Effects of trawling on the diets of common demersal fish by‐catch of a tropical prawn trawl fishery

The ecological effect of prawn trawling on the benthos of the Gulf of Carpentaria, northern Australia, was investigated by examining stomach contents of common demersal fishes incidentally caught as by‐catch in the fishery. Fishes were collected from high and low fishing intensity sites in three regions based on vessel monitoring system data. The diets of eight species of benthic fish predators were compared between regions and fishing intensities. A regional effect on diet was evident for seven species. Only one generalist species had no significant difference in diet among the three regions. For the comparisons within each region, five predator species had significantly different diet between high and low fishing intensities in at least one region. Across the three regions, high fishing intensity sites had predators that consumed a greater biomass of crustaceans, molluscs and echinoderms. At low fishing intensity sites, predators had diets comprising a greater biomass of cnidarians and teleosts, and a different assemblage of molluscs, crustaceans and fishes. These changes in diet suggest that there may have been a shift in the structure of the benthic community following intensive fishing. Analysis of predator diets is a useful tool to help identify changes in the benthic community composition after exposure to fishing. This study also provided valuable diet information on a range of abundant generalist benthic predators to improve the ecosystem modelling tools needed to support ecosystem‐based fisheries management.     

Trophic interactions and community structure in the upwelling system off Central Chile (33-39°S)

Trophic interactions and community structure in the upwelling system off Central Chile (USCCh) (33-39°S) are analyzed using biological and ecological data concerning the main trophic groups and the Ecopath with Ecosim software version 5.0 (EwE). The model encompasses the fisheries, cetaceans, sea lion, marine birds, cephalopods, large-sized pelagic fish (sword fish), medium-sized pelagic fish (horse mackerel, hoki), small-sized pelagic fish (anchovy, common sardine), demersal fish (e.g. Chilean hake, black conger-eel), benthic invertebrates (red squat lobster, yellow squat lobster) and other groups such as zooplankton, phytoplankton and detritus. Input data was gathered from published and unpublished reports and our own estimates. Trophic interactions, system indicators and food web attributes are calculated using network analysis routines included in EwE. Results indicate that trophic groups are aligned around four trophic levels (TL) with phytoplankton and detritus at the TL=1, while large-sized pelagic fish and cetaceans are top predators (TL>4.0). The fishery is located at an intermediate to low trophic level (TL=2.97), removing about 15% of the calculated system primary production. The pelagic realm dominates the system, with medium-sized pelagic fish as the main fish component in biomass, while small-sized pelagic fish dominate total landings. Chilean hake is by far the main demersal fish component in both, biomass and yield. Predators consume the greater part of the production of the most important fishery resources, particularly juvenile stages of Chilean hake. Consequently, mortality by predation is an important component of total mortality. However, fishery also removes a large fraction of common sardine, anchovy, horse mackerel, and Chilean hake. The analysis of direct and indirect trophic impacts reveals that Chilean hake is a highly cannibalistic species. Chilean hake is also an important predator on anchovy, common sardine, benthic invertebrates, and demersal fish. The fisheries heavily impact on Chilean hake, common sardine, anchovy, and horse mackerel. Total system biomass (B=476 t km⁻² year⁻¹) and throughput (T=89454 t km⁻² year⁻¹) estimated in the USCCh model are in accordance with models of comparable systems. Considering system attributes derived from network analysis, the USCCh can be characterized as an immature system, with short trophic chains and low trophic transfer efficiency. Finally, we suggest that trophic interactions should be considered in stock assessment and management programs in USCCh. In addition, future research programs should be carried out in order to understand the ecosystem effects of fishing and trophic control in this highly productive food web.     

Distribution and ecology of <Emphasis Type="Italic">Chaenocephalus aceratus</Emphasis> (Channichthyidae) around South Georgia and Shag Rocks (Southern Ocean)

Chaenocephalus aceratus (Family Channicthyidae) is one of the dominant species of demersal fish living on the South Georgia shelf where it is caught in low numbers as by-catch in the mackerel icefish and Antarctic krill commercial fisheries. Data collected during 14 demersal fish surveys, from 1986 to 2006, are analysed to investigate biomass, distribution, growth and diet. Biomass estimates from a swept area method ranged from 4,462 to 28,740 tonnes on the South Georgia and Shag Rock shelves although few fish were caught at Shag Rocks. Analysis of length frequency data indicated that growth was fast in the first five years with males and females attaining lengths at first spawning of 440 mm TL and 520 mm TL. The diet was comprised of fish and crustaceans, with an ontogenetic shift in diet from Euphausia superba and mysids to benthic fish and decapods observed to begin at 250 mm TL. In larger fish (>500 mm TL) the diet was dominated by fish. C. aceratus diet is sufficiently different from the other species of channichthyids around South Georgia to suggest that these species have undergone resource partitioning.     

