Janice M. Waite

Cetacean distribution and relative abundance on the central-eastern and the southeastern Bering Sea shelf with reference to oceanographic domains

Abstract Visual line-transect surveys for cetaceans were conducted in the central–eastern Bering Sea (CEBS) from 5 July to 5 August 1999, and in the southeastern Bering Sea (SEBS) from 10 June to 3 July 2000, in association with a pollock stock assessment survey aboard the NOAA ship Miller Freeman. Observers scanned for cetaceans with 25× (Big Eye) binoculars from the flying bridge (platform height =12 m) at survey speeds of 18.5–22 km h−1 (10–12 knots). Transect survey effort was 1761 km in 1999, in a study area 196,885 km2; and 2194 km in 2000, in a study area 158,561 km2. An additional 609 and 402 km of trackline was surveyed in 1999 and 2000, respectively, while in transit to or from pollock survey way points. Fin whales (Balaenoptera physalus) were the most common large whale, and Dall’s porpoise (Phocoenoides dalli) the most common small cetacean in both regions. In the CEBS (1999), uncorrected cetacean abundance estimates were: 3368 (CV=0.29) fin whales, 810 (CV=0.36) minke whales (B. acutorostrata), 14,312 (CV=0.26) Dall’s porpoise and 693 (CV=0.53) harbor porpoise (Phocoena phocoena). In the SEBS (2000), uncorrected abundance estimates were: 683 (CV=0.32) fin whales, 102 (CV=0.50) humpback whales (Megaptera novaeangliae), 1003 (CV=0.26) minke whales, 9807 (CV=0.20) Dall’s porpoise and 1958 (CV=0.21) harbor porpoise. These are the first estimates of cetacean abundance that can be directly compared between two regions of the eastern Bering Sea. Distributions of some species were associated with bathymetric features, and there were occasions when prey associations were obvious. For example, in the SEBS, fin whales occurred on the Middle Shelf (50–100 m) and on the Outer Shelf (100–200 m) near the Pribilof canyon, but in the CEBS fin whales occurred primarily on the Outer Shelf along the 200 m isobath (i.e. the Green Belt). Fin whales were sometimes associated with echo-sounder backscatter from a mixture of fish schools and zooplankton. Humpback whales were also seen on the Middle Shelf, near the 50-m contour where the Inner Front often develops. Non-pollock echosigns observed near cetaceans, some of which may have been cetacean prey, were not routinely identified during trawl sampling because the research focus was on pollock abundance assessment.

Alaska marine mammal stock assessments, 2009

NOTE – March 2008: In areas outside of Alaska, studies have shown that stock structure is more fine-scale than is reflected in the Alaska Stock Assessment Reports. At this time, no data are available to reflect stock structure for harbor porpoise in Alaska. However, based on comparisons with other regions, smaller stocks are likely. Should new information on harbor porpoise stocks become available, the harbor porpoise Stock Assessment Reports will be updated.

Alaska marine mammal stock assessments, 2015

NOTE – NMFS is in the process of reviewing humpback whale stock structure under the Marine Mammal Protection Act (MMPA) in light of the 14 Distinct Population Segments established under the Endangered Species Act (ESA) (81 FR 62259, 8 September 2016). A complete revision of the humpback whale stock assessments will be postponed until this review is complete. In the interim, new information on humpback whale mortality and serious injury is provided within this report.

Estimated abundance and trend in aerial counts of beluga whales, Delphinapterus leucas, in Cook Inlet, Alaska, 1994-2012

