Prey-specific Abundance Research Articles

The trophic ecology of an invasive predator in a novel ecosystem: Green sunfish Lepomis cyanellus in a restored urban stream

Rapid urbanization will increase the number of novel stream ecosystems in the Southeastern United States. The green sunfish (Lepomis cyanellus) is a globally widespread, invasive species that is particularly well-adapted to urban stream conditions. The trophic ecology of green sunfish is understudied, especially in the novel ecosystems where they appear to thrive. We assessed predation by green sunfish in the food web of a heavily engineered and restored urban stream in Raleigh, North Carolina. We sampled fish species composition, size structure, abundance, the benthic macroinvertebrate assemblage, and fish diets during two seasons. Green sunfish was the sole species inhabiting the study stream, with the exception of a single goldfish. The population size structure indicated potential overcrowding in our study ecosystem. Chironomidae was the most common taxa in both the benthic macroinvertebrate assemblage and in fish diets during the summer. We observed a seasonal shift in diets to lesser prey-specific abundance of Chironomidae and a greater overall abundance of terrestrial prey from summer to winter. Green sunfish can persist in small restored urban streams of the Southeast US where virtually no other fish occur, and they utilize benthic invertebrates and terrestrial prey as resources.

Diet and feeding strategy of the common silver-biddy, Gerres oyena (Forsskål 1775) in the seagrass beds of Karang Congkak Island, Kepulauan Seribu National Park

Diet and feeding ecology studies are a principal tool to understand the functional role of fish within their habitat. Like most coastal habitats, seagrass meadow provides food and refuge for many biotas. Karang Congkak Island is a small uninhabited island situated in the northern part of the Kepulauan Seribu National Park and surrounded by a seagrass ecosystem. The current study aims to analyze diet composition changes and trophic attributes of the common silver-biddy, Gerres oyena, in the seagrass ecosystem of the Karang Congkak Island. The research was carried out monthly from March to September 2018 by towing the beach seine net. Data analysis includes diet composition, niche breadth, and feeding strategy. During the study period, 1,196 individuals of G. oyena were captured, and most of them were juveniles. Fifty-nine types of prey were documented and arranged into six groups, namely phytoplankton, algae, zooplankton, zoobenthos, crustaceans, and unidentified material. G. oyena shows an ontogenetic change, from zooplanktivore to crustacivore and zoobenthivore. Moreover, this species has a TROPH value ranging from 3.00-3.31 and is categorized as omnivorous that tend to feed on animals. The interpretation of prey-specific abundance and niche breadth confirms that this species developed specialized and generalized feeding strategies.

Feeding ecology, trophic interaction and resource partitioning among four omnivorous finfish species of a tropical Estuary

A crucial aspect of sustainable resource management is understanding the trophic interactions amongst fish in the estuarine ecosystem. The goal of this study was to look into the food preferences, feeding strategies, trophic partitioning, as well as dietary overlap among four omnivorous species that live in the Cochin Estuary: Mugil cephalus (n = 73), Planiliza parsia (n = 35), Planiliza planiceps (n = 65) and Chanos chanos (n = 55) through the analyses of gut-content. Index of relative importance demonstrated that prey items in Mugil cephalus and Planiliza planiceps guts were dominated by Bacillariophyceae whereas in Planiliza parsia and Chanos chanos guts were dominated by Myxophyceae. The highest diet value (7.5) was recorded in Chanos chanos, while the lowest was recorded in Mugil cephalus (5.69). The highest niche breadth value (0.77) was recorded in Planiliza planiceps while the lowest value was recorded in Planiliza parsia (0.52). Pianka's overlap, evaluated with the help of null models structured by Ecosim 7.0, showed remarkable niche overlap between Mugil cephalus and Planiliza planiceps (0–0.92, P < 0.001), between Planiliza planiceps and Planiliza parsia ( 0–0.77, P < 0.05) and between Mugil cephalus and Planiliza parsia ( 0–0.7, P < 0.05). The fish's trophic niche width, along with prey-specific abundance confirmed that they are generalist feeders. The present results differed from the general hypothesis related to the omnivorous species and concluded that these four omnivorous species live in the same niche zones of the Cochin Estuary with no interspecific conflict.

