Age and growth of three marine sculpins, Myoxocephalus jaok, Enophrys diceraus, and Gymnocanthus herzensteini, and age composition of fishery-bycatch sculpins in the western coastal Pacific around Hokkaido Island, Japan

Abstract

The present study established an age determination technique and analyzed growth patterns in three sculpins, Myoxocephalus jaok, Enophrys diceraus, and Gymnocanthus herzensteini, which are major components of demersal fish assemblages in the subarctic Pacific. In all three species, only two or three otolith opaque zones were detected by surface observations, but numerous opaque zones were observed on otolith thin sections. For all species, the results of the study suggest that otolith opaque zones were formed annually. Although opaque zones were probably formed during summer for M. jaok and G. herzensteini, the timing could not be clarified for E. diceraus. The standard lengths at the same ages were greatest in M. jaok, moderate in G. herzensteini, and smallest in E. diceraus. In M. jaok and G. herzensteini, Bertalanffy growth curves were estimated for each sex, and were found to differ significantly between sexes. The bycatch of M. jaok and G. herzensteini in the western coastal Pacific around Hokkaido consisted mainly of young individuals, while that of E. diceraus was primarily older individuals. The results of this study may facilitate an understanding of the biological characteristics of sculpins not only around Hokkaido, but throughout the subarctic Pacific.