The food of barramundi, Lates calcarifer (Bloch), in coastal and inland waters of Van Diemen Gulf and the Gulf of Carpentaria, Australia

Examination of the diet of Lates calcarifer , based on 3684 specimens of 4–1200 mm total length (T.L.), from two localities in north Australia showed it is an opportunistic predator with an ontogenetic progression in its diet from microcrustacea to macrocrustacea to fish. The increasing importance of fish in the diet of L. calcarifer in salt water (up to 87% of food consumed) involved a dietary shift from feeding on bottom-dwelling forms to pelagic forms. There were few differences in the diet of L. calcarifer between the two localities. Cannibalism was rarely encountered in the Gulf of Carpentaria although it was significant (11–4% of the diet of L. calcarifer of 1001–1200 mm T.L.) in Van Diemen Gulf. A significant correlation between predator and prey length was found for Ariidae, Dorosomidae, Engraulidae, L. calcarifer , Mugilidae and Polynemidae. The maximum prey/predator length ratio observed was 0–61 for the dorosomid, Nematolosa erebi.     

Diet, prey selection, and growth of larval and juvenile burbot Lota lota (L.)

The diet, prey selection, and growth of larval and juvenile Oneida Lake burbot, Lota lota (L.), was investigated from the time of first hatch in mid-April until their disappearance from the pelagic zone at the beginning of June. Mean length increased exponentially from 3–20 mm on 18 April to 15–00 mm on 29 May. The number and size of prey in burbot stomachs, and the prey size most selected by burbot increased as they grew. Prey width, not prey length, limited the size of prey ingested. The smallest burbot ate and selected highly for the largest prey they could ingest, but older burbot did not. As burbot grew, prey selection was highest first for the rotifer Asplanchna , followed by copepod nauplii, then cyclopoid copepods. Daphnia and calanoid copepods and cyclopoid copepods were selected to similar degrees by 29 May. For a given size, however, cyciopoid copepods were selected more strongly than any other prey type from 18 to 29 May. There were no significant differences in prey selection among offshore, nearshore, and onshore habitats, nor among depths in the offshore habitat.     

崂山湾人工鱼礁区星康吉鳗摄食生态及食物网结构

根据2015年4月至2017年1月于崂山湾人工鱼礁区地笼网和延绳钓捕获的279尾星康吉鳗样本,从胃含物组成、食性类型、摄食等级、营养生态位和营养级等方面对其摄食生态进行研究,同时结合海区许氏平鲉、大泷六线鱼、斑头鱼、褐菖鲉、花鲈等9种鱼类的胃含物分析结果,构建人工鱼礁区鱼类关键种的简化食物网模型.食性研究结果表明:星康吉鳗共摄食7类30余种饵料,虾类是其最主要的饵料类群,其次为鱼类和头足类,大泷六线鱼、方氏云鳚、鹰爪虾、玉筋鱼和日本鼓虾等是其优势饵料.星康吉鳗的饵料生物组成随肛长和季节发生显著变化.四季均以鱼类和虾类为主,春季胃含物中包括头足类,秋季包括头足类和蟹类,冬季亦有蟹类出现.肛长≤120 mm的星康吉鳗主要摄食鱼卵和鹰爪虾,120~130 mm肛长组主要摄食玉筋鱼和日本鼓虾,肛长>130 mm的星康吉鳗主要摄食大泷六线鱼和方氏云鳚.其摄食强度也随季节和肛长而变化,空胃率的季节性差异显著,平均胃饱满系数的季节性差异不显著,不同肛长组的空胃率和平均胃饱满系数均不存在显著差异.人工鱼礁区简化食物网结构显示:鱼类关键种的营养级均在3级以上,星康吉鳗的营养级为4.636,处于海区食物网的最顶端.虾类、蟹类、端足类和软体动物等是鱼类关键种的主要饵料,甲壳类、方氏云鳚、大泷六线鱼和玉筋鱼是高营养级鱼类花鲈和星康吉鳗的主要饵料.     

