Speciation and sounds of fishes: Dividing up the bandwidth

Fishes in the drum family (Sciaenidae) make sounds to communicate, but they do not make the same sounds. The species-specific calls have different dominant frequencies, are produced in spawning aggregations at different times of the day and season, and there is spatial segregation among the spawning fish populations. We predicted that the pattern of bandwidth use by these species would show low overlap in space, time, and sound frequency. We monitored the seasonal pattern of sound production of Sciaenidae in Pamlico Sound (NC) using autonomous sound recorders that recorded 10 s of sound every 15 min during May–Nov. The observed bandwidth ranges and spawning season for species are weakfish 300–400 Hz in May–Aug, silver perch 800–1500 Hz May–Aug, spotted seatrout 200–400 Hz June–Sep, red drum 100–200 Hz in Sep–Oct. Overlapping calls in these species were rare temporally and spatially, as evidenced by long-term passive acoustic monitoring. Two other species of fishes (oyster toadfish and striped cusk eels), in unrelated families, also compete for acoustic bandwidth in Pamlico Sound, but overlap temporally with the sciaenids. There is low probabilty of signaling confusion for these species but higher probability for Sciaenids. It appears that bandwidth partitioning has evolved in the Sciaenidae.