P2.201 Thursday, Jan. 5 Orientation and movement strategies determine the success of down-slope movement in stranded Gambusia affinis BOUMIS, R.J.; GIBB, A.C*; Northern Arizona University; Northern Arizona University Robertjb78@gmail.com
Gambusia affinis are known to voluntarily strand themselves to avoid predators. In addition, this species is of interest as biological pest control agent, a model organism, and a highly invasive species. In the laboratory, individuals of G. affinis (n=53) were manually stranded on a ramp covered with damp sand that was elevated at one end to create a slope of thirty degrees. Individuals were placed on the slope in one of four orientations: “cranial-end-up,” “cranial-end-down,” “dorsal-surface-up,” and “dorsal-surface-down,” with “down” denoting the down-slope direction, where the water would be located in the wild. The response to stranding was recorded using a digital-video camera at 60 FPS. Statistical analysis revealed that two factors, starting orientation and the type of movement employed, affected how likely a fish was to make it to the bottom of the slope. Specifically, a fish in the “dorsal-surface-down” orientation was the most likely to return to the water in a single movement. Two separate types of movement, a jump pushing off from the caudal peduncle, and a bending motion where the tail bends towards the upper body were more likely to succeed than other observed movement types. This finding suggests that if a fish voluntarily strands itself, it will be more likely to successfully return to the water if it lands at a particular orientation on the bank.