Conservation aspects of natural populations and captive-bred stocks of turbot (Scophthalmus maximus) and Dover sole (Solea solea) using estimates of genetic diversity

Population genetic analyses have been highly successful in predicting inter- and intraspecific evolutionary relationships, levels of gene flow, genetic divergence, and effective population sizes. Parameters estimated are evolutionary averages and are therefore relevant for addressing contemporary ecological or conservation issues. Changes in genetic variation within the range of a species may indicate patterns of population structure resulting from past ecological and demographic events that are otherwise difficult to infer, so may provide an insight into evolutionary development. Genetic data, drawn from 14 enzyme loci amplified from two populations of turbot (Scophthalmus maximus) and five populations of Dover sole (Solea solea) from the Irish Sea were used to examine population structure estimated from measures of genetic diversity. The aim was to provide an empirical assessment of whether artificial propagation poses a genetic threat to conservation of naturally spawning populations, and whether the fitness for natural spawning and rearing can be rapidly and substantially reduced or increased by artificial propagation. Because of prolonged overfishing, turbot and sole populations in the region are below natural levels, and survive in small local populations in fragmented habitats. Genetic data derived from allozymes have shown that populations are characterized by relatively low levels of genetic diversity. A hypothetical model supporting genetic population substructure, such as range expansion with founder-flush effects, and subsequent population decline with small effective population sizes was considered. Observations support our belief that conservation measures based on genetic diversity have to be developed to ensure the survival of this diverse gene pool