Based on the available data for the 2021/2022 fishing season, the ecological structure and fishing biological parameters of the European anchovy (E. encrasicolus L., 1758), wintering in the coastal waters of Abkhazia, have been analyzed. This paper presents materials that make it possible to analyze the dynamic parameters of the Azov and Black Sea stocks of the European anchovy aggregating off the coast of Abkhazia in the winter season. A comparative analysis of the main biometric parameters has been carried out. For data analysis, well-established ichthyological methods have been used. The available data on the European anchovy (both Black Sea and Azov Sea forms) caught during the investigated period characterize the dynamics of the length–age catch composition and are indicative of its intra-annual fishing patterns. Changes in the population characteristics present in the catch composition as compared with the previous years have been identified. The absolute catch values and their fluctuations are presented by the month. Analysis of the available material has indicated the main dynamic changes that characterize the wintering anchovy population as stable with a tendency for its total biomass development on a moderate level, which is not conducive for increasing the fishing effort in the next 1–2 years.

Copper compounds accumulate in marine bottom sediments as the result of human activity and, being highly toxic, affect microphytobenthos. Evaluation of the tolerance ranges of benthic diatoms to copper pollution is important for biotesting and assessment of coastal marine environment. This work is aimed to reveal the dynamics of growth and cell death of marine benthic diatom Pleurosigma aestuarii (Bréb. in Kütz.) W. Smith, 1853 under the impact of a wide range of copper (II) ions concentrations over the course of a 10-day experiment in clonal culture, as well as to identify a tolerance threshold for this species, critical for its survival when exposed to the toxicant. The study has focused on assessment of the changes in the proportion (%) of alive cells, absolute cell number and specific growth rate of the culture at different exposure durations and concentrations of Cu2+ ions (32–1024 μg/L) and was meant to evaluate the applicability of this species as a new test object for ecotoxicology. In the control culture and in the cultures exposed to Cu2+ in the range of concentrations 32–256 μg/L, the proportion of alive cells did not change over the course of the experiment (95–99 %). At Cu2+ concentration 320 μg/L, the proportion of alive cells decreased to 23 % on the 3rd day and to 10 % on the 5th day, which provided a basis to consider this value as a threshold one for P. aestuarii survival. At Cu2+ concentrations 384 μg/L and higher, up to the maximum one (1024 μg/L), drastic inhibition of the culture was recorded as early as on the 1st day, and on the days 3–5, all the cells died. The increase in the absolute cell number in the concentration range 32–256 μg/L was consistent with the dose–response sigmoid model. Over the timespan of days 1–7, the cell number increased by 3–5 times, reaching its maximum, and then it decreased by 10–12 % by the 10th day. At Cu2+ concentrations 320 μg/L and higher, the increase in the cell number was strongly suppressed since the 1st day. Within the 32–256 μg/L range, the test culture is characterized by positive specific cell growth rate for the period up to 7 days; at the threshold concentration 320 µg/L and higher, this test parameter becomes negative. Thus, P. aestuarii should be recommended as a new appropriate test object both for toxicological experiments and for monitoring of coastal marine environment affected by technogenic pollution.

Curonian Bay of the Baltic Sea is a lagoon that is considered to be a water body of the highest fisheries importance. Its current geoenvironmental status is characterized by a number of problems: influx of biogenic substances from a large catchment area, algal bloom, etc. As part of the monitoring surveys of the habitat of aquatic living resources that were conducted in Russian waters of Curonian Lagoon in 2018–2022, the spatial distribution of hydrochemical parameters was investigated in 6 areas established on the basis of their morphometric and hydrological features: Teply (Warm) Bay, western, central, eastern, and southern areas, and the Neman River discharge zone. Hydrochemical conditions in Teply Bay were characterized by a considerable deviation of dissolved oxygen concentrations from the rest of Russian waters of Curonian Lagoon, as well as by the higher values of BOD5 and ammonia nitrogen, and lower values of pH and nitrate nitrogen. In the western area, the lowest content of dissolved oxygen, BOD5, ammonia, and nitrate nitrogen was recorded. In the southern area, there was a reduced content of ammonia nitrogen and nitrate nitrogen. In the central area, the values of hydrochemical parameters were close to the average ones for Russian waters. The eastern and Neman River discharge areas, exposed to significant influence of the Neman River runoff, were characterized by a high concentration of nitrate nitrogen during seasonal flood, as well as by increased values of ammonia nitrogen and BOD5 during algal bloom in summer.

The Mekong Delta is one of Asia's largest megadeltas. It is a region with unique biodiversity and the main food source for a large part of the population of Vietnam and Cambodia. The decrease in the biodiversity and resource capacity of the delta, associated with the growth of anthropogenic impact and other negative environmental factors, requires effort to maintain its ecosystem in a state favorable for the life of aquatic organisms, for which the first step is to organize effective monitoring of aquatic communities. Its organization must consider the complex structure of the delta and related features of the physicochemical characteristics of the habitat. The mean and interval values of the parameters were as follows: transparency was 47.7±16.4 (10–100) cm; in the surface water layer, the temperature was 29.7±1.37 (26.0–33.3) °C, electrical conductivity was 5490.4±8392.5 (133–33623) µS/cm, total dissolved solids were 3556.2±5445.8 (86.5–21853), pH was 7.6±0.3 (6.9–8.4), and dissolved oxygen was 4.8±1.05 (3.0–8.9) mg/L; in the bottom water layer, the temperature was 29.6±1.43 (26.0–34.1) °C, electrical conductivity was 7671.4±11193.2 (125–37870) µS/cm, total dissolved solids were 4905.3±7199.8 (78.0–24615.5), pH was 7.6±0.3 (6.9–8.2), and dissolved oxygen was 4.6±1.00 (2.6–7.7) mg/L. The zoning of the delta based on the knowledge of the environment makes it possible to organize the monitoring process in the most rational way. Following the results of the analysis of physicochemical parameters, the boundaries of zones with different environmental conditions that affect the formation of fish communities have been determined. The main contributing factors are salinity (3 zones), oxygen regime (3 zones), and runoff distribution (4 zones). The interrelation between the delta zoning according to the hydrochemical regime and the structural features of the fish communities at the family level has been found, which further supports the idea that such zoning must be taken into consideration when organizing monitoring surveys.