Population genetic studies in fish may start at the egg stage; examples from gadoid species in Norwegian waters

Abstract

Pelagic fish eggs were sampled in Lofoten and Vesterålen, northern Norway, during March to May 1981 and 1982. Individual eggs were identified by their species-specific LDH zymograms as revealed by isoelectric focusing and histochemical staining. Genetic polymorphisms at enzyme loci expressed in eggs provided a basis for the estimation of population allele frequencies. Egg-sample allele frequencies in cod, Gadus morhua L., haddock, Melanogrammus aeglefinus (L.), and Norway pout, Trisopterus esmarkii (Nilsson), were compared with observed values in samples of adult fish from the same areas and from Trondheimsfjorden. Egg samples seemed to provide reliable estimates of population allele frequencies. The results were related to current knowledge of the population structure of these species in Norwegian waters. Only Norway pout showed regional differences in allele frequencies.