Work number - M 20 FILED
Presented Institute of Marine Biology of the National Academy of Sciences of Ukraine
Authors:
Hulak Bohdan S. Doctor of Philosophy, Researcher, Institute of Marine Biology, National Academy of Sciences of Ukraine
The aim of the study was to investigate the dynamics of the population structure of Baltic shrimp (Palaemon adspersus) and Rapa Whelk (Rapana venosa) in the Ukrainian waters of the northwestern Black Sea under conditions of intensified fishing and to investigate the bycatch of non-target species in the beam-trawls for the Rapa Whelk fishery. For the first time in this region, a comprehensive analysis of the population structure of these species was conducted, the level of commercial exploitation was assessed using mathematical modeling, and commercial stocks of Rapa Whelk were determined. The study found that 98% of the shrimp in commercial catches are females, which is due to the smaller size of males. The calculations showed the optimal level of commercial pressure on the Baltic shrimp population (F/M = 1.2; B/BMSY = 1.0). For Rapa Whelk, the methodology for determining the age of mollusks was improved, its sex structure and growth rates were assessed, which revealed faster growth of males compared to females. The maximum theoretical height of the Rapa Whelk shell is 11.46 cm, and natural mortality in the northwestern part of the Black Sea is lower than in the waters of Bulgaria and Turkey. According to trawl surveys, the largest commercial reserves of Rapa Whelk are concentrated at depths of 5-15 m, in particular in the areas of the Danube estuary, the Dniester Bank, and the Tendra Spit. In 2020, the commercial stock of Rapa Whelk amounted to 72.7 thousand tons, but decreased to 43.3 thousand tons in 2021 due to the impact of unfavorable natural factors for the species. The analysis of bycatch in the Rapa Whelk fishery revealed a significant number of undesirable species, including valuable species of flatfish, representatives of the Red Data Book of Ukraine, and numerous invertebrates. This emphasizes the need to regulate the design of beam-trawls and restrictions on the timing and areas of their use. Thus, the studies of the population structure of Baltic shrimp and Rapa Whelk in the northwestern part of the Black Sea are important for the rational management of aquatic bioresources in Ukraine. The revealed patterns of age composition, growth rates, and natural mortality of these species allow us to assess the impact of commercial fishery and natural factors on their numbers. The rational use of these bioresources will contribute to the stability of the fishery industry, food security, and reduction of import dependence. At the same time, it is necessary to take into account environmental risks, in particular the impact of Rapa Whelk fishing on related species, which requires improving fishery methods.
Number of publications: 3 аrticles in journals included in category “A” (including __3__ of foreign journals) and __1__ article in a journal included in category “B”, _3__ abstracts. The total number of references to the authors' publications/h-index for the work according to the databases is respectively: Web of Science _0_/_0_, Scopus _2_/_1_, Google Scholar _4_/_1_. There are _0_ patents for inventions of Ukraine and _0_ other countries, _0_ patents for utility models, industrial designs (for social sciences and humanities, certificates of copyright registration for a work) or other received protection documents for intellectual property rights.
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