Changes In Diet Composition Research Articles

Dietary study using set-nets produces bias in prey choice of fish: A case of three coastal fishes inhabiting southern Korean waters

Prey selection by marine fishes is highly dependent on whether available food resources are abundant or deficient in their feeding grounds. The influence of fishing method on prey choice was analyzed via stomach content analyses of three coastal fishes: Pennahia argentata, Sillago japonica, and Thryssa kammalensis. Fish samples were collected from northern Jinju Bay, Korea, using two types of fishing gear that covered two different fishing layers in the water column: beam-trawl (bottom layer) and set-net (surface layer). When caught via beam-trawl, all three target species were function as bottom-feeding carnivores that consumed mainly benthic crustaceans and other invertebrates. In contrast, when caught via set-net, teleosts were the most abundant prey items in the diets of the three species. Significant differences in the diet composition between beam-trawl and set-net samples were revealed using permutational multivariate analysis of variance. Although seasonal changes in diet composition were also evident, the influence of season was weaker than that of fishing gear. Consequently, in this study, stomach content analysis demonstrated that set-net made a strong effect on prey selection by the co-occurring P. argentata, S. japonica, and T. kammalensis in southern Korean waters.

PSXIV-38 Short-term adaptation of milk yield and feed efficiency to individualized dietary changes

Abstract Automated in-parlor feeding and other precision individual animal feeding strategies are a primary interest of efforts to enhance precision animal nutrition. Our objective was to determine short-term effects of changes in diet composition on milk yield and feed efficiency in dairy cattle. A replicated latin square with 4 groups of 6 cows was used to evaluate responses to feeding increasing amounts of ground corn (GC), soybean meal (SBM), chopped grass hay (GH), or total mixed ration (TMR) for 9 d periods. Throughout each period, treatments were top dressed at incrementally increasing rates to provide 0 to 20 percent of calculated net energy intake. Cows were group housed and fed once daily in Calan gates for 36 days. Mean milk yield, efficiency, and the linear slopes of these responses to top dress intake were analyzed during each 9 day period. Mean responses and response slopes were analyzed using a mixed-effect model with fixed effects for top dress and random effects for animal, period, and square. Milk yield was significantly affected by top dress type (P = 0.010) and GH differed significantly from SBM (P = 0.015). However, feed efficiency did not differ with top dress type. The milk yield slope was not affected by top dress type (P = 0.268), but the efficiency slope was affected (P = 0.011). The efficiency response to dietary changes was greater for added SBM than for added GH (P = 0.012), but SBM responses did not differ from GC (P = 0.484) or TMR (P = 0.772). These results suggest opportunity to use individualized, automated feeding strategies to adjust dietary composition in the short-term to target economically optimal formulations without sacrificing production.

Impaired Metabolic Flexibility to High-Fat Overfeeding Predicts Future Weight Gain in Healthy Adults.

The ability to switch fuels for oxidation in response to changes in macronutrient composition of diet (metabolic flexibility) may be informative of individuals’ susceptibility to weight gain. Seventy-nine healthy, weight-stable participants underwent 24-h assessments of energy expenditure and respiratory quotient (RQ) in a whole-room calorimeter during energy balance (EBL) (50% carbohydrate, 30% fat) and then during 24-h fasting and three 200% overfeeding diets in a crossover design. Metabolic flexibility was defined as the change in 24-h RQ from EBL during fasting and standard overfeeding (STOF) (50% carbohydrate, 30% fat), high-fat overfeeding (HFOF) (60% fat, 20% carbohydrate), and high-carbohydrate overfeeding (HCOF) (75% carbohydrate, 5% fat) diets. Free-living weight change was assessed after 6 and 12 months. Compared with EBL, RQ decreased on average by 9% during fasting and by 4% during HFOF but increased by 4% during STOF and by 8% during HCOF. A smaller decrease in RQ, reflecting a smaller increase in lipid oxidation rate, during HFOF but not during the other diets predicted greater weight gain at both 6 and 12 months. An impaired metabolic flexibility to acute HFOF can identify individuals prone to weight gain, indicating that an individual’s capacity to oxidize dietary fat is a metabolic determinant of weight change.

