Distribution of eggs and adults of alaska plaice Pleuronectes quadrituberculatus and flathead sole Hippoglossoides elassodon (Pleuronectidae) in the Pacific waters of Kamchatka

Distribution and biological parameters are considered for eggs and adults of two flatfish species on the data of annual surveys conducted on the shelf of southeastern Kamchatka in summer of 2011–2014 and 2016–2019. The eggs of Pleuronectes quadrituberculatus were sampled mostly at the stage of a germinal strip forming, whereas the eggs of Hippoglossoides elassodon were mostly at the stage of embryo cleavage. The main congestions of the eggs were found in the Kronotsky Bay and northern Avachinsky Bay. The adults of both species concentrated mainly in the northern Kronotsky Bay, at Cape Povorotny. Old age groups prevailed in aggregations of P. quadrituberculatus, but middle-age and young fish — in the aggregations of H. elassodon.

On reproductive biology of tanner crab Chionoecetes bairdi Rathbun, 1924 (Crustacea, Decapoda) females at southeastern Kamchatka

Fecundity and some other reproductive characteristics of tanner crab Chionoecetes bairdi females are studied for the first time in the area at southeastern Kamchatka on the materials collected in spring and summer aboard research vessels (in 2016 and 2019) and fishing boats (in 2020). The females with new eggs prevailed in the catches. The size of functional sexual maturity was determined as 79 mm. The implemented fertility was estimated as 93.4 ± 28.1.103 eggs in 2016 and 115.7 ± 24.5.103 eggs in 2019, on average. Reproductive effort and K/r-coefficient were evaluated; their relatively high values confirmed r-strategy of tanner crab reproduction.

State of stocks of pacific salmons in the basin of Avacha Bay (southeastern Kamchatka) in 1985–2019

State of pacific salmon stocks is considered for the basins of the Avacha and Paratunka Rivers in 1985–2019. Significant decline of the stocks is noted that is associated with anthropogenic impact growth. Total number of producers for five salmon species in the Paratunka is almost twice higher than in the Avacha, with the largest portion of pink salmon, then chum salmon, lower portion of coho salmon, and the smallest portions of sockeye and chinook salmons, which need special protection. The main biological parameters of salmons are analyzed for both rivers, as body length, weight, fecundity, sex ratio and age structure, by species. Relationships between the parameters are revealed; their long-term trends are determined. Abundance of wildly and artificially hatched chum salmon is compared.

INFLUENCE OF ANTHROPOGENIC POLLUTION ON MACROPHYTE ALGAE OF AVACHA BAY (SOUTHEASTERN KAMCHATKA)

The results of assessing the sources and degree of anthropogenic pollution of the Avacha Bay (southeastern Kamchatka) are presented. The main sources of anthropogenic pollution of the bay and surrounding areas are towns and villages located on its shores, as well as its tributaries — the Avacha and Paratunka rivers. The Bay is permanently polluted with petroleum products, phenols, detergents, salts of heavy metals, and radioactive substances. The coastal waters of the Kamchatka Peninsula contain the most significant reserves of brown algae, mainly represented by the kelp order, including Fucus distichus subsp. evanescens and Eualaria fistulosa. In the Avacha Bay, micropopulations of some species of algae underwent changes, so the brown algae Eualaria fistulosa is currently found only in the estuary of the Avacha Bay. According to the latest data, E. fistulosa is found in the Bay in very small amounts, and in storm emissions it is recorded in the form of separate individual parts. The complex of indicators proves that the most contaminated hypertoxic sections of the coast include the shoreline starting from the Nikolskaya hill, coasts of Rakovaya, Mokhovaya, Seroglazka, and Petropavlovskiy Kovsh bays, where the entire fucoid belt was almost destroyed. The authors highlight the importance of regular environmental monitoring of the Avacha Bay. Much attention is given to urgency of technological reconstruction of sewage and sewage treatment plants, as well as the lifting of sunken ships and other large metal garbage.

CURRENT STATE OF STOCK FOR TANNER CRAB CHIONOECETES BAIRDI RATHBUN, 1924 (CRUSTACEA, DECAPODA) AT THE SOUTH-EASTERN COAST OF KAMCHATKA

Tanner crab Chionoecetes bairdi is the highly valuable object of commercial fishery dwelling in the seas surrounding Kamchatka Peninsula. Its landings started at the southeastern coast of Kamchatka in early 1980s and continued till 2009, when the fishery was stopped by reasons independent on the stock state. It was launched again in 2017. Now the species is landed mostly in the Petropavlovskaya fishery subzone (62 % of the total allowable catch of tanner crab in Russia in 2019), whereas its stocks at southwestern Kamchatka and in the northwestern Bering Sea are rather low. Modern condition of the tanner crab population and its distribution at southeastern Kamchatka are considered on the data of the trap surveys conducted in spring and summer of 2012 and 2018. Between these years, commercial males of these species spread wider at southeastern Kamchatka and formed commercial aggregations in the northern Avachinsky Bay and in the southern and central parts of the Kronotsky Bay, but were rare southward from Cape Povorotny. They became larger: while size of the males varied in the range 50–170 mm in both years, the males with the carapace width < 120 mm prevailed in 2012, but the large-sized males with commercial size were more numerous in 2018. Percentage of the females in the catches was low both in 2012 and 2018 that is typical for the trap catches. The crabs at the 3rd stage of molting dominated both in May and August of 2012 and 2018. Injury level of the commercial males was rather high and increased from 2012 to 2018 in 8 %. Good current condition of the tanner crab population at southeastern Kamchatka is concluded.