Selectivity of diamond and square mesh beam trawl cod ends for Parapenaeus longirostris (Lucas, 1846) (Decapoda, Penaeidae) in the Sea of Marmara

WOS: 000242817400003In this study, the effects of an increase in diamond mesh size from 24 to 28 and 32 mm, and changing mesh shape from diamond to square mesh on size selectivity for the deep-water rose shrimp, Parapenaeus longirostris were investigated. Fishing trials were carried out on commercial beam trawlers in the various fishing areas of the Sea of Marmara in two periods, between 28 August and 8 September 2001, and 29 April and 9 May 2002. Data were collected by twin trawl and analysed by means of a logistic equation with the Maximum Likelihood Method of the SELECT model. The 50% retention length (L-50) Of P longirostris increased consistently with diamond mesh sizes from 24 to 28 and 32 mm, and 28 mm square mesh gave a higher L-50 value than diamond at the same mesh size. The 32 mm diamond mesh size showed relatively better selectivity (L-50 = 104.1 mm) than the other cod ends, agreeing better with the Length at First Maturity (LFM) of 97 mm total length. The use of cod ends of 24 and 28 turn mesh size should be avoided in order to avoid a catch consisting mainly of small individuals. Such an increase in mesh size on beam trawl nets would contribute to reducing the amount of undersized P. longirostris in this fishery