Reproductive success associated with territoriality, sneaking, and grouping
in male rose bitterlings, Rhodeus ocellatus (Pisces: Cyprinidae)
Yoshihiko Kanoh (2000) Environmental Biology of Fishes
57:143-154（ＰＤＦ）
Department
of Biology, Osaka Kyoiku University, Asahigaoka, Kashiwara-shi,
Osaka.
Present address: Section of Biology, Seifu High School, 12-16
Ishigatsuji-cho, Tennoji-ku, Osaka, 543-0031 Japan.
Key words: alternative
reproductive tactics, isozyme electrophoresis, pre-oviposition ejaculation,
group spawning
Synopsis
The spawning success of male rose bitterlings, Rhodeus
ocellatus, adopting an alternative reproductive style, was estimated through
behavioural data and electrophoretic paternal analyses in field observations and
experiments. Three mating tactics were observed: territoriality, sneaking, and
grouping. Mating tactics depended on a male's relative size and on local male
density (the number of males around a spawning spot: a mussel). Spawning
patterns (pair spawning, pair spawning with sneaker, and group spawning) varied
with local male density. Time-budget data of the territorial males indicated a
trade-off between chasing and courtship behaviour as local male density changed.
Females spawned approximately 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 tactic, on an individual basis. The average reproductive success per
spawning for each tactic was: territorial (0.61), sneaking (0.31) and grouping
(0.11), and thus the successes of the tactics were not equal. Accordingly, the
alternative reproductive tactics of male rose bitterlings are best interpreted
as alternative phenotypes in a conditional strategy.