Understanding the Trophodynamics of Yellowfin Tuna, Thunnus albacares (Bonnaterre, 1788) from the Western Bay of Bengal

The trophodynamics of Thunnus albacares (Bonnaterre, 1788) from the western Bay of Bengal was studied during 2012 – 2015. Feeding intensity revealed that 34.6 % of the fishes had empty-trace stomachs, 52.77% of the fishes had quarter full-half full stomachs and 12.44% of the fishes had three fourth full-gorged stomachs. Feeding intensity increased with an increase in body size of the fishes with high prey to predator weight ratios and with a third of the fishes above 160 cm fork length possessing three fourth full-gorged stomachs. Cephalopods (47%) dominated the prey constituents, followed by semi digested finfishes and shellfishes (28%), finfishes (16%) and crustaceans (9%). Significant shifts in prey items were observed with an increase in fish size. Though squids were predominant in the diet, however, with the increase in size, feeding shift has clearly been observed towards finfishes. Feeding preferences did not vary between sexes. Annual and seasonal similarities were recorded in their food and feeding habits. Prey-specific abundance indicated a relative specialized feeding pattern with high occurence of species belonging to the orders Teuthidae and Perciformes. Levins Standardized Niche Breadth Index of 0.16 indicated limited niche width in the feeding strategy of Thunnus albacares.

Diets of Longnose Sucker in Yellowstone Lake, Yellowstone National Park, USA

Invasive species introduction and expansion is the second greatest threat to global biodiversity decline after habitat degradation. Introduced in the 1930s, the benthivorous Longnose Sucker (Catostomus catostomus) became established in Yellowstone Lake, Wyoming, USA, and used tributary streams for spawning. With this introduction, concerns were raised regarding their possible competition for food resources with native adfluvial Yellowstone Cutthroat Trout (Oncorhynchus clarkii bouvieri). Additionally, insufficient literature exists on Longnose Sucker feeding habits throughout their range, and there has been no comprehensive study of Longnose Sucker diet in Yellowstone Lake. The need exists for understanding the community ecology and food web dynamics in Yellowstone Lake, especially as non-native Lake Trout (Salvelinus namaycush) have caused declines in Yellowstone Cutthroat Trout through predation. The objectives of this study were to examine possible size-specific shifts in feeding habits, evaluate feeding strategy, and compare historical and contemporary diet data of Longnose Suckers in Yellowstone Lake. Diet data collected during summer of 2018 were analyzed by length-class to test for size-specific diet shifts. As Longnose Sucker length increased, copepods (Diacyclops bicuspidatus thomasi, Leptodiaptomus ashlandi or Hesperodiaptomus shoshone) decreased in proportion by weight. In contrast, dipterans (Chironomidae) and amphipods (Hyalella spp. or Gammarus spp.) varied in proportion by weight in the diet across length classes. We assessed the feeding strategy by evaluating the relationship between prey-specific abundance and percent frequency of occurrence. This assessment indicates that Longnose Suckers have a heterogeneous diet and generalized feeding strategy as all prey items had a prey-specific abundance value of <50%. Diet composition differed significantly between historical and contemporary samples, likely related to the differences in sampling locations and possibly due to a Lake Trout-induced trophic cascade. This study established the diet composition and feeding habits of Longnose Suckers residing in Yellowstone Lake, thus, expanding our knowledge of Longnose Sucker feeding patterns and ecology.

