The humpback shrimp researches in the Tatar Strait. 1. Approaches to assessment of the catches age structure

The aim of the research was to work out the methodic approach for assessment the age composition of the humpback shrimp catches which should be based on a priori knowledge of the number of size-age groups and their average sizes. Materials were the data of trawl surveys and fisheries monitoring by traps obtained in 1997-2002 and 2010- 2022. As results, an original algorithm, which allows assess the age composition of the humpback shrimp catches, was worked out. After calculations, averaged over different samples carapace lengths (CL) of males aged 2-6 years were 17,2; 22,4; 27,4; 31,8; 35,3 mm; intersexes aged 5-6 years had CL 34,2; 37,9 mm. For females, 5 size- age groups were distinguished. Each group, due to the incubation of eggs for 15 months and the possibility of changing sex at the age of either 4 or 5 years, can include up to 4 age classes of the same size. The average CL in these groups were 35,6; 38,9; 42,1; 44,1; 47,5 mm. The groups were divided into age classes by taking into account the presence or absence of the eggs in the fall and the degree of their maturity in the spring. For additional division, it is proposed to use a retrospective analysis based on the ratio between groups including only one age class. More reliable estimates are based on the fall survey data. The maximum longevity of a generation is estimated at 14 years. Practical value: The obtained results can be applied for the humpback shrimp stocks assessment with the help of cohort models.