Barbara A. Mahoney

Diet of beluga whales, Delphinapterus leucas, in Alaska from stomach contents, March-November

At least fi ve stocks of beluga whales, Delphinapterus leucas, are found in Alaska waters: Beaufort Sea, eastern Chukchi Sea, eastern Bering Sea, Bristol Bay, and Cook Inlet. The two northernmost stocks (Beaufort Sea and eastern Chukchi Sea) are highly migratory; the two southernmost stocks (Bristol Bay and Cook Inlet) are nonmigratory. Little is known about the seasonal movements and distribution of the eastern Bering Sea stock. Beluga populations in Alaska are thought to be stable or increasing, except for the Cook Inlet stock which is listed as endangered under the Endangered Species Act. We analyzed stomach contents from beluga whales collected between the months of March and November taken in subsistence harvests, from belugas found dead, and from belugas collected for research. We describe prey species and their percent frequency of occurrence (% FO) as well as potential biases from the seasonality of prey relative to the timing of sampling, and differential feeding and digestion. Diet was highly variable among stocks. The predominant fi sh species of the Beaufort Sea stock was Arctic cod, Boreogadus saida (21% FO), although shrimp (60% FO) and smoothskin octopus, Benthoctopus leioderma (42% FO) were found more frequently. Although the eastern Chukchi Sea stock ate more saffron cod, Eleginus gracilis (7% FO) than Arctic cod (3% FO), shrimp (73% FO) and echiurids (27% FO) were more prevalent than fi sh. The eastern Bering Sea stock had the most diverse diet, and dominant fi sh species included saffron cod (95% FO), rainbow smelt, Osmerus mordax (62% FO), several species of sculpin (Family Cottidae) and fl atfi sh (Family Pleuronectidae), both at 48% FO, and Arctic cod at 43%. Dominant invertebrates included shrimp (86% FO), with polychaetes, isopods, bivalves, amphipods, and echiurids ranging from 29 to 38% FO. Pacifi c salmon, Onchorhyncus spp., predominated over cod in Bristol Bay (81% FO) and Cook Inlet (67% FO) beluga stocks, and invertebrates appeared to be less prevalent prey. In Bristol Bay, smelt were also eaten more often (43% FO) than cod (3% FO), while in Cook Inlet cod were eaten more often (39% FO) than smelt (11% FO). Invertebrates were common in the diet of all Alaska beluga stocks and shrimp (mostly from the family Crangonidae) were the most prevalent. Introduction At least fi ve stocks of beluga whales, Delphinapterus leucas, occur in the waters of Alaska (Fig. 1). These stocks were tentatively identifi ed by their summer distributions (Frost and Lowry, 1990; Richard et al., 2001), and were later confi rmed genetically (O’Corry-Crowe et al., 1997, 2002, 2010). The distribution of beluga whales in Alaska is discontinuous from Yakutat Bay1, 2 to Cook Inlet to Bristol Bay. The entire area from Bristol Bay northward and eastward to Canada is used by belugas; the Bering and Chukchi seas are used year-round and the Beaufort Sea is used in summer (Frost and Lowry, 1990). 1There is a small group of <20 belugas that appear to be resident in Yakutat Bay, a deepwater fi ord (Laidre et al., 2000; Allen and Angliss, 2011) 2O’Corry-Crowe, G., W. Lucey, C. Bonin, E. Henniger, and R. Hobbs. 2006. The ecology, status and stock identify of beluga whales, Delphinapterus leucas, in Yakutat Bay, Alaska. Rep. to U.S. Mar. Mamm. Comm., NMFS-YSB-YTT, 22 p. Beluga whales in Alaska appear to follow one of two life history strategies: migratory and nonmigratory. Migratory stocks use shallow nearshore and deepwater offshore habitats (Hazard, 1988; Frost and Lowry, 1990), and include the eastern Chukchi Sea stock (population size ~4,000 (Allen and Angliss, 2011)) and the Beaufort Sea or Mackenzie stock (population size ~39,000 (Harwood et al., 1996; Allen and Angliss, 2011)). Nonmigratory stocks use shallow, estuarine habitats year-round and include the Bristol Bay and Cook Inlet stocks. The Bristol Bay population is increasing (Lowry et al., 2008) and is estimated to be ~3,000 (Allen and Angliss, 2011). Local sightings and satellite telemetry confi rm that belugas occur in Bristol Bay in all months of the year (Harrison and Hall, 1978; Frost and Lowry, 1990; Lensink3; Quakenbush and Citta4; Quaken bush5). The population in Cook Inlet is estimated to be 312 whales and appears to be decreasing at 1.6% per year (Hobbs et al., 2015). The population declined dramatically between 1994 and 1998 (Hobbs et al., 2000) and the stock was determined to be depleted under the Marine Mammal Protection Act in 2000 (NOAA, 2000); the original cause of the decline is believed to be overharvest. Between 1999 and 2006 the harvest was restricted to fi ve 3Lensink, C. J. 1961. Status report: beluga studies. Alaska Dep. Fish Game, Juneau. Unpubl. rep., 38 p. 4Quakenbush, L., and J. Citta. 2006. Fall movements of beluga whales captured in the Nushagak River in September 2006. Unpubl. rep. to Alaska Beluga Whale Committee, P.O. Box 69, Barrow Alaska 99723, 9 p. 5Quakenbush, L., Alaska Dep. Fish Game, 1300 College Road, Fairbanks. Unpubl. data.

