Negative effect of protective bag on trawl codend selectivity

Abstract

This study investigated the differences of selectivity between a plain codend and a codend surrounded with a protective bag. The experiments were carried out in the İskenderun Bay, located in the eastern Mediterranean Sea, between 15 January and 15 March 2012, when the amount of trawl catch was the lowest in the fishing season. The experiments were conducted on board Ali Kaptan-6 (22 m, 500 hp main engine) by employing a conventional bottom trawl commercially used in İskenderun Bay. The hooped covered codend method was used to obtain selectivity data. Eight valid hauls were carried out both with codend and protective bag. The data were collected for brushtooth lizardfish (<em>Saurida undosquamis</em>) and Randall's threadfin bream (<em>Nemipterus randalli</em>) which were Red Sea migrants and dominated fish for trawl catch in the area. Selectivity parameters were obtained by using logistic equation with the maximum likelihood method. As a result, protective bag had negative effects for especially the brushtooth lizardfish on codend selectivity, although the species were very successful in escaping trawl codend mesh openings due to is fusiform body.