Diet of six deep-sea grenadiers (Macrouridae)

Feeding habits of six deep-sea demersal trawl-caught macrourids on Chatham Rise, New Zealand, were examined from stomach contents during the austral summer. Three species were predominantly benthic foragers: smallbanded rattail Coelorinchus parvifasciatus on small epifaunal crustaceans, twosaddle rattail Coelorinchus biclinozonalis on epifaunal decapods and humpback rattail Coryphaenoides dossenus on benthic fishes and epifaunal decapods. Three species were predominantly benthopelagic foragers: banded rattail Coelorinchus fasciatus on hyperiid and gammarid amphipods and calanoid copepods, blackspot rattail Lucigadus nigromaculatus on small epifaunal crustaceans and suprabenthic mysids and Mahia rattail Coelorinchus matamua on epifaunal decapods and calanoid copepods. The most important predictors of diet variability were identified using distance-based linear models and included areal predictors in C. parvifasciatus, L. nigromaculatus and C. dossenus, fish size in C. dossenus, C. biclinozonalis and C. matamua, sample year in C. biclinozonalis and C. fasciatus and depth in C. matamua. Results are compared with previously published data for four other macrourid species from the same study area. The 10 grenadier species comprise benthic, benthopelagic and mesopelagic foraging guilds. This study brings the number of grenadier species for which diet on Chatham Rise has been described in detail to 12.     

Trophic interactions of fish communities at midwater depths enhance long-term carbon storage and benthic production on continental slopes

Biological transfer of nutrients and materials between linked ecosystems influences global carbon budgets and ecosystem structure and function. Identifying the organisms or functional groups that are responsible for nutrient transfer, and quantifying their influence on ecosystem structure and carbon capture is an essential step for informed management of ecosystems in physically distant, but ecologically linked areas. Here, we combine natural abundance stable isotope tracers and survey data to show that mid-water and bentho-pelagic-feeding demersal fishes play an important role in the ocean carbon cycle, bypassing the detrital particle flux and transferring carbon to deep long-term storage. Global peaks in biomass and diversity of fishes at mid-slope depths are explained by competitive release of the demersal fish predators of mid-water organisms, which in turn support benthic fish production. Over 50% of the biomass of the demersal fish community at depths between 500 and 1800 m is supported by biological rather than detrital nutrient flux processes, and we estimate that bentho-pelagic fishes from the UK–Irish continental slope capture and store a volume of carbon equivalent to over 1 million tonnes of CO₂ every year.     

Trophic Interactions and Distribution of Some Squaliforme Sharks,Including New Diet Descriptions for Deania calcea and Squalus acanthias

Squaliforme sharks are a common but relatively vulnerable bycatch in many deep water fisheries. Eleven species of squaliforme shark are commonly caught at depths of 200–1200 m on Chatham Rise, New Zealand, and their diversity suggests they might occupy different niches. The diets of 133 Deania calcea and 295 Squalus acanthias were determined from examination of stomach contents. The diet of D. calcea was characterised by mesopelagic fishes, and S. acanthias by benthic to pelagic fishes, but was more adaptive and included likely scavenging. Multivariate analyses found the most important predictors of diet variability in S. acanthias were year, bottom temperature, longitude, and fish weight. The diet of the nine other commonly caught squaliforme sharks was reviewed, and the spatial and depth distribution of all species on Chatham Rise described from research bottom trawl survey catches. The eleven species had a variety of different diets, and depth and location preferences, consistent with niche separation to reduce interspecific competition. Four trophic groups were identified, characterised by: mesopelagic fishes and invertebrates (Centroselachus crepidater, D. calcea, and Etmopterus lucifer); mesopelagic and benthopelagic fishes and invertebrates (Centroscymnus owstoni, Etmopterus baxteri); demersal and benthic fishes (Centrophorus squamosus, Dalatias licha, Proscymnodon plunketi); and a generalist diet of fishes and invertebrates (S. acanthias). The trophic levels of the species in each of the four groups were estimated as 4.18–4.24, 4.20–4.23, 4.24–4.48, and 3.84 respectively. The diet of Oxynotus bruniensis and Squalus griffini are unknown. The different niches occupied by different species are likely to influence their vulnerability to bottom trawl fisheries. Some species may benefit from fisheries through an increased availability of scavenged prey.     

