A new approach to prioritizing marine fish and shellfish populations for conservation

There has been increasing awareness of the vulnerability of marine organisms to population extirpation and species extinction. While very few documented cases of species extinction exist in the marine environment, it is anticipated that managers will face the dilemma of prioritizing populations of marine fish and shellfish for protection in the near future. Current prioritization procedures have been developed from salmonid models with the intent of applying them to all marine organisms, and in some cases to freshwater and terrestrial taxa. In this review we provide evidence for the relevance of such a process for marine species and further suggest five broad categories of marine organisms that have distinctive traits influencing their genetic structure. The current prioritization models have been adapted to account for each of these species groups. Emphasis is placed on 'Classical Marine Species' which represent the opposite end of the continuum from the salmon model, displaying high within-population genetic variance. From this category, three cod (Gadus morhua) stocks were selected to evaluate a revised scheme developed specifically for 'Classical Marine Species' that includes performance measures such as (i) reduction in number of spawning populations; (ii) reduction of Ne : Nc (ratio of effective to census population size): (iii) changes in life-history traits: (iv) critical density for spawning success; and (v) patchy vs. continuous distribution pattern. When the salmonid scheme was applied, the cod examples were allocated low values, indicating that they were not under threat. However, when the revised scheme was applied, all three cod stocks were allocated high values, indicating that the revised scheme was more reflective of the particular life-history traits of this category of organisms.