Feeding habits of sand smelt (Atherina boyeri, Risso 1810) in Trichonis Lake (Western Greece)

The feeding habits of sand smelt (Atherina boyeri, Risso, 1810) from Trichonis Lake (Western Greece) were investigated. Stomach contents were analyzed from 240 specimens with total lengths ranging from 35 to 112 mm. Samples were taken at monthly intervals (January–December 1997). Of the total number of stomachs examined, 53 were empty (22.1%). However, values varied greatly with season (maximum in January: 50%; minimum in August: 7.6%). Prey analyses of stomach contents identified 15 important items (%Rn > 0.05) belonging to six major groups: crustacean (copepods, cladocera), mollusca (bivalve: larvae), insects (larvae), cestode worms and finfish (fry and eggs). Dominant prey were larvae of the bivalve Dreissena polymorpha (%Rn = 33.8), the copepods Eudiadomus drieschi (%Rn = 26.4) and the cladocera Diaphanosoma brachyurum (%Rn = 24.2). The importance of cladocera and copepods decreased with increasing size of the sand smelt, while the importance of bivalve larvae, fish eggs and finfish fry increased with increasing sand smelt size. Seasonal changes in diet composition and prey abundance in sand smelt stomachs were recorded as coinciding with the seasonal composition and abundance of the zooplankton community in the surface layers of Trichonis Lake. Bivalve larvae were the dominant prey of A. boyeri during January to May, while copepods and cladocera dominated from June to December.     

Feeding ecology and prey preferences of a piscivorous fish in the Lagoa do Peixe National Park, a Biosphere Reserve in Southern Brazil

We investigated the diet, feeding strategy, size-related dietary shifts and prey preferences of South American Hoplias aff. malabaricus in an internationally recognized but poorly investigated Biosphere Reserve in southern Brazil. Fish were caught between April 2008 and March 2009 using a variety of fishing gear. The analysis of 113 individuals revealed a diet essentially composed of fish (16 species), particularly characid species (9). The diet became more diverse and contained larger fish prey with increasing predator size. Feeding strategy analysis revealed a clear specialization towards the consumption of fish. However, individuals did not prey upon particular prey species, instead opportunistically consuming many different fish species, which could be a strategy to avoid intraspecific competition. Characid species were the most important prey, followed by poecillids. A multi-gear sampling of the ichthyofauna revealed that these prey species were the most abundant (Characidae: 61.3%, Poeciliidae 18.8%) of the 14 fish families occurring at the study site, suggesting that the predator exploits the most abundant fish resources available rather than the rarer fish prey. These findings suggest that potential top-down controls exerted by H. aff. malabaricus in this system follow specific food web pathways that seem to be mediated by the abundance of prey resources.     

Effects of prey abundance,distribution, visual contrast and morphology on selection by a pelagic piscivore

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The effects and interactions of three invasive fish species introduced to the aquatic ecosystem of a Turkish Lake (Eğirdir Lake)

We studied feeding behavior and prey selection of topmouth gudgeon (Pseudorasbora parva), big-scale sand smelt (Atherina boyeri) and pike-perch (Sander lucioperca) in Lake E?irdir, the second largest freshwater lake in Turkey. Fish specimens were collected between January and August in 2010 and 2011 using gill-nets and purse seines. A total of 941 specimens were analyzed for stomach contents analysis. We expressed the importance of the food items present in their guts with the relative importance index (IRI) and estimated their diet selectivity indices with Pearre’s index. Pseudorasbora parva had a diverse diet comprising mainly Nitokra hibernica (copepod), Chydorus sphaericus, and Bosmina longirostris (cladoceran) (each, at p?<?0.01), but Chironomus sp. (insect) was not a significant component of its diet (p?>?0.05). Big-scale sand smelt often preferred B. longirostris, N. hibernica, and Alona quadrangularis (each at p?<?0.01). Pike-perch positively, but not statistically significant, selected Atherina boyeri (p?>?0.05), Carassius gibelio was not preferred by pike-perch as food item (p?>?0.05). Our results indicate that invasive species altered the food chain in Lake E?irdir. Thus, because these fish species constitute a major threat for native fish species for food and breeding grounds, extensive care should be taken to prevent invasive fish species entering lakes in Turkey.

