BIOLOGICAL RESOURCES
Saffron cod Eleginus gracilis, being a typical representative of the elittoral ichthyocene, is an important commercial species in the coastal areas of the Far-Eastern Seas. Small- and medium-sized vessels equipped with both active fishing gears as Danish seine or trawl and fixed nets are used for fishery of this species, it is also popular for amateur and sport fishing from the sea ice. The portion of saffron cod in the total landing is the largest in the Karaginsky fishing subzone (8.1 %) and West-Kamchatka fishing subzone (3.6 %). Annual catch of the species in the Far-Eastern Seas fluctuated in 2003–2022 from 16.7 . 103 to 50.6 . 103 t, on average 33.9 . 103 t. The bulk of this value was caught in the waters at Kamchatka, mostly at its western coast where the average catch was 10.5 . 103 t annually in the last decade. The main fishing grounds of saffron cod are located within the Kamchatka-Kuril, West-Kamchatka, East-Sakhalin and Karaginsky fishing subzones, whereas the stocks at Primorye and sparsely populated coasts of the western Okhotsk Sea and northwestern Bering Sea are underexploited. The saffron cod CPUE reaches 4.5 t per hour of trawling on the shelf of West Kamchatka. The biomass of saffron cod is estimated recently as 197.4 . 103 t in the West-Kamchatka subzone, 100.4 . 103 t in the Karaginsky subzone, 32.8 . 103 t in the West Bering Sea fishing zone, 17.2 . 103 t in the Petropavlovsk-Commander subzone, 17.1 . 103 t in the East-Sakhalin sunzone, and 8.7 . 103 t in the North Okhotsk Sea subzone. The species is distinguished by significant fluctuations of commercial stocks caused by both environmental impacts on its recruitment and fishing pressure. The strong year-classes appear usually in relatively warm or moderate environmental conditions. In modern times, abundance and biomass of almost all exploited stocks of saffron cod in the Far-Eastern Seas excess their average long-term level or fluctuate around, so the state of their populations is considered as quite satisfactory.
Diversity of life strategies of pacific salmon (gen. Oncorhynchus) is reviewed on the basis of published data. Cases of polycyclicity and changes in life strategy during the ontogenesis are described.
Dynamics of the main parameters of the Baikal seal population (age and sex structure, size and weight indices, reproductive activity) in the years of experiment with heightened commercial withdrawal of the seals (1977–1985) is analyzed on the base of primary field data collected during the spring hunting. The problem of natural limitation for the population abundance is discussed for the case when further growth is limited by carrying capacity of the habitat. The observed changes of age, sex, size, and reproductive parameters reflected intrapopulation processes of the abundance regulation, weakly associated with trophic and density factors. Despite intensive commercial load and negative consequences of unusually early ice melting in 1981, the number of Baikal seal grew until the late 1980s. The withdrawal did not lead to expected improvement of the population status that was explained by underestimation of the stock. Low level (or complete absence) of biological substantiation for the experiment is noted.
Prospects of resumption the Baikal seal (Pusa sibirica) commercial hunting are discussed. Inconsistency of the materials annually submitted by BaikalNIRO for the State report «On the state of Lake Baikal and measures for its protection» for making important decisions regarding the population of Baikal seal is shown. Studies on the population dynamics and methods of its assessment are considered critically, the problems in monitoring of the population are revealed. Adequacy of the presented data on the seals abundance to their real number is doubtful. Current state of the population is considered as quite prosperous, its abundance is high but not excessive. Carrying capacity of the habitat is a variable and difficult to determine, its dynamics is vague and cannot be considered as a reliable basis for resuming the commercial hunting. Groundlessness of such proposals is substantiated and possible negative consequences are shown.
Sublittoral vegetation in the northwestern Okhotsk Sea is described on the data of diving survey in 2020 and some additional data obtained from 2003 to 2022. Five macroalgae associations (Saccharinetum latissimae, Pseudolessonietum laminarioidae, Alarietum esculentae, Sargassetum miyabeae, and Zosteretum marinae) and one group of red algae communities are identified and classified into 5 alliances, 3 orders and 3 classes. All these associations occur over entire area (from 56º to 59º N), within almost whole range of the surveyed depths (2–11 m), and occupy a total of 88 % of the vegetation cover, with statistically uniform distribution. Coenofloras of the associations are poor: up to 5–6 species or multispecies groups have been noted in every association. The concept of an adaptive zone is proposed as an optimal methodological basis for describing marine sublittoral plant communities in the temperate zone. The sublittoral associations in the study area are considered as elementary Petersen-type communities with on average ¾ of the bottom cover and biomass formed by the main dominant species. These associations and higher syntaxa can be built into the most common floristic system of syntaxonomic classification. The adaptive zone concept allows to solve the problem of subjectivism in selection of syntaxa, so the syntaxonomy becomes closer to natural classification with ecological meaning. Successful applicability of the adaptive zone concept for the algae resources assessment is proven; the stock in the surveyed area of 64 km2 is evaluated as 200 . 103 t.
