Habitat Use and Shift of Two Sympatric Freshwater Sculpins (Cottus pollux and Cottus hangiongensis) during the Spawning and Non-Spawning Seasons

ABSTRACT

The spawning seasons and distributions of sympatric sculpins, namely, the small egg-type (SE) of Cottus pollux and C. hangiongensis, were investigated in a coastal river of northeastern Japan. The spawning seasons for both species last for four months, and the ovulation rate peaks in January and April for C. pollux and C. hangiongensis, respectively. The males of both sculpins nested in cavities under rocks in stony areas. C. pollux was distributed in reed marshes in summer and in stony areas during the spawning season, while C. hangiongensis was distributed in stony areas throughout the year. There was a difference in habitat use between the males and females of C. pollux during the spawning season; the males were distributed in stony areas for a longer period than the females. These results indicate that mature C. pollux shifts its habitat from marshes to stony areas for spawning.