ROLE OF GENETIC-MARKERS IN FISHERIES AND AQUACULTURE - USEFUL TOOLS OR STAMP COLLECTING

We comment on the role of genetic markers in fisheries and aquaculture with a view to the future. Our goal is to encourage researchers to ev aluate the molecular markers they need to deploy and shift their think ing away from analyses of stock structure towards more aggressive purs uit of questions related to genome structure and function. Examples il lustrate that no one marker type is appropriate for all applications. Choice should be based on the evolutionary genetic attributes of both the species and the marker loci themselves. We evaluate three relative ly new marker types: mitochondrial DNA (mtDNA) sequences, randomly amp lified polymorphic DNA, and hypervariable nuclear loci. We conclude th at (i) sequences of mtDNA do not necessarily detect greater polymorphi sm than restriction endonuclease analysis, (ii) the technical ease of randomly amplified polymorphic DNA is offset by questionable repeatabi lity, and (iii) simulations illustrate that even new marker systems wi th large numbers of alleles need not detect differences among closely related yet significantly differentiated populations. Increasing the n umber of alleles per locus did not increase the probability of detecti ng significant differences. Finally, we consider the roles of genetic markers in helping to determine family relationships in pooled lots of fishes and locate genes that control an organism's phenotype (quantit ative trait loci). We discuss how knowledge of quantitative trait loci can help us to understand the basis of individual differences in perf ormance.