Population genetic structure of the glacier lanternfish, Benthosema glaciale (Myctophidae) in Norwegian waters

It is hypothesised that the fjords with restricted water circulation may pa rtially isolate fish populations living there. The pelagic life history sta ges of the mesopelagic lanternfish may potentially subject to dispersal ove r vast areas, preventing population subdivision. In the present paper, we t est the hypothesis of no geographic population genetic structure of B. glac iale in Norwegian waters. Fish samples from six different locations, includ ing five western fjords were analysed using allozyme electrophoresis. Among the 17 loci analysed, nine loci were polymorphic by 0.99 criterion. Deviat ion from the global (pooled sample) HW equilibrium was detected at two loci , AAT-2* and PGM*, in terms of heterozygote deficiency, indicating a possib le population subdivision in the area studied. Supporting such postulate, t he allele frequencies at several loci were found significantly different, c onsequently rejecting the null hypothesis. The individual fjord samples wer e different from the offshore sample, and some between-fjord heterogeneity in allele frequencies was also found. However, Wright's F-ST value was appa rently low, but significantly different from zero, indicating a low level o f population differentiation in the area studied. Partial isolation of fjor d units of B. glaciate as a possible mechanism for genetic differentiation is discussed.