FASTING-MIMICKING DIET REDUCES RISK FACTORS FOR AGING-RELATED DISEASES IN PRECLINICAL AND CLINICAL STUDIES

Prolonged fasting promotes stress resistance, but its effects on longevity are poorly understood. Calorie restriction or major dietary composition changes can have profound effects on healthy aging but the inability of many subjects to adhere to chronic and extreme diets together with the potential of adverse effects limit their application. Fasting-mimicking diets (FMDs) are effective in increasing health and lifespan, possibly by inducing stem cell-based regeneration, or as therapies in mouse models of a variety of diseases. FMDs reduce cancer incidence/progression, modulate the immune response, reduce immuno-senescence, ameliorate or reverse disease progression of multiple sclerosis, Type I and Type II diabetes, and reverse inflammatory bowel disease pathology. In a randomized clinical trial, markers/risk factors for metabolic syndrome and other age-related diseases were favorably impacted after completion of 3 FMD cycles. These effects were larger in participants at risk for age-related diseases. Conclusions: We conclude that the FMD was safe and feasible in rodent and human studies. Larger studies on patients with diagnosed diseases are necessary to determine its impact on diabetes and cardiovascular disease treatment.

Covariation of diet and gut microbiome in African megafauna

A major challenge in biology is to understand how phylogeny, diet, and environment shape the mammalian gut microbiome. Yet most studies of nonhuman microbiomes have relied on relatively coarse dietary categorizations and have focused either on individual wild populations or on captive animals that are sheltered from environmental pressures, which may obscure the effects of dietary and environmental variation on microbiome composition in diverse natural communities. We analyzed plant and bacterial DNA in fecal samples from an assemblage of 33 sympatric large-herbivore species (27 native, 6 domesticated) in a semiarid East African savanna, which enabled high-resolution assessment of seasonal variation in both diet and microbiome composition. Phylogenetic relatedness strongly predicted microbiome composition (r = 0.91) and was weakly but significantly correlated with diet composition (r = 0.20). Dietary diversity did not significantly predict microbiome diversity across species or within any species except kudu; however, diet composition was significantly correlated with microbiome composition both across and within most species. We found a spectrum of seasonal sensitivity at the diet-microbiome nexus: Seasonal changes in diet composition explained 25% of seasonal variation in microbiome composition across species. Species' positions on (and deviations from) this spectrum were not obviously driven by phylogeny, body size, digestive strategy, or diet composition; however, domesticated species tended to exhibit greater diet-microbiome turnover than wildlife. Our results reveal marked differences in the influence of environment on the degree of diet-microbiome covariation in free-ranging African megafauna, and this variation is not well explained by canonical predictors of nutritional ecology.

Ontogenetic variation in the diet of the anuran community from a semi-arid environment in the southeastern Chihuahuan Desert.

Although ontogeny influences dietary composition and trophic niche breadth in many anurans, its effects on diet have been little analyzed in sympatric species. In this study, we analyzed interspecific and ontogenetic variation in dietary composition and trophic niche width in an anuran community from a semi-arid environment. We found a more profound effect of species identity than body size on dietary composition, with the diet of four species dominated by formicids, that of two others by coleopterans and formicids, and that of the remaining species not dominated by specific prey types. We found ontogenetic changes in dietary composition in three of four species analyzed, in which consumption of some small insects decreased as predator size increased, regardless of species. Additionally, we did not find ontogenetic change in prey number consumed in any of the four species, but prey size increased with increasing predator size in all of them. Most species exhibited a narrow trophic niche, which was even narrower in adults in three of the four species analyzed. Costello’s modified plots revealed a high variation among individuals in termite consumption in Anaxyrus punctatus, and in more prey types in Spea multiplicata. Our results suggest that this community is not size-structured, and that ontogenetic diet shifts are mainly caused by passive sampling toward prey of different sizes. Finally, comparisons with previous data revealed an interpopulation pattern, in which trophic niche width contracts as aridity increases, possibly because of an increase in interspecific competition for trophic resources.

Dietary specialization depending on ecological context and sexual differences in Asiatic black bears.