     

Feeding strategy of the Deepwater Goby,Chasar bathybius,in the Southern Caspian Sea (Osteichthyes: Gobiidae)

Eleven animal taxa were identified as prey of the Deepwater Goby, Chasar bathybius (Kessler, 1877), by analysing stomach contents: these were some species of Gobiidae, Clupeidae, Atherina boyeri, Carassius gibelio, Liza sp., Cardium sp., and Rhithropanopeus sp. With a frequency of 66%, Neogobius fluviatilis was the most prevalent food item, and was the dominant prey taxon in all seasons and age groups. C. bathybius exhibited a specialist feeding strategy on this fish and the other prey types. The dietary breadth is highest in spring according to the Shannon index.     

Ontogenetic niche shifts and resource partitioning in a subarctic piscivore fish guild

The feeding ecology of three piscivorous fish species (perch (Perca fluviatilis), pike (Esox lucius) and burbot (Lota lota)), was studied in the subarctic Pasvik watercourse (69 °N), northern Norway and Russia. All three species primarily occupied the benthic habitats in the watercourse. Perch and burbot exhibited distinct ontogenetic niche shifts in food resource use, perch changing from a dominance of zooplankton to zoobenthos to fish, and burbot from zoobenthos to fish. Fish prey dominated the diet of all the investigated size-classes of pike, but small-sized pike (<20 cm) were not represented in the sample. Fish prey size was positively related to predator size in all three species. Whitefish (Coregonus lavaretus) was the dominant prey of pike and large-sized burbot and perch. Nine-spined sticklebacks (Pungitius pungitius) was also an important prey and appeared to be a dietary stepping-stone enhancing the transition from invertebrate feeding to consumption of large-sized whitefish prey for all three predators. A cluster analysis separated the different size groups of the three predator species into five functional feeding groups, most of them containing two or all three species. Within these feeding groups, and especially among the piscivorous size-classes, there was a strong and significant interspecific overlap in prey selection, and the dietary similarities between the species were in general much larger than the intraspecific similarities between ontogenetic stages. All three piscivorous species are important top predators in the aquatic food web of the watercourse, and their ontogenetic diet shifts and resource partitioning patterns generate a substantial food web complexity in this subarctic ecosystem.     

Seasonal profile of the diet of the dace Telestes karsticus Marčić & Mrakovčić, 2011 (Cyprinidae,Leuciscinae) endemic to Sušik Creek,Croatia

The first data on the feeding ecology of the endemic Telestes karsticus are presented for specimens sampled monthly (July 2007–July 2008) from the Su?ik Creek in the Lug Polje field, Croatia. Macrozoobenthos density was calculated and compared with the stomach contents of T. karsticus and the seasonal profile of the diet was examined. The ratio of gut length vs. standard length was 0.9 ± 0.12. Gut contents revealed that benthic invertebrates accounted for the majority of food consumed, although terrestrial arthropods, plant material, algae and fish were also found. Since this is the only fish species in the investigated creek, T. karsticus can be concluded to be cannibalistic. The proportion of empty guts found in all seasons was small, indicating year round feeding. The number and diversity of prey species was highest in spring and lowest in summer. Ivlev's electivity index was very high for Cladocera, Coleoptera, Trichoptera, Heteroptera and Hymenoptera in all seasons, suggesting positive selection for these prey groups, as opposed to Oligochaeta, Isopoda and Bivalva, which showed negative values in all seasons. For Actinopterygii, the Ivlev coefficient of selection was highly negative in spring, and highly positive in summer. Plant matter was detected in stomach contents in all seasons, with the highest share found in summer when other prey species were less available. The karstic dace is a generalised feeder, consuming the most available prey, and therefore can be classified as a euryphagous omnivore.     

