ГлавнаяENAquatic Bioresources & Environment. Volume 4, Number 2, 2021

Aquatic Bioresources & Environment. Volume 4, Number 2, 2021


Environmental Concerns and the State of Aquatic Environment

Chlorophyll-α in the Azov Sea according to the data of remote sensing of the Earth in 2006–2019
A. T. Kochergin, L. V. Kriskevich
Based on satellite images of the sea surface, chlorophyll-α content in different areas of the Azov Sea in 2006–2019 has been estimated for several timeframes: its minimum, spring and summer–autumn peaks. The areas and timelines of the main pronounced and secondary peaks of chlorophyll concentration, its decline and the lowest point of its development are presented. During the investigated period, chlorophyll-α concentrations   in    the    context    of    the    spring   population    explosion   were    predominantly   lower   than 20 mg/m3, except for the central part of the sea and its eastern areas, where, in certain years, the content of this pigment reached 50 mg/m3. Particularly low concentrations of chlorophyll-α in spring were observed after 2013; they did not exceed the value of 16.5 mg/m3 in any area. A pronounced spring explosion mainly fell upon April and May, with its secondary weaker case in January – March, especially in the eastern and southeastern parts of the sea through the recent decade. The summer–autumn peak of chlorophyll-α content was characterized by increased concentrations: up to 40–50 mg/m3 in the northern, central and eastern parts of the sea until 2014, and up to 20 mg/m3 throughout the entire area since then. The summer–spring peak of chlorophyll-α concentration stretches predominately from June to September, and there exists the second peak in some areas. Second peak is less pronounced and falls upon October – December. In the course of the observation period, the minimum of chlorophyll-α content was decreasing from 10.0 to 4.0 mg/m3 throughout the entire sea area. The minimum was recorded mostly during the following months: October
– February for the western parts of the sea, and November – March for the central and eastern parts. It is possible that the negative trend in chlorophyll-α content   could be induced by salinization and changes in the biotic structure of the sea.
Keywords: chlorophyll-α, seasonal variatios, remote sensing, Azov Sea

Biology and Ecology of Aquatic Organisms

Biological characterization and spatial distribution of roach Rutilus rutilus heckelii and common bream Abramis brama juveniles in the Don River in 2020
M. M. Piatinskii, I. D. Kozobrod, S. Yu. Cherednikov, N. A. Zherdev
Abstract. The data collected during the scientific monitoring of the spawning run of roach Rutilus rutilus heckelii and common bream Abramis brama in the Don River have been analyzed. Investigation of the biological characteristics, spatial distribution and specific features of the downward migration of fish juveniles was carried out in the Lower Don area stretching from Romanovskaya Settlement to the Don River Delta in May–October, 2020. The obtained results show significant gain in average length and weight of roach and bream juveniles in the spring – summer season of 2020 and its absence in the summer – autumn season, which was caused by the downward migration of the partially grown juveniles in the Taganrog Bay. Hauls of fry drag nets showed that the juveniles in the investigated water bodies kept to the shallow coastal waters. Quantitative assessment of the spatial distribution of juveniles   indicates   spatial heterogeneity   of their aggregations and moderately productive spawning run in the context of low water content in 2020. Based on the outcomes of the scientific monitoring, the abundance of roach juveniles was assessed to be 49.3 million ind., and for bream juveniles it equaled 30.4 million ind. In the future, the research results factoring in statistical processing will make it possible to analyze the long-term dynamics of the biological characteristics of roach and bream juveniles.
Keywords: reproduction, Don River,Rutilus rutilus heckelii, Abramis brama, fry abundance, statistics, population parameters, biological characteristics

