Marginal increment analysis and Sr/Ca ratio in otoliths of the grass goby, Zosterisessor ophiocephalus

Monthly changes in marginal increments, determined front alternation of macroscopic opaque and translucent bands, of Zosterisessor ophiocephalus sagittae were examined. The time of annulus completion proved to be annual, occurring around June both for females and males, and coinciding with the end of the breeding season and a period of larger body condition. The translucent band is likely to start depositing in summer. Since Sr/Ca peaks coincided with annulus completion, the most likely hypothesis is that the Sr/Ca ratio is influenced by the reproductive season.