SEPARATING THE WHEAT FROM THE CHAFF - PATTERNS OF GENETIC DIFFERENTIATION IN HIGH GENE FLOW SPECIES

in many marine species, high levels of gene flow ensure that the genet ic signal from population differentiation is weak, As a consequence, v arious errors associated with estimating population genetic parameters that might normally be safely ignored assume a relatively greater imp ortance. This fact has important implications for the use of genetic d ata to address two common questions ire fishery conservation and manag ement: (1) How many stocks of a given species are there? and (2) How m uch gene flow occurs among stocks? This article discusses strategies t o maximize the signal:noise ratio in genetic studies of marine species and suggests a quantitative method to correct for bias due to a commo n sampling problem. For many marine species, however, genetic methods alone cannot fully resolve these key management questions because the amount of migration necessary to eliminate rarest genetic evidence of stock structure (only a handful of individuals per generation) will ge nerally be inconsequential as a force for rebuilding depleted populati ons on a time scale of interest to humans, These limitations emphasize the importance of understanding the biology and life history of the t arget species-first, to guide design of the sampling program, and seco nd, so that additional information can be used to supplement indirect estimates of migration rates based on genetic data.