Meeting Abstract
The plainfin midshipman (Porichthys notatus) is a vocal species of teleost fish that uses social acoustic signals for communication. During late spring and early summer midshipman migrate from deep water to the rocky intertidal region to breed. Type I or “singing” male midshipman construct nests beneath rocks and produce low frequency, long duration advertisement calls or “hums” to attract mates for spawning. Females locate nests via phonotaxis, lay their eggs in a single nest, and then return to deeper waters. Type I males care for the offspring until they are old enough to leave the nest. Field studies have demonstrated that larger males contain a greater number of offspring in their nests and laboratory two-choice experiments showed that females prefer to lay eggs in the nests of males with larger body size. We tested the hypothesis that male hums convey not only location but also fitness information to potential mates. We recorded the hum of eight captive male midshipman overnight in a tank maintained at a temperature between 12.8 – 14.4 °C and measured various call features such as the fundamental frequency (f0) and second harmonic (f1) of the hum, average call duration, and calling effort. We then correlated these quantities with potential indicators of male fitness such body length, body size, Fulton’s body condition, gonad mass, and gonadosomatic index. Call duration and calling effort did not correlate with any of the morphometric parameters, but the fundamental frequency (f0) and second harmonic (f1) of the hum correlated positively with Fulton’s body condition, but not with other parameters. Our preliminary data suggest the hum harmonics may serve as a condition-dependent or “honest” acoustic signal that provides important information related to the quality of the sender.
