Effect of oral suction and other friction-enhancing behaviors on the station-holding performance of suckermouth catfish (Hypostomusspp.)

Abstract

Effect of oral suction and other friction-enhancing behaviors on the ability to maintain position in a current (station-holding) was determined for the suckermouth catfish (genus Hypostomus Lacépède, 1803). Fish were tested using an increasing velocity test on three substrata (smooth Lucite®, rough Lucite®, and wire grid). On the smooth substratum, use of oral suction and other behaviors delayed the need to swim continuously out of ground contact from 9.1 ± 0.3 cm/s (uslip) to 89.2 ± 7.9 cm/s (uswim). Trials on the wire grid showed that oral suction was ineffective as predicted; however, fish were able to use other friction-enhancing behaviors instead to improve station-holding performance. Behaviors that increased friction by hooking the fish to the substrate via the odontodes and pectoral fin spines were very effective at delaying the need for steady swimming from 12.9 to 145.0 cm/s. On the rough substratum, fish were able to use both oral suction and the odontodes or fin spines to increase friction, and station-holding performance was similar to values on the wire substratum. Thus, while use of the oral suction disk was shown to improve station-holding performance, use of other morphological features such as the odontodes and fin spines may be equally important.