ABSTRACT

Since the development of allozyme electrophoresis in the 1960's, molecular genetics has been broadly applied to the identification of discrete genetic stocks of fishes (Utter 1991). Genetic traits useful for detecting stock structure are those that are polymorphic within populations and whose various forms (alleles or haplotypes) are presumed to be selectively equivalent (i.e. neutral). Such traits include allozymes (Murphy eta!. 1996; May 2003), mitochondria! DNA (mtDNA) restriction patterns (Lansman ct a!. 1981; Billington 2003) or sequences (Bernatchez and Danzmann 1993; Keeney et a!. 2004), and more recently microsatellite DNA (Ashley and Dow 1994; O'Connell and Wright 1997). Essentially, differences in the frequencies of variant forms of molecular markers (alleles for allozymes and microsatellites, haplotypes in mtDNA) among geographic groups are used to determine the presence and degree of reproductive isolation and hence stock structure.