Herring fishery in the Bothnian Sea (southern Gulf of Bothnia) and the North Sea : similarities and differences

In recent years, herring catches have increased in the Bothnian Sea (southern Gulf of Bothnia, northern Baltic). The assessment of a fish stock by virtual population analysis (VPA) is sensitive to the input values used, and thus the results include uncertainties. In this paper I examine, also independently of the results of the virtual population analysis, if there are signs of overfishing in the Bothnian Sea herring stock. The situation there is compared with that in the North Sea, where changes in the fishery leading to the collapse of the herring stock are well documented. Results from the Bothnian Sea show that changes in the herring catch composition, growth, maturity and larval abundance due to fishing have been minor. According to VPA and the other parameters measured, so far there are no obvious biological signs of the herring overfishing in the Bothnian Sea.