While evolutionary responses require heritable variation, estimates of heritability (h2) from wild fish populations remain rare. A 20-year molecular pedigree for a wild Scottish population of Atlantic salmon (Salmo salar) was used to investigate genetic contributions to (co)variation in two important, correlated, phenotypic traits: “sea age” (number of winters spent at sea prior to spawning) and size-at-maturity (body length just prior to spawning). Sea age was strongly heritable (h2 = 0.51) and size exhibited moderate heritability (h2 = 0.27). A very strong genetic correlation (rG = 0.96) between these traits implied the same functional loci must underpin variation in each. Indeed, body size within sea ages had much lower heritability that did not differ significantly from zero. Thus, within wild S. salar populations, temporal changes in sea age composition could reflect evolutionary responses, whereas rapid changes of body size within sea ages are more likely due to phenotypic plasticity. These inheritance patterns will influence the scope of evolutionary responses to factors such as harvest or climate change and, hence, have management implications for salmonid populations comprising a mix of sea ages.
Captive breeding is the last resort to protect a species that will become extinct because it is incapable of surviving in the wild without human intervention. The freshwater pearl mussel Margaritifera margaritifera is a prime candidate for such action: the species has experienced a recent range-wide decline, particularly in Europe. In Northern Ireland, M. margaritifera is now only found in six rivers and, because of a lack of natural recruitment in the wild, it has been predicted that these populations will become extinct within 80 years. Consequently, an ex situ breeding program was established with the aim of using a semi-natural method to propagate mussels for restocking. In the present study, we analysed the levels and patterns of genetic diversity in the captive-bred mussels, as well as their parent broodstock and remnant populations from their natal and other rivers in Northern Ireland where M. margaritifera is still found, to help develop best practice for the captive breeding program. Levels of genetic diversity were high, although there was a strong correlation between genetic diversity and census population sizes, as well as evidence of inbreeding in all populations. Small but significant levels of genetic differentiation were observed between both the captive-bred juveniles and their parent broodstock, and the samples from their source river, indicating a possible founder effect. In addition, three groups of genetically distinct clusters were observed among the remaining natural populations that could be used as the basis for defining conservation units. These findings allow us to make recommendations for efficient management of the captive breeding program, including rotation of the ex situ broodstock on a regular basis to avoid prolonged inbreeding, and the establishment of captive breeding of other populations to reflect genetic differences between putative conservation units in Northern Ireland and elsewhere. bs_bs_banner Animal Conservation. Print ISSN 1367-9430 Animal Conservation 15 (2012) 593-602
Understanding the extent, scale and genetic basis of local adaptation (LA) is important for conservation and management. Its relevance in salmonids at microgeographic scales, where dispersal (and hence potential gene flow) can be substantial, has however been questioned. Here, we compare the fitness of communally reared offspring of local and foreign Atlantic salmon Salmo salar from adjacent Irish rivers and reciprocal F1 hybrid crosses between them, in the wild ‘home’ environment of the local population. Experimental groups did not differ in wild smolt output but a catastrophic flood event may have limited our ability to detect freshwater performance differences, which were evident in a previous study. Foreign parr exhibited higher, and hybrids intermediate, emigration rates from the natal stream relative to local parr, consistent with genetically based behavioural differences. Adult return rates were lower for the foreign compared to the local group. Overall lifetime success of foreigners and hybrids relative to locals was estimated at 31% and 40% (mean of both hybrid groups), respectively. The results imply a genetic basis to fitness differences among populations separated by only 50 km, driven largely by variation in smolt to adult return rates. Hence even if supplementary stocking programs obtain broodstock from neighbouring rivers, the risk of extrinsic outbreeding depression may be high.
A flexible panel consisting of 38 informative microsatellite markers for Salmo trutta is described. These markers were selected from a pool of over 150 candidate loci that can be readily amplified in four multiplex PCR groups but other permutations are also possible. The basic properties of each markers were assessed in six population samples from both the Burrishoole catchment, in the west of Ireland, and Lough Neagh, in Northern Ireland. A method to assess the relative utility of individual markers for the detection of population genetic structuring is also described. Given its flexibility, technical reliability and high degree of informativeness, the use of this panel of markers is advocated as a standard for S. trutta genetic studies.
19Sea lice continue to be one of the largest issues for the salmon farming industry and the use 20 of ballan wrasse (Labrus bergylta) as a biological control is considered to be one of the most
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