Otolith development in wild populations of stickleback: Jones & Hynes method does not apply to most populations.

Abstract

This paper critiques Jones & Hynes (1950) findings by analysing sequential samples of otoliths from three wild populations of Gasterosteus aculeatus from North Uist, Scotland and Nottingham, England. Contrary to Jones & Hynes (1950), but coincident with the finding of later researchers, our results showed that no true translucent ring formed in the otolith of G. aculeatus during their first summer. The first translucent ring was probably starting to be formed by the end of summer and was completed by the end of their first winter. There was no second opaque ring in the otoliths of G. aculeatus before they passed their first winter. The second opaque ring was just starting to appear by early April of the second year in the southern population i.e. Nottingham, but later, by May, in the northern populations i.e. North Uist. Formation of the opaque ring in G. aculeatus mostly occurs in spring and summer, with younger fish starting earlier. In contrast, the formation of translucent rings is mostly during autumn and winter, but can be more widespread through the year, possibly as a result of reproductive investment.