DOI: 10.5061/dryad.4q50bp6
title: Data from: The trophic ecology of a desert river fish assemblage: influence of season and hydrologic variability

description: Foodweb analyses can provide insight as to how species persist in
 naturally dynamic environments and how these communities may respond to
 anthropogenic alteration. In the remaining undammed rivers of the arid
 southwestern United States, it is thought that plasticity in feeding
 behavior allows native fishes to thrive in the context of natural
 fluctuations in temperature, sediment, and resource availability
 associated with extreme swings in season and hydrology. There have been
 few evaluations of this hypothesis, in part owing to the rarity of rivers
 that retain their natural environmental dynamics and complement of native
 species. We investigated the feeding ecology of the fish assemblage of one
 such river, the Little Colorado River, Arizona, focusing on four native
 species: bluehead sucker (Catostomus discobolus), flannelmouth sucker
 (Catostomus latipinnis), speckled dace (Rhinichthys osculus), and
 endangered humpback chub (Gila cypha). Over two years, we sampled fish
 diets in July, September, January, March, and June, encompassing turbid
 and clear‐water conditions across seasons. We quantified food resource
 contributions to fish diets in fish‐centered food webs, comparing
 diversity of trophic linkages and linkage‐strength distribution across
 time. We used ordination analyses to investigate differences in diets
 among species and changes in diet composition across seasons and conducted
 seasonal comparisons of gut fullness. We observed a high diversity of
 dietary items (as absolute numbers and consumer–resource ratios) within a
 fish assemblage that was apparently resistant to extreme and recurrent
 environmental variability. Fish diet diversity was ~2× that of the nearby
 dammed Colorado River's tailwater, and over 50% of fish‐resource
 linkages were weak (&lt;1% of species’ diet). Native fishes consumed a
 mix of terrestrial and aquatic resources. Notably, the water
 column‐feeding humpback chub consumed the largest percentage of
 terrestrially derived food items and appeared to capitalize on food
 resources made available by a summer flash flood, consuming twice as much
 during this flood than during other seasons (based on gut fullness,
 corrected by estimates of food quality). Other fishes exhibited similar
 dietary variation. Such opportunist/generalist strategies, coupled with
 diverse food resources, may be important to the persistence of these and
 other native fishes in dynamic environments.
description: BehnBaxter_LCR_2012-2014_FishCatchLog of total fish catch from Little Colorado River including date, species, gear type, length, and weight. Dates span 2012-2014.BehnBaxter_LCR_2012-2014_FishDietCompleteDataset of weights of fish diet items in compiled form, both coarse and fine magnification.BehnBaxter_LCR_2012-2014_FishDietCoarseItemsDataset of weights of fish diet items collected via coarse magnification (10-40X) only.BehnBaxter_LCR_2012-2014_FishDietFineItemsDataset of weights of fish diet items collected via fine magnification (400X) only.BehnBaxter_LCR_2012-2014_DietItemsKeyAbbreviations of diet items and corresponding full descriptions.