Abstract
It is hypothesised that the fjords with restricted water circulation may partially isolate fish populations living there. The pelagic life history stages of the mesopelagic lanternfish may potentially subject to dispersal over vast areas, preventing population subdivision. In the present paper, we test the hypothesis of no geographic population genetic structure of B. glaciale in Norwegian waters. Fish samples from six different locations, including five western fjords were analysed using allozyme electrophoresis. Among the 17 loci analysed, nine loci were polymorphic by 0.99 criterion. Deviation from the global (pooled sample) HW equilibrium was detected at two loci, AAT-2 * and PGM *, in terms of heterozygote deficiency, indicating a possible population subdivision in the area studied. Supporting such postulate, the allele frequencies at several loci were found significantly different, consequently rejecting the null hypothesis. The individual fjord samples were different from the offshore sample, and some between-fjord heterogeneity in allele frequencies was also found. However, Wright's F ST value was apparently low, but significantly ditTerent from zero, indicating a low level of population differentiation in the area studied. Partial isolation of fjord units of B. glaciale as a possible mechanism for genetic differentiation is discussed.
