| Summary: | Many aspects need to be considered when evaluating the consequences of halting compensatory releases of salmon in the Baltic area. The present report focuses strictly on genetic concerns associated with large scale salmon releases. A majority of the original wild Baltic salmon populations, i.e. populations of Atlantic salmon (Salmo salar) in the Baltic Sea, has gone extinct. Historically, 84 rivers flowing into the Baltic Sea have harbored Atlantic salmon, but currently only 10 of these maintain self sustaining wild natural populations in safe numbers (CCB 2012). Large scale releases of salmon are carried out in the Baltic region to increase productivity of separate populations and to compensate for natural reproduction that has been lost due to hydroelectric power plants that are blocking previous migratory routes. Already in the 1980s observations of pronounced genetic differentiation between populations inhabiting different rivers, coupled with indications that salmon hatchery stocks are genetically divergent from the wild populations they were meant to represent, have warranted conservation genetics researchers to warn against potential negative effects of large scale releases (Ståhl 1981, 1983, 1987). In brief, current large scale releases can cause the following four types of genetic risks for native populations: 1) loss of genetic variation, 2) loss of adaptations, 3) change of population composition, and 4) change of population structure (Laikre et al. 2010). These adverse genetic impacts have been recognized and documented for salmonid fishes for decades (Ryman 1981; Ryman & Utter 1987; Hindar et al.1991; Waples 1999; Naish et al. 2008; Nielsen & Hansen 2008). In 2011 these potential risks of large scale releases gained attention when the European Commission put forward a proposal of phasing out all compensatory releases of salmon in the Baltic area (European Commission 2011). We have compiled and reviewed information regarding compensatory releases of salmon in Swedish rivers including ...
|
|---|