy.
The strongest data with which to evaluate population structure are the mtDNA data. Approximately half of the population of Hawaiian insular false killer whales has been sampled, and all but one individual has one of two closely related haplotypes that have not been found elsewhere.
Chivers et al. (2010) used the analytical method of Piry et al.
(1999) to test for evidence of a recent decline in abundance within the
Hawaiian insular population. The analysis takes advantage of the fact that when the effective size of a population is reduced, the allelic diversity of the population is reduced more rapidly than its heterozygosity, resulting in an apparent excess of heterozygosity given the number of alleles detected. Chivers et al. (2010) detected statistically significant evidence of a recent decline in Hawaiian insular false killer whales using this method, with all eight microsatellite loci exhibiting heterozygosity excess.
The microsatellite data were also used to estimate the effective population size of Hawaiian insular false killer whales as 46 (95 percent CI = 32-69). Because this population may have recently declined and the animals are long-lived, many of those individuals still alive likely were born prior to the decline. Thus, the estimate of effective population size is likely too high. Nevertheless, domestic animals have been shown to start displaying deleterious genetic effects (lethal or semi-lethal traits) when effective population size reaches about 50 individuals (Franklin, 1980). While negative genetic effects cannot be predicted for a group of individuals that are probably naturally uncommon with a strong social structure that limits genetic diversity, the current low effective population size is a concern.
DPS Determination
We have determined that Hawaiian insular false killer whales are discrete from other false killer whales based on genetic discontinuity and behavioral factors (the uniqueness of their behavior related to habitat use patterns). We have also determined that Hawaiian insular false killer whales are significant to the taxon, based on their unique ecological setting, marked genetic characteristic differences, and cultural factors.
Both mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) provide support for genetic discontinuity. As explained in the Population
Structure section of this proposed rule, genetic differentiation was examined at different spatial scales. The mtDNA data show strong differentiation between Hawaiian insular false killer whales and other false killer whale groups at both broad-scale strata (central North
Pacific and eastern North Pacific) and fine-scale strata (Hawaiian pelagic, Mexico, Panama, and American Samoa). The strongest DNA data come from mtDNA. The Hawaiian insular false killer whales have approximately half of the population sampled, and all but one individual has one of the two closely related haplotypes that have not been found elsewhere. The BRT concluded that this pattern alone argues for a strong possibility of a high degree of separation. Nuclear DNA
(microsatellite) data are also consistent with little gene flow between
Hawaiian insular false killer whales and other false killer whales and support discreteness. Nuclear DNA results showed highly significant differentiation among the Hawaiian insular, North Pacific, eastern
North Pacific, Hawaiian pelagic, Mexico, Panama, and American Samoa strata.
Hawaiian insular false killer whales are behaviorally unique because they are the only population of the species known to have movements restricted to the vicinity of an oceanic island group. This behavioral separation is supported by their linkage through a tight social network, without any linkages to animals outside of the Hawaiian
Islands. Phylogeographic analysis also indicates an isolated population with nearly exclusive haplotypes, and telemetry data show that all 20 satellite-linked telemetry tagged Hawaiian insular false killer whales remained within the main Hawaiian Islands (Baird et al., 2010; Baird et al., unpublished data), in contrast with a single tagged pelagic false killer whale, which ranged far from shore. Although it is not unusual for false killer whales to be observed close to land, long-term history of exclusive use of a specific mainland or island system has not been documented elsewhere.
