Kagawa Prefectural Fisheries Experimental Station, Takamatsu, Kagawa 761-0111, Japan.
The effects of high water temperature during the estivation period on the mortality and reproduction of Japanese sand lance Ammodytes personatus collected in the Seto Inland Sea were examined through a rearing experiment. Specimens were reared at three water temperatures (24, 26 and 28℃) during the months from August to September in 2010 after a two-month acclimation. Cumulative mortality in these conditions during the first three months was 3.0, 13.7 and 29.7%, respectively, showing a tendency to higher mortalities with higher temperature during the estivation period. The condition factor of the specimens in the 28℃ group significantly decreased one month later and this tendency continued until they were returned to the natural water temperature. In late December, specimens in each experiment generally matured. However, a decrease of both fecundity and male testicular weight was observed in specimens from the 28℃ group. In the Bisan Strait in 1994, a year with abnormally high water temperature, the water temperature remained above 28℃ for over one month. Therefore, we suggest that a sustained period of high water temperature during estivation affects not only the survival rate and condition factor of wild sand lance but also their reproduction.