Observations on the Reproductive Behavior of the Giant Kelpfish, Heterostichus rostratus (Pisces: Clinidae)

Abstract

The reproductive behavior of the giant kelpfish was observed at Santa Catalina Island, California, from 1972-79. Establishment of a territory, courtship, spawning, and parental care were examined, as were age and weight relationships. Reproductively active males were found to select and weakly defend an algal oviposition site. Nests were not modified or prepared by the males, but were present during most months of the year. Forty defended nests were observed (27 with eggs); 77% of these involved red algae with Gelidium nudifrons (56%) the principal species. The male's courtship repertoire includes five behavioral units and a distinctive nuptial body color pattern. The female is passive throughout. The female deposits a mass of adhesive eggs within the nest following a short courtship by the male. Spawning requires 40 to over 60 min to complete. In addition to fertilizing the eggs, the male chases intruding fishes from the area while the female is in the nest. The egg mass was apparently the result of a single spawning, because no nests were observed with multiple stages of egg development. The male guards the eggs after the spent female leaves. Male defense of the egg-laden nest is vigorous against all conspecifics and some alga searching fish predators, but minimal or non-existent for other fish species.