Analysis of Piebald Madtom (Noturus gladiator) diet

The Piebald Madtom, Noturus gladiator, is found in tributaries of the Mississippi River from the Obion River in northern Tennessee to the Big Black River in central Mississippi. The species is currently petitioned for listing under the federal Endangered Species Act of 1973, and is of conservation concern in both Mississippi and Tennessee. Yet little is known about the feeding ecology of the species. To this end, diets were extracted from stomachs and intestinal tracts from available formalin-preserved museum specimens (n = 57). These specimens came from the Hatchie River, Wolf River, Yazoo River, and Big Black River of Mississippi or Tennessee. All diet items were identified to the lowest possible taxonomic level, and contribution characterized as percent composition by number, total number of prey items, proportion of diets containing a prey item, frequency of occurrence, and prey-specific abundance. Twenty-one different diet items included larval trichopterans with sand cases, teleost scales, ostracods, and larval odonates (primarily Macromiidae). The relationship between prey-specific abundance and frequency of occurrence was described using an Amundsen plot, and revealed that trichopteran larvae and larval odonates are of high importance, and suggesting the species may forages on both sandy substrates and leaf packs.

Feeding strategy, dietary overlap and resource partitioning among four mesopredatory catfishes of a tropical estuary.

The feeding strategy, overlap and trophic interactions of four demersal catfishes inhabiting Cochin Estuary, Arius maculatus (n = 67), A. subrostratus (n = 63), A. arius (n = 21) and Mystus gulio (n = 69) were investigated through gut-content analyses. The indices of relative importance revealed that the prey items in their stomachs were dominated by crustaceans except in A. arius where molluscs constituted the major prey item. The highest diet and niche breadth values (3.93, 0.36 respectively) were recorded in A. subrostratus, while the lowest was recorded in A. arius (2.64, 0.23 respectively). Pianka's overlap, calculated through null models constructed by Ecosim 7.0, revealed significant niche overlap between A. maculatus and A. subrostratus (O-0.91, P < 0.001), between A. maculatus and M. gulio (O-0.72, P < 0.05) and between A. subrostratus and M.gulio (O-0.64 P < 0.05). However, no overlap was recorded between A. arius and other species. The trophic niche breadth along with prey specific abundance confirmed that these fishes are highly specific feeders. The present results on trophic level status indicate that these catfishes are mid-level carnivores that can be considered as moderate benthic mesopredators and are specialist feeders unlike most catfishes.

Feeding ecology of Anableps anableps (Actinopterygii: Cyprinodontiformes: Anablepidae) off the north-eastern coast of Brazil

Background. Diets, feeding ecology, and feeding strategies of several mangrove fish species have not been studied off the coast of Maranh&atilde;o, which is exposed to a significant tidal regime. This includes also the largescale foureyed fish, Anableps anableps (Linnaeus, 1758). The aim of the presently reported study was to characterize diet, feeding strategies and seasonal patterns of the diet of A. anableps. Materials and methods. The sampling was carried out in S&atilde;o Marcos Bay between May 2007 and April 2008 using block nets. The stomach fullness index was used for stomach content analysis. Dietary items were identified and parameters such as the prey-specific abundance and the frequency of occurrence were calculated. The feeding strategy was analysed with the aid of the Costello diagram. Seasonal patterns in the feeding behaviour and similarity in diet composition were also analysed. Results. Diet composition did not differ between seasons but stomach fullness was greater in wet season months. The diet of A. anableps consisted of a mixture of epiphytic microalgae and macroalgae, insects, crustaceans, molluscs, fishes, and digested material such as mud and detritus. Insects represented the greatest richness among the food items. The Costello diagram revealed that A. anableps had a generalist feeding strategy, with a dominance of macroalgae, insect, and fishes. A broad niche was also found, as indicated by a strong association with interphenotypical components. Conclusion. This study presents data that confirm the forage characteristic of A. anableps and the influence of seasonality on its feeding behavior, in which the species takes advantage of the greater availability of food due to runoff and the larger flooded area, during the wet season. Further studies should be carried out to determine the energy needs of this species in satisfying its reproductive demands as well as the abundance of food resources in the surrounding environment and the confirmation of the generalist feeding strategy.