Sexual differences in the diet of great cormorants <Emphasis Type="Italic">Phalacrocorax carbo sinensis</Emphasis> wintering in Greece

Sexual differences in the diet of the great cormorant, Phalacrocorax carbo sinensis, were studied in four Greek wintering areas, the Amvrakikos Gulf, the Axios and Evros Deltas and the Messolonghi Lagoon, through the analysis of stomach contents. Great cormorants are birds sexually dimorphic in size, with males being generally larger than females. Although similar prey species were found in the stomachs of both sexes in all the studied areas, significant differences were observed with respect to the proportion of species taken. Male birds ate higher proportions of large fish species such as grey mullets, European sea bass, Dicentrarchus labrax, and Prussian carp, Carassius gibelio, while female birds took higher proportions of smaller species such as big-scale sand smelt, Atherina boyeri, and black goby, Gobius niger. As a consequence, male great cormorants were found to feed on significantly larger prey than did females by means of fish standard length and body mass. There was no significant difference between the sexes in the mass of food found in stomachs.     

Diet composition of bluefin tuna (Thunnus thynnus L. 1758) in the Eastern Mediterranean Sea,Turkey

This study gives relevant information on the diet composition of the bluefin tuna (Thunnus thynnus) during the spawning period in the eastern Mediterranean Sea. The stomach contents of 218 bluefin tuna were sampled from 2003 to 2006 during the fishing season (May–June) aboard purse seiners operating in the northern Levantine Sea off the coast of Turkey. Stomachs were removed from the fish soon after landing and kept frozen at ?18°C until analysis. Prey items were classified into large taxonomic categories and preserved in 70% ethanol. A total of 745 different prey specimens belonging to 47 taxa were identified, including 34 species of fish, 11 of squid, and two of crustaceans. The most important fish and cephalopod prey belonged to the families Myctophidae, Carangidae, Chauliodontidae, Paralepididae, and Octopoda. This study marks the observation of myctophid fish in the stomach contents of bluefin tuna from the Mediterranean Sea. The paper offers some new information of regional importance and compares the feeding habits of the species to other regions, bringing confirmation on the opportunistic feeding ecology of the species in the enclosed Mediterranean Sea, where bluefin tuna seasonally occur as a strong cohort. New information on the diet composition of T. thynnus in the eastern Mediterranean Sea is revealed; the findings indicate that, depending on the abundance of the different prey species in the habitat, the dominant prey species can be distinctive.     

Diel shifts in the structure and function of nearshore estuarine fish communities

Day–night shifts in the nearshore fish fauna of a temperate microtidal estuary were assessed using a holistic suite of structural and functional community attributes. Mean fish species richness and diversity (taxonomic distinctness) were higher at night across all regions of the estuary and seasons, concurring with the findings of numerous comparable studies reviewed worldwide, while the diel period in which mean abundance was higher varied among seasons. Likewise, species and functional guild compositions (the latter based on feeding modes and habitat use) both differed significantly between day and night, with the extent of the diel shift again varying seasonally. Daytime fish communities were characterized by higher abundances of Atherinidae, Sillaginidae and Mugilidae, while Gobiidae were far more abundant at night. Marked shifts in size composition were also evident, with smaller fishes (<100 mm total length, L_T) being more prevalent during the day and larger fishes (≥200 mm L_T) proportionally more abundant at night. The above diel shifts were feasibly related to a range of predator–prey interactions and feeding‐related movements, namely a nocturnal decrease in top‐order avian piscivory coupled with an increase in invertebrate prey availability, resulting in changes in the presence and catchability of certain fish species in shallow estuarine waters.     

Diet and prey selection of six species of tuna baitfish in three coral reef lagoons in the Solomon Islands

The diets and prey selection of six species of tuna baitfish (the engraulids Stolephorus devisi and S. heterolobus, three dussumierids of genus Spratelloides, and the apogonid Archamiazosterophora. were examined at two heavily fished and one unfished site in the Solomon Islands. All species ate almost exclusively nektonic zooplankton, especially crustaceans. Calanoid copepods were the most importantpreyofallspeciesexcept A. zosterophora, whichateagreater biomassoflarvalfish. Baitfishcould be divided into two groups according to prey taxa: the apogonid A. zosterophora and the engraulids S. devisi and S. heterolobus ate similar prey in similar proportions; the three dussumierid species (Spratelloides) ate smaller zooplankton and a greater proportion of calanoids than the other species. The size of prey eaten differed greatly between baitfish species. A. zosterophora ate larger prey than other species. The two Stolephorus species ate similar-size prey, which were larger than the prey of the three species of Spratelloides. Among the Spratelloides, S. delicatulus ate smaller prey than the other two species. All species differed in the size of calanoids, carids and brachyurans they ate. In all cases, prey differed more by the minimum dimension (width) than by volume. There were significant relationships between fish length and prey width and volume, except for Archamia. However, in terms ofvolume, the prey of Stolephorus increased with fish size at a much greater rate than in Spratelloides species. Baitfish diets were compared to the zooplankton available. Prey selection by the three Spratelloides species and two Sfolephorus species was density-dependent for all common prey types, although Stolephorus positively selected hyperiid amphipods and brachyurans. Archamia showed strong negative selection for calanoids and selected larger zooplankters, including fish larvae and carids, avoiding smaller, more common, prey. Overall baitfish density and zooplankton density did not correlate at either of the heavily fished sites. Nor were there consistent differences for any species in diet or changes in prey selection between the heavily fished and unfished sites. This suggests that, in these lagoons, commercial baitfish catches are not directly influenced by the composition or density of prey.     

