Distribution and Abundance of Steller Sea Lions, Eumetopias jubatus, on the Asian Coast, 1720's-2005

We analyzed published and archived records for the past 250 years to assess changes in distribution and abundance of Steller sea lions, Eumetopias jubatus, along the Asian coast from the Bering Strait to the Korean Peninsula. We found that the northern extent of Steller sea lion distribution has not changed but that the southern limit has moved north by some 500–900 km (~300–500 n.mi.) over the past 50 years. Additionally, the number of animals and their distribution has changed on the Commander Islands, Kuril Islands, and Kamchatka Peninsula. We found no changes in the number of rookeries in the northern Sea of Okhotsk, but a new rookery was established at Tuleny Island on the eastern coast of Sakhalin Island. We estimate that the total abundance of Steller sea lions along the Asian coast in the late 19th century was about 115,000 animals; during the 1960’s, the total estimate was about 27,000 (including pups), most of which were in the Kuril Islands. The fewest number of Steller sea lions occurred in the northwestern Pacific in the late 1980’s–early 1990’s when only about 13,000 individuals (including pups) were estimated in the entire region. During the 1990’s, and especially in early 2000, an increasing trend in abundance occurred in most areas. Present estimated abundance of Steller sea lions in Asia is about 16,000 individuals (including about 5,000 pups), about half of which occur in the Kuril Islands. Changes in abundance occurred during all time periods but varied by site and period. Specifically, over the past 150 years Steller sea lion abundance at most sites has changed. There were no rookeries on the Commander Islands between 1850 and 1960 and abundance was low, but by 1977, abundance increased to 4,800 individuals and a rookery was established in the mid 1980’s; abundance there has declined since the early 1980’s and in 2004 only 895 individuals (including 221 pups) were counted during the breeding season. Between 1940 and 2004, abundance along the eastern coast of Kamchatka declined from ~7,000 to ~600 individuals, an overall reduction of 90%. Steller sea lion abundance on the Kuril Islands declined by >90% from the 1800’s to 2005; the most severe decline there occurred during 1969–1981. Steller sea lion numbers in the northern part of the Sea of Okhotsk declined during 1930–2002 from 7,200 to 3,100 individuals. Numbers at Tuleny Island have increased since establishment of a rookery there during 1983–2005 and by immigration from other sites

Results of instrumental aerial survey of ice-associated seals on the ice in the Okhotsk Sea in May 2013

Populations of ice-associated seals in the Okhotsk Sea are assessed using modern instrumental aerial technique. The aerial survey was conducted over a part of the ice-covered area of the Sea on May 1-9, 2013 by means of thermal scan and visual digital photography from the aircraft-laboratory An-38 «Vostok». The ice covered area of the Okhotsk Sea in the time of survey was estimated as 242,000 km2, and 2,993 km2 of it was covered by survey transects with total length 5,617 km. The number of animals on all transects within the equipment swath was counted. Four seal species were identified: bearded, spotted, ribbon, and ringed seals, and their number and distribution were determined. The infra-red scanner recorded 5,730 seals on the ice and 4,360 these animals were photographed including 844 ringed seals, 453 bearded, 721 spotted, 1,805 ribbon, 435 pups non-identified to the species, and 102 non-identified to species adult seals. These assessments were extrapolated over the whole ice-covered area of the Okhotsk Sea using a linear model framework, and the following estimations of the species total abundance were presented (95 % confidence intervals in brackets): 88,253 (64,120-130,320) ringed seals, 39,743 (27,868-60,026) bearded seals, 181,179 (118,392-316,995) ribbon seals, and 84,356 (55,172-113,540) spotted seals. A database on all recorded seals with their «portrait-photos» and accompanying information is created on materials of the aerial survey. The developed instrumental technology can be used as a basis for wider aerial surveys of ice-associated seals in the North Pacific

Pinniped Karyotype Evolution Substantiated by Comparative Chromosome Painting of 10 Pinniped Species (Pinnipedia, Carnivora)

Numerous Carnivora karyotype evolution investigations have been performed by classical and molecular cytogenetics and were supplemented by reconstructions of the Ancestral Carnivora Karyotype (ACK). However, the group of Pinnipedia was not studied in detail. Here we reconstruct pinniped karyotype evolution and refine ACK using published and our new painting data for 10 pinniped species. The combination of human (HSA) and domestic dog (CFA) whole-chromosome painting probes was used for the construction of the comparative chromosome maps for species from all three pinniped families: Odobenidae– Odobenus rosmarus Linnaeus, 1758, Phocidae – Phoca vitulina Linnaeus, 1758, Pusa sibirica Gmelin, 1788, Erignathus barbatus Erxleben, 1777, Phoca largha Pallas, 1811, Phoca hispida Schreber, 1775 and Otariidae – Eumetopias jubatus Schreber, 1775, Callorhinus ursinus Linnaeus, 1758, Phocarctos hookeri Gray, 1844, Arctocephalus forsteri Lesson, 1828. HSA and CFA autosome painting probes have delineated 32 and 68 conservative autosome segments in the studied genomes. The comparative painting in Pinnipedia supports monophyletic origin of pinnipeds, shows that pinniped karyotype evolution was characterized by slow rate of genome rearrangements (less then one rearrangement per 10 million years), provides strong support for refined structure of ACK with 2n = 38 and specifies plausible order of dog chromosome synthenic segments on ancestral Carnivora chromosomes. The heterochromatin, telomere and ribosomal DNA distribution was studied in all 10 species

Establishing of local population, population dynamics and current abundance of Steller sea lion ( <i>Eumetopias jubatus</i>) in the Commander Islands

