Report from the symposium on sea ranching of cod and other marine fish species [Arendal, 15- 18 June, 1993]

Abstract

Recent ranching experiments aimed to enhance the stocks of cod on the Norwegian and Danish coasts have led to disappointing results. The young stages were reared before releasing as juveniles. The use of tags and genetic markers showed that, although emigration was minimal, long-term enhancement of the stock did not occur. It appears that the "carrying-capacity" of the inshore areas is limited, leading to density-dependent mortality. Considerable insight has been obtained on fjordal ecology; this suggests that releases on a more open coastline might be beneficial. In addition the enhancement of sport fishing needed to be evaluated. Ranching of Pacific salmon by releasing reared smolts has also been disappointing. Some enhancement did occur but the fish were smaller and the catch dominated by the releases. Japanese flounder and Texan red drum stocks have, however, been enhanced by ranching.