Feeding habits of the fishes Lutjanus peru and Lutjanus guttatus (Pisces: Lutjanidae) of Guerrero, México

Diet composition of the Pacific snapper (Lutjanus peru) 130-684 mm fork length (FL) and the spotted snapper (Lugjanus guttatus) 120-550 mm FL, was analyzed. Monthly samples were obtained from commercial landings in three regions off the coast of Guerrero, Mexico. Percentage by number (%N), percentage by weight (%W), and percentage of occurrence (%O) were calculated for each prey and summarized as the index of relative importance. Both species are polyphagous predators feeding on a variety of prey: Sixty-eight prey items, mainly fish (%W = 50.9), crustaceans (%W = 35.6), and mollusks (%W = 7.2), were found in the stomach contents of L. peru, while 88 components were identified in the diet of L. guttatus, the most important prey being fish (%W = 50.8) and crustaceans (%W = 43.4). Diet overlap between species is not significant (p<0.05), indicating that competition for food is unlikely. Based on published values of the relative importance index, the diets of these Lutjanidae were analyzed considering different regions of the Pacific coast of Mexico and Costa Rica, and similarities among sites and species were discussed. The cluster analysis showed that similarities among species inhabiting in the same area are more important than within organisms of the same species living in different zones. Results suggest that prey availability rather than food selectivity, conditions the feeding behavior of these fish species.     

Behavioural aspects of predation by juvenile Atlantic salmon (Salmo salar L.) on particulate,drifting prey

A recirculatory flume tank simulating a simplified stream environment was used to study the feeding behaviour of juvenile Atlantic salmon (Salmo salar L.), 5.1 to 9.4 cm in fork length (from tip of snout to fork of tail), on artificial particulate prey passively drifting in the water current. Changes in feeding behaviour at two different times of the year and when fish were presented with prey of different sizes are described and quantified. Responsiveness to food was greatly reduced in autumn as compared to summer. The maximum distances at which prey elicited a response decreased in autumn to 40% of the summer value, and the maximum distances which fish traversed in order to capture prey decreased by 80% over the same period. During the peak growing season, the response to a range of prey sizes from 0.013 to 0.102 × fish fork length was directly related to prey size and could be accounted for on the basis of visual theory alone. Capture distances were closely related to fixation distances. Maximum capture distance increased to a peak value for prey of between 0.025 and 0.069 × fork length, while larger prey were never captured and the smallest prey rarely evoked a response. Prey size selectivity also operated after capture, through rejection versus retention of the prey.     

Prey selection of the shallow water fishPomatoschistus minutus (Gobiidae,Teleostei) in the SW Baltic

The aim of this investigation is to demonstrate the reasons of an opportunist feeder to select some components of the available food supply and to avoid others. Object of this test is the eurytopic and euryhaline sand goby,Pomatoschistus minutus (Pallas), from the Luebeck Bight. It inhabits both sand habitats as well as bottoms mixed with pebbles or continuous hard substrates. Therefore, it is often in close contact withMytilus-belts which present a very rich food supply of small crustaceans. The selectivity behaviour of sand gobies from a sand/clay ecotone was compared with that of populations from a stony pier and a sand bottom during the reproduction period. Regarding the numbers of prey organisms, crustaceans of the periphyton were generally preferred at the pier but avoided in the ecotone. The same is valid for prey organisms of the psammal which were preferred by gobies of the sand bottom but mostly avoided by populations of mixed bottoms. Analyses of size selections revealed that the preferred gammarids orJaera isopods were between 2 and 5 mm length. A balanced relation of goby biomass and utilizable food supply (predatory impact index) seems to effect positive selectivity of gammarids in theMytilus-belts or of harpacticoids in the sand bottom.     