Aquaculture and Methods of Artificial Reproduction

Abiotic environmental factors in classification of the water from energy facilities for aquaculture purposes
M. L. Kalayda, M. E. Gordeeva 
Abstract. This article proposes a water classification that is based on the means and practices of water supply to energy facilities with regard to the temperature parameter and accounting for the prospective possibility of using such water for the purposes of aquaculture. This water classification relies on physicochemical characteristics of water: temperature, pH, dissolved oxygen concentration, redox potential, and total antioxidant activity. The collection of the data on the actual status of abiotic environmental factors was conducted at natural water bodies, including the ones used for cooling purposes by the energy facilities of the Republic of Tatarstan, from 2010 to the present time. Based on the temperature parameter, three water classes have been distinguished: 1) with the physicochemical characteristics typical for a water body of that geographical location; 2) water of the water bodies used for cooling purposes by energy facilities with the presence of zones of increased temperatures; 3) water of cooling ponds. This investigation has revealed that the waters are characterized by a complex structure involving different sets of physicochemical characteristics. It is shown that three distinguished water classes are characterized by certain sets of values of the Water Structure Index (5–7, 2.7–3.2, and 9–16, respectively) and redox potential (in the range of 2.47 unitsEh, 2 unitsEh, and 3.43–4.5 unitsEh, respectively). For these classes the following types of uses in aquaculture are most applicable: 1) cultivation of fish species native for this fish farming area; 2) cage farms, including the ones with multiple cycles of production; 3) cultivation of phytovorous fish species in the overgrown and blooming environment.
Keywords: water supply, energy facilities, water temperature, redox potential, total antioxidant activity, aquaculture development

Reproduction results of the semi-anadromous fish species at the floodplain spawning and rearing farms (hatcheries) of the Azov Sea and Kuban River region in 2020
N. Khorosheltseva, E. V. Gorbenko, A. Ya. PoluyanA. A. Medvedeva, M. V. Voloshina
Abstract. Long-term observations over floodplain spawning grounds reveal the decrease in reproductive efficiency of zander (pike-perch) (Sander lucioperca, Linnaeus, 1758) and roach (Rutilus rutilus heckelii, Nordmann, 1840), resulting from   deterioration   of   hydrological   and   hydrochemical regimes.   Due to   its low water content, the year of 2020 has been recorded as most unfavorable for the reproduction of semi- anadromous fish species. This article considers the results of 2020 spawning migration at the spawning and rearing farms of a floodplain type (Beysug Hatchery and Yeysk Experimenal Hatchery). In the spring season of 2020, these two farms reached planned stocking amount of breeders. The best age, length and weigh characteristics were exhibited by the roach breeders entering the water bodies of Yeysk Experimenal Hatchery for spawning. At Beysug Hatchery, the quality of breeders belonging to the semi-anadromous fish species was at its average long-term level. Despite substantial entry of breeders to the water bodies of Yeysk Experimental Hatchery, abundance of the roach juveniles migrating down to the Azov Sea was almost 9 times lower than average long-term values, and for zander juveniles this value was 3 times lower. In Beysug Hatchery, due to low water content, abundance of zander juveniles during their downward migration was 22 times lower (in a long-term context).
Keywords: roach Rutilus rutilus heckelii, zander Sander lucioperca, semi-anadromous fish, spawning grounds, salinity, fish juveniles

Fisheries and Processing of Aquatic Bioresources

Preservation techniques for zostera (eelgrass) washed ashore as storm debris
V. V. Bogomolova, I. A. Belyakova, L. M. Esina, S. L. Chernyavskaya, O. N. Krivonos
Abstract. The results of organoleptic evaluation of seagrass Zostera marina (eelgrass) storm debris are presented. The chemical composition of Zostera during its mass aggregation along the wrack line of the Black Sea coast in the spring and summer seasons of 2020 has been investigated. The safety of Zostera storm debris for consumption has been evaluated based on such indicators as content of radionuclides and toxic elements, and microbiological characteristics. Preservation of the storm debris samples has been conducted using the following techniques: drying under natural conditions (average daily air temperature 19–25 °С, wind velocity 5–8 m/s, atmospheric humidity 56.5–80.0 %, height of a storm debris layer 5–10 cm), artificial drying (forced ventilation at 40±2 °С, layer height 5–10 cm), and salting (using dry method with addition of table salt in the amount equal to 20 % of the weight of macrophytes). Organoleptic properties of dried and   salted eelgrass under various storage times are described. It has been established that the eelgrass, inhabiting the Azov and Black Sea Fishery Basin and washed ashore, contains from 16.9 to 25.7 % pectic substances, which indicates high value of this macrophyte. A method of preservation does not severely affect the content   of   pectic   substances. Recommendations on eelgrass preservation by means of drying (both under natural and controlled conditions) and salting have been given to ensure the highest possible retention of its quality.
Keywords: seagrass, eelgrass, Zostera marina, macrophytes, drying, salting, pectic substances, zosterates, zosterin, Azov and Black Sea Fishery Basin.