Feeding performance of the Hawaiian sleeper,Eleotris sandwicensis (Gobioidei: Eleotridae): correlations between predatory functional modulation and selection pressures on prey

The eleotrid fish Eleotris sandwicensis inhabits lower reaches of streams in the Hawaiian Archipelago, where it feeds on juveniles of native amphidromous gobiid fishes migrating upstream from the ocean. Using high‐speed video and geometric modelling, we evaluated the feeding kinematics and performance of E. sandwicensis on free swimming prey, including two species with juveniles of different characteristic sizes, and compared successful and unsuccessful strikes. With fast jaw movements and a highly expansive buccal cavity, E. sandwicensis achieves high suction performance that enables the capture of elusive prey. Our analyses indicated that the species with larger juveniles (Sicyopterus stimpsoni) could be captured from a distance of up to 18.6% of the predator's body length (BL), but capture of the smaller species (Awaous guamensis) required a closer distance (12.2% BL). Predator–prey distance appears to be the predominant factor determining strike outcome during feeding on juvenile A. guamensis. However, during feeding on juvenile S. stimpsoni, E. sandwicensis shows modulations of strike behaviour that correlate with capture success. Moreover, the ability of E. sandwicensis to capture larger prey fish from longer distances suggests a potential biomechanical basis underlying observations that predation by eleotrids imposes significant selection against large body size in juvenile gobies. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 359–374.     

Prey selection and prey preferences of spotted hyenas <Emphasis Type="Italic">Crocuta crocuta</Emphasis> in the Etosha National Park,Namibia

The feeding ecology of the spotted hyena Crocuta crocuta was studied in the central and eastern part of the Etosha National Park, Namibia. Hyenas mainly hunted migratory ungulates such as springbok Antidorcas marsupialis, zebra Equus burchelli, and blue wildebeest Connochaetes taurinus, but also resident species such as the greater kudu Tragelaphus strepsiceros and gemsbok Oryx gazella. There were, however, major differences in the species most frequently killed by hyenas in central and eastern Etosha. The preferred prey species of spotted hyenas in central Etosha was springbok, whereas regarding the abundance of zebra and wildebeest, these two species were rather avoided. In contrast, the prey species preferred by hyenas in eastern Etosha was kudu. Zebra and gemsbok were taken in proportion to their abundance, whereas wildebeest and springbok seemed to be rather avoided. Differences in prey selection and preferences were also reflected in differences in hunting group sizes. In eastern Etosha, where spotted hyenas frequently hunted larger prey, hunting group sizes were significantly larger compared to those in the center of the park.     

基于高通量测序的象山港海域黑鲷(Acanthopagrus schlegelii)食性分析

选取象山港黑鲷个体为研究对象,以18S rDNA为靶标,利用Illumina Miseq高通量测序方法研究黑鲷饵料生物组成特征,分析不同龄组黑鲷的食性异同。通过序列比对,共在黑鲷胃含物中鉴定出41个属中的62种饵料生物,分属9个门,其中节肢动物门（Arthropoda）、绿藻门（Chlorophyta）和软体动物门（Mollusca）是黑鲷饵料生物的优势组成门类。从饵料生物相对丰度和出现频率上分析,石莼（Ulva lactuca）、熊本牡蛎（Crassostrea sikamea）、胸刺水蚤（Centropages hamatus）、日本蟳（Charybdis japonica）、毛蚶（Scapharca subcrenata）和褐菖鲉（Sebastiscus marmoratus）是黑鲷的优势饵料物种,所占饵料生物总相对丰度的比重达60.90%。相似性分析检验（ANOSIM）结果显示：1至4龄黑鲷个体的饵料生物组成不存在显著性差异。与传统食性分析方法相比,高通量测序法在黑鲷饵料生物检测灵敏性上显现了较为明显的优势,保障黑鲷等重要物种的种群稳定对于该海域具有重要的生态和经济意义。     

