EXPECTED FUTURE REPRODUCTIVE SUCCESS AND PATERNAL BEHAVIOR IN THE SAND GOBY, POMATOSCHISTUS-MINUTUS (PISCES, GOBIIDAE)

We studied egg care and guarding behaviour in the paternal sand goby, Pomatoschistus minutus, in relation to egg number and age. A male's expected reproductive success is assumed to increase with larger egg masses and older eggs. Non-shareable care, i.e. fanning, was higher in larger and older egg masses. Egg age explained 65% and egg mass size 22% of the total variation in the amount of fanning performed by a male. Contrary to expectation, egg removal did not affect a male's fanning behaviour. Males that were approached stayed longer in the nest when they guarded larger egg masses. Males with older eggs were also more reluctant to leave the nest. The time since a male had been chased away from his nest until he returned decreased as the season progressed. The results are discussed in relation to tradeoffs between present and future reproductive events.