Now showing items 1-20 of 4564

    • The role of rotifer in water quality improvement in a fishpond

      Gerasimova, T. N. (2022)
      Rotifers are common in fresh and brackish water bodies, in coastal areas of the seas, and can be an effective tool for analyzing the state of the environment. The ability of rotifers to adapt to unfavourable environmental conditions has been considered in the course of studying the species composition of rotifers in a fish pond near Moscow under the conditions of the supply of organic artificial food for fish and changes in the temperature regime of water. During the period of increased temperature of the water (21–25 °C) and decrease in the concentration of dissolved oxygen from the surface to the bottom layers of water from 3.8 to 0.2 mgO2/L in early July, Asplanchna priodonta helvetica, Brachionus angularis angularis and Brachionus calyciflorus dominated in the pond (98–100 % of the abundance and 99–100 % of the biomass of rotifers). During the period of elevated temperatures, the turbidity indices in the upper layer (0.2–0.5 m) were an order of magnitude lower than those in the deeper layers of the reservoir. Bacteria and tiny particles served as food for rotifers. The temperature of 18–25 °C was favourable for the development of B. angularis angularis in the fish pond. At a temperature of 18 °C, its abundance reached 1,500 ind./L (70 % of the abundance of rotifers). In August, when the temperature of the water column decreased from 20 to 18 °C, the biomass of A. priodonta helvetica changed from 0.3 to 9.5 mg/L (99 % of the biomass of rotifers). Polyarthra vulgaris dominated among small rotifers. During the period of low temperatures, the biomass of rotifers increased to 20 mg/L; its basis was A. priodonta helvetica. Rotifers are able to adapt to conditions of high organic input in a wide range of temperatures and participate in the restoration of water quality in a fish pond.
    • Bycatch of marine mammals in the Northwest Atlantic during commercial fishery (based on literature materials and observations by the Polar branch of VNIRO in 2013–2020)

      Mishin, Т. V. (2022)
      This paper describes one of the most acute problem for both environmental companies and fisheries – bycatch of marine mammals caused by bioresource exploitation in the Northwest Atlantic (NWA). There is no doubt that fishing has some impact on marine mammals, but information on bycatch of marine mammals is needed to understand the extent of the impact of different fishing gears. The paper is based on data from reports of observers of the Polar branch of VNIRO from fishing vessels in the 3LMNO NAFO zone (Newfoundland Island), as well as literary materials. As a result of the analysis, it has been found that small species of marine mammals, such as gray, common, harp seals from the Phocidae family, common dolphin, short-finned pilot whale (Delphinidae family) as well as harbour porpoise from the Phocoenidae family are most often injured by various fishing gears. Toothed whales (sperm whale, bottlenose whale) are the least susceptible to bycatch. Among the baleen whales, humpback whale, northern right whale and minke whale are often the victims of fishing. Gillnets, trawl fishing, and longlines are the greatest threats to small marine mammal species, while baleen whales are most vulnerable to traps, usually to catch ten-legged crustaceans Decapoda. Analysis of the literature has shown that, in general, the stocks of most marine mammal species in the NWA, excluding the northern right whale, are in a stable condition. The manuscript considers measures aimed at reducing bycatch of marine mammals.
    • Changes in the smoltification age of Atlantic salmon (Salmo salar L.) of the Yokanga, Kharlovka and Vostochnaya Litsa Rivers (the Murmansk Region)

      Dolotov, S. I.; Kuzmin, D. O. (2022)
      Throughout the world, in recent decades, there has been a decrease in the abundance of Atlantic salmon, the main reason for which is a decrease in its survival rate during life at sea. Its value has a direct dependence on the length and, accordingly, the age of the smolts. Foreign researchers have found that the nature of long-term changes in the age structure of smolts can vary significantly by region. At the same time, the age of Atlantic salmon in Russian rivers, which account for a significant part of the area of the range of this species, was not considered. In this regard, the analysis of long-term data characterizing the age composition of salmon smolts of some rivers of the Murmansk region has been carried out. It has found been that in the first years of the period 2000–2018, the age structure of Atlantic salmon smolts was transformed in the rivers Yokanga, Kharlovka and Vostochnaya Litsa. As a result, fish at the age of 6 ceased to occur among them, the abundance of fish at the age of 5+ significantly decreased and the abundance of fish in the age groups of 3+ or 4+ significantly increased. The most likely reason for this is the change in the temperature regime of rivers since the mid-1990s, as a result of which the life time in the rivers of juvenile salmon has been reduced. Rejuvenation of the smolt population may have ambiguous consequences for the abundance of adult salmon, which are determined by the cumulative effect of reducing natural mortality at the stage from eggs to smolts, increasing their abundance and reducing their length, and reducing the survival rate during salmon life in the sea.
    • Polychaeta fauna in the northeastern Barents Sea