The food habits of the Asiatic black bear (Ursus thibetanus) are well studied, but there is a little evidence of dietary specialization—that is, when individuals use a narrower set of resources compared to the population as a whole. To examine the dietary composition at the individual level, seasonal patterns of dietary specialization, and sex-based dietary differences in Asiatic black bears, we attached Global Positioning System (GPS) collars to 15 Asiatic black bears and collected their scats in Nagano Prefecture, Japan from 2017 to 2018. Our results showed that the dietary composition differed among individuals, although seasonal changes in dietary composition were observed at the population level. Dietary specialization was high in summer (resources less abundant) and low in spring and autumn (resources more abundant), indicating a relationship with general food abundance and the dietary diversity of bears. In spring, all bears consumed green vegetation and/or seed of Fagaceae family from previous autumn; in early- and late- summer, dietary composition, such as green vegetation, insects, and fruits, greatly differed among individuals. In autumn, most bears heavily depended on seeds of Fagaceae which is high-quality food for bears.Although we did not find statistical differences between sexes in terms of dietary specialization and diversity, we found variations in the timing of feeding on the Fagaceae family, being earlier in females compared with males. We also found considerable variation in dietary composition within sexes, suggesting that dietary specialization depends on multiple factors besides food abundance, food diversity, and sex.

Food and feeding habits of Otolithoides pama (Hamilton, 1822) occurring from Hooghly-Matlah estuary of West Bengal, India

The food and feeding habits of Otolithoides pama collected from three different sites of Hooghly-Matlah estuary, West Bengal, India for a period of 18 months (November 2016 to May 2018) were studied. Both fishes and prawns have dominated the food items in the gut. A very high percentage of empty stomach frequently occurred throughout the year. The species is a macrophagous carnivore and feeds mainly small fishes and prawns. The feeding intensity was more in juveniles stages with prawns and fishes dominated the gut contents while teleosts preferred by the adults. Among the teleosts the main food items were Otolithoides pama, Harpadon nehereus, Secutor insidiator, Sardinella spp., Setipinna spp., other sciaenids like Johnius spp., other clupieds like Tenualosa ilisha, Ilisha megaloptera, Polynemus paradesius, Arius spp., mullets like Mugil and Chelon spp., Rastrelliger kanagurta, Coilia dussumieri, Bregmaceros maclellandi, Trichiurus spp., and unidentified teleosts body parts. Among non-penaeid prawns Acetes spp. was the most dominant food items, among penaeids Parapenaeopsis spp., Metapenaeopsis spp., Metapenaeus spp., Parapenaeus spp., Solenocera spp. constitute food items. GaSI was found high during February, June and October and low during July–August for both the sexes. The monthly mean RLG values were highest during October for male and March for female. Both seasonal changes in diet composition and ontogenetic changes were noticed between juveniles and adults.

Qualitative and quantitative changes in dietary composition of marbled flounder Pseudopleuronectes yokohamae between periods of different stock sizes in Tokyo Bay, Japan.

Qualitative and quantitative changes in dietary composition of marbled flounder Pseudopleuronectes yokohamae between periods of different stock sizes in Tokyo Bay, Japan.

Isolated branched-chain amino acid intake and muscle protein synthesis in humans: a biochemical review.

ABSTRACTAlongside a proper diet, ergogenic aids with potential direct and/or indirect physical performance enhancing effects are sought after for improved adaptation to physical training. Nutritional ergogenics include diet composition changes and/or dietary supplementation. Branched-chain amino acids valine, leucine and isoleucine are widely popular among products with ergogenic claims. Their major marketing appeal derives from allegations that branched-chain amino acids intake combined with resistance physical exercise stimulates muscle protein synthesis. Evidence supporting the efficacy of branched-chain amino acids alone for muscle hypertrophy in humans is somewhat equivocal. This brief review describes physiological and biochemical mechanisms underpinning the effects of complete protein source and branched-chain amino acid intake on skeletal muscle growth in the postabsorptive and post-exercise state. Evidence in favor of or against potential anabolic effects of isolated branched-chain amino acid intake on muscle protein synthesis in humans is also examined.

