Length at Release Affects Movement and Recapture of Lake‐Stocked Brown Trout

The effect of length (total length = 15‐50 cm) at release on the yield and recapture of stocked brown trout Salmo trutta was examined by tagging experiments in a large boreal lake, Lake Oulujärvi in Finland (928 km 2 ). The time the fish spent in the lake before harvesting and the size of the area from which they were harvested diminished with increasing length at release. Small brown trout (<40 cm) moved towards a part of the lake where the highest densities of pelagic prey fish are found, whereas large brown trout (≥40 cm) were captured near their release sites. The longer the distance between the release site of the small brown trout and the good foraging area, the lower their recapture rate. Both relative yield and recapture rate (per 1,000 fish released) increased with increasing fish length at release. However, the positive relation between recapture rate and fish length at release disappeared or turned negative (depending on the release site) when the production costs of fish were taken into account and the recapture rate was calculated per constant investment (€100,000 (euros)).