Behavioral response of loach minnow, Tiaroga cobitis, to nonnative predators

Authors: Edward Wild, Keith Gido, Lindsey Bruckerhoff

Year: 2021

Abstract

Population declines of loach minnow, Tiaroga cobitis, throughout their range have been partially attributed to nonnative predation. Despite population declines, there are some systems where loach minnow coexist with nonnative predators, questioning the mechanisms that might allow coexistence of these species. Due to their endangered status, it is difficult to justify the removal of wild loach minnow to conduct predator-prey experiments that could result in mortality of individuals. As an alternative, we tested the behavioral response of captive reared loach minnow to the presence of smallmouth bass, Micropterus dolomeui, or flathead catfish, Pylodictus olivaris, in complex outdoor experiment stream mesocosms. We predicted increased movement associated with foraging in the absence of predators and that loach minnow would avoid pools with predators present. Movements of both predators and prey were monitored continuously by PIT tagging all fish and placing submersible PIT antennas in the stream mesocosms. Both smallmouth bass and flathead catfish consumed loach minnow during the experiment. Loach minnow movement decreased after the addition of smallmouth bass trials but not following the addition of flathead catfish. Contrary to our prediction, loach minnow did not avoid pools with flathead catfish or smallmouth bass. Compared to a similar experiment with co-evolved predator and prey fishes, loach minnow were less responsive to nonnative predators, particularly flathead catfish. These results might help prioritize the management of nonnative predators that expand into loach minnow habitats.