Fig. 4

Frequency of the most common alleles within loci Gmo132, Gmo34 and Pan I in Dataset 1. Populations are ordered from north to south and the first one, called NEAC, consists of the 76 Pan I BB individuals with otolith types 4 and 5 that were purged from the dataset. Alleles Gmo132_115 and Gmo34_96 experienced a highly significant negative trend southwards (τ = − 0.626, P = 1.11 e-13, and τ = − 0.448, P = 1.17e-07, respectively), whereas for Pan I _A, this tendency was reversed (τ = 0.23, P = 0.007). The allele frequency for NEAC assessed in the Barents Sea was 0.745 for Gmo132_115, and 0.959 for Gmo34_96 [28]