Reproductive success associated with territoriality, sneaking, and grouping in male rose bitterlings, Rhodeus ocellatus (Pisces : Cyprinidae)

The spawning success of male rose bitterlings, Rhodeus ocellatus, adopting an alternative reproductive style, was estimated through behavioural data a nd electrophoretic paternal analyses in field observations and experiments. Three mating patterns were observed: territoriality, sneaking, and groupin g. Mating patterns depended on a male's relative size and on local male den sity (the number of males around a spawning spot: a mussel). Spawning patte rns (pair spawning, pair spawning with sneaker, and group spawning) varied with local male density. Time-budget data of the territorial males indicate d a trade-off between chasing and courtship behaviour as local male density changed. Females deposited appoximately only 1 egg per egg-laying into the mussels. As a result of isozyme analysis, a minimum of 12% (two out of 17) of the offspring in the sample were found to have been fathered by sneaker males in pair spawning with sneaker. I scored through behavioural data the mating success per spawning for each pattern, on an individual basis. The average reproductive success per spawning for each pattern was: territorial (0.61), sneaking (0.31) and grouping (0.11), and thus the successes of the patterns were not equal. Accordingly, the alternative reproductive styles of male rose bitterlings are best interpreted as alternative phenotypes in a conditional behaviour.