The role of genetics in fisheries management under the E.U. common fisheries policy.

Exploitation of fish and shellfish stocks by the European Union fishing fleet is managed under the Common Fisheries Policy (CFP), which aims to ensure that fishing and aquaculture are environmentally, economically and socially sustainable and that they provide a source of healthy food for E.U. citizens. A notable feature of the CFP is its legally enshrined requirement for sound scientific advice to underpin its objectives. The CFP was first conceived in 1970 when it formed part of the Common Agricultural Policy. Its formal inception as a stand-alone regulation occurred in 1983 and since that time, the CFP has undergone reforms in 1992, 2002 and 2013, each time bringing additional challenges to the scientific advisory process as the scope of the advice increased in response to changing objectives arising from E.U. regulations and commitments to international agreements. This paper reviews the influence that genetics has had on fish stock assessments and the provision of management advice for European fisheries under successive reforms of the CFP. The developments in genetics since the inception of the CFP have given rise to a diverse and versatile set of genetic techniques that have the potential to provide significant added value to fisheries assessments and the scientific advisory process. While in some cases, notably Pacific salmon Oncorhynchus spp., genetics appear to be very well integrated into existing management schemes, it seems that for marine fishes, discussions on the use of genetics and genomics for fisheries management are often driven by the remarkable technological progress in this field, rather than imminent needs emerging from policy frameworks. An example is the recent suggestion to use environmental (e)DNA for monitoring purposes. While there is no denying that state-of-the-art genetic and genomic approaches can and will be of value to address a number of issues relevant for the management and conservation of marine renewable natural resources, a focus on technology rather than policy and management needs is prone to widen the gap between science and policy, governance and management, thereby further impeding the effective integration of genetic and genomic information into the fisheries management decision making process. Hence, rather than focusing on what is technically achievable, this review outlines suggestions as to which modern genetic and genomic approaches are likely to help address some of the most pressing fisheries management challenges under the CFP.

Regional environmental pressure influences population differentiation in turbot (Scophthalmus maximus).

Unravelling the factors shaping the genetic structure of mobile marine species is challenging due to the high potential for gene flow. However, genetic inference can be greatly enhanced by increasing the genomic, geographical or environmental resolution of population genetic studies. Here, we investigated the population structure of turbot (Scophthalmus maximus) by screening 17 random and gene-linked markers in 999 individuals at 290 geographical locations throughout the northeast Atlantic Ocean. A seascape genetics approach with the inclusion of high-resolution oceanographical data was used to quantify the association of genetic variation with spatial, temporal and environmental parameters. Neutral loci identified three subgroups: an Atlantic group, a Baltic Sea group and one on the Irish Shelf. The inclusion of loci putatively under selection suggested an additional break in the North Sea, subdividing southern from northern Atlantic individuals. Environmental and spatial seascape variables correlated marginally with neutral genetic variation, but explained significant proportions (respectively, 8.7% and 10.3%) of adaptive genetic variation. Environmental variables associated with outlier allele frequencies included salinity, temperature, bottom shear stress, dissolved oxygen concentration and depth of the pycnocline. Furthermore, levels of explained adaptive genetic variation differed markedly between basins (3% vs. 12% in the North and Baltic Sea, respectively). We suggest that stable environmental selection pressure contributes to relatively strong local adaptation in the Baltic Sea. Our seascape genetic approach using a large number of sampling locations and associated oceanographical data proved useful for the identification of population units as the basis of management decisions.

Sturgeon conservation genomics: SNP discovery and validation using RAD sequencing.

Caviar-producing sturgeons belonging to the genus Acipenser are considered to be one of the most endangered species groups in the world. Continued overfishing in spite of increasing legislation, zero catch quotas and extensive aquaculture production have led to the collapse of wild stocks across Europe and Asia. The evolutionary relationships among Adriatic, Russian, Persian and Siberian sturgeons are complex because of past introgression events and remain poorly understood. Conservation management, traceability and enforcement suffer a lack of appropriate DNA markers for the genetic identification of sturgeon at the species, population and individual level. This study employed RAD sequencing to discover and characterize single nucleotide polymorphism (SNP) DNA markers for use in sturgeon conservation in these four tetraploid species over three biological levels, using a single sequencing lane. Four population meta-samples and eight individual samples from one family were barcoded separately before sequencing. Analysis of 14.4 Gb of paired-end RAD data focused on the identification of SNPs in the paired-end contig, with subsequent in silico and empirical validation of candidate markers. Thousands of putatively informative markers were identified including, for the first time, SNPs that show population-wide differentiation between Russian and Persian sturgeons, representing an important advance in our ability to manage these cryptic species. The results highlight the challenges of genotyping-by-sequencing in polyploid taxa, while establishing the potential genetic resources for developing a new range of caviar traceability and enforcement tools.

The gene conversion hypothesis of MHC evolution: a review.

Gene conversion is often invoked to explain the evolution of sequence patterns observed in major histocompatibility complex (MHC) genes and their alleles. This is the gene conversion hypothesis of MHC sequence evolution. These observations and their interpretation probably belong in a larger theoretical framework, namely the evolution of systems of resistance to rapidly evolving pathogens. This review looks critically at the evidence in favor of the gene conversion hypothesis in this context. We conclude that the case for the existence of an adaptive mechanism in the MHC favoring gene conversion mutations is not proven.