Feeding strategy and prey selectivity in Cnesterodon decemmaculatus and Jenynsia multidentata in experimental enclosures: Importance for the biological control of mosquito populations

Mosquitoes pose a threat to human and animal health due they act as vectors for numerous pathogens and parasites which cause disease. Several methods are used to control mosquito populations. Chemical pesticides can be harmful to human health and others lifeforms, including natural predators, and mosquitoes have been well documented to develop resistance through time. Alternative methods for mosquito control must be explored, being the biological control an effective and environmentally friendly strategy; when this is carried out with native species that are not exported out of their natural limits. The most widely used biocontrol agents of mosquito populations are the fishes of the genus Gambusia spp., nevertheless, these species have become invasive species in several places where they have introduced affecting non-target species. Widespread native fish species could be an appropriate alternative to these invasive species and circumvent their negative impacts. C. decemmaculatus and J. multidentata are widely distributed native fish of temperate zones of South America. The main goal of our work was analyze the feeding strategy and prey selectivity in Cnesterodon decemmaculatus and Jenynsia multidentata focusing on mosquito biocontrol implications. The feeding strategy observed for both C. decemmaculatus and J. multidentata showed that the items that had the highest percent of prey-specific abundance were the mosquito larvae. The selectivity index displayed by C. decemmaculatus and J. multidentata suggested a significant selection for mosquito larvae and a significant avoidance of copepods. In this work, the active selection of C. decemmaculatus and J. multidentata for mosquito larvae was determined, allowing us to propose and support their use as useful species for the biological control of mosquitoes.

Changes in the diet of predatory ribbonfish Trichiurus lepturus Linnaeus, 1758 with increasing body size along Chennai coast

In recent years, it has been recognised that predatory fishes are rapidly declining in marine habitats. Hence, gathering information on biological characteristics such as dietary dynamics of predatory fishes has assumed importance. Considering this, the dietary dynamics of the predatory ribbonfish Trichiuruslepturusfrom Chennai coast was assessed by analysing the stomach condition and contents, with reference to body size. Representatives of the Order Clupeiformes (Index of relative importance, IRI 33.7%) comprising oilsardine, lesser sardines and anchovies were the major prey items of T. lepturus. Predation by T. lepturus was aided by morphological adaptations, such as dentition, hard and spinous gill rakers, short stomach, high body depth-total length ratio of 1: 17.1 and large mouth (gape area of 1534 mm2 in adult fish).With increasing body size, the capacity to predate upon relatively larger prey increased. The differences in diet composition between ribbonfish of small, medium and large size were well-represented byIRI, prey specific abundance and cluster analysis. The fish is a top predator (trophic level: 4.17) and a specialist feeder (niche breadth: 2.63). As specialist feeders have a narrow choice of food, they are more vulnerable to fishing. It is important that management of multispecies fisheries should focus more on the sensitive predatory species.

Trophic ecology and food consumption of fishes in a hypersaline tropical lagoon.

This study evaluated the trophic ecology (diet composition, trophic strategy, similarities and overlap between species, feeding period and food consumption) of six benthivorous fish species in Araruama Lagoon, the largest hypersaline tropical lagoon on the east coast of South America, with an area of 210 km(2) and an average salinity of 52. The burrfish Chilomycterus spinosus fed on Anomalocardia flexuosa shell deposits, ingesting associated fauna. The caitipa mojarra Diapterus rhombeus differed from all other species, having not only the highest proportions of algae and Nematoda, but also feeding on polychaete tentacles. The two mojarras Eucinostomus spp. showed similar trophic strategies, feeding mostly on Polychaeta. The corocoro grunt Orthopristis ruber also fed mainly on Polychaeta, but differed from Eucinostomus spp. in secondary items. The whitemouth croacker Micropogonias furnieri fed mainly on small Crustacea at night, showing a high number of secondary prey items with low frequencies and high prey-specific abundance. The daily food consumption (g food g(-1) fish mass) for Eucinostomus argenteus was 0·012 and was 0·031 and 0·027 for M. furnieri in two different sampling events. The diet similarities between Araruama Lagoon and other brackish and marine environments indicate that hypersalinity is not a predominant factor shaping the trophic ecology of fishes in this lagoon. The stability of hypersaline conditions, without a pronounced gradient, may explain the presence of several euryhaline fishes and invertebrates well adapted to this condition, resulting in a complex food web.

