BIOLOGICAL RESOURCES
Japanese anchovy Engraulis japonicus of the Tsushima Current stock migrate to the northwestern Japan Sea in warm season and play there an important role in the pelagic food web. According to survey and fishery data, the commercial stock of this species declines recently that determines decreasing of intensity of its migrations into the Russian waters, though its level is still appropriate for fishery. The anchovy releases ashore occur sometimes on the Far-Eastern coast, likely in cases of unstable environments that have become more frequent under climate change. More intense research of the pelagic ecosystem in the northwestern Japan Sea is necessary to clarify the status of fishery resources formed by southern migrants, including anchovy, sardine and mackerel.
For the first time, ecological evolution of salmonid fishes is analyzed using the method of historical biogeography, considering formation of ecology and reproductive biology for these species under planetary climatic and geological changes. Climate cooling in the Cenozoic and associated reconstruction of the food base for salmonids had a major impact on evolution of their ecology. This process began at the Asian coast of the North Pacific much earlier than at the American coast and was much more intense there. The salmonids developed marine and oceanic feeding that led to their stocks increasing and a subsequent imbalance with freshwater prey. Adapting to this imbalance, the species of gen. Oncorhynchus came to irreversible reduction of organs and functions in the fresh water and absolute mortality of producers. Egg development lengthened in cold environments, and anadromous and semi-anadromous salmonid species were forced to spawn earlier, so that the larvae would hatch during the spring bloom of their prey. Gradually, the timing of their spawning shifted from early spring to winter and then to fall; accordingly, the spawning run to the rivers began earlier, in particular in the northern areas. The spawning season of atlantic salmon Salmo salar and brown trout Salmo trutta shifted to a fall and spring-summer spawning run in the north of their range and to a winter-spring and fall spawning run in the south of their range, but there is currently no reason to consider these runs as seasonal races, given that both cases evolved from a single run in the process of evolutionary changes when the spawning season was interrupted by either winter cooling or summer warming in the lower river reaches and at the coast. The northern and southern populations of salmonid fishes in the Pacific separated, too, because of these ecological changes in the late Pliocene, in conditions of cold climate. Being in isolation, they diverged enough to be considered as separate taxa rather than seasonal races.
Dynamics of integral parameters for the species structure in ichthyocenosis of the upper epipelagic layer in the Pacific waters off the Kuril Islands in 2019–2023 is discussed in compare with previously published data since 2004 in context of a new bloom of japanese sardine Sardinops melanostictus. Results of trawl surveys are clustered using the method of multi-dimensional scaling. Species composition in the trawl catches in 2004–2013, before the time of mass expansion of subtropi-cal migrants, as japanese sardine and chub mackerel Scomber japonicus, was distinguished by domina-tion of mesopelagic fishes of families Myctophidae and Microstomatidae and pink salmon Oncorhynchus gorbuscha. From 2014 to the present, the dominant positions in the ichthyocenosis were held by japanese sardine and chub mackerel, with a decreasing role of the latter. In the last pentade (2019–2023), the species structure of pelagic ichthyocenosis in the Pacific waters of Russia has not undergone fundamental changes. At the same time, the tendency has increased for uneven distribution of biomass between the species of fish community in favor of japanese sardine. The polydominance index decreased significantly (P < 0.05, t-test 4.33) from 4.85 ± 0.44 in 2004–2013 to 2.37 ± 0.21 in 2019–2022, and the index of evenness of species structure decreased from 0.41 ± 0.04 to 0.15 ± 0.02 (P < 0.05, t-criterion 5.25). Growth of domestic and foreign catches of japanese sardine in the second decade of the 21 century is a sign of this species bloom beginning.
Several stages are determined in the early run of sockeye salmon into tributaries of Lake Nachikinskoye: i) maturation of adults at depth, ii) concentration of adults in the mouths of the main tributaries, iii) entry of small flocks of the spawners into tributaries over a short distance, iv) upstream movement of lager flocks, v) thinning of flocks and formation of pairs, vi) spawning, and vii) death of spawned fish. In the large, stable accumulations formed in the mouths of tributaries, salmon choose paths for onward movement in the process of homing, by decoding imprinting information. There, aggregations of spawners are differentiated into separate flocks going to spawn on different spawning grounds. A peculiarity of this population of sockeye salmon is the retention of individuals not ready for spawning in many pits and catches of the rivers, with formation of well-visible compact schools, which dissipate as the fish mature. Filling of the spawning grounds in tributaries is determined by their characteristics, and typically occurs with a dome-shaped dynamics of intensity. The upward long-term trend in filling of the spawning grounds is observed in the lower Taburetka River (before its tributaries), while the downward trend — in the tributaries. Data on the filling for the last 5 years are presented. The greatest contribution to reproduction of the early sockeye salmon in Lake Nachikinskoye is provided by the lower reaches of the Taburetka River (41 %), whereas its tributary, the Verkhnyaya River, contributes 20 % and inputs of other tributaries are noticeably lower. In conditions of degradation for a part of the spawning grounds due to increased anthropogenic impact, all existing subpopulations should be preserved as productive as possible.
