Sub-stock-specific assessment of cod in Öresund - an evaluation of the effects of fishing restrictions introduced in 2009

Worldwide, many fisheries are under severe stress and extensive depletion of fish stocks is common. Besides overfishing an important problem preventing depleted stocks from recovery is that fish stocks are commonly managed following administrative rather than biological reasons. This stresses the importance of sub-stock-specific assessments for sustainable fisheries. The present study performed such an assessment for cod in Oresund, where trawling has been banned since 1932. In 2009 more restrictions were introduced in parts of the area and in the adjacent Kattegat to protect cod stocks. The results indicate a decrease in spawning stock biomass of cod in the Sound after 2009, although with an increasing trend in recruitment due to a very strong year in 2013. In contrast, average recruitment has been lower in the time after 2009 compared with the period before. Average fishing mortality on cod at age 3-5 has been lower after 2009 compared to the time before. However, an increasing trend towards higher fishing pressure has been seen since the implementation of management actions. Overall, the implementation of restriction for fishing has had positive effects on cod in Kattegat, whereas in the Sound no obvious positive effects could be observed. (Less)