The effects of hesperidin or naringin dietary supplementation on the milk properties of dairy ewes.

Fortification of animal products with natural bioactive compounds appears to improve their quality and protects consumers against oxidation effects. An experiment was therefore conducted to examine the effects of hesperidin or naringin on milk oxidative stability, yield, composition, coagulation properties, and the fatty acid profile in dairy sheep. Thirty-six Chios ewes were assigned to four groups. A control group was fed a concentrate diet without supplementation. The other three groups were provided with the same diet further supplemented with hesperidin (6000 mg kg-1 ), naringin (6000 mg kg-1 ), or α-tocopheryl acetate (200 mg kg-1 ). The efficacy of flavonoids after a change in diet composition that lowered milk oxidation values by itself was also tested. The duration of the experiment was 28 days with alfalfa hay being the only forage source for the first 14 days, whereas after the 15th day a mixture of alfalfa hay and wheat straw (65:35) was provided. The oxidative stability of milk was improved after 14 days of addition of the examined flavonoids (P< 0.05). Milk malondialdehyde (MDA) values were also decreased as a result of flavonoid dietary supplementation, 14 days after the modification of the forage source. On the other hand, no significant differences in yield, chemical composition, coagulation properties, and fatty acid profile of ewe milk were observed among the treatments throughout the experiment. Enrichment of dairy ewes' diets with hesperidin and naringin might be effective in improving milk's oxidative stability without any effects on the milk's chemical composition, coagulation properties, and fatty acid profile. © 2019 Society of Chemical Industry.

Effectiveness of Changes in Diet Composition on Reducing the Incidence of Cardiovascular Disease

To highlight dietary changes shown to be associated with a lower risk of cardiovascular events in epidemiological studies and that have been proven to be effective in preventing cardiovascular diseases in clinical trials RECENT FINDINGS: Since dietary changes always involve multiple variables, recent observational and intervention studies on dietary prevention of cardiovascular disease focus not only to the limitation of a single nutrient/food intake but also to the other dietary changes implemented to replace it. The available evidence supports three major dietary strategies for cardiovascular disease prevention: (1) the replacement of saturated fat with unsaturated fat and/or fiber-rich carbohydrate foods; (2) the reduction of salt intake; (3) the implementation of dietary patterns resembling the traditional Mediterranean diet. This support derives not only from RCTs but also from the combination of large observational cohort studies and relatively short-term randomized trials on cardiovascular risk factors.

Effect of population density on diet composition and dietary niche breadth of guanaco (Lama guanicoe, Müller 1776) in northeastern Patagonian steppes

The optimal foraging theory postulates that as animal population density increases, the progressive decline in preferred forage availability results in changes in diet composition and widening of dietary niche breadth. For sedentary guanaco populations, some authors proposed a mechanism of population density limitation below the environmental carrying capacity, mediated through territoriality. Under the optimal foraging theory, increased density would lead to changes in guanaco diet selectivity and composition. Conversely, under the self-regulation hypothesis, guanacos would not affect preferred forage availability and no differences in guanaco diet would be expected. We tested these contrasting hypotheses by assessing both the differences in the proportion of grasses and shrubs present in guanaco diet and dietary niche breadth at three contrasting densities in northeastern Patagonian steppes. We did not find guanaco density effects on preferred forage availability, grass-shrub proportions in the diet and diet selectivity. Guanacos showed a mixed diet composed by plant species of both high and low nutritional quality independently of population density. The lack of changes in diet composition suggests that guanacos did not perceive a restriction in forage availability in terms of either biomass or nutritional content, regardless the observed increase in population density.