      Dikaeva, D. R. (2022)
      The northeast of the Barents Sea (the area between the Franz Josef Land and Novaya Zemlya archipelagos) is one of the little-studied areas characterized by a complex structure of the hydrological regime, bottom relief and bottom sediment structure. This area is characterized by the predominance of brown soils with a large number of foraminifera shells, which affects the species composition and structure of benthic communities. The species composition and quantitative characteristics of polychaetes in the northeastern part of the Barents Sea were analyzed on the basis of material collected in December 2019 during Murmansk Marine Biological Iinstitution expeditions on the r/v Dalnie Zelentsy. Faunal complexes of polychaetes have been identified in the study area depending on environmental conditions (type of bottom sediments, depth, hydrological conditions). In the areas of marginal troughs, the detritophagus Spiochaetopterus typicus dominates in terms of biomass and abundance, forming abundant settlements on soft silty-sandy, silty-clay soils. Low values of biomass and abundance have been noted on brown silts with a large number of foraminifera, dominated by Laonice cirrata. On the slopes of underwater hills, washed more strongly by bottom currents, on rough sandy soils with low nutrient content, the dominance of Nephtys ciliata has been noted. The species Sphaerodoridium kolchaki sp. n. recently encountered in the Barents Sea has been noted in the study area as well. The obtained data complement information on the species composition of the northeastern part of the Barents Sea and make it possible to trace further changes in the composition and structure of benthic communities.
    • Evaluation of maximum catch limits and closure areas in the Western Mediterranean (STECF-22-01).

