A Potential Mechanism for Episodic Recruitment of a Coral Reef Fish

Most marine animals have complex life histories with dispersive larvae. Recruitment to marine populations should then result from larval production external to each population (i.e., an open population). However, it has been suggested that self-recruitment to these populations may also be important (i.e., a closed system). The contribution of these two sources of larval supply to recruitment were explored using the Hawaiian domino damselfish, Dascyllus albisella. Spawning and recruitment were monitored daily and weekly in the southeast section of Kaneohe Bay, Oahu, Hawaii, during 1992. Daily increment formation in the otoliths of this species was validated, and the spawning dates of arriving recruits were back-calculated using otolith rings. Since this section of Kaneohe Bay is sheltered, with a water exchange rate of only 26% per day, I predicted larvae would be retained (passively and behaviorally) after hatching; therefore recruitment from locally spawned larvae would be important. Contrary to my prediction, no self-recruitment was evident. Spawning times and back-calculated production of recruits did not overlap on a daily or seasonal basis. During the first half of the year, recruitment pulses were large and associated with rises in water temperature. During the latter half of the year, recruitment rates were lower and recruitment events were not associated with water temperature. Given the apparent absence of self-recruitment and the seasonal pattern of oceanographic currents in the Hawaiian Islands, recruitment episodes in the first half of the year may have originated from distinct reproductive episodes at upcurrent islands. Recruitment episodes in the latter half of the year may have resulted from a general increase in D. albisella spawning external to Kaneohe Bay.