Meeting Abstract

83.3  Friday, Jan. 6  High Speed Examination of Pectoral Stridulation Sound Generation in Blue Catfish, Ictalurus furcatus MOHAJER, YJ*; FINE, ML; GHAHRAMANI, ZN; Virginia Commonwealth Univ.; Virginia Commonwealth Univ.; Virginia Commonwealth Univ.

The blue catfish Ictalurus furcatus is an invasive species whose population numbers have exploded in Chesapeake Bay estuaries. Catfishes produce stridulation sounds by rubbing ridges on the dorsal process of the pectoral spine against a rough surface on the cleithrum to produce a series of pulses during abduction. We studied the mechanism of sound generation by synchronizing audio recordings with a high speed camera at 2000 frames per second. Unlike channel catfish that typically keep their pectoral fins retracted (adducted), blue catfish tend to maintain them in a forward position. Therefore sound production requires the fish to adduct the spine before forward stridulatory movement. Adduction movements were about a third as long as abductions (means of 49 and 152 ms respectively). The amplitude of abduction and adduction movements was similar at 25.9 and 26.5 degrees. Stridulatory abductions consisted of a series of 3-17 short rapid movements (median of 13) with an average rotation of 3.1 degree over 1.5 ms. Movement was followed by an interpulse period of 13.2 ms in which the spine was stationary. Sound amplitude was low during movement and increased during the stationary period suggesting time was required to activate vibrations in the pectoral girdle. Sounds are produced by a slip-stick mechanism similar to a bow over a violin string.