Meeting Abstract
In structurally complex environments, fish have two choices when faced with predation: flee or hide. Habitat degradation tends to structurally simplify aquatic habitats, resulting in limited access to hiding spots. Since juvenile fish are most at risk from predator-induced mortality, habitat degradation may affect juveniles disproportionally. We examined background matching, in which animals position themselves over areas that are not visually similar to themselves instead of fleeing, as a possible behavioral response in predator-naïve brown trout (Salmo trutta) when exposed to a great blue heron decoy in a simple environment. We recorded overhead video of predator-naïve brown trout exposed to a heron decoy and a control in tanks with randomly distributed dark substrate patches over a light-colored floor. We digitally tracked trout position during reactions to the decoy and control using DLTdv6 through MATLAB, and tracked pathway, distance moved, and time spent over dark versus light substrate. Our results showed strong support for predator-naïve fish responding to a heron decoy. Fish exposed to a heron decoy deviated from the shortest path away from the heron decoy, and spent more time over dark substrate. We found that group size influences trout response, with larger groups of fish more likely to remain in light areas during exposure to the heron decoy. Our data suggests that small groups of predator-naïve brown trout attempt to background match, possibly due to greater chances of predation on a single fish. Our research has implications for predation outcomes for predator-naïve brown trout, such as hatchery-raised fish, in degraded and simplified environments.