Changes in the spawning part of the Bolshaya River population of coho salmon are considered for 1941–2023. Long-term trends are revealed for the most important biological parameters of adults, in particular, decreasing in size, weight (except of late-race females), and fecundity of returning fish. The parameters for different races and sexes in different periods of time are compared statistically, with frequency analysis. Influence of duration of freshwater and marine feeding on size, weight and fecundity of coho salmon is estimated. The portion of this species in salmon catches in the Bolshaya River basin was 19 %, on average, in 1941–2023, the second after pink salmon. In 2007–2023, the catch and reproduction rate of coho salmon exceeded the average values for 1972–2002 by an order, though their registered escapement to the river decreased in 3 times. Obviously, the spawning runs were underestimated. Increasing the funding of aerial surveys on coho salmon is proposed, to make them longer and more extended and detailed. Besides, the passing of salmon to the spawning grounds can be modeled on the data of reproduction multiplicity.
Resources of red algae Ahnfeltia tobuchiensis (Kanno et Matsubara) and volumes of this alga storm releases in the Okhotsk and Japan Seas are considered. In the last decade, the stable commercial stocks are maintained in the Izmena Bay (about 70∙103 t) and Peter the Great Bay (about 45∙103 t); the field in Aniva Bay is depressed with a tendency to disappear. Storm releases accumulate annually on shores of Peter the Great Bay about 5,000 t of A. tobuchiensis suitable for use in agriculture. Prospects for using the red algae as a source of various chemical compounds in the food industry and agriculture are described. Particular attention is paid to polysaccharides, pigments, polyphenols, peptides and other biologically active compounds. Recommendations are given for processing the storm emissions of A. tobuchiensis, primarily in organic farming.
ENVIRONMENTS OF FISHERIES RESOURCES
Lake Blagodatnoye is an oligohaline meromictic reservoir with the two-layer vertical structure — a typical lagoon lake for the southern Far East of Russia. Its upper layer is occupied by fresh water and the lower layer — by brackish water. The greatest warming of water (up to 22 оC) is observed at the lake surface in late July — early August. In total, 274 species are found in phytoplankton of the lake that is the largest number among all surveyed lagoon lakes in the south of Sakhalin-Kuril region. Bacillariophyta form the basis of the phytoplankton species composition (64 % of species). Abundance and biomass of the phytoplankton vary widely from 1.15 . 106 to 160.44 . 106 cells/L and from 0.41 to 6.14 g/m3, respectively. Several peaks are noted in seasonal dynamics of these indices. Zooplankton in the lake includes 25 species. All these species are typical for lagoon lakes in the south of Sakhalin-Kuril region. Wide variations in abundance and biomass are noted for the zooplankton: from 10550 to 99350 ind./m3 and from 47.1 to 231.0 mg/m3, respectively. Two types of species composition are identified in the summer succession of the phytoand zooplankton communities. The phytoplankton groups change at the border between June and July, when temperature at the surface passes the value of 14–16 оC. The key species of the early-summer phytoplankton are Cyanobacteria of genera Aphanocapsa, Chroococcus, Microcystis, Anabaena and Bacillariophyta of the genus Asterionella, whereas Aulacoseira granulata and A. granulata var. angutissima are the most abundant in late summer. For zooplankton, the boundary between the early-summer and late-summer seasons is shifted to middle July when the water temperature rises to 17–18 оC. Rotifera of Asplanchna priodonta, Cladocera of Bosmina sp., younger copepodites of Cyclops and Eurytemora caspica tethysiana dominate in early summer, whereas Bosmina sp. and juveniles of Cyclops — in late summer. Macrozoobenthos in the lake is represented by 25 species of invertebrates. The basis of species diversity is formed by amphibiotic insects. Number of species and total distribution density and biomass of macrozoobenthos mostly declined with the depth: there were 18 species, 370 ± 50 ind./m2, 3.023 ± 0.459 g/m2 in the intertidal zone, 14 species, 580 ± 59 ind./m2, 3.477 ± 0.447 g/m2 in the elittoral zone, and 10 species, 364 ± 36 ind./m2, 2.110 ± 0.248 g/m2 in the profundal zone, and dominant species were changed from Amphipoda Eogammarus barbatus in the intertidal zone to Chironomidae Chironomus dorsalis in the elittoral zone and to Gastropoda Cincinna japonica, Oligochaeta Lumbriculus variegatus and Chironomidae C. dorsalis in the profundal zone. The phytoplankton production in the coastal zone (depth of 0–3 m) was estimated as 552.86 kcal/m2 in June-August. Zooplankton consumed only 0.7 % of this production and produced 767 cal/m2. The production of non-predatory zoobenthos was 8644 cal/m2, with the inputs of 70.2 % for detritus feeders of 70.2 %, 11.8 % for macroalgae feeders, 11.6 % for deposit feeders, 5.8 % for grazers, and 0.6 % for filtered suspension feeders. A part of this production (6.9 %) was transmitted to the feed of carnivorous zoobenthos, so 8286 cal/m2 of the macrozoobenthos production could be used for fish feeding in the coastal zone. The phytoplankton production in the open waters (depth of 3–9 m) was estimated in 2580 kcal/m2. Zooplankton consumed 1.01 % of this production and produced 3578 cal/m2. The production of non-predatory zoobenthos in this zone was 6179 cal/m2 (detritus feeders 68.1 %, deposit feeders 18.8 %, grazers 6.6 %, macroalgae feeders 3.0 %, and filtered suspension feeders 3.5 %). The portion of 12.7 % of this production was transmitted to the feed of carnivorous zoobenthos. The total macrozoobenthos production in the open waters was 5708 cal/m2. The total reserve of food for fish, including zooplankton and benthos, was evaluated in 9286 cal/m2.
