Microsatellite analysis of genetic diversity in the squid Illex argentinus during a period of intensive fishing

Levels of genetic diversity and population differentiation were examined in temporally (1990 to 1997) and geographically separated samples of the argentine short-finned squid Illex argentines using 7 microsatellite loci. Number of alleles (mean number of alleles per locus over all samples = 24.1) and heterozygosity (mean observed heterozygosity per sample = 0.84) were high for all samples, indicating that these loci have a greater potential utility for investigating population genetic structure than allozyme markers used in previous studies. Genetic diversity did not differ significantly between samples taken 5 yr after commencement of the fishery (1990) and those collected during a period of progressively intense fishing pressure (1994 and 1997). Several small but significant differences in between-sample genetic variation (FsTw) were observed, but these could not confirm the previous suggestion of cryptic species or several well-defined stocks within the fished population.