Sea trout (Salmo trutta)

There are naturally reproducing, wild, sea trout populations in at least 250 rivers in the entire Baltic area. Besides the naturally spawning sea trout, compensatory rearing and releases are legally enforced in some rivers utilised for hydro electric power production. In many rivers enhancement releases to increase the status of the populations is undertaken. Some of the wild populations are in a poor shape due to, in some cases, overexploitation and in other cases due to decreased spawning opportunities due to human activities. The total production of sea trout smolt has been estimated to be some 3-3,5 million annually, of which almost 20% of wild origin. It must be noted that the production level of wild sea trout is largely unknown as many populations are not surveyed at all.

The life patterns of sea trout populations differ depending on the latitude of their home river. It could be found that the more northern the river, the less migration distances from the river occur. The southernmost populations have migration patterns similar to those of salmon and they also reach much heavier weights than those in the northern part of the Baltic area.

The fishery of sea trout mostly takes place in the coastal areas distance from home rivers depending on the above mentioned migration pattern. However, the southern wide migrating populations are partly exploited in the salmon fishery off shore. The total catch of sea trout has been estimated to be in the level of 1000-1500 tonnes, but this figure is probably a low estimate as a great part of the catch is taken in recreational fisheries.

In some rivers, especially in the southern part of Sweden, there are incidences were the populations are effected by the M74 syndrome. In the rivers Emån and Mörrumsån, densities of parr sea trout have decreased even more than those of salmon parr. There is some evidence that also the sea trout populations in the Gulf of Finland are affected by M74, but the extent is not known.