The time course of the establishment of a local population of Steller sea lions in the Commander Islands, population dynamics and current abundance were studied using literature published since the 1930s and the author’s observations conducted during breeding seasons 2008-2011. The local population of Steller sea lions started formation in the early 1960s, when mature females first began to populate the islands and the population was fully established in the early 1990s. The whole process of development the Commander Islands Steller sea lion sub-population took about three decades. Abundance of adult and juvenile sea lions fluctuated highly in 1991-2011 without any statistically significant trend, but numbers of pups had a pronounced negative slope mostly due to three sharp declines in pup production in 2000, 2009, and 2011. A total of about 700 animals of age 1+ inhabit the islands during the breeding season and about 200 pups are born annually at the present time. This total number of Steller sea lions is close to the mean value for the period after 1990s. Nevertheless, occasional sharp declines in pup production cause some anxiety, so far as they could lead to extinction of the Steller sea lion sub-population in this area as had occurred in the middle of the 19th century

Karyotype Evolution in 10 Pinniped Species: Variability of Heterochromatin versus High Conservatism of Euchromatin as Revealed by Comparative Molecular Cytogenetics

Pinnipedia karyotype evolution was studied here using human, domestic dog, and stone marten whole-chromosome painting probes to obtain comparative chromosome maps among species of Odobenidae (Odobenus rosmarus), Phocidae (Phoca vitulina, Phoca largha, Phoca hispida, Pusa sibirica, Erignathus barbatus), and Otariidae (Eumetopias jubatus, Callorhinus ursinus, Phocarctos hookeri, and Arctocephalus forsteri). Structural and functional chromosomal features were assessed with telomere repeat and ribosomal-DNA probes and by CBG (C-bands revealed by barium hydroxide treatment followed by Giemsa staining) and CDAG (Chromomycin A3-DAPI after G-banding) methods. We demonstrated diversity of heterochromatin among pinniped karyotypes in terms of localization, size, and nucleotide composition. For the first time, an intrachromosomal rearrangement common for Otariidae and Odobenidae was revealed. We postulate that the order of evolutionarily conserved segments in the analyzed pinnipeds is the same as the order proposed for the ancestral Carnivora karyotype (2n = 38). The evolution of conserved genomes of pinnipeds has been accompanied by few fusion events (less than one rearrangement per 10 million years) and by novel intrachromosomal changes including the emergence of new centromeres and pericentric inversion/centromere repositioning. The observed interspecific diversity of pinniped karyotypes driven by constitutive heterochromatin variation likely has played an important role in karyotype evolution of pinnipeds, thereby contributing to the differences of pinnipeds’ chromosome sets

Assessment of genetic structure among eastern North Pacific gray whales on their feeding grounds

Although most eastern North Pacific (ENP) gray whales feed in the Bering, Beaufort, and Chukchi Seas during summer and fall, a small number of individuals, referred to as the Pacific Coast Feeding Group (PCFG), show intra- and interseasonal fidelity to feeding areas from northern California through southeastern Alaska. We used both mitochondrial DNA (mtDNA) and 12 microsatellite markers to assess whether stock structure exists among feeding grounds used by ENP gray whales. Significant mtDNA differentiation was found when samples representing the PCFG (n = 71) were compared with samples (n = 103) collected from animals feeding further north (Fₛₜ = 0.012, P = 0.0045). No significant nuclear differences were detected. These results indicate that matrilineal fidelity plays a role in creating structure among feeding grounds but suggests that individuals from different feeding areas may interbreed. Haplotype diversities were similar between strata (hₚCFG = 0.945, hₙₒᵣₜₕₑᵣₙ = 0.952), which, in combination with the low level of mtDNA differentiation identified, suggested that some immigration into the PCFG could be occurring. These results are important in evaluating the management of ENP gray whales, especially in light of the Makah Tribe’s proposal to resume whaling in an area of the Washington coast utilized by both PCFG and migrating whales

Killer whales and marine mammal trends in the North Pacific : a re-examination of evidence for sequential megafauna collapse and the prey-switching hypothesis

This paper is not subject to U.S. copyright. The definitive version was published in Marine Mammal Science 23 (2007): 766–802, doi:10.1111/j.1748-7692.2006.00093.x.Springer et al. (2003) contend that sequential declines occurred in North Pacific populations of harbor and fur seals, Steller sea lions, and sea otters. They hypothesize that these were due to increased predation by killer whales, when industrial whaling's removal of large whales as a supposed primary food source precipitated a prey switch. Using a regional approach, we reexamined whale catch data, killer whale predation observations, and the current biomass and trends of potential prey, and found little support for the prey-switching hypothesis. Large whale biomass in the Bering Sea did not decline as much as suggested by Springer et al., and much of the reduction occurred 50–100 yr ago, well before the declines of pinnipeds and sea otters began; thus, the need to switch prey starting in the 1970s is doubtful. With the sole exception that the sea otter decline followed the decline of pinnipeds, the reported declines were not in fact sequential. Given this, it is unlikely that a sequential megafaunal collapse from whales to sea otters occurred. The spatial and temporal patterns of pinniped and sea otter population trends are more complex than Springer et al. suggest, and are often inconsistent with their hypothesis. Populations remained stable or increased in many areas, despite extensive historical whaling and high killer whale abundance. Furthermore, observed killer whale predation has largely involved pinnipeds and small cetaceans; there is little evidence that large whales were ever a major prey item in high latitudes. Small cetaceans (ignored by Springer et al.) were likely abundant throughout the period. Overall, we suggest that the Springer et al. hypothesis represents a misleading and simplistic view of events and trophic relationships within this complex marine ecosystem