Population dynamics of goby Paragobiodon echmocephalus and host coral Stytophora pistillata

Abstract

The goby Paragobiodon echinocephalus is an obligate associate of the branching coral Stylophora p~stlllata Population fluctuations of both specles were observed over 3 yr on the reef flat of Sesoko Island, Olunawa Japan Coral growth was negatively corlelated with size because partial death or destruction often occurred in large corals The number and maximum slze of gobies in a coral were positively correlated with coral size Small corals ( < 5 cm diameter) were seldom used, whlle large corals ( > l 5 cm) were almost always inhabited by 2 or more fish The goby spawned from Aplil to November, and juveniles (7 to 15 mm] increased in summer The number of gobies and the corals occupied by gobies increased with the influx of juveniles The goby population declined durlng winter and spnng except in a year when corals > 5 cm became abundant When the number of large corals decreased large gobies (30 to 40 mm) decreased in number and the occupation rate of smaller corals increased Mortality of marked fish (> 15 mm) was correlated with that of corals Thus the population fluctuation of the goby was affected by both the availab~lity of host coral and the goby s seasonal reproductive cycle