WAINWRIGHT, P.C.*; FERRY-GRAHAM, L.A.; WALTZEK, T.B.; HULSEY, C.D.; CARROLL, A.M.; SVANBACK, R.: Evaluating suction feeding performance in fishes

There is no widely-accepted metric for evaluating suction feeding performance, in spite of the widespread use of this method of prey capture among vertebrates. We studied the efficacy of Suction Distance, the distance over which the prey is drawn toward the mouth, in an analysis of suction feeding performance in seven species of cichlid fishes known to differ radically in feeding ecology and the ability to generate suction pressure. Species known to generate stronger buccal pressure were predicted to draw prey from further away. Using 500 Hz video we recorded 20 strikes from three fish per species feeding on live brine shrimp and guppies. We measured Suction Distance and the distance the predator moved toward the prey (Ram Distance). Surprisingly, species did not differ significantly in Suction Distance, but showed a six-fold range in Ram Distance. We suggest that previously observed diversity in relative use of ram and suction by fishes is due mostly to variation in the ram component of the strike. Suction feeders draw water into their mouth from a large region around the mouth and thus it is expected that the flow velocity falls rapidly with distance from the mouth. In a separate analysis of suction feeding in largemouth bass we synchronized video with recordings of buccal pressure. We were able to account for over 80% of the variation among strikes in peak suction pressure using a multiple regression model with cranial kinematic variables. However, neither buccal pressure variables nor kinematic variables accounted for more than 17% of the variance in Suction Distance. These results indicate that Suction Distance is an ineffective metric of suction feeding performance.