Diet of a Cryptic but Widespread Invader, the Oriental Weatherfish (Misgurnus anguillicaudatus) in Idaho, USA

Abstract The oriental weatherfish (Misgurnus anguillicaudatus) is invasive to 13 U.S. states and at least 9 other countries. Although this cryptic fish species is widespread, very little is known regarding its ecology. We used baited minnow traps to collect 237 individuals from water bodies connected to the Boise River, Idaho. To determine the diet of the fish within this invasive population, we dissected and examined stomach contents of the sampled fish. Most of the stomachs (158 of 237) were empty, and 42 contained only the trap bait. However, 37 contained natural food items. Gravimetric analysis, frequency of occurrence, and mean percent by number all indicated macroinvertebrates as the primary diet component, with chironomid larvae as the most numerous prey eaten. Graphical analysis of prey-specific abundance also indicated that oriental weatherfish fed on a generalized diet, of which detritus is likely an important part. An omnivorous diet may, in part, explain the species' ability to expand its inva...

Larval feeding of Chionodraco hamatus (Pisces, Channichthyidae) in the Ross Sea and its relation to environmental conditions

Feeding habits of early life stages of the channichthyid Chionodraco hamatus were investigated on samples collected in the western Ross Sea in early summer of 1996 and 2004. The stomach content analysis was carried out on larval and postlarval specimens ranging from 14 to 39 mm SL. Unlike larvae and juveniles of other channichthyids, which elsewhere largely rely on early life stages of Antarctic krill or ice krill, no euphausiids were found in the stomach contents of C. hamatus, except for a single large individual of Thysanoessa macrura. In both years, dietary composition consisted almost exclusively of notothenioid fish larvae. Early larvae of Pleuragramma antarcticum overwhelmingly dominated the diet in terms of abundance, biomass and frequency of occurrence, accounting for 98.4% of the index of relative importance (IRI). Other fish larvae consumed occasionally in small amount were Trematomus lepidorhinus, T. scotti and C. hamatus itself. As a result, the feeding strategy of C. hamatus was considerably shifted toward specialization, relying on relatively few taxa of prey, each of them showing a high prey-specific abundance. Comparing both dietary composition and feeding strategy of C. hamatus in the two different sampling years, several differences were observed, probably due to different environmental conditions, mainly linked to a significant delay of ice retreat and formation of the Ross Sea polynya verified in the 2003–2004 summer season.

Assessing diet composition of seahorses in the wild using a non destructive method: Hippocampus reidi (Teleostei: Syngnathidae) as a study-case

This paper presents the results of the first analysis of the natural diet of Hippocampus reidi, one of the most sought after seahorse species in the international aquarium trade. Its main goals were to investigate food items and prey categories consumed by the species, and to discuss feeding strategy and inter and intra-individual components of niche breadth. Data were gathered from October 2005 to September 2006 at the Mamanguape estuary, State of Paraíba, NE Brazil. Food items from seahorses anaesthetized with clove oil were obtained by using a modified version of the flushing method, and were counted and identified to the lowest possible taxonomic level. Specimens were marked and had their height, sex, life and reproductive stage recorded, and then returned to the same place where they were found for the further assessment of anaesthetization/gut flushing on seahorses. Food items were analyzed using frequency of occurrence, relative abundance, index of preponderance and prey-specific abundance using the points method. The graphic method of Amundsen et al. (1996) was used to interpret the feeding strategy and contribution to niche breadth. Nematodes and crustaceans were the most important items found, the latter item usually being the most commonly found in the gut contents of syngnathids. No significant differences in diet composition were found between reproductive stages, however, a higher proportion of large items were consumed by the larger seahorses. The feeding strategy and niche breadth analysis suggests that H. reidi has a generalist feeding strategy, with high variation between phenotypes. Our results suggest that the anaesthetization-flushing technique has the potential to be a useful tool in seahorse research.

