The conservation and management of endangered species requires information on their genetic diversity, relatedness and population structure. The main genetic markers applied for these questions are microsatellites and single nucleotide polymorphisms (SNPs), the latter of which remain the more resource demanding approach in most cases. Here, we compare the performance of two approaches, SNPs obtained by restriction‐site‐associated DNA sequencing (RADseq) and 16 DNA microsatellite loci, for estimating genetic diversity, relatedness and genetic differentiation of three, small, geographically close wild brown trout ( Salmo trutta ) populations and a regionally used hatchery strain. The genetic differentiation, quantified as F ST , was similar when measured using 16 microsatellites and 4,876 SNPs. Based on both marker types, each brown trout population represented a distinct gene pool with a low level of interbreeding. Analysis of SNPs identified half‐ and full‐siblings with a higher probability than the analysis based on microsatellites, and SNPs outperformed microsatellites in estimating individual‐level multilocus heterozygosity. Overall, the results indicated that moderately polymorphic microsatellites and SNPs from RADseq agreed on estimates of population genetic structure in moderately diverged, small populations, but RADseq outperformed microsatellites for applications that required individual‐level genotype information, such as quantifying relatedness and individual‐level heterozygosity. The results can be applied to other small populations with low or moderate levels of genetic diversity.

Low survival of stocked fish has been associated with fitness declines of the captive reared fishes because of genetic domestication and unnatural rearing environments. The effects of broodstock origin (wild or captive) or rearing method (standard or enriched) on survival and migration of hatchery-reared Atlantic salmon smolts (Salmo salar) were investigated in the Tornionjoki River using radiotelemetry. Smolts that were reared with enriched methods had a twofold increase in survival (∼38%) compared with smolts that had been reared in a standard hatchery environment (∼19%). Nature-caught smolts had highest survival (∼57%). Smolts from enriched rearing had a higher initial migration speed than fish from standard rearing. Initial migration speed during the first 3 km was positively correlated to survival probability after 290 km for hatchery fish. There was no clear effect of origin on survival or migration speed. The results of this study show that enriching the rearing environment with methods easily applicable to large-scale production promotes smolt survival and migration speed during river migration, which is imperative for stocking success.

21Animals, including fish, display individually consistent behavioral differences that may affect 22 an individual's vulnerability not only to predation, but also to fishing. Compared to complex 23 natural environments, plain hatchery environments might induce development of behaviors 24 that increase vulnerability to fishing, which would in turn have major implications for the 25 management of stocks by supportive releases. We studied whether the vulnerability of 26 hatchery-reared brown trout Salmo trutta to angling could be predicted by rearing method 27 (standard vs. enriched) or behavioral variation that was assessed using long-term observations 28 of moving activity in groups. High moving activity in the beginning of the behavioral tests, 29i.e. exploration behavior, predicted increased vulnerability to angling independently of fish 30 body size. Standard rearing promoted high exploration rate among fish, whereas enriched 31 rearing promoted improvement in body condition in (semi-)natural conditions. However, the 32 driving influence of hunger on vulnerability could not be ruled out, as the most explorative 33 standard-reared fish appeared unable to maintain their body condition during the experiments. 34This study provides direct evidence that standard hatchery rearing method promotes 35 behaviors that directly predict vulnerability to angling. 36 37

–  After release to the wild, captive reared salmon have shown lower foraging rates on natural prey and impaired ability to avoid natural predators and thus lower survival compared with wild‐born conspecifics. Here, we examine whether captive breeding influences learning of foraging on natural prey and how enriched rearing methods may improve foraging on natural prey by Atlantic salmon (Salmo salar) parr. We reared offspring of hatchery or wild salmon of the same population in either a standard or enriched environment at production‐scale densities. The enriched environment featured submerged overhead shelter, varying water current, depth and direction and consequently alterations in food dispersion. Parr reared in the enriched environment expressed higher feeding rates, and parr of wild origin started to forage earlier on natural prey. The enriched method promoted foraging of hatchery reared parr on natural prey and is easily applicable to commercial production of salmonids for reintroduction or stock enhancement purposes.

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