      Pinto, C; Bastardie, F; Bitetto, I; Borges, L; Certain, G; Gourguet, S; Grati, F; Kupschus, s; Leutha, S; Mannini, A; et al. (Publications Office of the European UnionLuxembourg, 2022)
      Commission Decision of 25 February 2016 setting up a Scientific, Technical and Economic Committee for Fisheries, C(2016) 1084, OJ C 74, 26.2.2016, p. 4–10. The Commission may consult the group on any matter relating to marine and fisheries biology, fishing gear technology, fisheries economics, fisheries governance, ecosystem effects of fisheries, aquaculture or similar disciplines. This report is the eighth of a suite of STECF EWG reports dedicated to the evaluation of the implementation of the Western Mediterranean Sea Multi-Annual management Plan (hereafter, MAP), following EWG reports 18-09, 18-13, 19-01, 19-14, 20-13, 21-01 and 21-13. The group was requested to implement mixed fisheries bio-economic models to run a number of scenarios up to 2025 with varying parameters and up to 2030 with fixed parameters, to evaluate existing closure areas implemented since 2020 and 2022, maximum catch limits (MCLs) implemented since 2022 and draft a mixed fisheries advice. For all mixed fisheries models applied during the EWG, the data from the DCF official data calls and from the western Mediterranean stock assessments, were the same as the ones used during STECF EWG 21-13, as there were no updates since 2021. The non-spatially explicit mixed fisheries models, IAM (for EMU 1) and BEMTOOL (for EMU 2), focused on the scenarios evaluating MCLs on ARA, ARS and HKE. Reference MCLs for ARA and ARS where obtained from the Regulation EU 2022/110 and from STECF EWG 21-11, while for HKE were obtained solely from EWG 21-11. IAM was updated to differentiate between a coastal and a deep-water trawling within the Spanish fleet segments, as France does not have a deep-water fishery at present. As the model timescale has a yearly resolution, it was not possible to estimate the effect of a monthly MCL. The scenarios considered had a MCL for HKE, one for ARA, and one for both HKE and ARA. These scenarios were run for a decreasing MCL through time (forward scenario: aims at reaching catch at Fmsy by 2025) and an increasing MCL through time (inverse scenario: starting value is catch at Fmsy) accounting for the distribution of stocks by GSA, for a total of 10 scenarios alternative to the baseline. None of the scenarios allowed reaching Fmsy for all six species targeted by the MAP, except when applying a MCL on both ARA and HKE, simultaneously. The results for the HKE stock should be taken with caution as the MCL was applied only to trawlers in these scenarios, but this species can generally be targeted also by longliners and gillnetters. The economic consequences of scenarios accounting for a MCL on HKE, or both ARA and HKE, lead to a massive drop of GVA for the Spanish and French trawling fleets, while economic advantages are observed for longliners and gillnetters. BEMTOOL was updated and refined to consider the different types of fishing activity exerted by each fleet segment at metier level. The model timescale is set at a monthly resolution, so it was possible to run scenarios accounting for a monthly MCL (monthly flexibility was not considered). Only scenarios accounting for a MCL either for ARA or ARS where run, but never in combination (ARA+ARS), nor considering a MCL on HKE, for a total of eight scenarios: forward scenario, inverse scenario, monthly forward scenario, monthly inverse scenario, once with an MCL on ARA and once with an MCL on ARS. Implementing a MCL on the deep-water fisheries suggested an improvement for all stocks except for HKE. ARA and ARS would improve thanks to the control of the MCL, while MUT, DPS and NEP would stay within the upper and lower limits of Fmsy, despite the reallocation of fishing effort from deep to coastal fisheries. The implementation of a reverse MCL did not show a recovery of the stocks. Moreover, a MCL split by month seems to have a lower impact on the catches of ARA and ARS in the short term. The GVA shows an increase for the passive gears fleets (i.e., gillnetters and longliners) and a strong decrease for all trawling fleets in the first two years, with a stable trend over the following years. The spatially explicit mixed fisheries model ISIS-Fish also ran scenarios accounting for MCLs, but only for HKE in GSA 7, implementing a forward, an inverse and a monthly MCL for a total of four scenarios. The forward scenario led to fishing mortalities below Fmsy in 2025 because the value defined for MCL did not account for biomass rebuilding. On the other hand, the fishing mortality achieved using the HCR in the inverse scenario, never fell below Fmsy, because of the unrestricted catches of netters and long-liners. In terms of revenues, both MCL paths led to strong decreases for trawlers. The spatially explicit mixed fisheries models, ISIS-Fish (GSA 7) and SMART (EMU 2), focused on the evaluation of closure areas: existing closure areas, existing closure areas which were seasonal to become permanent, existing closure areas extended to all fishing gears, additional closure areas (only EMU 2), expansion of closure areas by 50% (only EMU 2) and expansion of closure areas by 100% (only EMU 2). ISIS-Fish was applied only for HKE in GSA 7 being the first time this model was used within this working group. The extension of closure areas to all fishing gears (passive gears on top of trawlers) in GSA 7 did not show any improvement, while shifting from a seasonal to a permanent closure showed a decrease in F and an increase in SSB. A decrease of catches of juvenile hake of 20% was observed both with seasonal and permanent closures. Catches of adults increased due to recovery of the stock and considering the low level of initial catches. It should be noted that revenues increased for passive gears but decreased for trawlers. SMART was updated, increasing the spatial resolution of the spatial grid of the model, to be in line with outputs of the ad-hoc contracts preceding the EWG and with ISIS-Fish. None of the scenarios considered for EMU 2 evaluating spatial closures allowed to reach Fmsy by 2025, except for MUT in 10 and NEP in 9 which remains underutilized. SSB shows, nevertheless, an increase across years. None of the scenarios allowed to reduce catches by 20% for all species. All scenarios are associated with a sharp decrease in revenues; spatial closures not widened or seasonal would involve lower decrease of the profits than widened and permanent closures. Loss of profits is more evident for VL12-18 and VL18-24, although the loss is evident for all fleet segments. During EWG 22-01 no explicit comparison between the implementation of an effort regime and a MCL regime was run. The group advices to do so accounting for the limitations encountered in the implementation of MCLs during EWG 22-01. It should be noted that the reduction of GVA is estimated in the short term (up to 2025), but further tests should be done to estimate the trend of GVAs in the mid- and long-term. It is highlighted that given the large number of other species exploited beyond the key ones included in the management plan and in the simulation models, the actual socio-economic impact of the plan remains uncertain. Also, the economic results are presented considering a constant number of vessels, and would differ if the number of vessels is reduced. Additionally, it is difficult to evaluate the socio-economic impact of the MAP on the fleets as at present no socio-economic reference points are used to compare the results against those.
    • Management Strategy Evaluation of alternative approaches for the anchovy and sardine stocks in the Adriatic Sea (STECF-21-04)

