Spatial distribution of brown trout (Salmo trutta) was studied on the Finnish coast of the
northern Baltic Sea in 1998–2010 based on smolt tagging. The studied trout stocks were
hatchery reared, and smolts were tagged with Carlin tags before release into the rivers. The
distance between the release and recapture sites as well as location of the recapture site in
relation to the release site (north, south, west, east) were analysed, taking the stock and
sea age of the trout into account. The most important tag recovery areas at sea were the
estuaries of the spawning rivers and coastal areas surrounding them. The natural direction
of movement was along the coast line, north or south on the western coast and east or west
in the Gulf of Finland. The release site and age affected migration direction. The distance
of recoveries from the release sites varied for the same genetic stock released at different
sites. The longest median recapture distances were recorded during the second sea year.
The stocked brown trout (80%–95%) were mainly caught during their first two years in the
sea before they become mature. Knowledge of spatial dispersal of sea trout is important for
the management of the stocks and fisheries.