Genetic variation in halibut Hippoglossus hippoglossus (L.) from Norwegian waters

Tissue extracts (muscle, heart and liver) from 79 mature halibut Hippoglossus hippoglossus (L.) caught on three spawning locations along the Norwegian cost were investigated for genetic variability by using isoelectric focusing and histochemical staining techniques. Minimum 25 loci were identified, including 11 enzymes, myoglobin and haemoglobins. The tissue distribution and approximate pI (4°C) of the coded proteins are reported. As measured by the frequency of polymorphic loci (P) and average heterozygosity (H), the genetic variability was very low (P = 0.04 and H= 0.0044±0.0043). Allele frequencies at the only locus showing genetically interpretable polymorphism (PGI-2) did not vary significantly between samples from the three locations. An at present unidentified tissue protein (UTP) showed variation which may be of genetic origin. The frequencies of the UTP characters varied significantly between locations. However, the inheritability of UTP variants must be confirmed before conclusions on population structure are drawn.