PETERSEN, C.W.; College of the Atlantic: Sexual conflict and cooperation in hermaphroditic fishes

Mating behavior in simultaneously hermaphroditic seabasses has been often cited as an example of cooperation among unrelated conspecifics. The predominant mating behavior in this group involves egg trading, where individuals reciprocally fertilize parcels of eggs from a partner. Egg trading has been suggested as a good example of a tit-for-tat cooperative mating strategy. Although simultaneous hermaphroditic fishes are often held up as strong examples of cooperation in mating behavior, a closer examination reveals significant sexual selection and sexual conflict between male and female roles among individuals. Although there are several aspects of the mating system that do not precisely fit the assumptions of this solution to the Prisoner�s Dilemma game, the model does appear to be a useful starting point for both understanding egg trading and understanding the deviations from complete cooperation that have been found in all species studied to date. The variations from complete reciprocity can best be understood by including aspects of traditional mating-system theory, with individuals increasing male mating success through a variety of behavioral tactics. Supporting data come both from published studies of hermaphroditic seabasses and new data on reproductive behavior and social interactions in these species.