Migratory culture, population structure and stock identity in North Pacific beluga whales (Delphinapterus leucas)

The annual return of beluga whales, Delphinapterus leucas, to traditional seasonal locations across the Arctic may involve migratory culture, while the convergence of discrete summering aggregations on common wintering grounds may facilitate outbreeding. Natal philopatry and cultural inheritance, however, has been difficult to assess as earlier studies were of too short a duration, while genetic analyses of breeding patterns, especially across the beluga’s Pacific range, have been hampered by inadequate sampling and sparse information on wintering areas. Using a much expanded sample and genetic marker set comprising 1,647 whales, spanning more than two decades and encompassing all major coastal summering aggregations in the Pacific Ocean, we found evolutionary-level divergence among three geographic regions: the Gulf of Alaska, the Bering-Chukchi-Beaufort Seas, and the Sea of Okhotsk (Φst = 0.11–0.32, Rst = 0.09–0.13), and likely demographic independence of (Fst-mtDNA = 0.02–0.66), and in many cases limited gene flow (Fst-nDNA = 0.0–0.02; K = 5–6) among, summering groups within regions. Assignment tests identified few immigrants within summering aggregations, linked migrating groups to specific summering areas, and found that some migratory corridors comprise whales from multiple subpopulations (PBAYES = 0.31:0.69). Further, dispersal is male-biased and substantial numbers of closely related whales congregate together at coastal summering areas. Stable patterns of heterogeneity between areas and consistently high proportions (~20%) of close kin (including parent-offspring) sampled up to 20 years apart within areas (G = 0.2–2.9, p>0.5) is the first direct evidence of natal philopatry to migration destinations in belugas. Using recent satellite telemetry findings on belugas we found that the spatial proximity of winter ranges has a greater influence on the degree of both individual and genetic exchange than summer ranges (rwinter-Fst-mtDNA = 0.9, rsummer-Fst-nDNA = 0.1). These findings indicate widespread natal philopatry to summering aggregation and entire migratory circuits, and provide compelling evidence that migratory culture and kinship helps maintain demographically discrete beluga stocks that can overlap in time and space.

Beluga whale, Delphinapterus leucas, satellite-tagging and health assessments in Cook Inlet, Alaska, 1999 to 2002

Cook Inlet beluga whales, Delphinapterus leucas, are currently listed as ‘Endangered’ under the U.S. Endangered Species Act (ESA). The National Marine Fisheries Service (NMFS) began monitoring this population during the 1990s after it was added to the ESA Candidate Species list in 1988. Monitoring efforts included aerial surveys, and in 1995, the first attempts to capture and satellite-tag whales. Working with Canadian scientists and Alaska Native subsistence hunters in 1995 and 1997, tagging methods were adapted to conditions in Cook Inlet (muddy water, extreme tides, and extensive mudflats), culminating in successful capture and tracking of a whale during the summer of 1999. This was followed by three more years of capture and tagging studies during late summer. Tags were attached to 18 whales between 1999 and 2002. We do not have detailed accounts of these later tagging seasons (e.g., similar to the Appendix chronicling events from the 1997 and 1999 seasons in Ferrero et al. (2000)). Litzky et al. (2001) summarized field operations for the 2000 tagging season, but no reports exist for 2001 and 2002. A reanalysis of the tag dataset (Goetz et al. 2012) led to questions about the captures and how tags were programmed during this time period. Given the Cook Inlet population has continued to decline (Hobbs et al. 2015, Shelden et al. 2017), and was listed as an Endangered Distinct Population Segment under the ESA in October 2008 (NOAA 2008), future recommendations for tagging will depend on lessons learned from these past projects. Lacking detailed field reports, we consolidated information from multiple sources. Herein, we bring these varied sources together to provide a thorough documentation of the tagging operations undertaken in Cook Inlet each summer in 2000, 2001, and 2002. We include revised tag transmission timelines, monthly movement maps, dive behavior data, and ice-association graphs and maps for all whales (where applicable) tagged in 1999, 2000, 2001, and 2002. Whale locations were compared to sighting records (opportunistic and systematic) to determine how many whales were likely proximate to tagged whales. Animations of whale movements are available at http://www.afsc.noaa.gov/News/Cook_Inlet_Beluga_Range_Contracted.htm (accessed 17 Aug. 2016).

Aerial surveys of beluga whales in Cook Inlet, Alaska, June 1991

The National Marine Mammal Laboratory (NMML), in cooperation with the NMFS Alaska Regional Office, the Alaska Beluga Whale Committee (ABWC), and the Cook Inlet Marine Mammal Council (CIMMC), conducted an aerial survey of the beluga whale population in Cook Inlet, Alaska, during 11-17 June 1996. This provided a thorough coverage of the coasts around the entire inlet (1,388 km) as well as 1,538 km of offshore transects. Therefore, 100% of the coastal areas where belugas were expected to be during this season were searched one or more times, and 29% of the entire inlet was searched. The 40 hr survey was flown in a twin-engine, high-wing Aero Commander at 244 m (800 ft) altitude and 185 km/hr (100 kt). Throughout this survey, a test of sighting rates was conducted with multiple independent observers on the coastal (left) side of the plane, where most sightings occur. A single observer and a computer operator/data recorder were on the right side. After finding beluga groups, a series of aerial passes were made to allow at least two pairs of observers to make 4 or more counts of whales. Each pass was also videotaped for later analysis. The sum of the aerial estimates (using median counts from each site, not corrected for missed whales) ranged from 154 to 361 whales, depending on survey day. Estimates of group size ranged from 1 to nearly 300. Half (49%) of the initial sightings occurred more than 1.4 km from the aircraft the perimeter of the standard viewing area. Of 40 groups recorded in 1994-96, 17 were reported by only one primary observer and missed by the other, while 23 groups were reported by both observers. Most (81%) of the beluga whales seen in Cook Inlet were in the upper Inlet near the mouth of the Susitna River, which is typical of their summer distribution.