The diet of blue whiting, hake, horse mackerel and mackerel off Portugal

This paper deals with the diets of blue whiting Micromesistius poutassou (Risso 1810), hake Merluccius merluccius (L. 1758), horse mackerel Trachurus trachurus (L. 1758), and mackerel Scomber scombrus (L. 1758) off Portugal and explores variations in fish length, water depth, latitude and season. All four species feed on fish; however, hake and mackerel are the first and second most important predators, respectively, blue whiting being the most important fish prey for both species. The diets of blue whiting and horse mackerel are composed mainly of crustaceans. Diet variations according to predator fish size are more important than either latitude or depth. In the diets of blue whiting, hake and horse mackerel, prey importance increases with predator size. For blue whiting and horse mackerel, diet variations with fish length and water depth are correlated: small fish are closely associated with coastal areas where they feed on copepods and decapod larvae. Seasonality in the diet is apparent for blue whiting, hake and mackerel. For blue whiting, the decapod Pasiphaea sivado is the most important prey in summer and autumn, being replaced by the euphausid Meganyctiphanes norvegica in winter. In the diet of hake, seasonality was characterised by the major importance of Macroramphosus scolopax in autumn, whereas the diet of mackerel consisted of zooplankton in summer, fish and decapods in autumn and decapod larvae in winter. Seasonal changes in the diet of horse mackerel correspond to a higher diversity of prey in autumn compared to other seasons (although euphausids are the main prey in all seasons). Seasonality in feeding activity is not as marked for the other species as it is for horse mackerel; the percentage of empty stomachs of horse mackerel is greatest in winter, when spawning takes place at the Portuguese coast.     

Recent increase in Nybelinia surmenicola prevalence and intensity in Pacific hake (Merluccius productus) off the United States west coast

A larval marine cestode was found in 82.0% of 834 Pacific hake (Merluccius productus) stomachs collected from 341 trawl stations along the United States west coast during the summers of 2008 and 2009. Morphology and DNA sequencing was used to identify the cestode as Nybelinia surmenicola. In an examination of 131 Pacific hake stomachs collected from the same region in 1999, N. surmenicola prevalence was 35.1%. The results from a general linear model suggested that their prevalence is influenced by year and latitude, Pacific hake size, and sex. Mean intensity of N. surmenicola in 2008-2009 was 20.22 (±1.13 SE) and was positively related to Pacific hake length and the latitude of collection. Year-1 Pacific hake (<27 cm length) had significantly lower prevalence and intensity of N. surmenicola compared to older and larger fish. Pacific hake collected south of Point Conception, California (32.5 to 35°N) had lower prevalence and intensity of N. surmenicola compared to those collected in northern latitudes (35.1 to 48.4°N). Higher N. surmenicola prevalence in Pacific hake in recent years suggests food-web fluctuations in the northern California current ecosystem caused by changes in ocean transport of zooplankton or pelagic fish distributions and warrants future monitoring as a metric for ecosystem change.     

Fine Spatial Structure of Atlantic Hake (<Emphasis Type="Italic">Merluccius merluccius</Emphasis>) Stocks Revealed by Variation at Microsatellite Loci

Genetic variation at 5 microsatellite loci was analyzed for European hake Merluccius merluccius sampled from 9 different regions in the Atlantic Ocean and the Mediterranean Sea. Significant genetic differentiation was found between samples, suggesting a fine subdivision of Atlantic and Mediterranean hake stocks. These results are discussed in the context of the decline of demersal fish species, probably due to overfishing.     

Diet of the Antarctic starry skate Amblyraja georgiana (Rajidae, Chondrichthyes) at South Georgia (Southern Ocean)

Stomach contents were identified from 206 Antarctic starry skate (Amblyraja georgiana) that were collected during three groundfish surveys (September 2007, April 2008 and January 2009) at South Georgia, Southern Ocean. The diet of A. georgiana varied with skate size and between years. Preferred prey included fish (particularly for larger individuals) and Antarctic krill, Euphausia superba, as well as amphipods, polychaetes and other benthic fauna. The skate A. georgiana appears to be an opportunistic predator, and the clear presence of Antarctic krill in this demersal predator’s diet may indicate a benthic habit of this euphausiid species, which has hitherto mainly been considered as occupying a purely pelagic niche.     

