The Swimbladder and Hearing

Abstract

There is adequate experimental evidence to show that the hearing ability of fish is enhanced by the presence of a swimbladder. Sand and Enger (1973) found that removing gas from the swimbladder of Gadus morhua (cod) reduced the sensitivity at 300 Hz by about 20 dB, while Fay and Popper (1975) found a decline in the sound pressure sensitivity of Ictalurus punctatus (catfish) above 100 Hz after swimbladder deflation. In a neat experiment on the dab Limanda limanda, a species without a swimbladder, Chapman and Sand (1974) found that the presence of a small air-filled balloon below the head increased the sensitivity by about 3 dB at 30 Hz and by nearly 20 dB at 200 Hz; the upper limit of the frequency response also increased from about 200 Hz to 350 Hz. a gas-filled structure very close to the ear, such as the otic bullae of the clupeoids which lies near the utriculus, also improves hearing (Blaxter, Denton, and Gray, Chapter 2). a coupling mechanism between the swimbladder and the ear enhances hearing still further as shown by comparing the audiograms of the Ostariophysi, which possess Weberian ossicles, with nonostariophysine fish (Popper and Fay 1973). The auditory sensitivity of different holocentrid (squirrelfish) species can also be related to the degree of connection between the swimbladder and labyrinth (Coombs and Popper 1979).