All available information on gametogenesis of chum salmon Oncorhynchus keta cited in scientific literature is summarized. The phases of indifferent development and sex differentiation are overviewed, specific features of the testes and ovaries development are noted, forming of fecundity is analyzed.
Absolute fecundity of chum salmon Oncorhynchus keta is investigated for the commercial herd dwelled at Iturup Island. Currently, the herd is formed mostly by fish of hatchery origin but has retained the same species and regional features that distinguished it when it was formed mainly due to natural spawning. The value of absolute fecundity is determined for 3833 females and ranges from 769 to 4400 oocytes. For the fish of two dominant age groups (3+ and 4+), this number usually decreases with age, with the exception of particularly large older fish with greater fecundity. Same factors that promote abundance of hatchery fish in the herd also contribute to decreasing of abortive processes in the ovaries, therefore the absolute fecundity correlates closely and positively with the catch of chum salmon in the coastal waters.
A new approach for assessment of the spawning stock of walleye pollock in the northern Okhotsk Sea on the data of ichthyoplankton surveys is proposed. To estimate the actual number of spawned eggs, average age of eggs at each stage of development was determined and the eggs mortality was estimated in dependence on age. For the spring ichthyoplankton surveys in 2019–2023, the eggs mortality was evaluated as 27 % for stage I, 57 % for the stage II, 74 % for the stage III, and 86 % for the stage IV – these portions of the spawned eggs were not caught and counted. So, the number of counted eggs was in 1.7–2.1 times lower that the actual number of spawned eggs. The spawning stock biomass was amounted as 12.9 . 106 t in 2019–2023, on average, on the base of the actual number of eggs determined taking unto account the eggs mortality (while the biomass calculated from the counted number of eggs only would be 6.9 . 106 t). Results of the spawning stock estimation with this new method are comparable with the stock assessments by trawl surveys. The eggs number correction through mortality is recommended for calculation of the spawning stock for walleye pollock in the Okhotsk Sea using the ichthyoplankton method.
The data of trap surveys and observations aboard fishing vessels conducted in the northwestern Tatar Strait (northward from Cape Zolotoy) in 2009–2022 are analyzed. Horsehair crabs dwell along the entire continental coast from Cape Zolotoy in the south to Cape Nakatov in the north, but commercial aggregations with the density on average 232 ind./km2 are concentrated in the southern part of this area (south of 49о N). Seasonal bathymetric migrations of the crab include the fall moving of commercial males from the depths of 10–40 m to the depths of 40–60 m for wintering and their return to shallows in spring. Two dense wintering aggregations are formed usually between Cape Peschany – Cape Mapatsa and southward from 48о00′ N, whereas sparse summer aggregations are widely distributed along the coast. Regardless the season, the aggregations density decreases from south to north. The males are generally larger in the southern aggregations than in the northern ones (on average, 100.3 and 89.8 mm of carapace width, respectively), the difference is statistically significant (p < 0.0001). The stock of horsehair crab in the northwestern Tatar Strait has increased in the last 20 years from136 tons in 2003 to 1580 tons in 2022. Over the past 10 years, the optimal allowable catch in the Primorye subzone north of Cape Zolotoy was utilized less than 50 %. There is no specialized fishery of horsehair crab; the species is caught mainly as bycatch for other shelf crab species. High current level of the stock gives a good background for commercial removal of at least 158 t of horsehair crab without damage to the local population of this species.
