Effects of a Varied of Pectoral fin movement in Visual Looming Stimulus for Pacific staghorn sculpin (Leptocottus armatus) and shiner perch (Cymatogaster aggregata)

Abstract

When startled, fish perform an escape response to flee from predators. Looming, a technique to visually stimulate a fish, has been extensively studied; however, studies have focused on a simplified loom that approximates the silhouette of an approaching predator as an expanding disk. We hypothesize that more detailed silhouettes of species-specific predators may have different effects on fish of different ecology. To this end, we look at the effect of adding flapping fins to the loom, simulating a seal attack, which adds both spatial and temporal detail to the loom. We use this to startle two different species of fish: staghorn sculpin (Leptocottus armatus), a benthic and cryptic species, and shiner perch (Cymatogaster aggregata), a benthopelagic species active in the water column, both of which are commonly preyed upon by local harbor seals. Four loom treatments were used: a black disk with flapping fins (additional spatio-temporal detail), a black disk with stationary fins (additional spatial detail), a black disk without fins (control), and a pair of flapping fins with no disk (control).