Diel periodicity of spawning activity in a permanently territorial damselfish: a test of adult feeding hypotheses

Synopsis Among species of damselfish in which both sexes defend individual feeding territories, spawning nearly always begins at first light and is completed within 2 h. According to the anti-competitor hypothesis, such dawn spawning occurs because it minimizes the rate of intrusion by diurnally active food competitors while the female is away from her territory. An alternative hypothesis pertaining to adult feeding biology is that dawn spawning minimizes interference with the female's own feeding activity. Diel patterns of spawning and mate-searching activity were documented for a population of garibaldi damselfish, Hypsypops rubicundus, and compared with their diel feeding patterns and those of their food competitors. Female garibaldi spawned at approximately constant levels from dawn through late afternoon and showed peaks in mate-searching activity in the late morning or in the afternoon. However, feeding activity of both female garibaldi and their food competitors increased significantly from dawn to early afternoon. Thus, there was no inverse relationship between garibaldi spawning activity and feeding activity as predicted by these hypotheses.