The food and feeding habits of young perch, Perca fluviatilis, in Windermere

SUMMARY. The food of 0+ perch, Perca fluviatilis L. has been investigated in Windermere, the largest lake in the English Lake District. Whole guts and stomachs from 800 fish were investigated during four 24-h periods between June and September in 1975 and in 1976. Ciliates, algae, rotifers and cyclopoid nauplii constituted the first food of larval perch in Windermere. Vertical samples were taken from the zooplankton, at the same time and in the same location where the fish were sampled, and the concentration of the different food organisms studied. Electivity of the different food organisms was studied from lvlev's index, which showed positive electivity, or selection for some organisms, e.g. Bosmina obtusirostris (Sars.) and copepods (both cyclopoid and calanoid), and negative for others such as Daphnia hyalina var. galeata (Sars.), Leptodora kindti (Focke) and Bythotrephes longimanus (Leydig). In studying predatorprey relationships, Daphnia hyalina was chosen as the 'standard prey', being the most abundant of all food organisms in the diet of young perch, also because its maximum body-depth (carapace width (mm)) was among the largest of the cladocera and copepods in Windermere. Comparison of the maximum carapace width of Daphnia eaten with that of the plankton revealed that smaller specimens were taken by juvenile perch in July, but they tended to select larger organisms during August and September.     

Feeding ecology of the lesser weever, Echiichthys vipera (Cuvier, 1829), on the western coast of Portugal

The feeding ecology of the lesser weever, Echiichthys vipera, from the adjacent coastal areas of the Douro and Tagus estuaries (Portugal) was studied between October 2000 and July 2002. The stomach contents of 246 individuals were analysed and diet was characterized by the numerical, gravimetric, occurrence and vacuity indices. Variation of feeding habits with fish length (<95 and >95 mm) and geographical area was considered. Diet of the lesser weever comprised a large variety of prey (28 species), the most important of which were crustaceans (numerical index, NI = 93.5%; occurrence index, OI = 75.6%), namely Mysidacea (especially Schistomysis sp.), Amphipoda (mainly Gammarus subtypicus) and Isopoda (Idotea spp.), and also Teleostei (mostly larval stages that posted a gravimetric index, GI = 53.0%). Diet varied with fish length, with large individuals showing a larger diversity of prey items. Furthermore, specimens from Douro also showed a higher diversity of prey items than those from Tagus. More than 50% of the stomachs were empty, being the highest vacuity values relative to smaller fishes as well as to individuals from the Tagus estuary adjacent coastal area.     

Ontogenetic variations in the type and size of prey consumed by juvenile coho,Oncorhynchus kisutch,and chinook,O. tshawytscha,salmon

Synopsis Stomach contents of juvenile coho,Oncorhynchus kisutch, and chinook,O. tshawytscha, salmon collected in purse seines off the coast of Washington and Oregon were examined for variations related to predator size. There was a general trend toward increasing consumption of fish with increasing body size, due mainly to the increase in northern anchovy biomass consumed by the larger salmon. Most of the major prey taxa showed significant differences among the size classes examined for both salmon species. There was a direct relationship between predator and prey size for both coho and chinook, but considerable variation was found in prey length consumed within each size class. Prey width did not provide as good a fit as prey length for either species. In general, coho consumed larger fish prey in relation to their body length than chinook but there were substantial differences by month or year of collection.     

Food habits, ontogenetic diet shift and selectivity in Zeus faber Linnaeus, 1758

The feeding habits of Zeus faber Linnaeus, 1758 were studied by examining digestive tracts in I2 size classes of individuals. It is a stenophagus species which begins life feeding almost exclusively on zooplankton until it is about 80 mm long, then switches gradually from zooplankton to small demersal fish, and finally when > 140 mm switches to feeding exclusively on benthic and demersal fish. Mysids were the most important food component in Z.faber < 141 mm and Cepola macrophthalma (Linnaeus, 1758) in Z.fiber > 140mm. The switch to fish prey was followed by a greater body weight per unit length. Z.faber > 140 mm selected primarily for small-and intermediate-sized C. macrophthalma (and to a lesser extent for Callionymus maculatus Rafinesque-Schmaltz, 1810, Gaidropsarus sp. and Trigla Iyra Linnaeus, 1758). Our results suggested that the ratio of vertical to horizontal dimension of prey, the motion and coloration of prey as well as the visual capabilities and perceptual potentialities of Z. faber may all in a synergetic fashion account for prey type and size selection and the positive relations found between the size of Z.faber and the size and variance of its ingested prey. Possible co-evolutionary relationships between Z.faber and C. macrophthalma are also discussed.     

