Selectivity of the diamond and square mesh of the trawl cod end, biological and economic consequences and fish behavior comparative study.
The objective of this project is to study the selectivity of diamond and square mesh of the codend in the bottom trawl, the biological and economic consequences of their implementation and the behavior and condition of the retained fish and escapees. In this context, we will study the selectivity of the 40 mm square and 50 mm diamond mesh size in the codend of the trawl, which were determined based on the EU regulation (EC 1967/2006) as the minimum mesh sizes for this gear. For comparison purposes, the selectivity of the 40 mm diamond mesh size will also be examined, which was used until now, but is no longer in use based on EU regulation (EC 1967/2006).
Data collection will take place during experimental fishing, in conditions as close as possible to those carried out by commercial fishery (using commercial fishing vessels, trawls and other commercial fishing equipments, testing hauls of commercial fishery). The study will be carried out by covering the codend with cover. Based on these data, the selectivity parameters, the composition of the catch, the percentage of commercial catch, by-catch and discards and quantity of the retained and escapees will be studied for each mesh size, for two seasons and three depth zones. In addition, underwater cameras inside the trawl and between the codend and the cover will be used for the study of the behavior and condition of the retained fish and escapees. Finally, economic data, related to each mesh size, will be collected (quantity and quality of landings, landings’ commercial value, fuel cost, gear cost etc).
All the above will form the basis for assessing the biological and economic consequences of the application of each mesh size in order to propose the most adequate one. The results of this project will be disseminated through a website, publications, participation in conferences and a workshop with the related stakeholders.