Some issues of ecology and biology of brown king crab (Lithodes aequispinus, Bеnedict, 1895) in the east part of the Sea of Okhotsk

Analysis of the distribution of size-functional groups of brown king crab on the continental spole in the eastern part of the Sea of Okhotsk was provided based on the data collected in 1998–2003. Aggergation rates were evaluated for males and females. Size structure of the population depended on the depth and site. Recommendations for maximum efficient fishery are provided.

On the intraspecific competition of yellowfin sole Limanda aspera (Pallas, [1814]) (Pleuronectidae) in the eastern part of the Sea of Okhotsk

Based on the longterm observations for 1963–2019, the article provides an assessment of the yellowfin sole generation mortality dynamics depending initial abundance and population dynamics in view of abundance and biomass. Individual growth and matiration rates were evaluated in generations with different initial abundance and in different states of population dynamics. Results indicated about intraspecific competition in yellowfin sole in the eastern part of the Sea of Okhotsk, expressed in specifics of the dynamics of stock abundance, growth and maturation. Forming generation stock abundance in early and later ages has different character. The more exceeding number of parental eggs spawned, the more generation abundance of yearlings getting exactly compensated by mortality (complete compensation). Older generations demonstrate the phenomen of “overcompensation”, when mortality of generations appeared in the years of higher egg production exceeds fertility. In the period of population growth and stabilization at a high level the period of the Yellowfin sole abundance fluctuation cycle gets shorter and the amplitude – smaller. Effects of intraspecific competition on the growth of individuals are revealed. Negative effects of the competition authentically revealed in elder age groups were not observed in younger age groups. An increase of the Yellowfin sole abundance brings negative effects on maturation rate of males with almost no such effects on females. To the greatest extent such effects can be seen in young age groups, at the beginning and middle stage of maturation.

Частота встречаемости клубных пар большой конюги (Aethia cristatella) при высокой и резко снизившейся численности птиц в колонии.

The crested auklet is a medium-sized planktivorous seabird of the Alcidae family with complex social behavior, one of the interesting forms of which is the formation of club pairs in addition to existing breeding pairs. The occurrence of club pairs in this species was studied on the Talan Island (Sea of Okhotsk) in 1988-1989, when the colony was in a good condition, and in 2008-2015, when its population decreased several times. The research showed that the proportion of individuals with club partners is higher in a high-population period (35 %) and lower in a low-population period (18 %); the differences, however, are not significant. In both study periods, from 73% (1988-1989) to 80 % (2008-2015) individuals were consistent in following the chosen strategy of forming or not forming club pairs for at least two seasons. The presence of club pairs seems to facilitate the change of mate in the next breeding season, but club mates then become partners relatively seldom.

Частота встречаемости клубных пар большой конюги (Aethia cristatella) при высокой и резко снизившейся численности птиц в колонии.

The crested auklet is a medium-sized planktivorous seabird of the Alcidae family with complex social behavior, one of the interesting forms of which is the formation of club pairs in addition to existing breeding pairs. The occurrence of club pairs in this species was studied on the Talan Island (Sea of Okhotsk) in 1988-1989, when the colony was in a good condition, and in 2008-2015, when its population decreased several times. The research showed that the proportion of individuals with club partners is higher in a high-population period (35 %) and lower in a low-population period (18 %); the differences, however, are not significant. In both study periods, from 73% (1988-1989) to 80 % (2008-2015) individuals were consistent in following the chosen strategy of forming or not forming club pairs for at least two seasons. The presence of club pairs seems to facilitate the change of mate in the next breeding season, but club mates then become partners relatively seldom.

Some data on the biology of stone cockscomb Alectrias alectrolophus (Stichaeidae) from the Tauysk Bay of the Sea of Okhotsk

On the basis of the materials collected in the period of 2010–2018 the features of biology: the size-age structure, linear growth pattern and body mass growth of the stone cockscomb Alectrias alectrolophus from the Tauysk Bay, the Sea of Okhotsk, have been studied. In the intertidal zone, in the period from May to September, individuals of this species the body length 31.2–133.4 mm and body weight 0.1–12.8 g at the age of up to 6+ years are found in large quantities. The size and age characteristics, rates of growth of females and males are quite similar, but in general, females are slightly larger than males.

