Distribution of escaped farmed salmon and rainbow trout in the sea and possible effects of salmon lice on wild stocks

Abstract

The aims and first results of a recently started project are presented. The geographical and seasonal distribution of the catch and catch per unit effort of escaped farmed salmon and rainbow trout are studied in an area in western Norway characterized by dense farming activity. The general condition of the escapees during the year is monitored by various parameters. The migration behaviour of the escapees is studied by tagging experiments. Possible effects of salmon lice on wild salmon populations is estimated by the number of adult female sea lice parasitasing escaped farmed fish during the period of the natural smolt run, and by release of smolts treated/untreated with slice (an oral anti lice drug). In addition, the sea survival and incidence of male parr maturity (precocious maturation) of river stocked family groups is estimated.