Importance of zooplankton patches in foraging ecology of the planktivorous reef fish Chromis chrysurus (Pomacentridae) at Kuchinoerabu Island, Japan

Abstract

Adult C. chrysurus fed primarily on larger planktonic copepods (0.8-5.5 mm body length) that originated offshore, despite the dominance of smaller ones (<0.8 mm) in the water column. Siphonophores, appendicularians and chaetognaths were also utilized. Low overall densities (<50 m-3) of such zooplankton prey were common in the water column, whereas high densities (>500 m-3) occurred rarely. A high proportion of fishes (31-59%) sampled each month, regardless of season, had empty stomachs, but composition analysis of satiated stomachs showed that adult C. chrysurus utilize high density zooplankton patches when available. Adult C. chrysurus feed intermittently on available prey, according to fluctuations in prey density, and are probably subject to extreme food deprivation. Zooplankton patches are therefore an indispensable food resource. -from Authors