Comparison of the size-age composition and growth rate of two species of arrow-toothed halibuts Atheresthes spp. in shared habitat

Analysis of the size composition of two sympatric sibling flatfishes – arrowtooth flounder ( Atheresthes stomias ) and Kamchatka flounder ( A. evermanni ) on the continental slope in areas of cohabitation revealed a similarity in size range, with different size–age classes dominating. In their original habitats, the native species is usually represented by a wide range of size groups with a large number of juveniles, whereas the invader is represented mainly by adult individuals with a distribution close to normal. In areas where both species are native, their size structure is similar. This divergence in size at certain depths reduces trophic competition. A comparison of growth showed that up to age 4 the sizes of the two species are similar, after which arrowtooth flounder slightly surpasses Kamchatka flounder in length and weight. However, apparently due to a longer life cycle, Kamchatka flounder attains a larger size.