Effects of water temperature and fish size on predation vulnerability of juvenile humpback chub to rainbow trout and brown trout

Transactions of the American Fisheries Society
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Abstract

Predation on juvenile native fish by introduced Rainbow Trout and Brown Trout is considered a significant threat to the persistence of endangered Humpback Chub Gila cypha in the Colorado River in the Grand Canyon. Diet studies of Rainbow Trout and Brown Trout in Glen and Grand canyons indicate that these species do eat native fish, but impacts are difficult to assess because predation vulnerability is highly variable, depending on prey size, predator size, and the water temperatures under which the predation interactions take place. We conducted laboratory experiments to evaluate how short-term predation vulnerability of juvenile native fish changes in response to fish size and water temperature using captivity-reared Humpback Chub, Bonytail, and Roundtail Chub. Juvenile chub 45–90 mm total length (TL) were exposed to adult Rainbow and Brown trouts at 10, 15, and 20°C to measure predation vulnerability as a function of water temperature and fish size. A 1°C increase in water temperature decreased short-term predation vulnerability of Humpback Chub to Rainbow Trout by about 5%, although the relationship is not linear. Brown Trout were highly piscivorous in the laboratory at any size > 220 mm TL and at all water temperatures we tested. Understanding the effects of predation by trout on endangered Humpback Chub is critical in evaluating management options aimed at preserving native fishes in Grand Canyon National Park.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Effects of water temperature and fish size on predation vulnerability of juvenile humpback chub to rainbow trout and brown trout
Series title Transactions of the American Fisheries Society
DOI 10.1080/00028487.2015.1077160
Volume 144
Year Published 2015
Language English
Publisher American Fisheries Society
Contributing office(s) Southwest Biological Science Center
Description 8 p.
First page 1184
Last page 1191
Online Only (Y/N) N
Additional Online Files (Y/N) N