Feeding strategy of juvenile (age‐0+ year) Argentine hake Merluccius hubbsi in the Patagonian nursery ground

Age‐0+ year juvenile Argentine hake Merluccius hubbsi (60–150 mm total length, L_T) from San Jorge Gulf, north Patagonian shelf region of the Argentine Sea, had an almost exclusively pelagic diet dominated by the hyperiid amphipod Themisto gaudichaudii and the euphausiid Euphausia lucens. This suggested that final settlement and permanent demersal habitat utilization might not, as previously reported, occur at earlier sizes (c. 20 mm L_T). Their feeding strategy involves specialization at a population level towards both the main pelagic prey, indicating a narrow trophic niche. Novel data are provided which contribute to the growing body of information in relation to the age‐0+ year transitional stage in demersal fishes and particularly to M. hubbsi recruitment in the Argentine Sea.     

Fish functional diversity as an indicator of resilience to industrial fishing in Patagonia Argentina

The relationship between fish functional diversity and fishing levels at which its baselines shift is important to identify the consequences of fishing in ecosystem functioning. For the first time, the authors of this study implemented a trait-based approach in the Argentine Patagonian Sea to identify the vulnerability and spatiotemporal changes in functional diversity of fish assemblages incidentally captured by a trawling fleet targeting the Argentine red shrimp Pleoticus muelleri (Spence Bate, 1888) between 2003 and 2014. The authors coupled seven fish trophic traits to a reconstructed fish assemblage for the study area and by-catch and evaluated changes in fish species richness and four complementary functional diversity measures (functional richness, redundancy, dispersion and community trait values) along with fishing intensity, temporal use, latitudinal location and depth of fishing grounds, and vessel length. Resident fishes larger than 30 cm in length, with depressed and fusiform bodies, intermediate to high trophic levels, and feeding in benthic, demersal and midwater areas were vulnerable to by-catch. In addition, fish assemblages exhibited a low functional trait redundancy, likely related to species influxes in a biogeographic ecotone with tropicalisation signs. Significant increases in fish trait richness and dispersion poleward and deep suggested new functional roles in these grounds, matching trends in community body size, reproductive load, maximum depth and trophic level. Finally, a temporal increase in fish species and functional trait removal in fishing grounds led to trait homogenisation since 2003. The authors identified that tipping points in temperate fish functional trait diversity showed the importance of trait-based approaches within ecosystem-based fisheries management.     

Changes in the fish fauna of the Ria de Aveiro estuarine lagoon (Portugal) during the twentieth century

The fish biodiversity of the Ria de Aveiro has been analysed during the 20th century, as an indicator of the biological integrity of the ecosystem. Ninety-two distinct species and 38 families of Agnatha, Chondrichthyes and Osteichthyes occurred during the period. The family and species richness showed two levels of magnitude, from the 1910s, with high values (26–28 families and 51–52 species), and during the last two decades with more variable values (20–27 families and 38–55 species). A total of 13 species (four non-sporadic species) have disappeared recently. The lagoon system has been affected by large-scale anthropogenic influences mainly the substantial development of industries and the increasing population in the watershed, in addition to overfishing, climatic changes and dredging. In general, as shown by an analysis of the ecotrophic guilds present, the area maintained a similar structure during the whole period. No significant differences in time were recorded for any of the designated guilds. The twenty-two frequent species, which occurred in six or seven surveys, were mainly estuarine resident species or marine adventitious species, living in the substratum (benthic fish), on soft substratum and vegetated bottoms. They were feeding either on invertebrates alone or on invertebrates and fish, and producing pelagic or benthic eggs. The 19 sporadically-recorded species, recorded only once, were mostly marine adventitious, demersal fishes, living above rough bottom and vegetation, feeding strictly on invertebrates, and producing eggs benthically or deposited into vegetation. It is concluded that the Ria de Aveiro estuarine coastal lagoon has supported similar fish communities during the past century and that these comprise representatives of various ecological types.     

