Variable pelagic fertilization success: implications for mate choice and spatial patterns of mating

Abstract

Fertilization success was measured in bluehead wrasse Thalassoma bifasciatum (Labridae), a tropical reef fish with external fertilization of pelagic eggs. Females either spawn with single males (pair spawning) or spawn with a group of at least three and often >20 males (group spawning). Fertilization success averaged c75% and did not differ between pair and group spawning, despite an estimated 80-fold increase in sperm release in group spawns. There was also no evidence that pair-spawning males suffered sperm depletion over the course of the spawning period. Thalassoma bifasciatum occurs in a variety of habitats and is exposed to varying levels of water turbulence. Fertilization success varied among days, and decreased with rougher water conditions. Within a reef, the calmer spawning sites behind the reef relative to the current had higher fertilization success. -from Authors