Contribution to Some Biological and Fishery Aspects of Commercial Penaeid Prawns in Mersin Bay (Northeastern Mediterranean, Turkey).

This study examines the impact of shrimp trawling on the multi-species shrimp and prawn fishery in the northeastern Mediterranean. Fishing trials were carried out on a commercial prawn trawler between 18 and 23 September 2006. Data were collected with a conventional trawl net, designed specifically for prawns. During six valid trawl hauls, 32 species were caught in total and of the 17 species regarded as commercially valuable, individuals of all sizes of 12 species and those of the relatively larger sizes of 5 species were retained. The other 15 species were discarded as these are regarded as non-commercial due to a lack of market demand. The discard ratio was calculated as 2.37 : 1 for this fishery. The length-frequency distribution of the targeted penaeid prawn, Marsupenaeus japonicus, shows one peak at about 33 mm CL, and the larger specimens, over 35 mm, are all females (25%). However, the also targeted Penaeus semisulcatus shows two major peaks, at 29 and 39 mm CL, and the approximate size ranges connected with those peaks extend from 26 to 32 mm and from 36 to 40 mm CL, respectively; larger specimens, over 34 mm, are all females (37%). The female-male ratio was 1.07 : 1 for M. japonicus and 1.99 : 1 for P. semisulcatus. In the framework of by-catch and discard evaluation, this fishery should be defined as having high by-catch and discard rates. For this reason, gear-based and management-based solutions or measures should be developed to secure those resources for the future, and also to decrease the impact of fisheries on non-targeted species and their stocks. [ABSTRACT FROM AUTHOR]