*WINNER* Testing Diel Fish Migrations Between Riffle-Pool Habitats

Abstract

This won best undergraduate poster for Biology.

Diel turnover in assemblage composition is reported from a number of aquatic species, including stream fishes. However, there is a paucity of work addressing diel fluctuations by small-bodied stream fishes. We tested for fish migrations between riffle and pool habitats across transitional diel periods (i.e., sunrise and sunset) in Little Creek, Putnam County, TN using directional weir traps placed between four riffles and the adjacent upstream and downstream pools. We hypothesized that small-bodied fishes use pools during diurnal hours, migrate into riffles during the transition to night (i.e., sunset), and then move back into pools during the transition to day (i.e., sunrise). We compared the number of fishes captured in weirs blocking movement out of pools and into riffles with fish captured moving out of riffles and into pools for both transitional periods and in upstream and downstream directions. We found that fish movement (i.e., weir capture) during sunset was higher than sunrise, and the largest amount of movement was into riffles at sunset. There was no apparent difference between movements into riffles from upstream or downstream directions. We then set bidirectional weir traps in the center of riffles and assessed capture rates every four hours for 72 consecutive hours and found capture rates were greatest during nocturnal hours. Our results suggest fish movement into and activity within riffles is greatest during nocturnal hours, and that small-bodied stream fishes exhibit diel migrations between riffle and pool habitats.