Male and female mate choice in the redlip blenny: why bigger is better

Mate choice and mating success were investigated in a natural population of the redlip blenny, Ophioblennius atlanticus (Pisces: Blenniidae). Male mating success was correlated significantly with male size and with the inner surface area of the male's nest. Females preferred to mate with large males; they approached the territories of large males more often, their probability of spawning after entering the nest was greater, and they released more eggs when spawning with larger than with smaller males. Large males may be preferred because they spend more time guarding and therefore lose a smaller proportion of egg batches per reproductive period. In addition, last batches have half the hatching success of batches laid earlier. Since large males guard longer per reproductive period, a female may decrease the probability of being the last to spawn in a nest by mating with larger males. Females may prefer nests with larger surface area because such nests can hold more egg batches, and the predation risk to individual egg batches may therefore decrease. Feeding rate is reduced during guarding and the effect of this cost on future reproduction may constrain increased guarding investment by small males. Male preference for larger females was observed directly; females accepted in a nest were larger than females chased from the nest. A computer simulation showed that males mating selectively should obtain eggs at a faster rate than males mating indiscriminately.