Habitat specialization in tropical continental shelf demersal fish assemblages

The implications of shallow water impacts such as fishing and climate change on fish assemblages are generally considered in isolation from the distribution and abundance of these fish assemblages in adjacent deeper waters. We investigate the abundance and length of demersal fish assemblages across a section of tropical continental shelf at Ningaloo Reef, Western Australia, to identify fish and fish habitat relationships across steep gradients in depth and in different benthic habitat types. The assemblage composition of demersal fish were assessed from baited remote underwater stereo-video samples (n = 304) collected from 16 depth and habitat combinations. Samples were collected across a depth range poorly represented in the literature from the fringing reef lagoon (1-10 m depth), down the fore reef slope to the reef base (10-30 m depth) then across the adjacent continental shelf (30-110 m depth). Multivariate analyses showed that there were distinctive fish assemblages and different sized fish were associated with each habitat/depth category. Species richness, MaxN and diversity declined with depth, while average length and trophic level increased. The assemblage structure, diversity, size and trophic structure of demersal fishes changes from shallow inshore habitats to deeper water habitats. More habitat specialists (unique species per habitat/depth category) were associated with the reef slope and reef base than other habitats, but offshore sponge-dominated habitats and inshore coral-dominated reef also supported unique species. This suggests that marine protected areas in shallow coral-dominated reef habitats may not adequately protect those species whose depth distribution extends beyond shallow habitats, or other significant elements of demersal fish biodiversity. The ontogenetic habitat partitioning which is characteristic of many species, suggests that to maintain entire species life histories it is necessary to protect corridors of connected habitats through which fish can migrate.     

Fishery and Ontogenetic Driven Changes in the Diet of the Spiny Dogfish, Squalus acanthias, in Patagonian Waters, Argentina

The diet of the spiny dogfish in northern and central Patagonian waters was studied from the by-catch of the bottom trawling fisheries directed to Argentine hake Merluccius hubbsi and Argentine red shrimp Pleoticus muelleri between 1996 and 1998. Food habits were analyzed in relation to sex and maturity of sharks. Also, the relationship between diet and abundance of the main prey was explored. Intraspecific diet comparisons were performed. Differences in diet were found between immature individuals, mature males, and mature females. The Argentine shortfin squid Illex argentinus, the Argentine hake and ctenophores Pleurobrachia pileus were the most important prey for the spiny dogfish. Immature and small individuals were pelagic predators. After sexual maturity, the spiny dogfish shifted its diet. Mature and large individuals tended to reduce the consumption of ctenophores, and increase the consumption of demersal and benthic species. Previous diet studies on the spiny dogfish in 1984–1985 and 1994 indicated that the Argentine hake was the most important prey. In the present study, carried out in 1998, squid was the most important prey, followed by the hake. This diet change was related to the major decrease of hake due to overfishing and the increase of squid abundance between 1994 and 1999.     

Feeding patterns of the dominant benthic and demersal fish community in a temperate estuary

The diet and feeding relationships of the 12 most abundant benthic and demersal fish species of the Mondego Estuary, Portugal, were studied between June 2003 and May 2006. Fishes were caught during the night using a 2 m beam trawl. The stomach contents were analysed for prey identification, counting and weighing. According to prey importance in diets, three main feeding guilds were identified: (1) invertebrate feeders, (2) invertebrate and fish feeders and (3) plankton and invertebrate feeders. Besides these main feeding guilds, some fishes also presented fractions of algae and zooplankton in their stomach contents. The most abundant prey items were macroinvertebrates, with several polychaetes ( Nephtys spp., Capitellidae, Spionidae and Eunicidae), Corophium spp. and Crangon crangon among the dominant prey. Pomatoschistus spp. were the most preyed on fishes. Several fish species showed a tendency for a specialized diet, but almost all also showed some degree of opportunistic feeding by preying on other food resources. High diet overlap was found between some fish species, yet exploitative competition could not be concluded.     

Scavenging on discarded saury by demersal fishes off Sendai Bay, northern Japan

Pacific saury Cololabis saira were found in 24 out of 1314 stomachs of demersal fishes collected by bottom trawling at 245–393 m depths. The same area was occupied by the stick-held dipnet fishery for saury, in which a landing limitation was enforced to avoid overfishing. The fish species containing saury were: Pacific cod Gadus macrocephalus , walleye pollock Theragra chalcogramma , and oilfish Ruvettus pretiosus . These demersal species would not encounter living saury naturally, which normally are distributed above thermoclines. The ingested saury were smaller than market size which suggests that the saury from fish stomachs were discarded by fishermen because of small sizes to maximize profits under the landing limitation.
The scavenged saury made up 41.5, 24.6 and 77.7% of the diets of large-sized (>30cm)Pacific cod, walleye pollock and oilfish, respectively in terms of DW composition. The extent to which discarded saury contributed to the total diet in the demersal fish assemblage, calculated by considering species composition and diets of bottom fishes, was 21.8% of the total diet. The discarded saury seemed to compensate the less productive feeding environment during autumn for the bottom fishes.     