Changes in diet composition with urbanization and its effect on the polycystic ovarian syndrome phenotype in a Western Indian population

To study the effects of increasingly prosperous diet content on clinical features of polycystic ovary syndrome (PCOS). A cross-sectional cohort study of 711 women with PCOS from a heterogeneous population spanning a wide spectrum of socioeconomic strata. Independent hospital. A total of 711 women with PCOS in whom the diagnosis was based on Rotterdam criteria. Results were compared with a locally recruited reference group. Clinical assessment of women with PCOS. Clinical characteristics were assessed with particular reference to diet composition. Four diet groups were identified: simple rice with vegetables, vegetarian with mixed carbohydrates, nonvegetarian with mixed carbohydrates, and an urban diet of processed foods. Women with PCOS showed the characteristic features of raised LH and androstenedione concentrations and increased ovarian volume and antral follicle count. There was a notable association between an increasingly affluent diet, the presence of hirsutism, raised body mass index, insulin resistance, and higher serum antimüllerian hormone concentrations. The positive association between antimüllerian hormone and body mass index is an unusual feature possibly explained by the wide spectrum of lifestyles in this cohort. Urbanization of women in India is associated with increasingly severe phenotype of PCOS, which is likely to have implications on fertility outcomes.

Impaired Metabolic Flexibility to High-Fat Overfeeding Predicts Future Weight Gain

The ability to switch fuels for oxidation in response to changes in macronutrient composition of diet (metabolic flexibility) may be informative of the individual susceptibility to weight gain. Seventy-nine healthy, weight-stable subjects underwent 24-h assessments of energy expenditure and respiratory quotient (RQ) in a whole-room calorimeter during energy balance (EBL; 50% carbohydrate, 30% fat) and then during 24-h fasting and three 200% overfeeding diets in a crossover design. Metabolic flexibility was defined as the change in 24-h RQ from EBL during fasting and standard (SOF: 50% carbohydrate, 30% fat), high-fat (FNP: 60% fat, 20% carbohydrate), and high-carbohydrate (CNP: 75% carbohydrate, 5% fat) overfeeding diets. Free-living weight change was assessed after 6 and 12 months. Compared to EBL, RQ decreased on average by 9% during fasting and by 4% during FNP, while increasing by 4% during SOF and by 8% during CNP. Smaller decrease in RQ, reflecting smaller increase in lipid oxidation rate, during FNP but not during other diets, predicted greater weight gain at both 6 and 12 months. An impaired metabolic flexibility to acute, high-fat overfeeding identify individuals prone to gain weight, indicating that the individual capacity to oxidize dietary fat is a metabolic predictor of weight change.

Feeding habits of striped piggy, Pomadasys stridens (Forsskal, 1775) (Haemulidae) in northern part of the Persian Gulf

Feeding habits of Pomadasys stridens were studied in northern part of the Persian Gulf. A total of 591 specimens were collected from the coastal water of Bushehr Province using trawl boats from May 2012 to April 2013 and diet composition, feeding intensity and season changes in diet composition were investigated. Vacuity Index was 81% during the study. RGL was 0.98±0.03 classifying this species as carnivorous to omnivorous fish. Pomadasys stridens had consumed 48 different food categories in 7 taxonomic classes. Crustacean, Mollusca, foraminifera, nematodes, Echinodermata, Annelida and miscellaneous were the main observed food items. There was no significant difference between males and females regarding diet composition in different months.

Intraspecific variation in a dominant prey species can bias marine predator dietary estimates derived from stable isotope analysis

AbstractIt is often assumed that variation in consumer stable isotope values (δ15N and δ13C) reflect shifts in diet between isotopically distinct prey species. However, an alternate hypothesis is that such variation could be as a result of spatial, temporal, or ontogenetic variation in the stable isotope values of a key prey species that propagate up marine food chains. In the Southern Ocean, Antarctic krill (Euphausia superba) occupy a key position, linking primary production to secondary consumers including fish, squid, seabirds, and marine mammals. As such Antarctic krill represent an ideal prey species to test the critical assumptions behind what has become a common method of dietary analysis in marine predators. Similar to previous studies, we found that stable isotope values of Antarctic krill exhibit significant intraspecific variation associated with both ontogenetic (size) and oceanographic factors (chlorophyll a concentration). Our modeling results showed that intraspecific variation in the stable isotope values of Antarctic krill has the potential to force mean isotope values of krill predators by as much as 2.4‰, independent of changes in the species composition of diet. Our findings indicate that intraspecific variation in the stable isotope values of a single, dominate prey species, such as Antarctic krill, has the potential to bias both absolute and relative estimates of marine predator diets using stable isotope mixing models. Therefore, caution is warranted to avoid spatial, temporal, and ontogenetic mismatches between the stable isotope values of prey sources used in mixing models and the actual stable isotope values of prey consumed by marine predators.

