The grey seals in the Baltic Sea compete for
fish with the fishing industry. The seals locally eat about the same quantities of cod, common whitefish, salmon, sea trout and eel as those taken by fishermen.
This is the conclusion from research carried out at the University of Gothenburg.
The grey seals in the Baltic Sea eat largely the same species and the same sizes of fish as
those taken by the fishing industry. So even if the amount of fish eaten by seals is small relative to the total amount of fish caught in the Baltic Sea, the seals' dietary habits may have a major impact on the local availability of fish in the areas where they are common.
If you compare the estimated consumption of fish by grey seals in their main range in Sweden, which is north of the Kalmar Sound, it is of the same order of magnitude as the total catch taken by Swedish professional and leisure fishermen in the same area, says scientist Karl Lundström.
The grey seal was common at the beginning of the 20th century, but was hard hit by hunting and by environmental toxins, and only a remnant remained in the 1970s. However, the seal population has grown continuously since the middle of the 1980s, and this has led conflicts with the fishing industry.
The scientists have studied the dietary habits of the seals in order to understand the role they play on the ecosystem, and how they influence the surroundings.
It became clear that the diet of grey seals differs between the northern and the southern Baltic. Herring was the most common food eaten by all seals, followed by common whitefish in the Gulf of Bothnia and sprat in the main body of the Baltic Sea.
This is the first comprehensive investigation into the diet of the grey seal in the Baltic Sea since the 1970s.
The thesis: "Assessment of dietary patterns and prey consumption of marine mammals: Grey seals (Halichoerus grypus) in the Baltic Sea" has been successfully defended at a disputation held at the University of Gothenburg.
Source: University of Gothenburg