Geographical differences in early growth of walleye pollock Theragra chalcogramma,estimated by back-calculation of otolith daily growth increments

The relationship between otolith length and body length (total length) was examined in walleye pollock Theragra chalcogramma (Pallas), collected from Pacific Ocean waters adjacent to Hokkaido, Japan, and in larvae reared from fertilized eggs. A linear relationship was found between log-transformed body length and otolith length data with two inflection points at ca. 11 mm and 100 mm total length. This relationship was found to be applicable also to samples from the Japan Sea, Bering Sea and Okhotsk Sea. The early growth pattern estimated by back-calculation of otolith increments of 1-yr fish from Funka (Uchiura) Bay (Hokkaido) accorded with that obtained from size-at-age data of 0 yr fish collected in the preceding year. Differences were found in comparisons of the back-calculated early growth pattern between samples from waters adjacent to Hokkaido, the Pacific Ocean, the Japan Sea and the Okhotsk Sea. The growth curve of the Okhotsk samples was markedly different from others, showing rapid initial growth up to about 100 d after hatching and attaining a small body size in the first year.