Evidence for selective angling of introduced trout and their hybrids in a stocked brown trout population

Comparisons of the genetic composition or brown trout Salmo trutta captured by anglers and by electrofishing based on three diagnostic microsatellite loci provided strong evidence that angling is selective in a stocked brown trout population. At two sites, anglers caught significantly younger trout and proportionally more introduced hatchery trout and hybrids than were obs erved in electrofishing surveys. Selective angling, in combination with a s mall legal catch size, may have considerably eliminated introduced trout an d hybrids before spawning at the study sites, and thus may have reduced the introgression of alien genes into the local gene pool. Angling can be an i mportant factor influencing the genetic structure of fish populations and s hould be taken into account in studies of introgressive hybridization in st ocked fish populations and their management. In this study, demographic con sequences of stocking were not assessed. Thus, even though the genetic cons equences of stocking may be minimal or largely reversible through angling, resource competition between native and introduced trout, until they reach legal catch size, is expected to have a negative effect on the productivity of the indigenous trout population. (C) 2001 The Fisheries society of the British Isles.