Abstract
Harvesting of marine resources raises concerns about how to identify and preserve biocomplexity, including the diversity of life histories found within and among wild populations of a species. In order to fully accomplish this, there is a need to elucidate the underlying causes of phenotypic variation, and how this variation responds to environmental changes. In general, both evolutionary (genetic) and nonevolutionary (plastic) responses may occur. Plastic responses to environmental change are expected to shift the phenotype along a reaction norm, while an evolutionary response is expected to shift the reaction norm itself. Here, we assess the maturation patterns of coastal Atlantic cod (Gadus morhua) in Skagerrak, where studies using neutral markers have revealed genetically differentiated populations of this harvested fish within tens of kilometres of coastline. Our results suggest that physiological state prior to the spawning season, as well as juvenile growth, both influence the probability of completing sexual maturation at a given age. Furthermore, our results point towards a spatial structuring of this plasticity (i.e. the maturation reaction norms) comparable with population connectivity inferred from neutral markers. We argue that such fine-scale biocomplexity calls for a Darwinian approach to fisheries management.
Highlights
Throughout the world, fish stocks are threatened by overharvesting, and there is growing concern that fishing has negative effects on stock productivity through evolutionary processes (Conover and Munch 2002; Reznick and Ghalambor 2005)
Biocomplexity in Pacific salmon is manifested by a network of local populations, where overall stock productivity is maintained through periods of shifting environmental conditions because certain geographicand life-history components perform well under some environmental conditions whereas other components perform well under other environmental conditions (Hilborn et al 2003)
We have assessed biocomplexity in coastal Atlantic cod, a broadcast-spawning marine fish, and found evidence for a fine-scale spatial diversity in life histories that is associated with patterns of population connectivity based on
Summary
Throughout the world, fish stocks are threatened by overharvesting, and there is growing concern that fishing has negative effects on stock productivity through evolutionary processes (Conover and Munch 2002; Reznick and Ghalambor 2005). By tailoring fishery effort to target the most productive components at any given point in time, all geographic- and life-history components are conserved, which ensures the long-term sustainability of the overall stock complex (Hilborn et al 2003). The spatial component of biocomplexity may involve adaptations to local environmental conditions (Hilborn et al 2003). Such spatially structured evolution depends on the interplay between heritability (history), gene flow (connectivity) and local a 2008 The Authors Journal compilation a 2008 Blackwell Publishing Ltd 1 (2008) 524–533
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