Representative sets of biotic and abiotic parameters were taken from maps of their distribution at the sea bottom, using interpolation. Good correspondence between real and modeled data was noted that allowed to engage the latter for correct estimation of the mean explained variance (MEV) by regression analysis. The magnitude and structure of MEV variability depended on external influence that proves possibility of its application as a measure for total effect of abiotic factors. Among many variants of the ecological stress index (PES), the more convenient for modeling was that one with the maximum correlation between distribution density or biomass of certain taxa and the total density or biomass of macrozoobenthos at stations (in samples). This approach provides better biological plausibility, as well, so as the benthic dwellers, like other animals, are very diverse in size and interspecific relations, that’s why the distribution density of a species correlates well with either total density or total biomass, and the same for biomass of a species. Results of in situ studies of PES dependence on MEV were confirmed by modeling with virtual MEV values. The difference between real and modeled PES values was statistically insignificant, but the MEV ranged wider in the models with virtual values and the dependence curve had weaker inflection when reached a plateau. The final dependence is S-shaped (r2 = 0.939), with the greatest curvature at 85.4 % of MEV (PES of 15 %), and the point of minimum or beginning of growth (beginning of the model curve plateauing) at 94.0 % of MEV (PES of 36 %). These levels are critical for macrozoobenthos communities. The PES level for the 2nd critical level was previously estimated as 30 %, but this value was corrected to 36 % by calculation with biologically more reasonable method.
Long-term dynamics of the food base for nekton in the deep-sea waters of the western Bering Sea are analyzed on the data of ecosystem surveys in 1986–2022. The main patterns of species composition and structure are determined for the main taxonomic groups of zooplankton and their production is evaluated. These features are influenced by climateoceanographic and biocenotic factors, with priority of the climate-oceanographic ones, whereas the biocenotic factors are conditioned by them. As an example of biocenotic impact, the effect of chaetognats on copepods is considered. Trophic characteristics of the most abundant species of pacific salmon (chum salmon Oncorhynchus keta and pink salmon O. gorbuscha) and their consumption of zooplankton production were estimated for 2020–2022. Comparing productivity and grazing of the main zooplankton groups, there is concluded that pacific salmon consume a small portion from seasonal production of their prey, therefore, food competition between the species of pacific salmon is absent in the deep-sea waters.
Accumulation of persistent organochlorine pesticides (OCP) in fat tissue was examined for the mammals found released ashore along the Crimean coast of the Black Sea in 2018–2022. This group of animals is positioned at the top of food chain in the local marine ecosystem. Statistically significant dependence of the accumulation on sex (males are more contaminated than females) and age (adults and juveniles are more contaminated than calves and neonates) is found. Besides, the pesticides concentration in fat from dorsal tissue is generally higher than in fat from caudal stem, but the difference is not significant. In the tissue of harbor porpoises and common dolphins, the mean OCP concentration decreased in the order: p,p′-DDE > β-HCH > p,p′-DDD > p,p′-DDT, whereas bottlenose dolphins had the order: p,p′-DDE > p,p′-DDD > β-HCH > p,p′-DDT. The most common metabolites were DDE, and their accumulation was the highest. The concentration of DDD was considerably lower, and significant accumulation of DDT was observed rarely, so the mean concentration of these group of metabolites was the lowest.
