مرکز منطقه ای اطلاع رساني علوم و فناوري - A case study for preventing illegal trawl fishery: The application of anti-trawl artificial reef and design criteria

Abstract :

The case study was carried out to prevent illegal trawl fisheries in İzmir Bay. Fishing ports, fishing vessels (length, engine power, commercial fishing licence etc.) and trawl net specifications (horizontal mouth opening, NH; trawl net length, NL etc.) were surveyed. The number of trawlers fishing illegally off İzmir which were seized by Turkish Coast Guard (TCG) between 2010 and 2014 was approximate 160. The plots of illegal trawlers caught in fishing area by TCG were marked on the map. It was obtained that trawlers fishing illegally smaller than 12 m and engine power of vessels were between 7 and 452 kW in İzmir. 98.2% of seized illegal trawlers in İzmir Bay had no fishing license and had maximum 286 kW engine power. Of these, 64% of trawlers were caught near coasts of Tuzla and Güzelbahçe localities. Therefore, two artificial reef sites (Tuzla and Güzelbahçe) were concluded in the Middle Bay of İzmir. While planning the project, banned dive sites for Preservation of Culture and Natural Heritage, previous artificial reef projects in the area, mud disposal site that is used during the cleaning of the inner bay, legal fishing activities, wave and current data in İzmir Bay and water depths were considered. Anti-trawl blocks were planned to construct reinforced concrete with 2.9 tones and 110x110x100 cubic centimeter. In the case where anti-trawl reefs are placed parallel to the coastline, total length of trawl gear (LG) was found as 167 m from the distance between the blocks (DB); warp length (WL), sweep length (SL), and NL. In other case (perpendicular to the coastline), minimum trawler was considered and distance between trawl doors (TD) was found as 22 m from NH, NL and, SL. Consequently, the distance between anti-trawl blocks and deployment depths were determined as between 25-200 m and 23-47 m, respectively. The protection ratio was 0.2 ha/number and total number of anti-trawl reefs was estimated as 6,808 for two artificial reef sites. The duration of the project was expected as nine months and the total budget of the project (construction, transportation, deployment, renting etc.) was estimated as 8,046,856 TL.