By-catch is everything that was caught unintentionally. Other than targeted fish species, birds, mammals and others sea creatures can be the by-catch. With unselective commercial fishing gears by-catch is caught rather often. There are two types of victims in the passive fishing gears (i.e. gill and trap nets) of the fishermen working on the Baltic Sea. These are marine mammals: ringed and grey seals and water birds, first of all diving ducks.

Both seals and water birds dive for food. If they swim into a fishing nets, they get entangled and finally suffocate and drown.
Some birds, e.g. long-tailed ducks (Clangula hyemalis), are rather abundant, which might mean that the problem of these ducks drowning in the fishing nets is not that severe. However, some others, like Steller’s eider (Polysticta stelleri) are very rare and fully protected. Since the populations of such species are small and unfortunately permanently declining each such by-caught bird is a small tragedy. 

Both of the seal species, grey seal (Halichoerus grypus) and ringed seal (Phoca hispida), are protected in most of the Baltic Sea countries. While the grey seal population shows now some signs of growth, the ringed seals are still rare. Moreover, very mild winters have seriously impacted the reproduction possibilities. Ringed seals can give birth only on ice, which has become a scarcity. Additional by-catch mortality can be critical.

What can be done? There is a way to prevent this from happening! Go to Alternative fishing gears to find it out.
By-catch
Project's main site - www.balticseaportal.net
Bycaught Steller's Eider, highly endangered bird species and a grey seal (Photo: Markus Vetemaa)