Spring distribution of capelin Mallotus villosus catervarius in the eastern part of the Sea of Okhotsk in 2000–2019

Data on the local distribution of capelin in the eastern part of the Sea of Okhotsk in 2000–2019 are very limited. Maps of the distribution were made based on results of complex pelagic surveys in 2000–2019. It is demonstrated, that spring distribution of capelin in the Eastern Sea of Okhotsk varied depending temperature conditions in each particular year. Major aggregations of capelin were observed within Shelikhov Gulf in spring. In the “cold” years these aggregations were in the south-western part of the West Kamchatkan shelf, and in the “warm” years – in the north-western part. In sense of bathymetric distribution the main body of the capelin aggregations was observed in the upper part of the shelf at the depth <125 m at the temperatures bit lower zero.

High genetic diversity of bivalve transmissible neoplasia in the blue mussel Mytilus trossulus Gould from the subarctic Sea of Okhotsk

There are increasing findings of the bivalve transmissible neoplasia derived from the Pacific mussel Mytilus trossulus (MtrBTN) in populations of different Mytilus species worldwide. The Subarctic is an area where this disease has not yet been sought despite the fact that Mytilus spp. are widespread there, and M. trossulus itself is a boreal species. We used cytological and histological techniques to diagnose disseminated neoplasia in a sample of M. trossulus from Magadan in the subarctic Sea of Okhotsk. Neoplasia was identified in 11 of 214 mussels studied. Using mtDNA COI sequencing, we revealed genotypes identical or nearly identical to known MtrBTN ones in the hemolymph of most of the diseased mussels. Both MtrBTN evolutionary lineages have been identified, the widespread MtrBTN2, and MtrBTN1, so far only known from M. trossulus in British Columbia on the other side of the Pacific from Magadan. In addition, MtrBTN2 was represented by two common diverged mtDNA haplolineages. These conclusions have been confirmed for selected cancerous mussels by molecular cloning of COI and additional nuclear and mtDNA genes. On the background of high genetic diversity, different cancers were similar in terms of ploidy (range 4.0 - 5.8n) and nuclear to cell ratio. Our study provides the first description of neoplasia and MtrBTN in mussels from the Sea of Okhotsk and from the Subarctic, of both MtrBTN1 and MtrBTN2 in the same mussel population, and the first direct comparison between these transmissible cancers.

ЛЕТНЕЕ ПИТАНИЕ СИВУЧА В ВОДАХ ДАЛЬНЕГО ВОСТОКА РОССИИ В 2004–2008 ГОДАХ

The diet of Steller sea lion Eumetopias jubatus was studied based on undigested food parts found in feces collected in the summer season on 20 rookeries in the Russian Far East. A total of 915 samples were analyzed between 2004 and 2008, in which 65 food items were identified. The frequency of occurrence of 11 diet items was greater than 5%, including Atka mackerel Pleurogrammus monopterygius (64.8%), Pollock Theragra chalcogramma (44.3%), Pacific salmon Salmonidae (20.5%), Irish lord Hemilepidotus sp. (20.4%), Pacific sand lance Ammodytes hexapterus (15.8%), Pacific herring Clupea pallasi (9.5%), Squid and Octopus Cephalopoda (8.4%), Pacific cod Gadus macrocephalus (5, 9%), Pacific sandfish Trichodon trichodon (5.9%), Flatfishes Pleuronectidae (5.8%), Threespine stickleback Gasterosteus aculaeatus (4.9%). Three regions with different diets were identified – the Sea of Okhotsk, the Kuril Islands, and Kamchatka with the Commander Islands. In the Sea of Okhotsk, Pollock and Herring (83.6% by frequency of occurrence) dominated among undigested food remains in feces. The diet at the Kuril Islands rookeries was variable within the region. The general pattern was a low diversity of diet at each Kuril Island sites and predominance of 1-3 food items, probably the most accessible near the sites (Pollock, Squid and Octopus, Atka mackerel, Pacific salmon). The diet pattern in Kamchatka and the Commander Islands in the summer season was characterized by a high diet diversity. In contrast to other regions, the diet includes in high proportion small non-commercial species – Sand lance, Irish lord, Pacific sandfish, Flatfishes, Threespine stickleback and others. The regional patterns of sea lion diets show the spatial distribution and areas of abundant biomass of the main food items. The diet patterns of sea lions from rookeries differed from haulouts in having a higher content of abundant food items. Long-term changes in diet structure were not statistically significant.