Haemoglobin variation in cod: A description of new variants and their geographical distribution

Abstract

Blood from 1209 individual cod was sampled from nine localities in the Northeast Atlantic, and analysed using agar gel electrophoresis (AGE) and isoelectric focusing (IEF) to reveal individual and population variation in haemoglobin genotypes. The second aim of the study was to compare our data with data collected some 30 years ago in the same area to investigate possible directional selection. A new haemoglobin polymorphism of Atlantic cod was documented in samples from Danish waters using IEF electrophoresis (pH 5.5-8.5) and, in addition to the five genotypes seen in earlier studies, 11 subtypes are described. Significantly different genotype distributions were found between the samples from northern Norway on the one hand and southern Norway and Danish waters on the other, and the frequency of the Hb-I(1) allele increased from north to south. With the possible exception of two samples, the frequency of the main haemoglobin genotypes was found to be very similar to corresponding frequencies described in these areas three decades ago. The frequencies of the Hb-I subtypes off Norway varied among the sampling sites and were only found in Norwegian coastal cod with increasing frequency from north to south. In the Danish samples, 11 novel Hb-I subtypes were found and are described.