ENVIRONMENTS OF FISHERIES RESOURCES
Current ecological state of the Vostok Bay (Peter the Great Bay, Japan Sea) in spring, summer, and autumn seasons is described on the data of CTD profiling, chemical analysis of the water sampled at the sea surface and bottom, and microbial indication of the surface water. Strong seasonal variations are revealed for all examined parameters, driven by monsoon cycle. The winter monsoon in autumn with northwestern wind predominance causes the river runoff weakening and off-shore surge with the water removal from the top of the bay and the compensating inflow along the eastern coast distinguished by heightened values of salinity and dissolved oxygen and low values of biochemical oxygen demand (BOD5 < 1 mg/L). The summer monsoon in spring and summer with southeastern winds increases the river runoff and simultaneously the inflow of fresh water from the open sea, so causes a sharp difference in the water properties between parts of the Vostok Bay. Bioproductivity increases in these seasons that is reflected in increasing of BOD5 (up to 2 mg/L and sometimes more) and organic phosphorus concentration (up to 50 μg/L and more). In July, when the river runoff is blocked in the northwestern sector of the bay by onshore surge, the maximum number of bacteria is recorded there (up to 105 CFU/mL), including Escherichia coli group at all coastal stations in concentrations of 10–100 CFU/mL, which are not observed in the central and open parts of the bay. Among the groups of metal-resistant microorganisms, relative abundance of nickel-resistant bacteria is noted (up to 103 CFU/mL) that is a sign of hydrocarbon fuels combustion. The hydrocarbon pollution is confirmed by ubiquitous distribution of oil-oxidizing and diesel-resistant microorganisms detected mostly (up to 2.8 ∙ 104 CFU/mL in summer) in the northern part of the bay. Generally, the internal northern part of the bay is distinguished by high abundance of microorganisms belonged to different ecological and trophic groups, because of mutual impacts of the rivers, the coastal highway, nearby settlements, and sandy beaches occupied by vacationers in summer.
There is shown using the two-factor covariation analysis ANCOVA that, from the position of statistics, TPFbio is the only truly suitable index for monitoring and assessment the ecological state of the marine environment, whereas the indices AMBI, M-AMBI and BOPA should be considered as limited suitable and the others as unsuitable. Poor efficiency for the most of biota characteristics has the following three main reasons. Firstly, the number of species in samples from the areas subjected to anthropogenic stress is usually insufficient for correct calculations. Secondly, the influence of seasonal and interannual variability is usually significant and cannot be excluded. Thirdly, accurate taxonomic identification is difficult for juveniles of many species that can lead to unjustified under- or overestimation of many biotic parameters.
Typical patterns of the water temperature distribution in the upper mixed layer of the Bering Sea in winter are determined on all available oceanographic data obtainedby research institutions of Russia, Japan, USA, and China. Previously [Luchin, 2023], the data were sorted to two sets presenting «cold» and «warm» winters. The proper set includes 2,492 oceanographic stations and the latter one – 2,130 stations. Spatial distribution of the temperature has some common patterns for both sets: the highest values (3–4 to 5–6 оC) are observed at the central and eastern passages between Aleutian Islands, primarily reflecting the Pacific waters invasion to the sea, then these waters are involved into the large-scale cyclonic gyre over the deep-water basin and transported along the continental slope that is indicated by 3оC isotherm. However, different types of the temperature distribution are well distinguished by prominent difference of its values that is amounted in 1.0–1.5о, up to 3–4о at the northwestern coast including the western part of the eastern Bering Sea slope. A wide set of potential predictors for interannual variability of thermal and dynamic conditions in the Bering Sea are examined using correlation analysis,including the global and regional climatic indices. There is concluded that the winter temperature fields are formed by several key factors, as the warm Pacific waters advection, the basin-scale cyclonic circulation, the vertical and lateral water mixing in the Aleutian sounds and at the continental slope, and fall-winter cooling of the surface layer driven by air–sea heat exchange.
Spatial distribution of chemical parameters, as concentration of dissolved inorganic phosphorus (DIP), inorganic silica, nitrite nitrogen, nitrate nitrogen, ammonium nitrogen, total iron, dissolved oxygen, and biochemical oxygen demand (BOD5) is considered together with species composition, abundance and biomass of phytoplankton on the data of complex survey conducted in the estuary of the Kievka River in May 2020, with special attention to DIP and phytoplankton variations along the salinity gradient in the zone of mixing fresh and saline waters. In the lower Kievka, phytoplankton was studied for the first time. The phytoplankon biomass varied from 0.05 to 0.21 g/m3, proportional to changes in primary production calculated from the DIP balance in the river water moving downstream through the estuary (from 0.02 to 0.23 g/m3km). The highest production and the highest biomass were found in the upper part of the external estuary. The water of Kievka River was initially poor in nutrients, so primary production in its estuary was supported by DIP regenerated in the process of organic matter mineralization in the internal estuary.
