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

Abstract

Comparisons of the genetic composition of 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 observed in electrofishing surveys. Selective angling, in combination with a small legal catch size, may have considerably eliminated introduced trout and 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 important factor influencing the genetic structure of fish populations and should be taken into account in studies of introgressive hybridization in stocked fish populations and their management. In this study, demographic consequences of stocking were not assessed. Thus, even though the genetic consequences 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. 2001 The Fisheries Society of the British Isles

Anthropogenic and habitat correlates of hybridization between hatchery and wild brook trout

“…Although this contradicts some previous findings in which fishing was negatively correlated with hatchery admixture (García-Marín et al 1998), potentially because of anglers being more efficient at catching hatchery fish than wild fish (Mezzera and Largiadèr 2001;Champigneulle and Cachera 2003), it does support the hypothesis proposed by Evans and Willox (1991). These authors showed, through modeling, that fishing preferentially removes large, highly fecund wild and hatchery fish alike, but while wild fish have only one source of replacement (natural recruitment), hatchery fish are potentially replaced by both natural recruitment and further stocking events.…”

“…Recent studies have found that the extent of admixture from stocking can be correlated with a species' life history (Utter 2000), stocking intensity (Almodovar et al 2006), fishing pressure (García-Marín et al 1998;Mezzera and Largiadèr 2001), population size (Hansen et al 2009), abiotic factors (Rasmussen et al 2010;Marie et al 2012), and human activities . Few of these studies have rigorously examined the relative influence of multiple habitat and anthropogenic factors in driving variation in hatchery-wild admixture among populations (but see Marie et al 2012), though such investigations may bear practical results.…”

Assessment of three strategies practiced by fishery managers for restoring native brown trout (Salmo trutta) populations in Northern French Alpine Streams

“…Deviations from Hardy-Weinberg equilibrium (HWE) were tested using the exact probability test of Guo & Thompson (1992) available in GENEPOP 3.4 (Raymond & Rousset 1995). Mezzera & Largiadèr 2001). These tests used a Markov chain method (1000 dememorisation steps, 100 batches and 1000 iterations per batch).…”

Comparative analysis of introgression at three marker classes: a case study in a stocked population of brown trout

“…  cohorts (Mezzera, 2000). In another study, there were strong indications that selective angling may be the main factor for a decrease of these genotypes at this stage (Mezzera & Largiadèr, 2001).…”

“…All observed alleles were assigned to two distinct allele classes, a ' hatchery specific ', and a ' native specific ' allele class, respectively. The assignment and pooling of alleles at microsatellite loci was carried out as described in Mezzera & Largiadèr (2001). Allele frequencies are given in Appendices I and II.…”