Hawaiian insular false killer whales are significant to the taxon based on persistence in a unique ecological setting, marked genetic characteristic differences, and cultural factors. Hawaiian insular false killer whales persist in an ecological setting unusual or unique from other false killer whale populations because they are found primarily in island-associated waters that are relatively shallow and productive compared to surrounding oligotrophic waters. The following lines of evidence supporting this unique ecological setting include:
Utilization of prey associated with island habitat that may require specialized knowledge of locations and seasonal conditions that aggregate prey or make them more vulnerable to predation. In an insular habitat, such foraging grounds may occur more regularly or in more predictable locations than on the high seas. The contaminant levels found in insular animals also suggest that both insular false killer whales and their prey may be associated with the urban island environment. And despite their small population size, the density
(animals per km\2\) of Hawaiian insular false killer whales is high relative to other false killer whale populations, suggesting the
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nearshore habitat or a unique habitat-use strategy may support a higher density of animals, which may have implications for differences in social structure and interactions within the population or with the pelagic population. Additionally, movement and photographic resighting data suggest Hawaiian insular false killer whales employ a unique foraging strategy compared to other false killer whales.
Hawaiian insular false killer whales differ markedly from other populations of the species in their genetic characteristics. Hawaiian insular false killer whales exhibit strong phylogeographic patterns that are consistent with local evolution of mitochondrial haplotypes.
Eighty of 81 individuals had one of two closely related haplotypes found nowhere else. These haplotypes are a sequence of a non-coding portion of the mtDNA and as such do not provide direct evidence for selection. The BRT found that the magnitude of mtDNA differentiation is large enough to infer that time has been sufficient and gene flow has been low enough to allow adaptation to the local Hawaiian habitat. The
BRT noted that geneticists use one effective migrant per generation as a rule of thumb for the level of gene flow below which adaptation to local habitat is likely. Comparisons using mtDNA of the Hawaiian insular animals to those in all other geographic strata indicate less than one migrant per generation.
Finally, culture, or knowledge passed through learning from one generation to the next, is likely to play an important role in the evolutionary potential of false killer whales. The insular population contributes to cultural diversity in the species, and this may provide the capacity for different amounts of cultural capabilities such as the ability of false killer whales to adapt to environmental change.
Evidence in support of the significance of cultural diversity includes:
Insular false killer whales may have unique knowledge of nearshore foraging areas and foraging tactics that are transmitted through learning. Learning is a common feature of other social odontocetes.
False killer whales are highly social mammals with long interbirth intervals and reproductive senescence suggesting transfer of knowledge is important to successfully persist in this unique Hawaiian habitat.
Learning to persist in this unique habitat, and knowing the intricacies of localized prey distribution and prey movements, may take many generations.
Overall, the combination of genetic and behavioral discreteness coupled with ecological, genetic, and cultural significance led us to conclude that Hawaiian insular false killer whales are a DPS. There was some uncertainty in the genetic discontinuity factor of the discreteness conclusion based primarily on the lack of information on the adjacent population of pelagic false killer whales off the coast of
Hawaii, and due to gaps in genetic sampling to the west of Hawaii.
However, the BRT did not find this lack of information sufficient to alter the significance finding for Hawaiian insular false killer whales. We agree with the BRT's conclusion that the Hawaiian insular population of the false killer whale is a DPS.
Extinction Risk Assessment
Evaluating Threats
The BRT qualitatively assessed potential individual threats to
Hawaiian insular false killer whales and organized its assessment of threats according to the five factors listed under ESA section 4(a)(1).
They evaluated the potential role that each factor may have played in the decline of Hawaiian insular false killer whales and the degree to which each factor is likely to limit population growth in the foreseeable future. Within the five factors, specific threats were individually ranked by considering the severity, geographic scope, the level of certainty that insular false killer whales are affected, and overall current and future (60 years) risk imposed by that threat.
Consideration of future threats was limited to 60 years duration as this corresponds roughly to the life span of a false killer whale and represents a biologically relevant time horizon for projecting current conditions into the future.
Section 4(a)(1) of the ESA and NMFS's implementing regulations (50
CFR 424) state that the agency must determine whether a species is endangered or threatened because of any one or a combination of the five factors described under the ESA Statutory Provisions. The BRT was not asked to determine whether the DPS was endangered or threatened; it was only asked to assess the risk of extinction and the impact of factors affecting the DPS. The following discussion briefly summarizes the BRT's findings regarding threats to the Hawaiian insular false killer whale DPS. More details, including how the BRT voted, can be found in the status review report (Oleson et al., 2010). Overall, there were 29 threats identified to have either a historical, current, or future risk to Hawaiian insular false killer whales. Of these, 15 are believed to contribute most significantly to the current or future decline of Hawaiian insular false killer whales. The following is a summary of each of the 15 current and/or future potential threats that could result in either a high risk or medium risk of extinction, categorized according to the five section 4(a)(1) factors.
