High Diet Overlap between Native Small-Bodied Fishes and Nonnative Fathead Minnow in the Colorado River, Grand Canyon, Arizona

TitleHigh Diet Overlap between Native Small-Bodied Fishes and Nonnative Fathead Minnow in the Colorado River, Grand Canyon, Arizona
Publication TypeJournal Article
Year of Publication2014
AuthorsSeegert, SEZ, Rosi-Marshall, EJ, Baxter, CV, Kennedy, TA, Hall, RO, Cross, WF
JournalTRANSACTIONS OF THE AMERICAN FISHERIES SOCIETY
Volume143
Pagination1072-1083
PublisherTAYLOR & FRANCIS INC
Place Published530 CHESTNUT STREET, STE 850, PHILADELPHIA, PA 19106 USA
Type of ArticleArticle
ISSN0002-8487
Abstract

River regulation may mediate the interactions among native and nonnative species, potentially favoring nonnative species and contributing to the decline of native populations. We examined food resource use and diet overlap among small-bodied fishes in the Grand Canyon section of the Colorado River as a first step in evaluating potential resource competition. We compared the diets of the predominant small-bodied fishes (native Speckled Dace Rhinichthys osculus, juvenile Flannelmouth Sucker Catostomus latipinnis, and juvenile Bluehead Sucker C. discobolus, and nonnative Fathead Minnow Pimephales promelas) across seasons at four sites downstream of Glen Canyon Dam using nonmetric multidimensional scaling and Schoener's similarity index. The diets of these fishes included diatoms, amorphous detritus, aquatic invertebrates (especially simuliid and chironomid larvae), terrestrial invertebrates, and terrestrial vegetation. Diets varied with season and were affected by high turbidity. Fish consumed more amorphous detritus and terrestrial vegetation during the summer monsoon season (July-September), when turbidity was higher. The diets of all species overlapped, but there was large variation in the degree of overlap. The diets of juvenile suckers and Fathead Minnows were most similar, while Speckled Dace had relatively distinct diets. The differences took the form of higher proportions of diatoms and amorphous detritus in the diets of Bluehead Suckers and Fathead Minnows and higher proportions of simuliids and chironomids in those of Speckled Dace. If food resources are or become limiting, diet overlap suggests that competition may occur among native and nonnative species, which could have implications for the population dynamics of these fishes and for the management of the Colorado River ecosystem in Grand Canyon.

DOI10.1080/00028487.2014.901250

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