      Konrad, Christoph; Winker, Henning; Gras, Michael; Uriate, Andrés; Orio, Alessandro; Pierucci, Andrea; Raid, Tiit; Accadia, Paulo; Mravlje, Edo Avdic; Tičina, Vjekoslav; et al. (Publications Office of the European UnionLuxembourg, 2021)
      Commission Decision of 25 February 2016 setting up a Scientific, Technical and Economic Committee for Fisheries, C(2016) 1084, OJ C 74, 26.2.2016, p. 4–10. The Commission may consult the group on any matter relating to marine and fisheries biology, fishing gear technology, fisheries economics, fisheries governance, ecosystem effects of fisheries, aquaculture or similar disciplines. Within a management strategy evaluation harvest control rules were tuned and robustness tested for the anchovy and sardine stocks in the Adriatic Sea. This investigation was done in support of GFCM and a continuation of the preliminary report (EWG 21-adhoc-02). For the sardine stock no meaningful MSE could be conducted. For the anchovy stock two HCRs were identified to be achieving the management targets and being robust.
    • About terraces on the shore of the Teriberskaya Bay of the Barents Sea (the Kola Peninsula)

      Neradovsky, Yu. N.; Miroshnikova, Ya. A.; Companchenko, A. A.; Chernyavsky, A. V. (2022)
      The paper considers the results of the study of modern terraces on the coast of the Lodeyny Peninsula in the Barents Sea. According to field observations, decoding of space and geodetic maps and volumetric modeling, signs of three terraces have been identified. Two terraces having a rear seam, a cliff, a brow and horizontal platforms have been studied in more detail. The rear seams are located at 7 and 30 m, and the edges at 10 and 40 m above the sea level. The third terrace is confined to the level of 40–60 m, and has not been studied in detail. According to estimates, the first two terraces were formed about 3,300 and 6,000 years ago respectively. The 1st terrace characterizes the period of slow land rise by 10 m, at the speed up to 3 mm/year, which began about 3,300 years ago and continues to the present. It is characterized by a uniform sea retreat of about 15 mm/year. The erosion products of this terrace are common in the lateral zone and represent modern marine sediments, including beaches forming a new terrace. The 2nd terrace characterizes to the dynamics of rapid land rise by 30 m at a speed of about 11 mm/year, which occurred in the period from 6,000 to 3,300 years ago. The erosion products of this terrace are most common on the coast and are found at a distance of 100 m to 2–3 km from the shore. It is assumed that the speed of movement of the coastline during the retreat of the sea was different and reached up to 900 mm/year. According to the authors, preliminary data indicate the instability of the territory and the manifestation of block movements, which may have a negative impact on the development of infrastructure.
    • Aquatic Bioresources and Environment, vol. 5, issue 1

      Bragina, T.M. (Azov-Black Sea Branch of FSBSI VNIRO (AzNIIRKH)Rostov-on-Don, Russia, 2022)
      Vertical distribution of biogenic elements in Gelendzhik area in 2019 has been presented. Hydrochemical criteria for typification of the Azov limans of the Krasnodar Territory as the spawning grounds for semi-anadromous fish species have been enlisted. Use of the thermohaline method for determining the quasi-heterogeneity of the water masses in the Azov Sea is discussed. Age composition and linear growth of the invasive ark clam species (Anadara kagoshimensis (Tokunaga, 1906)) in the Kerch Strait have been estimated. Effect of different doses of pituitary hormone on the reproductive performance of shemaya females (Alburnus leobergi, Freyhof & Kottelat, 2007) has been studied. Heavy metals and arsenic in water, bottom sediments and Black Sea turbot (Scophthalmus maeoticus, Pall., 1814) in the Caucasian Shelf area in the Black Sea (1995–2020) have been traced. Exotic fish species off the Black Sea coast of the Krasnodar Territory are presented. Problems of using riverbed ponds in aquaculture (in the context of recent legislative changes) are considered.
    • Problems of using riverbed ponds in aquaculture (in the context of recent legislative changes)

      Sennikov, S.A. (2022)
      For a long time in the field of aquaculture existed the uncertainty, associated with the use of the ponds formed by water-retaining structures on watercourses (the so-called “riverbed ponds”), despite numerous attempts to resolve emerging contradictions legislatively—including another such attempt made last year by the adoption of Federal Law No. 163-FZ of June 11, 2021 “On the amendment of the Federal Law “On aquaculture (fish farming) and amendment of some legislative acts of the Russian Federation” and some legislative acts of Russian Federation”. The amendments introduced by this law establish new legal mechanisms for the use of riverbed ponds for the purposes of pond aquaculture, which makes their study particularly relevant. However, it will not be possible to fully understand the essence of these legislative changes without understanding the history and development of the legal framework applicable to these water bodies. In this regard, this article shows how riverbed ponds through numerous legislative changes were gradually introduced into the property circulation and how the principle of separation of the water resources of riverbed ponds and the land under them appeared, which means that the water in such ponds remains federal, but the land under them may be in other forms of ownership. This article also discusses the questions of the correlation of this principle with other principles of the legal regulation underlying water and land legislation, and how it is perceived by judicial practice. The author analyzed in detail the amendments, adopted by Federal Law of 11.06.2021 No. 163-FZ, concerning the regulation of riverbed ponds, proposed a classification of the legal basis for the use of water bodies in fish farming, and concluded what problems in the use of riverbed ponds remained, despite recent legislation attempts to eliminate them. Finally, this article suggests directions for further changes, according to which, as it seems to the author, the legislator could go to solve the identified problems.
    • Exotic fish species off the Black Sea coast of the Krasnodar Territory