Seasonal diet composition of Pyrenean chamois is mainly shaped by primary production waves.

In alpine habitats, the seasonally marked climatic conditions generate seasonal and spatial differences in forage availability for herbivores. Vegetation availability and quality during the growing season are known to drive life history traits of mountain ungulates. However, little effort has been made to understand the association between plant phenology and changes in the foraging strategies of these mountain dwellers. Furthermore, this link can be affected by the seasonal presence of livestock in the same meadows. The objective of this work was to study the seasonal changes in diet composition of Pyrenean chamois (Rupicapra p. pyrenaica) and its relationship to primary production trends in a Mediterranean alpine environment. Moreover, diet composition in two populations with contrasting livestock pressure was compared in order to study the effect of sheep flocks on the feeding behaviour of chamois. From 2009 to 2012, monthly diet composition was estimated by cuticle microhistological analysis of chamois faeces collected in the eastern Pyrenees. The primary production cycle was assessed by remote sensing, using the Normalized Difference Vegetation Index. Additionally, the diet of sheep sharing seasonally the subalpine and alpine meadows with chamois was analysed. Diet selection of chamois and sheep and their overlap was also assessed. Our results show an intra-annual variation in the diet composition of Pyrenean chamois and demonstrate a strong relationship between plant consumption dynamics and phenology in alpine areas. In addition, Calluna vulgaris, Cytisus spp. and Festuca spp., as well as forbs in the summer, are found to be key forage species for Pyrenean chamois. Furthermore, this study couldn’t detect differences between both chamois populations despite the presence of sheep flocks in only one area. However, the detection of a shift in the diet of chamois in both areas after the arrival of high densities of multi-specific livestock suggest a general livestock effect. In conclusion, Pyrenean chamois are well adapted to the variations in the seasonal availability of plants in alpine habitats but could be disturbed by the seasonal presence of livestock. Due to the key plants in their diet, we suggest that population management programmes should focus on the preservation of mixed grasslands composed of patches of shrubs and herbs. The effects of climate change and shrub expansion should be studied as they may potentially affect chamois population dynamics through changes in habitat composition and temporal shifts in forage availability.

18S rRNA metabarcoding diet analysis of a predatory fish community across seasonal changes in prey availability.

Predator–prey relationships are important ecological interactions, affecting biotic community composition and energy flow through a system, and are of interest to ecologists and managers. Morphological diet analysis has been the primary method used to quantify the diets of predators, but emerging molecular techniques using genetic data can provide more accurate estimates of relative diet composition. This study used sequences from the 18S V9 rRNA barcoding region to identify prey items in the gastrointestinal (GI) tracts of predatory fishes. Predator GI samples were taken from the Black River, Cheboygan Co., MI, USA (n = 367 samples, 12 predator species) during periods of high prey availability, including the larval stage of regionally threatened lake sturgeon (Acipenser fulvescens Rafinesque 1817) in late May/early June of 2015 and of relatively lower prey availability in early July of 2015. DNA was extracted and sequenced from 355 samples (96.7%), and prey DNA was identified in 286 of the 355 samples (80.6%). Prey were grouped into 33 ecologically significant taxonomic groups based on the lowest taxonomic level sequences that could be identified using sequences available on GenBank. Changes in the makeup of diet composition, dietary overlap, and predator preference were analyzed comparing the periods of high and low prey abundance. Some predator species exhibited significant seasonal changes in diet composition. Dietary overlap was slightly but significantly higher during the period of high prey abundance; however, there was little change in predator preference. This suggests that change in prey availability was the driving factor in changing predator diet composition and dietary overlap. This study demonstrates the utility of molecular diet analysis and how temporal variability in community composition adds complexity to predator–prey interactions.

The trophic ecology of a desert river fish assemblage: influence of season and hydrologic variability

AbstractFoodweb 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.