Species composition, distribution density and biomass of phytoplankton were surveyed in the coastal area of eastern Aniva Bay in May-October 2018. In total, 297 species and intraspecific taxa of microalgae belonged to Bacillariophyta, Chlorophyta, Cryptophyta, Dinophyta, Euglenophyta, Crysophyta were found. Their total abundance ranged from 14.8 . 103 to 1024.7 . 103 cells/L, biomass was 19.4–324.6 mg/m3. Two peaks in the abundance (in June and October) and five peaks in the biomass (in May, June, September and October) were noted. The bulk of population was formed by diatoms in spring and autumn, and flagellates in summer. A bloom of potentially toxic diatoms of genus Pseudo-nitzschia was registered. In this connection, monitoring of toxic species is necessary for planning and development of aquaculture farms.
AQUACULTURE
A plant and method of the sea cucumber cultivation have been developed and successfully tested. The technology allows to grow sea cucumber Apostichopus japonicus (Selenka, 1867) from juveniles of the current year to adults of commercial size on grounds in unprotected water areas and bottom landscapes unfavorable for habitat of this species. The plant consisted of 5 open-type cages with the size 20x20x1 m mounted on the sea bottom and occupied the area of 400 m2 each (2000 m2 in total). The tests were carried out from the fall of 2018 to late November 2023. After the first two years, only 20.5 % of initial number of resettled factory juveniles had survived, then the number of sea cucumbers stabilized and their distribution density was on average 2.7 ind./m2 (364.4 g/m2) by the end of the experiment. The stock in the cages was replenished annually by larvae from the natural larval pool that was estimated in 6.9 % per year. Monthly weight gains were on average 2.6 g in the last three years of cultivation, though sea cucumbers grew in 3−4 times slower in winter than in summer. The body weight of sea cucumbers by the end of the experiment was 143.9 g/ind., on average. After 5-year exposition, the portion of commercial-sized sea cucumbers (weight ≥ 130 grams) in the cages reached 58.5 % by number and 74.7 % by biomass; their average body weight was 183.6 g. The density of such sea cucumbers distribution in the bottom open-type cages of the plant was 1.5 ind./m2 (272.2 g/m2), on average. Total yield of commercial-sized sea cucumbers harvested from the plant in late November 2023 was 435 kg.
Technology of feed additive for fry feeding in fish farms is developed to provide both important nutrients (proteins, lipids, etc.) and optimal peptide composition of protein that is achieved using proteolysis of raw materials under certain conditions. For this purpose, enzymatic hydrolysis of substandard small-sized frozen pollock was used. The rational duration of the hydrolysis process was 60 min. that provided the degree of protein hydrolysis of 26–28 %. The experimental fermentolysate was concentrated to a water content of 3–4 % and presented as a feed additive TINRO-60. This product is compared with other feed additives (dried fermentolysates) produced in Russia from fish raw materials using bioconversion, such as Biomarin, Bioprom and Vakhob. General chemical composition of tested products was determined by standard methods of analytical chemistry; composition and content of fatty acids — by gas-liquid chromatography; microand macroelements, as well as toxic metals — by atomic absorption spectrophotometry; fractional composition of proteins and peptides — by high pressure gel permeation chromatography; amino acid composition — by ion exchange chromatography on a high-speed analyzer. All tested samples contain similar amount of the main feed component — protein substances. The quantitative ratio of peptide fractions is also comparable, the sum of the most active fractions (MW 0.1−10.0 kDa) in TINRO-60 and Biomarin is close to their level in tissues of Artemia, natural food for fish fry. The content of essential amino acids, EPA and DHA is significant in Biomarin, TINRO-60 and Bioprom, but almost twice lower in Vakhob. Analysis of mineral composition showed that bioconversion into dry fermentolysates does not cause concentration of toxic elements. High quality of the protein feed additive TINRO-60 produced by bioconversion of nonstandard fish raw materials under certain conditions is proved.
METHODS OF INVESTIGATIONS
Several regression models for predicting returns of pink salmon in the Kamchatka region are presented. The data for 1990–2023 were analyzed. Among available climatic and oceanological indices, the most suitable for using as predictors for forecasting of pink salmon returns were the Pacific Decadal Oscillation (PDO) index, Western Pacific Cyclonic Index (WP), Arctic Oscillation (AO) index, and the sea surface temperature anomaly in the North Pacific. Multi-dimensional models of the «stock–recruitment» type were built on identified statistical patterns, which allowed to estimate potential abundance of the pink salmon returns to northeastern and western Kamchatka. Besides, methods for predicting the abundance of pink salmon returns on the data of fish counting in the sea are considered, using the materials of TINRO trawl surveys conducted in the Bering and Okhotsk Seas in the fall seasons of 2012–2023. To determine the abundance of pink salmon originated from West Kamchatka, genetic identification of regional composition of juveniles in mixed trawl catches was used. All tested methods have a high level of determination, but simpler regressive models are more prospective for practical forecasting of general trend in dynamics of pink salmon stocks in the Kamchatka region due to very weak generalization ability of more complicated models.
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