Atlantic Research Institute of Fisheries and Oceanography

The Curonian Lagoon is located in the southwestern part of the Baltic Sea and is geographically under the administrative control of the Russian Federation and the Republic of Lithuania. The water body is connected to the Baltic Sea by a narrow strait in the northern part located in the Republic of Lithuania. About 50 species of fish live in the lagoon, of which 25 species are of commercial importance. The European smelt Osmerus eperlanus is a migratory species; it spawns in the rivers of the Curonian Lagoon, the main spawning grounds are in the Neman, Deima, and Matrosovka rivers. Most of their life smelts live in the Baltic Sea where they fatten up. The spawning part of the smelt population is caught in the Curonian Lagoon. In commercial catches, smelt are represented by individuals from 1 to 6 years old, for the most part, individuals mature at the age of 2 to 3 years. The research used reproductive figures for smelt from 1989 to 2001. The weight of females varied from 8.3 to 113.4 g, averaging 47.2 g. The absolute individual fertility of smelts varied from 3,300 to 93,100 eggs averaging 32,000 eggs. The relative individual fertility averaged 900 eggs/g. The gonadosomatic index (reproductive effort) averaged 0.27, the egg diameter varied from 0.59 to 0.98 mm averaging 0.77 mm. It can be concluded that the reproductive performance of the European smelt O. eperlanus exceeded the reproductive performance of smelts in other water bodies of the northwest of the Russian Federation. The smelt fertility study in the Curonian Lagoon showed that the reproductive capacity of the species is in good condition, which is apparently due to good trophic conditions in the feeding area, the Baltic Sea.

The work provides information on the patterns of species composition of catches from the Russian fishing vessels conducted fishing of jack mackerel (Trachurus murphyi Nichols 1920), chub mackerel (Scomber japonicus Houttuyn 1782) and redbait (Emmelichthys spp.) in the South-Eastern Pacific Ocean outside the economic zones of the coastal States. According to scientific observations, an analysis of the composition of species caught by the Russian fishing vessels is given. When fishing in the pelagic zone over ocean depths, jack mackerel was the main target species, chub mackerel formed the bycatch. At the same time, the proportion of chub mackerel in catches in the northern parts was higher than in the southern ones. When fishing on seamounts of the Nazca Ridge, catches were dominated by redbait with jack mackerel and alfonsino (Beryx splendens Lowe, 1834) as bycatch. According to the similarity of the species composition of catches, three areas – 1) all the Southern and Central subareas and part of the Northern subarea; 2) seamounts of Nazca ridge; 3) part of the Northern subarea near the border of the EEZ of Peru between 17–20°S, were singled out using the cluster analysis method.

The structure and dynamics of plankton communities in the coastal zone of the Curonian Lagoon of the Baltic Sea from January to December 2017–2021 has been studied. It was found that, at the coastal shallow littoral station surrounded by macrophytes, the species diversity was higher and the quantitative characteristics of phytoplankton and zooplankton were lower in all seasons and years of the study than at the deeper coastal station located behind the macrophyte belt. The exception was the period when, as a result of surge events, the phytoplankton biomass in the coastal littoral in October–November 2018 increased to 326–627 g/m3. Every year, Cyanobacteria "blooms" with different intensities and durations were observed at the Lagoon. The abundance of cells of potentially toxic Сyanobacteria exceeded the World Health Organization standard, as a rule, in summer months at a deepwater coastal station, especially in 2017–2018. This had a negative impact on the state of the entire ecosystem, primarily on zooplankton organisms, in which communities the proportion of dead individuals increased. Water during the period of Cyanobacterial blooms in summer and autumn 2017–2018 also had an acute toxic effect on planktonic test organisms.

The aim of this article: analysis of information and software for forecasting of the Baltic Sea sprat stock Sprattus sprattus balticus at 22–32 ICES subdivisions in the context of the suspension of Russia’s activities in the International Council for the Exploration of the Sea (ICES).Methods used: The data of estimates of sprat abundance and biomass by hydroacoustic methods, commercial and biostatistical characteristics of the species were used to assess the stock and predict its catch in the Baltic Sea. Estimation of the sprat stock was carried out using the traditional method of virtual population analysis (VPA) adjusted according to the method of extended survival analysis (XSA) using the internationally approved VPA module software within the framework of ICES and the R software environment. The recruitment calibration program RCT3 (Recruitment calibration) was used for the abundance of recruitment (age 1 year) according to XSA and forecast. A multivariate short-term forecast was carried out at different levels of development of the total allowable catch (TAC) under the MFDP program (Multi Fleet Deterministic Projection). As an alternative, the domestic software «KAFKA» was tested.Novelty: for the first time, estimates of the sprat stock were made in the conditions of limited access of Russian specialists to primary data in ICES in full.Result: modern methodological and informational support of scientific research in the Baltic Sea in the conditions of the suspension of the activities of Russian experts in ICES makes it possible to obtain information in the minimum necessary amount for assessing the stock of sprat and predicting its catch. Modeling with the «KAFKA» software showed satisfactory results.Practical significance: The current level of information support for forecasting the state of the stock and catch of sprat in the Baltic Sea will allow solving a complex of problems of managing this resource in modern conditions.