      Nadolinsky, V.P. (2022)
      Each species strives to expand its range and spreads in all directions. Its expansion occurs in the direction where biological and abiotic factors are similar to its native habitat. Entering the area with different conditions activates the mechanism of adaptation to new conditions. If such an adaptation is successful, the range of this species expands in this direction, otherwise this area remains unclaimed. Possible migration routes of exotic species run along the coast of Turkey through the coast of the Republic of Georgia or along the coasts of Bulgaria, Romania and the Crimean Peninsula. Taking into account the existing system of currents in the sea, the most likely option seems to be their invasion into the Russian sector of the Black Sea as a result of migration from the Sea of Marmara through the Bosphorus Strait and further along the direction of the Anatolian and Caucasian currents. Another way is with ballast water. In 1995–2014, 7 monitoring stations under the authority of AzNIIRKH operated near the Black Sea coast of the Krasnodar Territory on a year-round basis. They were equipped with all the necessary types of fishing gear (set nets with a mesh size from 25 to 200 mm, bottom set nets with a minimum mesh size of 6.5 and 10 mm, cast nets with 30 mm mesh, etc.). AzNIIRKH-trained observers were present at each haul of the fishing gear and conducted the necessary catch analyses. All unusual species were preserved by freezing or taxidermy and transferred to the institute. As a result of the operation of AzNIIRKH monitoring stations, in the catches of commercial fishing gear off the Black Sea coast of the Krasnodar Territory in 2005 and 2012, two exotic species have been recorded: Siganus luridus (Rüppell, 1828) and Lophius piscatorius Linnaeus, 1758.
    • Heavy metals and arsenic in water, bottom sediments and Black Sea turbot (Scophthalmus maeoticus, Pall., 1814) in the Caucasian Shelf area in the Black Sea (1995–2020)

      Korablina, I.V.; Gevorkyan, Zh.V.; Gorgola, L.G.; Barabashin, T.O. (2022)
      The results of investigation of the pollution of the water and bottom sediments of the Caucasian Shelf in the Black Sea by heavy metals (copper, zinc, lead, cadmium, mercury) and arsenic, as well as their content in the Black Sea turbot Scophthalmus maeoticus (Pallas, 1814) are presented for 1995–2020. In the water and turbot, the determination of Zn, Cu, Pb, As, and Cd has been conducted using the method of atomic absorption with electrothermal atomization; mercury in all components of the ecosystems was measured using the method of atomic absorption with “cold steam”; in the bottom sediments, the content of Zn, Cu, Pb and As was identified using X-ray fluorescence method. In 1995–2020, in some water samples, the concentrations of zinc, copper and mercury exceeded the maximum permissible level established for the water bodies of fisheries importance, while the lead and cadmium were below it. The arsenic content during the entire observation period was extremely low. A noticeable decrease in the concentrations of zinc, lead and copper in the shelf waters of the Black Sea in the present period as compared with the years of the greatest pollution (1995–2002) was recorded. In the bottom sediments, the content of lead, zinc and mercury exceeded their content in the earth's crust for several years; for arsenic, the excess was recorded throughout the entire observation period. This mostly results from the peculiarities of the granulometric composition of the shelf bottom and, to a much lesser extent, from anthropogenic influence. The differences in the bioaccumulation of heavy metals and arsenic in the organs of the Black Sea turbot are shown. Out of the identified elements, only lead, mercury and arsenic in isolated cases exceeded the permissible level in the organs of the turbot in some years.
    • Effect of different doses of pituitary hormone on the reproductive performance of shemaya females (Alburnus leobergi, Freyhof & Kottelat, 2007)

