Painted gobies sing their quality out loud: acoustic rather than visual signals advertise male quality and contribute to mating success

1. Females use multiple cues from different sensory modalities to choose males of high phenotypic or genetic quality to mate with. Fish may use visual and acoustic communication during mating, but few studies have associated multimodal signals with male quality and reproductive success. 2. We examined whether visual and acoustic courtship signals reflect male quality and influence mating success in the painted goby (Pomatoschistus pictus), a highly visual and vocal fish species with paternal care. Painted gobies make conspicuous courtship visual displays such as body quivering and eight-shaped swimming patterns and two types of sounds: drums that are composed of a sequence of low-frequency pulses and a thump-like non-pulsed sound. We predicted that both sensory modalities would advertise male size and condition and influence mating success. 3. We found that larger number of pulses in a drum, lower fatigue (where fatigue is the increase in pulse period during drum production) and higher drum absolute amplitude levels were good predictors of larger male size. Males with high condition factor (Fulton's K) showed high drumming activity and low thumping and visual courtship levels. Drumming activity was a good predictor of male fat reserves. 4. Males that succeeded to mate emitted sounds with higher number of pulses and longer pulse periods and showed higher drumming but lower thumping activity than unsuccessful males. All traits (except pulse period) reflected higher male Fulton's K or fat reserves, suggesting that females are selecting for male condition. Neither male size nor visual courtship was apparently used in mate selection. 5. Contrary to our expectations, females did not seem to prefer larger or vigorous visually displaying males but chose mates in better condition using multiple cues of drumming sounds. We suggest that preference for high mate condition is related to preference for increased parental ability and hatching success in species with paternal care. To the best of our knowledge, this is the first study that addresses the relative role of signals from different sensory modalities including acoustics, in advertising male quality and in contributing to reproductive success in fish.