The influence of prey abundance on the feeding ecology of two piscivorous species of coral reef fish

Despite the potential importance of predation as a process structuring coral reef fish communities, few studies have examined how the diet of piscivorous fish responds to fluctuations in the abundance of their prey. This study focused on two species of rock-cod, Cephalopholis cyanostigma (Valenciennes, 1828) and Cephalopholis boenak (Bloch, 1790) (Serranidae), and monitored their diet in two different habitats (patch and contiguous reef) at Lizard Island on the northern Great Barrier Reef, Australia, over a 2-year period. The abundance of the rock-cods and the abundance and family composition of their prey were monitored at the same time. Dietary information was largely collected from regurgitated samples, which represented approximately 60% of the prey consumed and were unbiased in composition. A laboratory experiment showed that fish were digested approximately four times faster than crustaceans, leading to gross overestimation of the importance of crustaceans in the diet. When this was taken into account fish were found to make up over 90% of the diet of both species. Prey fish of the family Apogonidae, followed by Pomacentridae and Clupeidae, dominated the diet of both species of rock-cod. The interacting effect of fluctuations in prey abundance and patterns of prey selection caused dietary composition to vary both temporally and spatially. Mid-water schooling prey belonging to the families Clupeidae and to a lesser extent Caesionidae were selected for over other families. In the absence of these types of prey, apogonids were selected for over the more reef-associated pomacentrids. A laboratory experiment supported the hypothesis that such patterns were mainly due to prey behaviour. Feeding rates of both species of rock-cod were much higher in summer than in winter, and in summer they concentrated on small recruit sized fish. However, there was little variation in feeding rates between habitats, despite apparent differences in prey abundance. In summary, our observations of how the feeding ecology of predatory fish responded to variation in prey abundance provide potential mechanisms for how predation may affect the community structure of coral reef fishes.     

Distribution and diet of 0-group cod (<Emphasis Type="Italic">Gadus morhua</Emphasis>) and haddock (<Emphasis Type="Italic">Melanogrammus aeglefinus</Emphasis>) in the Barents Sea in relation to food availability and temperature

Distribution of 0-group cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) in August–September 2005 and 2006 was mainly restricted to the Atlantic waters of the western and central areas of the Barents Sea. The main distribution of 0-group fish overlapped largely with areas of high biomass (>7 gm⁻² dry weight) of zooplankton. The copepod Calanus finmarchicus and krill Thysanoessa inermis, which are dominant zooplankton species in both Atlantic and boreal waters of the Barents Sea, were the main prey of 0-group cod and haddock. The main distribution, feeding areas and prey of 0-group cod and haddock overlapped, implying that competition for food may occur between the two species. However, though their diet coincided to a certain degree, haddock seems to prefer smaller and less mobile prey, such as Limacina and appendicularians. As 0-group fish increased in size, there seems to be a shift in diet, from small copepods and towards larger prey such as krill and fish. Overall, a largely pelagic feeding behaviour of 0-group cod and haddock was evident from this study.     

Mechanisms of selectivity in a nocturnal fish: a lack of active prey choice

Fish that feed on individual zooplankton usually exhibit strong selectivity for large prey. Such selectivity can result from the predator’s active choice of larger prey or from differential encounter rate due to lower detectability of small prey, or both. In diurnal fishes, selectivity is thought to be determined mostly by active choice. In spite of a lack of direct observations, active choice is also considered the prevailing mechanism of prey selectivity in nocturnal fishes. Our objective was to resolve this mechanism in the highly selective, nocturnal zooplanktivorous fish Apogon annularis. Laboratory experiments indicated that the fish’s encounter rate with small prey was lower than that with large prey and that its selectivity became stronger with decreasing light intensity. Feeding efficiency, defined as the ratio between feeding and encounter rates, ranged 41–89% and was positively correlated with prey size. When feeding on a mixture of prey sizes, the fish fed on each size group at a rate similar to that of its feeding on the respective size alone, indicating that selectivity in A. annularis was due to size-dependent encounter rate and differential feeding efficiency. A low visual acuity in A. annularis, as inferred from its inability to detect small prey (<0.9 mm in length), together with the low abundance of large zooplankton in situ, can explain the dominance of differential encounter over active choice in this nocturnal coral-reef fish.     

