Plasma insulin-like growth factor-1 is unrelated to female reproductive development in a wild population of Dolly Varden charr Salvelinus malma (Walbaum, 1792)

Abstract

Insulin-like growth factors (IGFs) are endocrine agents that signal growth in fishes. Because of the interplay between growth and reproduction, endocrine control of the growth axis is thought to have a connection to the reproductive axis. Seasonal patterns and relationships between IGF-1, fish condition, and gonadal development were investigated in a wild population of female Dolly Varden charr Salvelinus malma (Walbaum, 1792) during the summer growing season prior to spawning. Fish were sampled from Florence Lake, Alaska on five sequential sampling trips during April–October 2006. Body and gonad morphometric measurements, and blood plasma samples were obtained for IGF-I quantification. IGF-I increased during summer with fish condition. The gonadosomatic index indicated a pattern of advancing reproductive development in one cohort of fish by August, which indicated impending spawning compared to an immature (non-reproductive) cohort. However, plasma IGF-I levels were not predictive of the sexually maturing cohort. We conclude that IGF-I is not a useful endocrine marker of advancing reproductive state in female Dolly Varden charr but does relate to fish condition during the summer growth period.