Effects of marine survival, precocity and other life history traits on the cost-benefit of stocking salmon in the Baltic Sea

Cost-benefit analysis was applied to estimate the economic consequences of precocious maturation among hatchery-reared Atlantic salmon (Salmo salar) sea-ranched in the Baltic Sea. Data on the rearing and release costs, fishing costs, catch benefits, catch size, catch age and survival of previously immature and mature salmon in Carlin-tagged groups released into the Gulf of Finland in 1981–2005 were used in the analysis. Previously immature and precociously mature salmon differed in their marine growth, survival, sea age at maturity and migration behaviour. Precocity reduced the net present value (NPV) of the releases due to the lower catch age and marine survival of the previously mature compared to the immature salmon. Assuming that all the salmon were harvested by professional fishermen, the estimated NPV for the whole study period 1981–2005 was positive at a discount rate of 0.04 and a producer price of 5.2 euros/kg or over. During the period of lower survival in the late 1990s and later, the NPV was, however, negative for all assumed producer prices of capture salmon in the professional fishery, i.e. prices between 4.2 and 9.2 euros/kg. The NPV only turned positive if the value of the catch was assumed to be the estimated value of the recreational fishery catch, i.e. 21 euros/kg. The results suggest that if the catch age and marine survival of salmon do not markedly increase from their present low levels, there will be practically no potential to render the NPV positive in the professional fishery by introducing novel breeding practices capable of reducing parr maturation rates. A shift in the fishery from commercial to recreational fishing could to some extent increase the NPV of salmon releases.

► Immature salmon smolts and precociously mature salmon males (Salmo salar) differed in their marine survival and migration behaviour.
► Precocity reduced the net present value (NPV) of the releases.
► The survival greatly affected the NPV.
► During the period of low survival (2-3%) the NPV was negative for all assumed producer prices of capture salmon in the professional fishery.
► The recreational fishery catch could increase the NPV of salmon releases.