Aerial surveys of beluga whales, Delphinapterus leucas, have been conducted annually in Cook Inlet, Alaska, from 1993 to 2012. Beluga whales were seen near the coast and within river mouths in all years, with nearly all of the sightings in the northernmost portions of the inlet after 2000. In this paper, we revisit abundance estimates from 1994 to 2012 and present changes in methods and statistical analyses that have occurred since an earlier publication in 2000. Our objectives include a reanalysis of the abundance estimates over the 19-year aerial survey time series (1994–2012), revising the population trajectory through 2012, and estimating population trend rates for endangered Cook Inlet beluga whales. Annual surveys documented a decline of nearly 50% between 1994 and 1998 from an estimated 653 (CV = 0.24) whales to 347 (CV = 0.17) whales. With a very limited hunt (5 whales total taken between 1999 and 2012), the anticipated recovery at a rate of at least 2% per year did not materialize. Instead, from 1999 to 2012, the rate of decline has been -1.60% (SE = 0.75%) per year, with a 97% probability that the growth rate is declining (i.e., less than zero) and a 99.9% probability that the growth rate is less than +2% per year. Introduction In general, beluga whales, Delphinapterus leucas, have strong site fi delity to natal areas and very low dispersal rates (O’Corry-Crowe, 2002). In Alaska, these natal areas occur in the Beaufort Sea, Chukchi Sea, Norton Sound, Bristol Bay, and Cook Inlet. Geographically separated from beluga whale populations in western Alaska, Cook Inlet belugas are genetically distinct (O’Corry-Crowe et al., 1997) and are rarely observed in waters outside the inlet (Laidre et al., 2000). The closest beluga whale population is in Bristol Bay (Lowry et al., 2008), 1,500 km away by sea and separated by the Alaska Peninsula that extends three degrees of latitude south of the southern limit of the Bristol Bay population. If the Cook Inlet population goes extinct, it is highly unlikely that Cook Inlet would be repopulated with beluga whales in the foreseeable future; the result would be a permanent loss of range. Until 1999, Cook Inlet beluga whales were subject to an unregulated subsistence hunt (Mahoney and Shelden, 2000). Following abundance estimates that indicated this stock had declined nearly 50% (from 1994 to 1998), the National Marine Fisheries Service (NMFS) designated the stock as depleted under the U.S. Marine Mammal Protection Act (NOAA, 2000a). During this period of decline, beluga whales taken during the annual hunt ranged in number from 21 to 147 per year (Mahoney and Shelden, 2000), averaging about 70 whales per year killed and struck but not recovered. In 1999, the hunt was suspended and thereafter NMFS co-managed the hunt through a series of agreements with the Native hunting community (NOAA, 2000b). Considering how few whales (only 5) were killed in the subsistence hunt in the 13 years between 1999 and 2012, wildlife managers anticipated that the population would begin to recover. However, the population showed no signs of recovery; accordingly, NMFS determined that the Cook Inlet beluga whale distinct population segment (DPS) was endangered as defi ned by the U.S. Endangered Species Act (ESA) (NOAA, 2008). The abundance estimates noted above were generated from data collected by NMFS personnel from the Alaska Fisheries Science Center’s National Marine Mammal Laboratory and Alaska Regional Offi ce. NMFS conducts annual aerial surveys to study beluga whale distribution and abundance in Cook Inlet, Alaska. These surveys typically occur in June and have been repeated each year since 1993 (Rugh et al., 2000; 2005; Shelden et al., 2013). Abundance estimates from 1994 to 2000 were published in Hobbs et al. (2000a,b). This paper revisits that time period and presents changes in methods and statistical analyses that have occurred since 2000. The objectives of this paper include a reanalysis of the abundance estimates over the 19-year aerial survey time series (1994–2012), revising the population trajectory through 2012, and estimating population trend rates for endangered Cook Inlet beluga whales.

The Northern Extent of Pacific White-Sided Dolphin (Lagenorhynchus obliquidens) Distribution in the Eastern North Pacific

Abstract We present updated distribution information for the Pacific White-sided Dolphin (Lagenorhynchus obliquidens, PWSD) in the southeastern Bering Sea, including Bristol Bay. The northern extent of this dolphins range currently includes Bristol Bay and a 150-km swath north of the Aleutian Island chain, and presence in the Bering Sea has been described as rare. Our review of National Marine Fisheries Service marine mammal survey data (1991 to 2010) and sighting reports from sources such as the Platforms of Opportunity Program, whaling and fisheries catch records, and naturalist reports (1975 to 2016) found numerous sightings (n = 191) and year-round presence within the current range. We also found 18 sightings, 2 of which were bycatch in commercial fisheries, that occurred north of the existing range and in all seasons. Based on these results, we suggest PWSD presence in the Bering Sea is not rare, occurs year-round, extends farther north than shown on current range maps, and that site-fidelity may occur in areas near and within Bristol Bay.