Feeding ecology of the Kızılırmak toothcarp, <Emphasis Type="Italic">Aphanius marassantensis</Emphasis>: ontogenetic shift and seasonal diet variation

We studied the feeding ecology of an endemic cyprinodontid fish, Aphanius marassantensis (K?z?l?rmak Toothcarp), with special emphasis on seasonal and ontogenetic diet shift. The dietary composition revealed an omnivorous diet with great seasonal and ontogenetic variation. Cladocera and Calanoid Copepods (Diaptomus sp.) dominated the diet in Spring and Summer, whereas the food items of plant origin e.g. filamentous algae and diatoms were the most important components in Autumn and Winter. An ontogenetic diet shift was also demonstrated. While the feeding of juveniles was based mostly on planktonic organisms, adult individuals preferred larger prey taxa, such as Gammarus sp. and Gastropods. There was no significant sex-related variation in feeding with the exception for the volume of gut content. The investigation on the feeding strategy of A. marassantensis suggested a generalised feeding pattern with some specialised individuals. This generalist feeding habits may account for the well-established population of this species in a big reservoir under coexistence of two non-native fish species, Pseudorasbora parva and Atherina boyeri.     

Observations on feed size and capture success in the larval butterfly splitfin (Ameca splendens Miller & Fitzsimons, 1971, Pisces: Goodeidae) reared on zooplankton

In this study, we quantified the feeding behaviour (encounter, attack, capture. and ingestion) of larval A. splendens on micro‐crustacean prey [cladocerans: Alona rectangula, Simocephalus vetulus (separately neonates and adults), Ceriodaphnia dubia, Daphnia pulex (juveniles), Moina macrocopa and ostracods: Heterocypris incongruens]. Although we initially (first 4 weeks) offered rotifers (Brachionus calyciflorus and B. patulus), they were not consumed by the larvae and hence observations with these prey were discontinued. Feeding behaviour was observed during the first 10 weeks. Fifteen observations were made with each prey species (seven diets × four replicates). Experiments were conducted in 50 ml transparent containers with 20 ml fish‐conditioned water into which one fry was introduced. Before introducing the fish, 20 individuals of a given cladoceran prey species or 50 individuals of a rotifer prey species were introduced. Until the fourth week, we used 20 ml of medium and thereafter 30 ml, but the prey density used remained constant (1 ind. ml⁻¹). Observations (10 min per fry per cladoceran replicate) were taken under a stereomicroscope (20×) for the first 2 weeks and later with a lamp and a magnifying lens. The number of encounters (E), attacks (A), captures (C) and ingestions (I) were recorded. During the study period, there was a 60% increase in gape size but only a 30% increase in body length. The number of encounters of larval A. splendens was highest (192) on M. macrocopa and lowest (29) on ostracods and adult S. vetulus (59). The inverse relationship between capture success and prey size was more pronounced during the latter half of the study period. Compared with all the other prey types offered, A. splendens fed maximally on M. macrocopa, which therefore could be a suitable diet for the larval rearing of this fish species.     

Population interactions among free-living bluefish and prey fish in an ocean environment

Summary We used sonar to measure relative abundance, location, and depth of prey fish schools (primarily Anchoa and Ammodytes) in the ocean near Fire Island Inlet, New York from May to August for 4 years to examine predatorprey interactions. Prey fish numbers built through May, peaked in June, and thereafter declined coincident with the arrival of predatory bluefish. Bluefish abundance and feeding behavior correlated inversely with prey fish abundance and depth. Bluefish may drive seasonal patterns of prey abundance and distribution in this area through direct predation and by causing prey to flee.