UC Irvine

From a total of 524 microsatellite loci considered in nearly 40 000 individuals of 78 species, freshwater fish displayed levels of population genetic variation (mean heterozygosity, h=0.46, and mean numbers of alleles per locus, a=7.5) roughly similar to those of non-piscine animals (h=0.58 and a=7.1). In contrast, local population samples of marine fish displayed on average significantly higher heterozygosities (h=0.79) and nearly three times the number of alleles per locus (a=20.6). Anadromous fish were intermediate to marine and freshwater fish (h=0.68 and a=11.3). Results parallel earlier comparative summaries of allozyme variation in marine, anadromous, and freshwater fishes and probably are attributable in part to differences in evolutionarily effective population sizes typifying species inhabiting these realms. (C) 2000 The Fisheries Society of the British Isles.