Evidence of a marine larval stage in coastrange sculpin Cottus aleuticus from a small coastal stream in California, USA , based on otolith strontium isotopes

Cottus aleuticus (coastrange sculpin) is one of two North American facultatively amphidromous sculpins, but habitat use during its planktonic larval stage is poorly documented. We analysed strontium isotopes (⁸⁸Sr and ⁸⁷Sr/⁸⁶Sr) in otoliths of 10 adult C. aleuticus from a small coastal California stream. All showed elevated ⁸⁸Sr signal intensities in the otolith core and a marine ⁸⁷Sr/⁸⁶Sr value in the core that rapidly shifted to and then remained at the stream value. Our results confirm a marine larval stage in this species and help explain its widespread distribution across diverse watersheds.