Long-term dynamics of the bream stocks in the Azov Sea (Russian waters) based on the results of CMSY modeling under the conditions of limited data availability (2002–2020)
S. Yu. Cherednikov, M. M. Piatinskii, I. D. Kozobrod
 Abstract. Analytical assessment of the Azov Sea stock of the common bream Abramis brama (Linnaeus, 1758) for the   time range 2002–2020 has   been performed using CMSY trend model in R that is suitable for application in the context of limited data availability. Current state of the stock is at the level of the reference point based on stock biomass, and shows evidence of substantial overexploitation (B2020/BMSY=0.989; F2020/FMSY=1.82). Accounting for the volumes of IUU-fishing using indirect estimates increases comprehensiveness of the results and ensures adequate stock assessment and evaluation of fishing mortality. Pooled estimates of bream stock biomass for the investigated period indicate a collapse of population abundance that fell upon 2005–2013 and, presumably, stemmed from climatic and hydrochemical changes in the Azov Sea environment, not being associated with overexploitation of the population in those years. At present, the bream population still remains in depressed state, with prerequisites for stock recovery. Following the results of modeling and after a consideration of forecast scenarios, the size of recommended legal catch for 2022–2023 could be set within the range between 40 and 110 t, depending on the efficiency of control, accounting, prevention and suppression of IUU-fishing. So long as the population is exploited within these limits, stock biomass will remain at a safe level and has the possibility of reaching 950 t. The results of this investigation highlight the necessity of control and prevention of bream IUU-fishing in the Azov Sea and Don River Basins; this is a crucial factor influencing bream population in the recent years.
Keywords: bream, stock assessment, Azov Sea, population, biological reference points, stock forecasting

Possibilities of short-term forecasting of the catch of the European sprat from the Black Sea stock off the western coast of Crimea
B. N. Panov
, E. O. Spiridonova
Abstract. This research work presents the results of the analysis of the data collected during the multi- method monitoring of the European sprat fishing (the Black Sea stock) off the western coast of Crimea in July–September, 2019. The monitoring was aimed at   identification of a relationship between the   behavior of biological resources and their environmental conditions with the purpose of developing the methods of short-term forecasting of fishing efficiency. Graphical and correlation analysis of the daily data on vessel catches and sea surface temperature, as well as satellite altimetry data and characteristics of atmospheric transfers in the fishing area made it possible to suggest an environmental mechanism for the formation of commercial sprat aggregations in the investigated area. During its summer feeding in the coastal waters, sprat forms denser aggregations under the influence of synoptic anticyclonic vortices that develop near the shelf. Intensification of those aggregations is associated with an increase in the western atmospheric transfers in this region. Southern currents, uncharacteristic for the investigated area, and a decrease in the temperature of surface waters in the coastal zone indicate escalation of the stable impact of anticyclonic vortices on the coastal waters. The presence of statistically significant anticipatory relationships between average daily fishing pressure and abiotic factors holds a promise for the possibility of short-term forecasting of the sprat fishing efficiency off the western coast of Crimea in the summer season with the forecast interval equaling 1–7 days.
Keywords: European sprat, Black Sea stock, Crimea, coastal waters, fishing monitoring, commercial aggregations, graphical analysis, correlations

Informational Messages

Book Abstract ‘‘Physiological and genetic aspects of so-iuy mullet Planiliza haematocheila (Temminck & Schlegel, 1845) biology in the Azov and Black Sea Basin’’
Bibliographic reference: Fiziologicheskie i geneticheskie aspekty biologii pilengasa Planiliza haematocheila (Temminck & Schlegel, 1845) v Azovo-Chernomorskom   basseyne   [Physiological and genetic aspects of so-iuy mullet Planiliza haematocheila (Temminck & Schlegel, 1845) biology in the Azov and Black Sea Basin]. G.G. Kornienko, S.I. Dudkin, L.A. Bugaev, S.G. Sergeeva, L.P. Ruzhin- skaya, E.A. Kozhurin, N.I. Tsema, M.A. Makhotkin. (Eds.). Rostov-on-Don: Mini Tayp [Mini-Type], 2021, 208 p. ISBN 978-5-98615-467-1.
Available at: https://yadi.sk/i/7fZ6I6pifsGPaw