A: The Present or Threatened Destruction, Modification, or Curtailment of Its Habitat or Range
Reduced Total Prey Biomass and Reduced Prey Size
The impacts of reduced total prey biomass and reduced prey size represent a medium risk for insular false killer whales. Although declines in prey biomass were more dramatic in the past when the insular false killer whale population may have been higher, the total prey abundance remains very low compared to the 1950s and 1960s as evidenced by catch-per-unit-effort (CPUE) data from Hawaii longline fisheries and biomass estimates from tuna stock assessments (Oleson et al., 2010). Long-term declines in prey size from the removal of large fish have been recorded from the earliest records to the future (Oleson et al., 2010).
Competition With Commercial Fisheries
Competition with commercial fisheries is rated as a medium level of risk to current and future Hawaiian insular false killer whales. This risk exists because false killer whale prey includes many of the same species targeted by Hawaii's commercial fisheries, especially the fisheries for tuna, billfish, wahoo, and mahimahi.
Until 1980, distant-water longliners from Japan caught between 1,300 and 5,000 t of tuna and billfish annually within the U.S. EEZ around Hawaii (Yong and Wetherall, 1980). Since 1980 no foreign longline fishing has been legally conducted in this zone, but the U.S.
Hawaii-based longline fisheries now harvest similar quantities of tuna and billfish in the EEZ. In terms of total hooks deployed by the U.S. domestic fisheries, the fisheries declined slightly in the 1960s and 1970s, and then began to grow again in the 1980s. Total hooks in the
U.S. EEZ around the main Hawaiian Islands in the period of 1965 and 1977 were around 1.6 to 2.9 million hooks per year. As the domestic fisheries declined in the 1960s and 1970s, foreign fishing in the U.S.
EEZ around the main Hawaiian Islands increased, and then ceased in 1980. Domestic longlining was revitalized in the 1980s based on new markets for fresh tuna and the introduction of new shallow-set swordfish fishing methods.
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Hooks deployed inside the U.S. EEZ around the main Hawaiian Islands in the 1990s were double that estimated for the 1970s, and doubled again in the 2000s. Participation in the Hawaii longline fisheries approximately doubled from 37 vessels in 1987 to 75 in 1989 and doubled again to 156 (vessels with permits) by the end of 1991. As the Hawaii- based longline fisheries expanded during the late 1970s through the early 1990s, longline fishing effort increased in waters near the
Hawaiian Islands and within the range of insular false killer whales.
The expansion in these nearshore waters within the 40 km core habitat of the Hawaiian insular false killer whales was pronounced during an influx of new fisheries participants in the late 1980s (Ito, 1991) and this led to conflicts in the fishing areas previously dominated by troll and handline fishermen. The growing conflict between commercial longliners and near-shore troll and handliners was finally resolved in 1992 with a prohibited area limiting nearshore longlining. Although the fraction of total Pacific longline tuna catches that are from the EEZ around the main Hawaiian Islands has declined from about half to about a quarter over the last two decades, the absolute quantity caught in the EEZ continued to increase through 2005, declining moderately thereafter (WPRFMC, 2010).
The present-day Hawaiian insular false killer whale population requires an estimated 1.3 to 1.8 million kg of prey per year (Oleson et al., 2010). Competition with longline fisheries for potential prey within the insular false killer whale habitat seems to have represented a higher risk prior to the early 1990s when the longline fisheries were harvesting many millions of pounds of fish per year, and where reported catch locations were almost all in what is now the longline prohibited area. In the core nearshore habitat (
