Actual State of Population and Harvesting of the Baltic Shrimp Palaemon adspersus (Decapoda, Palaemonidae) in the North-Western Section of the Black Sea

Abstract

Data on the sex and size-mass composition of the Baltic shrimp Palaemon adspersus Rathke, 1837, population were obtained basing on the analysis of samples from 35 fyke net catches in the north-western section of the Black Sea over 2017-2020. The Baltic shrimp in the catches was represented by the specimens 20-65 mm long, and the main portion (52%) was formed by the specimens 40-50 mm long. According to LBB model, over 2017-2020 the relative fishing mortality level increased from 0.7 to 1.2. At the same time, in 2020 relation of the actual biomass to the biomass ensuring the maximum sustainable yield (B/B_msy) was equal to 1.0, indicating the optimal intensity of the Baltic shrimp harvesting in the Ukrainian waters. According to the model calculations, the minimal allowed length for harvesting should be 35 mm. Analysis of the fyke nets catches revealed significant number of undersized specimens of the commercial and protected fishes in the bycatch, including juveniles of gobies, turbot and flounder. Actual harvesting intensity do not result in P. adspersus overfishing in Ukrainian waters. In order to mitigate the negative impact of shrimp harvesting on the non-target species, it is necessary to regulate it by limitation of the fishing gears number and optimization of their designs. It was revealed that the fyke nets number in the Ukrainian waters should be limited to about 800 units.