Report of the Working Group on the Application of Genetics in Fisheries and Mariculture (WGAGFM) [3-6 May 2005 Silkeborg, Denmark]
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The Working Group on the Application of Genetics in Fisheries and Mariculture (WGAGFM) met at the Danish Department of Inland Fisheries Lab at Silkeborg, Denmark from 3–6 May 2005. Attendance was good with nineteen present, twelve official representatives of their countries, and seven Chair-appointed experts. A new WG Chair for 2006–2008 was elected. Dr. E. Eg Nielsen of the Danish Fisheries Institute for Fisheries Research at Silkeborg replaces outgoing Chair, Dr. E. Kenchington of the Department of Fisheries and Oceans, Canada. Five terms of reference were addressed at the meeting. The first dealt with the issue of cli-mate change and the evolutionary ability of fish stocks to respond. The current and predicted rates of change greatly exceed any previous periods of climatic warming over evolutionary time. Faced with rapid temperature increases species can either move to higher latitudes or adapt to prevailing conditions. In the latter case the rate of change may exceed capacity to adapt genetically, with the problem being more severe for species with limited thermal toler-ance. Biodiversity, which is fundamentally genetic diversity, will be reduced due to the loss of populations on the southern limits. Evolutionary processes will only slowly restore lost among-population diversity where a species is able to extend its range northward. With regard to phenotypic traits, the impacts are less predictable but, in general, a reduction in abundance and changes in traits would be expected. The WG proposed five recommendations related to this ToR. Marine species are often characterised by high dispersal potential and annual migration to common feeding areas. These aggregations are often the target of high intensity fishing activi-ties. Harvesting of mixed stocks can lead to overexploitation and risk of extirpation of minor population components when harvest rates are high. Information on spatial and temporal variations in stock composition in mixed-stock fisheries is therefore essential for effective fisheries management and conservation, and generation of stock estimates has long been an important tool in fisheries management. Genetic mixed stock analysis is a powerful tool for establishing differential individual population contributions to many mixed-stock fisheries. For these cases, it is likely to present the only way to address questions about specific stock contributions to fisheries. These techniques can be applied to both adult and juvenile aggrega-tions yielding useful information even where levels of population structure among contribut-ing populations is low. This information can be used to define exploitation rates of different populations in the mixed groups as well as helping to elucidate adult movement and juvenile dispersal patterns in numerous important fisheries species. The WG reviewed the various sta-tistical methods commonly used in mixed stock analyses, and their applications to date. We then compared and evaluated the properties of the different methods, giving examples from Baltic salmon and Atlantic herring and discussed which are likely to perform the best in MSA in marine species. With the likelihood of increased usage and application of MSA to marine fisheries questions and problems, a number of specific recommendations are made with refer-ence to the implementation and analysis of such studies. Local adaptation in marine fish populations is a crucial topic and of utmost relevance to fish-eries management and conservation biology. The topic is very complicated, as it encompasses theoretical and empirical information from a number of different disciplines, including general fish biology, ecology, evolutionary biology, physiology, population genetics, quantitative ge-netics, molecular biology and genomics. Further, we are at a point in time where novel con-ceptual, statistical and methodological developments have the potential to provide numerous ways to target the issue of local adaptation. The WG considered that the scope of ToRc was too complex to deal with in a single year. Rather than provide a cursory treatment, the WG discussed the outline in detail, providing the scope for further treatment of the topic. The WG recommends putting this ToR on the agenda for the 2006 meeting. We also recommend that we modify the justification to include shellfish. The WG will work intersessionally to under-take this comprehensive review. The WG considered the usefulness of Probabilisitic Maturation Reaction Norms (PMRN) as an Ecological Quality Objective metric, including appropriate reference points, and provided some useful discussion for consideration by ACE. The principle of PMRN analysis is rather simple. When observing changes in life history traits, the challenge is to be able to disentangle variation due to phenotypic plasticity (the capacity of a genotype to express different pheno-types according to the environment experienced) and variation due to modifications in the genetic basis of the life history trait considered. Reaction norms allow disentangling these two components in the sense that they describe variation in the trait considered as a function of the environment, the genotype being fixed. A life history trait’s reaction norm is thus a genotype’s property and temporal trends in reaction norms are evidences of genetic evolution for the traits considered. This methodology is theoretically applicable to any life history trait as soon as one can access the related reaction norm. However, in practice, accessing the reaction norm re-quires being able to measure environmental variation affecting the life history trait considered, which is far from easy in the field. One exception is maturation, because growth (or size-at-age) is (supposedly) a proxy accounting for environmental variation affecting the maturation process. Finally, the WG evaluated the evidence for genetic erosion and changes in life history charac-teristics of local stocks due to mariculture activity. Since the topic was last addressed (2003) there has been very little new data to evaluate. However, a new EU Concerted Action project has just been announced which should provide information about genetic impact of maricul-ture activities on wild populations, specifically on their genetic interaction. This project, enti-tled GENIMPACT, includes many WG members, and will deal with important marine species such as Atlantic cod, European sea bass, gilthead sea bream, turbot, halibut, scallops, mussels, oysters and European lobster. In the current document we discuss the topic and provide rec-ommendations on the types of data that are needed to fully evaluate this potential impact.
Contributor: Geir Dahle
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