Impact of warming on the physiological condition of ridged-eye flounder Pleuronichthys lighti during the summer in the central Seto Inland Sea, Japan

Abstract

Ridged-eye flounder Pleuronichthys lighti is a commercially important flatfish in East Asia. Water temperature has been increasing in the central Seto Inland Sea, Japan, with high levels (> 25 °C) in the bottom layer for 1–2 months during the summer since 1994. To study possible impact of warming on the physiological condition of the flounder, we examined the feeding activity and somatic condition of the flounder monthly from July to November in 1999–2006. Stomach content weight decreased during period with high water temperature > 25 °C from August to September, and physiological condition from August to November. Generalized linear mixed models suggested the negative effects of water temperature on stomach weight, while water temperature did not explain the variability in the physiological condition of the flounder. However, the decrease in relative condition factor from August to September was greater in the year with higher water temperature in this period. These results suggest that high water temperature during the summer in recent years appears to have been unfavorable for the flounder through negative impacts on their feeding and somatic condition.