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Effective management of migrating fish stocks requires an understanding of population structure and each stock's contribution to the fishery. Water bodies spanning across national borders pose a particular challenge. We investigated the genetic structure of 13 adfluvial brown trout populations from natal rivers and conducted a genetic mixed‐stock analysis of brown trout from the cross‐border Lake Pyaozero Basin in eastern Fennoscandia, using 16 microsatellite loci. Our analysis revealed a clear genetic structure of three distinct geographic groups, consisting of river‐specific populations. The Western and Southern groups, which included 11 rivers, contributed over 90% to the mixed stock in the lacustrine rearing area. This mixed stock of several river‐specific subpopulations renders poorly managed fishing in the area a significant threat to the entire native adfluvial brown trout population complex. [ABSTRACT FROM AUTHOR]

Effects of temperature on Atlantic salmon (Salmo salar) were analysed using Carlin tag recovery data (1985–2014), and mixed‐stock catch data (smolt years from 2001 to 2012) in northern parts of the Baltic Sea. During warmer summers, the mean smolt length of the recaptured salmon tended to be smaller, and salmon were recaptured more frequently in feeding grounds closer to the home rivers in the Gulf of Bothnia, while colder summers were associated with more recaptures further south, in the Baltic Main Basin. Moreover, a warmer spring in the smolt year was associated with decreased weight of male grilses in mixed stock data. Further, warmer spring temperatures during the smolt year were associated with a higher proportion of one‐sea‐winter (1SW) males during the return migration in mixed stock data. These results suggest that the increasing global temperature may affect Atlantic salmon life history demographics. [ABSTRACT FROM AUTHOR]

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 FST, 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. We compared the performance of restriction‐site‐associated DNA sequencing (RADseq) and DNA microsatellite markers for estimating genetic diversity, relatedness, and genetic differentiation in brown trout (Salmo trutta) populations. The results indicate that moderately polymorphic microsatellites and SNPs from RADseq found similar genetic structure of moderately diverged, small populations, but RADseq outperformed microsatellites for quantifying relatedness and individual‐level heterozygosity. The results can be applied to other small populations with low or moderate levels of genetic diversity. [ABSTRACT FROM AUTHOR]

Abstract: Inferring the dynamics of populations in time and space is a central challenge in ecology. Intra‐specific structure (for example genetically distinct sub‐populations or meta‐populations) may require methods that can jointly infer the dynamics of multiple populations. This is of particular importance for harvested species, for which management must balance utilization of productive populations with protection of weak ones. Here we present a novel method for simultaneous learning about the spatio‐temporal dynamics of multiple populations that combines genetic data with prior information about abundance and movement, akin to an integrated population modelling approach. We apply the Bayesian genetic mixed stock analysis to 17 wild and 10 hatchery‐reared Baltic salmon (S. salar) stocks, quantifying uncertainty in stock composition in time and space, and in population dynamics parameters such as migration timing and speed. The genetic data were informative about stock‐specific movement patterns, updating priors for migration path, timing and speed. Use of a population dynamics model allowed robust interpolation of expected catch composition at areas and times with no genetic observations. Our results indicate that the commonly used “equal prior probabilities” assumption may not be appropriate for all mixed stock analyses: incorporation of prior information about stock abundance and movement resulted in more plausible and precise estimates of mixture compositions in time and space. The model we present here forms the basis for optimizing the spatial and temporal allocation of harvest to support the management of mixed populations of migratory species. [ABSTRACT FROM AUTHOR]