Distribution of protein variation in skipjack tuna (Katsumonus pelamis) from the central and south-west Pacific

Abstract

Forty-two loci were electrophoretically surveyed for protein variation in the skipjack tuna. A new polymorphism in guanine deaminase was found as well as low-frequency variation in glucosephosphate isomerase and adenosine deaminase. Average heterozygosity for the species was 0 032. The gene frequencies at four variable loci for 70 sample sets, each of approximately 100 animals, collected at locations throughout the South Pacific Commission region, are given. East-west clines in allele frequencies for carboxylesterase and guanine deaminase occur across the study area. There is also within-area heterogeneity in allele frequency at these loci. Previously proposed discrete-stock models and a new isolation-by-distance model for the population structure of skipjack tuna are examined in the light of the genetic data.