Biochemical genetics and recognition of a western stock of the common gemfish, Rexea solandri (Scombroidea: Gempylidae), in Australia

Protein electrophoresis and analysis of restriction fragment polymorphism in mitochondrial DNA (mtDNA) provided information on population/stock structure of Rexea solandri. Two distinct Australian stocks are evident, with one (AAT-2) of 36 enzymatic loci and all 11 mtDNA digestion profiles showing highly significant differences between eastern and southern/western Australian specimens. The split is at the western end of Bass Strait, with limited mixing off western Tasmania. No external characters were found that would allow determination of the provenance of an individual fish. Stock distinction between eastern Australian and New Zealand fish is less clear; some differences, usually statistically non-significant, in genetic frequencies were found and some rare allozymic or restriction fragment variants were found in one or other but not both regions. Estimates of gene flow suggest that only tens of individuals per generation migrate between the regions. In an experiment on tissue deterioration, after six days of exposure out of doors, significant amounts of intact mtDNA were present in all tissues, and all fragments of the HINF 1 phenotype were clearly scorable. Of 19 enzymes tested, only three showed reduced activity on Day 6. Gonad and muscle tissues were more resistant to degradation than was liver tissue.