Whitemouth croaker Micropogonias furnieri (Desmarest, 1823) feeding strategies across four southern Brazilian estuaries

We test the hypothesis that predatory benthic fishes play a similar ecological role in different estuaries by displaying the same feeding strategy. We used whitemouth croaker (Micropogonias furnieri) populations in four southern Brazilian estuaries (Mampituba (29°12′ S), Tramandai (30°02′ S), Patos Lagoon (32°10′ S) and Chui (33°44′ S)) as a model. We compared feeding strategies based on a graphical method proposed by Amundsen et al. [(1996) J Fish Biol. 48:607–614], with confidence intervals of frequency of occurrence of prey (FO) and prey-specific abundance (PSA) estimated by bootstrap analyses. We test differences among diets in the four estuaries used the ANOSIM and SIMPER analyses. We minimize the effect of fish size on prey selectivity by restricting the diet analysis to 70–130 mm size classes. Across all estuaries, infaunal prey was the dominant item in the whitemouth croaker’s diet. Most individuals fed on dominant infaunal prey such as Polychaetes (Chui: FO = 0.55 ± 0.018 SD; PSA = 0.88 ± 0.016 and Mampituba: FO = 0.73 ± 0.037; PSA = 0.56 ± 0.056), Bivalves (Tramandai: FO = 0.58 ± 0.032; PSA = 0.92 ± 0.024) and Tanaidaceans (Patos Lagoon: FO = 0.63 ± 0.027; PSA = 0.62 ± 0.043). A between-phenotype contribution to the niche width was observed in all four estuaries, where individuals generally consumed relatively large amounts of different prey types in the same habitat and season. Whitemouth croaker have a zoobenthivore feeding strategy and seemed to maintain the same feeding strategy in all the four estuaries. Specialization on consuming infaunal prey displayed by juveniles of whitemouth croaker could be an important factor leading to the successful colonization of South American estuaries.

Ontogenetic changes in morphology and diet in the snakehead, Channa limbata, a predatory fish in western Thailand

We examined the diet of Channa limbata, a predatory fish from western Thailand, in relation to mass, mouth and body morphology and intestine length. The cluster analysis we performed on the prey-specific abundance values of the dietary items yielded four size-classes based on diet. There was a shift from detritus and smaller benthic invertebrates in the diet of the first size class, to a mainly piscivorous diet in the fourth size-class as well as a steep increase in mass at the onset of piscivory. We found no significant change in relative intestine length with ontogeny, and the average relative intestine length value for C. limbata indicated primarily carnivorous feeding habits throughout ontogeny. Ontogenetic changes in mouth dimensions account primarily for the shift in diet, however the ontogenetic change in body morphology is of secondary importance.

A preliminary examination of the diet and feeding of sea sweep Scorpis aequipinnis (Pisces: Scorpididae) from coastal waters of south-western Victoria, Australia

The diet and feeding of sea sweep (Scorpis aequipinnis) was investigated from 230 specimens collected from the south-western Victorian coastline between January and July, 2002. Stomach content analysis indicated that S. aequipinnis are browsing omnivores (55.6% algae, 25.4% animal, by dry weight), with rhodophytes found to be the most important component of their diet (93.5% frequency of occurrence; 42.6% dry weight; 45.5% prey-specific abundance). However, the relative proportions of the major dietary components differed significantly between size classes. The dietary composition of small individuals ( < 150 mm total length) was significantly different to larger individuals, primarily due to a higher degree of carnivory exhibited by the smaller fish. S. aequipinnis were found to be highly flexible feeders exploiting both benthic and pelagic food resources, characterised by irregular periods of selective carnivorous feeding.