Behaviour of fish by-catch in the mouth of a crustacean trawl

The behaviour of fish by-catch was recorded and characterized by in situ observations in the mouth of a crustacean trawl using an underwater camera system with artificial light, at depths between 106 and 461 m, along the central coast of Chile. The groups or species studied were rattails (family Macrouridae), Chilean hake Merluccius gayi gayi, sharks (orders Carcharhiniformes and Squaliformes), skates (family Rajidae), flatfishes (genus Hippoglossina) and small benthopelagic and demersal fishes (orders Osmeriformes, Stomiiformes, Gadiformes, Ophidiiformes and Perciformes). The fish behaviour was categorized in terms of (1) position in the water column, (2) initial orientation with respect to the trawl, (3) locomotion and (4) swimming speed with respect to the trawl. Rattails, sharks, skates and flatfishes were passive in response to the trawl and showed similar behavioural patterns, with most fishes observed sitting or touching the bottom with no swimming or other activity. Merluccius gayi gayi was the most active species, displaying a wide combination of behavioural responses when the trawl approached. This species showed several behavioural patterns, mainly characterized by swimming forward at variable speed. A fraction of small bentho-pelagic and demersal fishes also showed an active behaviour but always at lower speed than the trawl. The species-specific differences in behaviour in the mouth of the trawl suggest that improvements at the level of the footrope can be made to reduce by-catch, especially of passive species.     

Variation in the diet of Genypterus blacodes(Ophidiidae) around the Falkland Islands

The diet change with size, season and area was investigated using the stomachs of 496 kingclip Genypterus blacodes collected around the Falkland Islands (south‐west Atlantic) between August 2001 and September 2002. The key prey species were rockcod Patagonotothen spp., benthic isopods and Patagonian grenadier Macruronus magellanicus . Kingclip <50 cm total length ( L _T) fed mainly on crustaceans and small fishes. With size the diet shifted away from crustaceans towards Patagonotothen spp. in kingclip 50–100 cm L _T, and finally towards larger fishes such as M. magellanicus and Micromesistius australis australis in kingclip >100 cm L _T. The niche breadth was highest in fish >100 cm L _T and the lowest in fish <50 cm L _T. The larger kingclip generally selected larger individuals of the same prey species, with the exception of the Patagonian squid Loligo gahi , where all ingested squid were of similar size, regardless of the predator length. The importance of the main prey species varied substantially between five consequent seasons studied, and appeared to follow the seasonal abundance and availability of prey. The spatial variability in the diet was found in kingclip caught in regions occupied by transformed temperate and sub‐Antarctic waters. The rockcod, which is available throughout the year around the Falkland Islands, was the most important prey in the kingclip diet. Kingclip takes advantage of other seasonally abundant prey species during their seasonal migrations ( e.g . L. gahi ) and also scavenge on discards from fishing vessels when available.     

黄山陈村水库河源溪流鱼类群落的食性

基于2010年11月在黄山陈村水库河源溪流中所采集的鱼类标本,对其中9种优势鱼类的食性特征进行了研究。结果表明:宽鳍鱲(Zacco platypus)、光唇鱼(Acrossocheilus fasciatus)和麦穗鱼(Pseudorasbora parva)等9种鱼类都以有机碎屑、藻类和无脊椎动物为主要食物,属典型的杂食性或无脊椎动物食性鱼类;食物组成的相似性分析结果表明,不同物种间的食物组成差异显著但存在部分重叠(P<0.001)。不同物种间的食物多样性和食性宽度也存在显著性差异(P<0.05),其中底栖型鱼类具有相对较高的饵料来源,而鱼类的食物多样性可能与其小生境选择性有关。根据食物重叠指数,9种优势鱼类之间存在明显的食物重叠(D>0.3),尤其是宽鳍鱲、光唇鱼、麦穗鱼、高体鰟鮍(Rhodeus ocellatus)和稀有花鳅(Cobitis sinensis)间的食物重叠指数超过0.9。陈村水库河源溪流的鱼类群落所表现出的食物组成、食物多样性、食性宽度和种间食物重叠性等特征,可能与其生态系统所具有的营养外源性和物理栖息地周期动荡性等密切相关。