      Golovko, G.V. (2022)
      The stage of obtaining high-quality gonads was explored in the course of development of the biotechnology for artificial reproduction of the anadromous Azov-Black Sea shemaya Alburnus leobergi (Freyhof & Kottelat, 2007), a valuable species of the Azov Sea ichthyofauna. This research is aimed at the assessment of the maturity status of shemaya females and males after their wintering in the ponds of a fish farm on the Lower Don at a thermal constant of 849 degree days (DD) and at the evaluation of the reproductive parameters of shemaya females exposed to different doses of the pituitary extract. In all literary sources available, the information on this topic has been scarce and fragmentary, and in the foreign sources, it was entirely absent. Our investigation has shown that the gonads of 55 % of males were at 5th and 5th–6th stages of maturity. At the same time, females significantly differed by the degree of gonad maturity: 26.0 % of females had first-generation eggs at different stages of resorption, the sexual products of 15.8 % of females were at the 5th stage of maturity, and 58.2 % of females had immature sexual products at the 3rd–4th and 4th stages of maturity. The investigation of the effect of two doses (6.0 and 9.0 mg/kg) of the pituitary gland extract with application of the fractional method showed that 15.0 % and 16.7 % of injected shemaya females with the most mature eggs responded to the preliminary dose of the pituitary extract by ovulation of physiologically sound eggs (0.6 and 0.9 mg/kg, respectively). 20.0 % and 6.7 % of females responded to the provoking dose of pituitary hormone by ovulating physiologically high-quality eggs in accordance with the concentration applied. The fertilization rate of physiologically sound eggs in both scenarios had similar values (97.4 and 97.9 %). Since the thermal constant of 849 DD is excessive for the start of artificial reproduction of the Azov-Black Sea shemaya, it is necessary to conduct research in order to identify the thermal constant precluding the loss of the first-generation eggs caused by the incipient processes of resorption.
    • Age composition and linear growth of the invasive ark clam species (Anadara kagoshimensis (Tokunaga, 1906)) in the Kerch Strait

      Zhavoronkova, A.M.; Sytnik, N.A.; Zolotnitskiy, A.P. (2022)
      Age composition and linear growth rate in the ark clam (Anadara kagoshimensis) population in the Kerch Strait are investigated. Based on the analysis of seasonal annual growth rings and chevron grooves on the hinge ligament of the ark clam, the age of this species has been examined, which, in this population, was found to be 7 years (6+). Based on the age and annual length gain of the molluscs in the course of their ontogenesis, a theoretical growth curve is presented; it has been calculated following the von Bertalanffy growth equation, where L∞, k, and t are the parameters equaling to 50.2, 0.428, and 0.022, respectively. The highest growth rate was observed in the first year of life, 17 mm; however, later on, it was consistently decreasing and did not exceed 2 mm/year in the oldest individuals. The relationship between the ark clam’s growth rate (PL) and its length, approximated by the inverse linear function is presented. Based on the parameters of the von Bertalanffy growth equation, a theoretical maximum age of the investigated species has been calculated; it was found to be 8.74 years. It has been shown that the linear growth rate of the ark clam in various areas of the Azov and Black Sea Basin is determined by the water salinity to a considerable extent, because in the desalinated areas (Azov Sea, Kerch Strait, Danube River Delta and Northwestern Black Sea with 10–14 ‰ salinity), the growth rate of this mollusc was 1.5–2 times lower than in the Southeastern Black Sea (18 ‰).
    • Use of the thermohaline method for determining the quasi-heterogeneity of the water masses in the Azov Sea

      Shishkin, V.M.; Zhukova, S.V.; Karmanov, V.G.; Lutynskaya, L.A.; Burlachko, D.S.; Podmareva, T.I.; Taradina, E.A. (2022)
      This paper considers the possibility of applying the thermohaline method (using the construction of T,S-diagrams) to determine the quasi-heterogeneity of water layers in the Azov Sea drawing on the expedition data obtained in 2016–2020. The diagrams allowing to identify a two-layer water structure in the aquatic environment of the Azov Sea (excluding the area of Taganrog Bay) have been constructed. The analysis of water stratification in the conditions close to the natural regime of the sea (thus, including salinity), as well as in the present conditions of its salinization, has been carried out. The data obtained through the analysis of sample observations have been verified with mathematical methods; the explanations from the standpoint of T,S-analysis of the aquatic environment have been presented. The hydrological features of the salt regime of the Azov Sea are given with the specification of the situations during the advection of the Black Sea waters, which precondition a stable separation of the waters in the southern part of the sea into surface and bottom “water masses”. These possibilities are justified mathematically, and for the modern period of considerable salinization of the sea, in accordance with the theory of T,S-analysis of water masses, a classification assessment of the aquatic environment is proposed.
    • Hydrochemical criteria for typification of the Azov limans of the Krasnodar Territory as the spawning grounds for semi-anadromous fish species