The aim of this article: assess the impact of abiotic conditions on aquatic biological resources (sprat, herring, cod) of the Baltic Sea. The need for this study is due to the pronounced climate variability in the modern period. There is an increased role of the impact of environmental conditions on commercial fish species and, often, unfavorable for their spawning, survival of offspring, feeding, etc. Methods used: carried out an integrated ecosystem analysis using the method of principal components in the R software environment. To detect statistically significant levels of changes in the time series of principal components, the STARS program, represented by an Excel add-in, was used. For the analysis of abiotic conditions, long-term series of air temperature, data from regular oceanological observations at a monitoring station were used. Since the stocks of commercial fish species in the Baltic Sea are transboundary, the values of their spawning biomass and biological parameters of populations were analyzed according to the data ofthe ICES Working Groups. Novelty: this is the first time that such an analysis for a 30-year period adapted to the Russian water area in SD ICES 26 has been carried out. Result: an integrated analysis of the abiotic and biotic components of the sea over the past three decades showed «mesoscale» shifts in 2002 and 2013. The direct and indirect impact of climate on the fish stocks of the Baltic Sea was an important unfavorable factor determining the current state, size and weight parameters, reproductive capacity and stocks dynamics. The most pronounced negative impact of environmental factors was noted for the stock of cod. Practical significance: the results of the analysis carried out are necessary when predicting the catch of aquatic biological resources in the Baltic Sea for the short and long term, for making management decisions on the regulation of fishing in terms of understanding the risks in the current conditions of climate change.

Two closely related, difficult to diagnose calanoid copepod species, Eudiaptomus transylvanicus (Daday, 1891) and E. vulgaris (Schmeil, 1898), were studied based on the new material from the Sura River floodplain (the Middle Volga region, European Russia). The redescriptions and illustrations of two species are provided. The main diagnostic differences between these species are refined. New characters useful in the identification of E. transylvanicus are proposed. The data on distribution and habitats of the two species are reviewed and briefly analysed.

The perspective of the production of domestic compound feed for the development of industrial aquaculture in Russia is shown. Alternative sources of protein in mixed fodder for salmon and sturgeon have been investigated. The advantages of using protein hydrolysates instead of a part of fishmeal in compound feed are described. The advantages of protein hydrolysates from fish by-products are considered, the chemical composition and molecular fractional composition of sublimated protein hydrolysates obtained by enzymatic and thermal pathways from sardinella scales and ridges are studied. The presence in hydrolysates of 53.3 - 97.7% of low molecular weight peptides with a molecular weight of less than 10 kDa with a total protein content of 80.8-94.1% was established. Indicators of amino acid balance (scor) of hydrolyzates of scales and ridges of sardinella were calculated in relation to the established requirements for amino acids in salmonids. Indicators of amino acid balance (scor) of hydrolyzates of scales and ridges of sardinella were calculated in relation to the established requirements for amino acids in salmonids.It was found that the introduction of an enzymatically obtained hydrolyzate is more favorable for an increase in the content of limiting amino acids in mixed feed, and the use of sardinella scales for hydrolysis is more preferable than its ridges.

Globally, cephalopods support large industrial-scale fisheries and small-scale to partly large-scale local artisanal fisheries. They are of increasing economic importance as evidenced by the rapid rise in their global landings from 1950 to 2014. Cephalopods are sensitive to environmental variability and climate change and many if not all species show wide fluctuations in abundance. This is most evident in ommastrephid nerito-oceanic squid since their life cycle is associated with boundary currents that are changing with climate change. The inter-annual variability in catch presents challenges for fishers and managers due to the ‘boom-or-bust’ nature of the fishery. A key barrier to rational management of squid fisheries is the low level of development of fishery forecasting. Despite substantial progress made in relating squid population dynamics to environmental variability and change, several challenges remain to develop forecast products to support squid fisheries management. Ideally, squid fisheries management needs a forecasting system that includes all time-scales of forecasting, and especially short - and medium-terms forecasts. The present overview first provides current knowledge of the effects of climate change and variability on squid population dynamics, challenges and opportunities to advance ecological-fishery forecast products, and finally a roadmap is proposed for future development of forecasts products to support squid sustainable fisheries management. As for the adoption of specific forecasting methods to the squid fishery management process, what is important is the relationship between needs, feasibility, and the ultimate success of a forecast will be determined by whether it is used by end-users.

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