Annual, semilunar, and diel reproductive rhythms in the Hawaiian labrid Thalassoma duperrey

Abstract

Reproduction of the labrid Thalassoma duperrey was studied for the population in Kaneohe Bay, Hawaii, from 1978 to 1981. Field observations of female reproductive behavior and histological study of the ovaries revealed annual, semilunar, and diel cycles. The percentage of females with ripe ova was greatest in winter and least in summer; moreover, the percentage of females spawning each day in summer was low in comparison to the rest of the year. A semilunar cycle was superimposed on the annual cycle, since the percentage of ripe, spawning females was greatest at new and full moons and least during the first and third quarters. On a daily basis, the percentage of ripe, spawning females was greatest during daytime high tide. The reproductive strategies of this and other species of shallow-water labrids are interpreted as evolutionary responses to both predation pressure and the need for short-range, within-habitat dispersal. A winter reproductive peak probably reduces the loss of pelagic larvae from the reef habitat due to weak oceanic currents. A semilunar reproductive peak on new and full moons probably maximizes short-range, within-habitat dispersal due to strong tidal currents. Spawning on the high tide should maximize the distance between newly spawned eggs and reef planktivores and may be the most effective anti-predator tactic available to daytime broadcast spawners.