Investigation of some shrimp species in terms of population dynamics and distribution caught by beam trawl in the Southern Black Sea (Rize coast)

This study was conducted to determine distribution of shrimp species caught by beam trawl with 2 m beam length and 15 mm cod-end mesh size between December 2012 and November 2013 in the Black Sea (Rize coast) and to determine reproduction time of most sampled shrimp species, Palaemon adspersus and reproduction biology (50% size at sexual maturity, spawning time), growth characteristics (seasonal and non-seasonal von Bertalanffy growth equation parameters, length-weight relationship and length composition) of Philocheras trispinosus. A total of 618 P. adspersus, 550 P. trispinosus, 12 Palaemon serratus, 11 Philocheras fasciatus and 10 Crangon crangon were sampled during the study in consequence of 146 beam trawl sampling. Sampled 5 shrimp species' catch per unit efforts (CPUE; individuals/hours) were estimated as 0.3±0.12 for C. crangon, 0.4±0.22 for P. fasciatus, 13.1±2.93 for P. trispinosus, 25.4±16.22 for P. adspersus and 0.4±0.17 for P. serratus. Densities (N 1000 m2) of P. adspersus and P. trispinosus were estimated as 1349.7±632.5 and 1877.7±737.3, respectively. Ovigerous females were recorded between April and September for P. adspersus and from January to April for P. trispinosus. The size at sexual maturity of P. trispinosus was estimated as 25.7 mm total length in females. The seasonal growth parameters, computed from monthly 1 mm length intervals -frequency distribution, were estimated as L∞ = 29.3 mm TL, K = 0.860 year-1, C = 0.180, WP = 0.510. The lowest growth time (WP = 0.510) of P. trispinosus was determined mathematically as at the end of the June and beginning of the July. Longevity of P. trispinosus was estimated as 2.58 years. Growth performance index (Φ´) was also estimated as 2.8678.