Balticsea 2020

Trawling for Sticklebacks in the Gulf of Bothnia

Stickleback populations have increased significantly in the Baltic Sea and the Gulf of Bothnia. It is also a species that currently has no commercial value. With support from the BalticSea2020 foundation, researchers at Umeå University are examining the possibility of commercially fishing stickleback to provide fish feed. Fishing for stickleback could have a positive impact on the environment in terms of the promotion of species of predatory fish, but also by the reduction of the symptoms of eutrophication along the coasts of the Baltic.

Background
The increase in the numbers of stickleback has been associated with negative effects on Baltic coast ecosystems. This is most likely due to the stickleback eating the fry of predators such as perch and pike and thus having an effect on the growth of stocks of such. Stickleback also feed on organisms living on the sea bed, such as zooplankton. This has the effect of reducing their consumption of phytoplankton, which in turn leads to increased propagation of algae in the Baltic Sea’s coastal areas.

Purpose and goals
With this project, biologists at Umeå University are considering the possibility of commercially fishing stickleback as fish feed and are determining whether reduced populations of stickleback could reverse the negative trends along the Baltic coast.

Their expectations are that commercial fishing of stickleback will be favourable to the environment of the Baltic. Inter alia, reduced stickleback populations can have positive effects on the populations of coastal predatory fish and increase the opportunities for the recovery of perch and pike, for example. It would also produce additional income for the fishing industry, since such activities are not likely to conflict with those of other stakeholders and users of the Baltic’s fish stocks. Using stickleback as fish feed can also promote future expansion of the aquaculture industry in the Baltic Sea catchment areas, for example in power reservoirs, where net nutrient salt loads into the Baltic Sea would be reduced to zero if the feed used is based on ingredients from the same maritime source.

Method
The project was divided into two phases. In the first of these, the viability of fishing stickleback for the production of fish feed was examined. If this precondition exists, the project would continue into its second phase, where the aim was to stimulate commercial fishing of stickleback, production of fish feed and large-scale evaluation of the impact on the coastal ecosystem, as the quantity of stickleback diminishes.