Effect of Baiting on Hoop Net Catch Rates of Endangered Humpback Chub

Abstract

The effects of unbaited, scented (odor emitted by inaccessible hatchery feed), and baited (accessible feed) single-throated hoop nets on the catch rates of the federally endangered humpback chub Gila cypha (≥100 mm total length) were assessed in the Little Colorado River, Arizona, to determine how baiting affected the catch of these fish. Of a total of 1,297 unique humpback chub captured, 262 (20%) were caught in 179 unbaited nets, 330 (25%) in 179 scented nets, and 705 (54%) in 178 baited nets. Humpback chub retention in unbaited nets did not differ from a 50:50 chance event (P = 0.075) but probably peaked in baited nets where these fish were preoccupied with feeding (i.e., gorging themselves), which would explain the higher catch rates in baited than in scented or unbaited nets (P ≤ 0.001). Moreover, humpback chub catch rates were not significantly higher in scented than in unbaited nets (P = 0.779), which suggests that elevating both “fish attraction” and “fish retention” are essential to substantially increase their captures in these nets. However, scenting may still be a viable option when used in conjunction with passive gears possessing higher fish retention capabilities or to target species less prone to escape. The findings of this study should provide valuable insight to anyone wishing to optimize catch rates by baiting or scenting passive entrapment gear.