Short-Term Dynamics of Tidepool Fish Community: Diel and Seasonal Variation

Short-term temporal dynamics in a tidepool fish community were quantitatively examined through a series of direct observation at consecutive low tides in a temperate-subtropical intertidal of southwestern Japan. The visual observation was sufficiently effective compared with the capture by anaesthetics and allowed a continual, undisturbed monitoring. Species composition markedly varied between consecutive day versus night in spring-autumn, but not in winter. In contrast, species composition on consecutive days and on consecutive nights was relatively stable all through the year. The pattern of diel change in abundance varied among species and seasons. C. gulosus, Istiblennius sp. and Girella spp. showed the tendency of night-time occurrence, while B. fuscus individuals tended to occur by day. These trends of day–night differences were mainly observed in spring and summer and rarely in winter. Size differences between day and night were detected in B. fuscus, C. gulosus, Istiblennius sp. and Girella spp. This tidepool fish community demonstrated variation in abundance and body size on short time scales, which may be attributable to behavioural differences among species.