Occurrence of reared salmon in natural salmon rivers in Iceland

Abstract

Over 10 million salmon smolts were produced in Iceland in 1989. That is ten-fold the production 5 years ago. Thereof, about 6 million smolts were used in ocean ranching and about 2 million smolts went to cage-rearing operation. The rest is reared in land-based tanks.The number of reared fish entering salmon rivers has increased as the salmon culture growed, especially in S.W. Iceland where large part of the salmon-culture is operated.To evaluate the proportion of reared fish in salmon rivers, scale samples have been taken from salmon catches in rivers of Iceland. The scales have been used to identify escapes from cage farms and straying fish from ocean-ranching stations. From such analysis it is observed that the proportion of reared fish is low in North Iceland but is high in S.W. Iceland and is increasing from year to year, being up to 70% of the catch in one river.In River Ellidaar, a famous salmon river in Reykjavik the proportion of reared salmon in the catch in 1989 was 30.1%, compared to 15.9% in 1988. The reared fish were distributed evenly up the river in 1988, but in 1989 a higher proportion of the reared fish was caught downstream.Salmon escapees generally ascend the rivers later than the natural salmon. Almost all the reared fish examined in the rivers were sexually mature. Reared fish have been caught as kelts in the spring in River Ellidaar.