Biological features of the shrimp Palaemon adspersus Rathke, 1836 (Decapoda: Caridea: Palaemonidae) from the Black Sea Karkinit Bay in 2016-2017

The Black Sea grass shrimp Palaemon adspersus Rathke, 1836 is the sole commercially valuable species among the 43 species of decapod crustaceans in the Azov-Black Sea basin. It inhabits the bottom of the upper shelf in the waters of the Northeast Atlantic and the Mediterranean basin and is known for its high tolerance. As a ben-thophagous polyphage and a food source for fish, this species plays a significant role in the aquatic food chains. Given the intense fishing of this species in the Azov-Black Sea basin, monitoring the state of its populations is crucial. Samples (a total of 360 specimens) were collected from fishing gear near the Lebyazhye Islands in the Karkinit Bay in September 2016 and May 2017. A comprehensive laboratory analysis of P. adspersus individuals revealed the population's sex composition (with females accounting for 87-100%); female body length reached 58.1 mm, while males were smaller, up to 44.1 mm, with carapace lengths of up to 16.7 and 11.4 mm, respectively. The body weight of the shrimps ranged from 0.46 to 3.78 g; females had a higher maximum body weight due to their larger size compared to males; the weight growth of individuals is closely linked to linear growth (power dependence). May marked the period of active spawning in the bay, with egg-bearing females predominating, most of which had recently spawned; egg-bearing individuals were observed maturing again, and among females without eggs, about 70% had maturing ovaries. In September, the start of the “inter-spawning rest” was noted, during which females had undeveloped ovaries and did not carry embryos. The synchronization of ovarian maturation and embryo development on pleopods allows females to lay and carry multiple clutches of eggs during the spawning season. Fecundity reached 2 263 eggs, with the length of freshly laid eggs being 0.72 ± 0.04 mm and the volume 0.15 ± 0.02 mm³; during incubation, the egg size increased by 1.2 times. The maximum age of the shrimp in the bay was approximately 3 years.