Eastern Pacific Crown-Of-Thorns Starfish Populations In The Lower Gulf Of California

Abstract

Populations of Acanthaster ellisii (Gray) were investigated on three islands in the southern Gulf of California. Average density (0.0045/m' or 1/225 m") exceeded that given in several definitions of normal densities for A. planci populations in the Indo-Pacific. Small patches of Porites were the most frequent food item; other hermatypic scleractinians, gorgonians, and algae were also fed upon. Estimates of coral coverage and growth rates, and Acantluister feeding rates, indicate that /I rw/u/iai^rcr predation is a significant source of coral mortality but that corals are not being eliminated from the areas studied. Gonad analysis suggests an extended spawning season rather than a short synchronous one. Size-frequency data do not necessarily lead to the conclusion that populations of Acanthaster are expanding.