To compare the trophic characteristics of pelagic- and bottom-dwelling fish in the western Chukchi Sea, isotopic composition of carbon and nitrogen (δ13С and δ15N) is considered separately for the Subarctic water mass (invaded from the Bering Sea) and local Arctic water mass. In summer of 2018 and 2019, the proper water mass occupied mostly the area southward from 71оN and the latter one – northward from this latitude. The isotopic composition of both pelagic and bottom nekton in the southern area was characterized by higher values of δ13C (up to 2 % higher) and low values of δ15N (up to 1 % lower) in comparison with those in the northern area. That was interpreted that in the southern area, within the water from the Bering Sea, more than 90 % of the sampled bottom fish species were linked with prey from the bottom community. In the northern area, within the Arctic water, all samples of bottom fish were characterized by minimal content of heavy carbon δ13C isotope, comparable with the values in samples of pelagic fish that indicated a significant role of pelagic prey in nutrition of the bottom nekton.
Results of parasitological investigation of saffron cod Eleginus gracilis Tilesius, 1810 are presented. The fish samples were collected in 6 distanced marine areas at the coast of Magadan Region, generally corresponded with local stocks or herds of this species. In total, 29 helminth species are identified, including 8 cestodes, 11 trematodes, 5 nematodes, and 5 acanthocephalans. The highest species diversity of helminths is detected for the saffron cod from the Odyan Bay (24 species) and the lowest – for the saffron cod from the Amakhton Bay (16 species). Occurrence and intensity of infestation is the highest for trematodes Hemiurus levinseni, Podocotyle reflexa, and Brachyphallus crenatus, nematodes Ascarophis pacifica, and acanthocephalans Echinorhynchus gadi and Corynosoma strumosum. The number of detected worm species is close to the total number of these parasites recorded for saffron cod in the Far-Eastern Seas and adjacent Pacific – 33 species (excluding monogeneans). Cestodes Diplocotyle olrikii, trematodes Bucephaloides iskaensis, and acanthocephalans Bolbosoma caenoforme are registered for the first time for saffron cod in the Okhotsk Sea. There is found for the first time in the studied area that saffron cod is a definitive host for trematodes Steganoderma formosum and a paratenic host for acanthocephalans Andracantha mergi. Eight species dangerous from medical and (or) veterinary point are detected: Nybelinia surmenicola, Diphyllobothrium sp., Pyramicocephalus phocarum, Anisakis simplex, Pseudoterranova decipiens, Bolbosoma caenoforme, Corynosoma semerme, and C. strumosum. The data on helminth infestation are not useful for differentiation of the saffron cod sub-populations in the northern Okhotsk Sea because of almost permanent partial mixing of these groups.
The first case of Pyramicocephalus phocarum pl. parasitism on pacific capelin Mallotus catervarius is registered.
AQUACULTURE
Otoliths from 3473 chum salmon spawners caught at the mouth of Naiba River and at Bereznyakovsky and Sokolovsky salmon hatcheries in 2013–2019 are investigated. Almost all of the chum adults caught at the hatcheries were marked at one of them and obviously migrated toward the point where they were released being the fry. Moreover, the most of chum spawners caught at the mouth of Naiba River also had the mark of either Bereznyakovsky or Sokolovsky hatchery, which definitely contributed a significant portion of the total stock of chum salmon in Dolinsky district of Sakhalin region.
A breeding stock of chinese perch was gotten in a warm-water farm located in the southern Far East of Russia, where the experiment is conducted on growing this species up to three years. Combined method of growing in tanks, warm-water fry ponds and cages was used for growing the fingerlings, but two- and three-year old perches were kept in cages only and fed with live and non-living low-value forage fish. There were attempts to train two-year-old perch to feed on wet artificial pellets. By the end of the experiment, three-year-old chinese perches of two size groups had the body weight of 700−880 g with the maximum of 1600 g. Feed costs for the growth of two- and three-year-old fish in the growing seasons were 2.7−3.9 and 5.3−5.6 kg per 1 kg gain, respectively; their survival was 98−100 %. In 2023, the two-year-old perches weighing 0.5−1.1 kg were used for the first time in spawning and their offspring were raised to an average weight of 60 g.
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