MONITORING OF COMMERCIAL CRUSTACEAN POPULATIONS IN THE NORTHERN AZOV REGION IN 2024

Background. In the Azov Sea, an increase in the abundance and catches of shrimp of the genus Palaemon has been observed. The key area for their harvesting is the Northern Azov Region (Northern Cis-Azov littoral zone). Relevance. Due to the absence of information on the status of crustacean populations in the Northern Azov Region, it is relevant to conduct their investigation in the coastal part of this Azov Sea area. The aim of this work is to assess the status of commercial crustaceans in the coastal zone of the Northern Azov Region (Northern Cis-Azov littoral zone). Methods. Pontogammarus samples were collected in the coastal zone using a benthic frame and a sampling trap; shrimp samples were collected by a hand net. The samples were fixed with a 4 % aqueous formaldehyde solution. The laboratory processing included determination of the species, sex, size characteristics, the number of individuals in the sample, and the individual weight of the crustaceans. Results. Three shrimp species have been recorded in the catches: Palaemon adspersus Rathke, 1836, P. macrodactylus Rathbun, 1902 and Crangon crangon (Linnaeus, 1758). P. adspersus was the most abundant species, occurring in seagrass thicket biotopes, as well as on sandy, sandy silt and sandy gravel sites. Shrimp species C. crangon and P. macrodactylus were recorded in sandy silt and sandy gravel biotopes. Within the salinity range of 16.07-21.29 ‰, a positive relationship (r=0.80-0.98; p˂0.05) between the weight gain and the length gain has been established for P. adspersus ; it can be described by a linear function (R2=0.65-0.97). The highest growth rate of shrimp was recorded in the northern part of Sivash Bay, the lowest one was observed in Obitochny Bay. At a salinity of 16.07-17.61 ‰, the individual weight gain relative to the length gain in males and females was essentially the same, and at a salinity of 21.29 ‰, it was higher in males than in females (p<0.05). P. macrodactylus was recorded in commercial catches by set (fixed) seines in Obitochny Bay in areas with a salinity of 14.64-16.07 ‰. C. crangon occurred in Obitochny Bay and the Utlyuk Liman in the catches obtained by set seines at a salinity of 16.07-17.61 ‰. A positive relationship (r=0.92-0.98; p˂0.05) between the weight gain and the length gain described by a linear function (R2=0.91-0.97) has been established. At a salinity of 16.07 ‰, the highest individual weight gain relative to the length gain in the population was observed in males. Pontogammarus maeoticus occurred within the salinity range of 6.76-14.67 ‰. The dependence of the Рontogammarus abundance and biomass on the salinity level in 2024 is described by an exponential function (R2=0.98-0.99). This dependence represents a strong negative significant relationship (r=-0.90). Conclusion. The formation of numerous shrimp aggregations of the genera Palaemon and Crangon is recorded in the coastal waters of the Northern Azov Region, providing considerable resources for coastal fisheries. The obtained data indicate that the salinity regime in the range of 16.07-21.29 ‰ both provides favorable environment for P. adspersus in the Azov Sea and does not present the upper boundary of the comfort zone in terms of the salt content. Within the salinity range of 16.07-21.29 ‰, the abundance and biomass of exploitable aggregations of the genera Palaemon and Crangon should be expected to persist with a tendency for their exploitable biomass to increase. The increase in the salinity of the Azov Sea water reduces the distribution area of P . maeoticus with high abundance and biomass and confirms the previously established similar relationship for the Eastern Azov Sea (R2=0.98-0.99).