Meeting Abstract
California grunion (Leuresthes tenuis) face an unusual set of physical challenges when they emerge onto sandy beaches to spawn. Are locomotor behaviors produced by grunion associated with particular environmental conditions? Grunion were filmed spawning on Cabrillo Beach (CA) in May 2014 with a camcorder (120 fps). Data were analyzed in a series of five-second clips during which at least five individuals were moving throughout the sampling period. We observed tail flip jumping (a fish rotates its head over the posterior body, then pushes the tail against the substrate and leaps into the air), swimming-like movements (cyclical undulation in the posterior body), and two previously undescribed behaviors: “inching” and “frontfliping.” During inching, the fish presses the tail and head onto the substrate, then elevates the center of mass and displaces it laterally. During frontfliping, a fish plants its head on the substrate and pushes the tail against the substrate to rotate the tail about the head; at the end of the movement, the tail is positioned ~180° from the starting point. Tail flip jumping was usually observed in high density conditions and where the substrate was variable. Swimming-like movements were produced only when water was present. Inching and frontflip movements were observed at low fish densities, when there was no wave action, and where the substrate was composed of small particles. Inching and swimming-like movements were used to move rapidly in a direct path, while jumping and frontfliping were used to navigate obstructions. Grunion employ diverse locomotor behaviors when faced with physical obstacles and heterogeneous substrates in the sandy intertidal zone.