      Kosenko, Yu.V.; Barabashin, T.O.; Shevtsova, E.A.; Poroshina, E.A.; Belousov, V.N.; Kartamysheva, T.B.; Glubokov, A.I. (2022)
      The Azov limans of the Krasnodar Territory are of major fishery importance, as they serve as the spawning grounds for valuable semi-anadromous fish species. Roach and zander at their early stages of development are highly susceptible to the negative effects of various abiotic environmental factors, which makes them very dependent on the hydrochemical status of the water bodies during the spawning season. As the hydrochemical regime, in turn, closely depends on the hydrological regime and the overgrowth area of the limans, it can be used as a criterion parameter that affects the success of spawning of the semi-anadromous fish species and growth of their juveniles. This paper proposes a system of hydrochemical scoring and establishes the criteria for the typification of the limans based on their suitability for spawning and growing of zander and roach following the data collected in the spring season of 2017–2021. Based on the analysis of the hydrochemical data, 3 main blocks for the typification of limans according to their suitability for spawning of semi-anadromous fish species were identified: gas conditions, ionic composition and the content of biogenic components in water along with an assessment of the primary production of phytoplankton. It has been found out that the Azov limans of the Krasnodar Territory vary significantly in terms of the hydrochemical composition of their water. Some limans are characterized by pronounced fluctuations of the hydrochemical and ichthyological characteristics in interannual dynamics. Based on the hydrochemical criteria, the limans of the Kulikov-Ordynsk group (Bolshoy Bashtovy, Donchikov, Bolshoy Grushchany) and the Kulikovskiy Liman were the most favorable for the spawning of zander and roach, and the Ryasnoy, Boykievskiy and Kurchanskiy Limans were the least favorable. The low production coefficient in the water of most limans can be indicative of their high degree of overgrowth with macrophytes, which control is crucial in increasing the efficiency of natural reproduction of semi-anadromous fish species. The correlation between the criterion scoring of the limans based on the hydrochemical regime and the density of distribution of zander and roach juveniles has been established, which confirms the validity of this study.
    • Vertical distribution of biogenic elements in Gelendzhik area in 2019

      Borodulina, P.A.; Chasovnikov, V.K.; Fedorov, A.V. (2022)
      Investigation of the vertical distribution of nutrients is an important component in studying the entire ecosystem of the Black Sea. Biogenic elements play a crucial role in the primary production in the sea coastal zone and are among the main indicators of the ecological state of marine waters. Any changes in nutrient regime are reflected in biological marine plankton communities. This work was aimed at the investigation of the seasonal vertical dynamics of biogenic elements in the northeastern part of the Black Sea near the city of Gelendzhik in 2019. To determine concentration of nutrients, the methods standard to the practice of marine hydrochemical studies have been used. As a result of this investigation, it has been found that nitrate and ammonium forms of nitrogen, and mineral phosphorus have well-defined concentration maxima that correspond to certain values of conditional density. There is one deep maximum in the vertical distribution of nitrates; on average, the concentration of nitrate nitrogen is 5.57 μmol/L. Vertical profile of phosphates has an upper maximum (average concentration of 1.39 μmol/L), a minimum (1.19 μmol/L) and a lower maximum (6.64 μmol/L) of concentrations. Seasonal changes in climatic conditions, coastal runoff and rate of phytoplankton consumption determine the dynamics of nutrient concentrations in the photic layer of marine waters.
    • Determination of the catchability coefficient of a survey dragnet for the juveniles of common carp and herbivorous fish species (silver carp, grass carp) with the purpose of improving the appraising method for the juveniles of the species targeted by artificial reproduction in the Azov and Black Sea Fishery Basin

