KOROBOV, N*; BRAINERD, EL; MADDEN, P; LAUDER, GV; University of Massachusetts Amherst; Brown University; Harvard University; Harvard University: Novel pectoral fin kinematics during steady swimming in a benthic fish, the Longhorn sculpin, Myoxocephalus octodecimspinosus

Myoxocephalus octodecimspinosus (Cottidae: Scorpaeniformes) is a benthic fish that lacks a swim bladder and is negatively buoyant. This species uses large, fan-shaped pectoral fins in a previously undescribed swimming behavior. We filmed four individuals using two synchronous high-speed, high-resolution cameras, one in lateral and one in dorsal orientation. These views were calibrated to produce a 3-D view of the pectoral fins during swimming. We were then able to digitize and examine the 3-D position of individual fin rays at different stages of the behavior. When the fish is at rest on the substrate, the fin is adducted against the body. The 10 most dorsal rays are long, and are oriented in the cranial-caudal direction. The much shorter ventral rays are oriented in the dorsal-ventral direction and are usually in contact with the substrate when the fish is at rest. At the initiation of slow swimming, the most dorsal fin ray acts as the leading edge when the fin is drawn craniad, parallel to the flow. The fin rays are feathered, with the medial face of the fin oriented dorsally and the lateral face of the fin oriented ventrally. The fin is then held still as the caudal fin provides the propulsive force during swimming. The swimming bout ends when the fins are adducted and the fish returns to rest. The short ventral rays likely play a role when the fish transitions from swimming to resting on the substrate. This wing-like conformation of the fin without oscillation is a novel use of the pectoral fins in fishes. We hypothesize that the pectoral fins are used as aerofoils to generate lift during caudal fin-propelled swimming thereby counteracting the weight of the fish in water.