6. World Fisheries Congress, United Kingdom, 1 - 04 May 2012, pp.172
Fishery by-catch and discarding have attracted serious attention in the world fisheries
research recently due to the increasing recognition of their negative impact on marine
ecosystems. Here we investigate the effects of demersal trawl fishery on non-targeted
species in the Marmara Sea.
The Marmara Sea forms a transition environment between the Black Sea and the
Mediterranean Sea. This unique marine environment exchanges waters with the Black
Sea through Istanbul Strait and with the Mediterranean Sea through Dardanelles Strait. Besides the well-established importance of the Black Sea fisheries for Turkey, the catches from the Marmara Sea, despite its small surface area, constitute a significant fraction of catches in Turkey. According to Turkish fisheries law, any kind of trawling (mid and bottom) is strictly forbidden in The Marmara Sea and both Dardanelles and Istanbul Straits. However, coast-guard records show illegal trawling activity while data of Turkish statistical organization also indicates the three times increase of fleet size in the past 10 years. Moreover, our personal communications with the fishery cooperatives revealed that the trawling activity may be more intense than the official records. Three demersal trawl surveys were performed to determine the effects on non-target species in 40 critical points in the Marmara Sea. We found that 85% of total catches included nontargeted species, which consist of mostly rays, sharks, tiny crabs, ascidians, annelids, and sea stars. We evaluated that 2/3 of those by-catch species were also discarded.
Our study demonstrates how bottom trawling severely affects the sea floor life and increase discarded by-catch species. We conclude that the enforcement of the present
fishery law as well as raising public awareness on marine conservation may reduce the
negative impacts of by-catch in the Marmara Sea.