      Stafikopulo, A.M.; Gorbatyuk, Ya.I. (2021)
      This article considers the main results of experimental research work aimed at determination of the catchability coefficients of a fingerling survey dragnet for the juveniles of common carp and herbivorous fish species (silver carp, grass carp), conducted in the rearing ponds of the Aquaculture Research Center “Vzmorye” (“Seacoast”) in 2019–2020 with the purpose of improving the appraising method for fish assessment. The factors influencing and determining the catchability coefficient of the survey fishing gear are discussed. The methods for conducting the appraisal surveys of fish juveniles are presented. According the methodology developed by the authors for conducting experimental research work and for determination of the calculated catchability coefficient for a survey dragnet, the source data were collected and processed; based on those data, the catchability coefficients for a survey dragnet, size 15×2 m, targeting the common carp juveniles weighted 10 g and 40–85 g, have been evaluated. The possibility of using a fingerling survey dragnet for the juveniles of herbivorous fish species (silver carp of the average weight 10 g, and grass carp of the average weight 15–25 g) has been considered, and its catchability coefficients have been identified. The possibility of using a longer dragnet, of the size 302 m, in the appraising surveys of herbivorous fish species (silver carp) has been evaluated experimentally. The results showing the unfitness of the 15×2 m dragnet for the appraisal surveys of the juveniles of herbivorous fish species (silver carp, grass carp) in the rearing ponds of the Azov Sea and Don River Region upon a headwater level 0.6–1.2 m have been obtained.
    • Results of artificial reproduction of vimba bream (Vimba vimba) juveniles in the Azov Sea and Don River Region

      Zipelt, L.I.; Gorbenko, E.V.; Pavlyuk, A.A. (2021)
      Recruitment to the vimba bream (Vimba vimba natio carinata (Pall.)) population with juveniles in the Azov Sea Basin occurs through both natural and artificial reproduction. This work presents the results of long-term studies aimed at the assessment of artificial reproduction and rearing the juveniles of vimba bream in the Azov Sea and Don River Region. The quality of the juveniles released into a natural water body has been assessed based on their morphometric characteristics and the chemical composition of their muscle tissue. The criteria for quality assessment based on the fat, protein, and ash content have been established. The correlation between morphobiological characteristics and fecundity has been identified; the equations for calculation of some parameters, such as weight of the gonads and estimated operational fecundity, have been derived. The recruitment to the stocks of aquatic biological resources with vimba bream juveniles for the last 7 years (2015–2021) is presented.
    • Results of rearing roach (Rutilus rutilus L.) juveniles in the spawning and rearing farms in the Krasnodar Territory in 2020

      Poroshina, E.A.; Sergeeva, S.G.; Gorbenko, E.V.; Khorosheltseva, V.N.; Bugaev, L.A. (2021)
      This work presents the data characterizing qualitative and quantitative parameters of the roach juveniles, reared in 2020 in the spawning and rearing farms (hatcheries) of the Krasnodar Territory; the hatcheries belong both to the liman (East-Akhtarsk and Chernoerkovsk Hatcheries) and floodplain (Beysug and Yeysk Hatcheries) types. In the East-Akharst Hatchery, all migrating juveniles reached their standard weight and were characterized by good physiological status. In the Chernoerkovsk Hatchery, the weight of around 70 % of the released juveniles was lower than the normative values (300 g); their physiological status was acceptable. Density of the roach juveniles distribution in this hatchery exceeded 40,000 ind./ha, which led to high food competition. In the water bodies of the Beysug Hatchery, the average body weight and physiological status of the released roach juveniles were compliant with the normative values. In the Yeysk Hatchery, due to poor hydrological regime during the reproductive season, the efficiency of roach reproduction was extremely low.
    • Status of the zooplankton in the central Syvash Bay in the summer season of 2019

      Terentyev, A.S.; Zaremba, N.B. (2021)
      The Syvash Bay is located in the Western Azov Sea and is separated from it by the Arabat Spit. After the channel was shut off in 2014, the water salinity in the bay gradually increased, which leads to the changes in the Syvash biota. During the desalinization period, the bay served as an important spawning and feeding ground for the juveniles of the Azov Sea fish species that mainly feed on zooplankton. The increase in salinity has inevitably influenced its state. It is shown that the highest indices of zooplankton development have been recorded in the northern part, the most desalinated one, and the lowest values have been observed in the southern part, characterized by the highest salinity. That said, in the northern part of the bay, zooplankton abundance was 1.2–1.4 and biomass was 2.7–2.9 times lower in July than in June. At the same time, in the southern part of the bay, characterized by the highest salinity, the average abundance of zooplankton in July was 2.1–4.4 times lower as compared to June, and for zooplankton biomass, this value was 1.5–4.1 times lower. Furthermore, rotifers and isopods were virtually absent in this area, and no nematodes and flatworms were recorded. The study has shown that, as the result of the further salinization, the Syvash Bay has the possibility to become a hypersaline water body again. In this case, the species richness of zooplankton will deteriorate considerably, and ultrasaline species will be prevalent in its species composition. This work was aimed at the investigation of the status of the zooplanktonic community in the summer season (June–July) of 2019.