Relationship between seasonal variations of lipid content and gonadal development in the chub mackerel Scomber japonicus landed at the port of Choshi

摘要

The suitability of the chub mackerel Scomber japonicus for processing depends on its lipid content. Therefore, there is a need for prompt information on fish lipid content on-site at fish markets. Several studies have shown that seasonal variations in fish lipid content are related to gonadal development. In addition, it is known that gonadal development in chub mackerels is affected by stocks. In this study, we examined the seasonal variation of meat lipid content with body size of chub mackerel landed at the port of Choshi between 2007 and 2017. Furthermore, the relationship between lipid content and gonad index was examined. Lipid content was high in the autumn and winter. As the stocks increased, the rise in lipid content appeared earlier. Moreover, lipid content increased with fish size because chub mackerels require lipid as an energy source for spawning. Furthermore, lipid may be required as an energy source for gonadal development. It took seven or eight months for the gonad to develop after the lipid content in chub mackerels increased.