Feeding ecology of the orb-weaving spiderArgiope aurantia [Araneae: Araneidae] in a cotton agroecosystem

Twenty females of the orb-weaving spiderArgiope aurantia Lucas were introduced into a cotton field in east Texas in order to study the feeding ecology of this spider. In the 24 h after the release of these spiders in the cotton field, one had moved over a distance of 53 m. The released spiders spun webs with an average diameter of 33.5 cm with the hub an average of 39 cm above the ground. The diet ofA. aurantia was diverse which characterizes this species as a food generalist. Major food components were aphids (30%), Diptera (26.8%), grasshoppers (17.9%), and Hymenoptera (12.6%). The spiders' prey length ranged from 0.4 to 47 mm (mean =7.7±0.83 mm). Adult females ofA. aurantia have the potential to kill prey of up to ca. 200% of their own size. However, two-thirds of the prey items had a length of <3 mm, while only 25% of the prey items had a length of ≥20 mm.A. aurantia was found to be a predator of the cotton fleahopper (about 1% of the spiders' diet), which is a key pest of cotton.      

Feeding Patterns in Different Size Larvae of Walleye Pollack, Theragra chalcogramma (Pallas, 1814) on the Shelf of Western Kamchatka

The stomach contents were examined in 373 walleye pollack larvae of different sizes. The diet of pollack larvae included more than 20 plankters of different sizes. Phytoplankton was the major food source of 4- to 6-mm-long larvae. The proportion of phytoplankton in the larval diet decreased as the larvae grew, and the late larval stages shifted entirely to a diet of zooplankton. As the larvae increased in size, the spectrum of food organisms changed from smaller to larger sizes. In the larvae 4 to 31 mm long, the length of prey varied from 0.1 (Coscinodiscus) to 6.0 mm (Neocalanus plumchrus). The average daily repleteness of pollack larvae varied from 32 to 210. The minimum repleteness was registered in 4- to 6-mm-long larvae with mixed feeding (endogenous and exogenous); in 30- to 35-mm-long fish the repleteness was the greatest. The daily food rations calculated for the most abundant size groups of larvae ranged from 4.3 to 6.6% of their body weight.     

Shift in pike, Esox lucius L., predation pressure following the introduction of ruffe, Gymnocephalus cernuus (L.) to Loch Lomond

Rapid and dramatic change in the fish community of Loch Lomond has resulted from a series of fish introductions in recent years. A comparison of the diet of pike, Esox lucius L., in 1989–1990 with data from 1955–1967, prior to recent introductions, demonstrates a shift in prey choice. In 1955–1967 powan, Coregonus lavaretus (L.), dominated in the diet (57% of prey by number) by 1989–1990 the introduced ruffe, Gymnocephalus cernuus (L.), was the commonest prey species (44% by number). This shift in pike predation to an abundant population of introduced ruffe has consequences for native species. Assuming that the pike population has not increased in response to increased food availability due to the introduction of ruffe, pike predation pressure on native species will be relieved. This is likely to have the greatest effect on powan. Comparison of the predation rate in 1955–1967 with 1989–1990 supports the hypothesis that the rate of predation on powan has declined, although the effect that this may have on the powan population is unclear, as the role of predation in the regulation of population size is unknown for this species.     

Predation by xanthid crabs on early post-settlement gastropods: the role of prey size, prey density, and habitat complexity

Small predators in marine benthic communities create a hazardous environment for newly settled invertebrates, especially for the smallest individuals. To explore the effects of predation on a newly settled gastropod, queen conch (Strombus gigas Linnaeus), by a xanthid crab (Micropanope sp.), prey size, prey density, and habitat complexity were manipulated in five laboratory experiments. All crabs >3.1 mm CW killed all conch <2 mm SL when individual crabs (<14 mm carapace width (CW)) were offered individual conch that were 2–35 days old after metamorphosis (1.2–8.8 mm shell length (SL)). Only 10% of the crabs >5.0 mm CW, however, killed conch that were >5.0 mm SL, suggesting that conch may reach a size refuge from xanthid crabs at 5 mm SL. Furthermore, when given a choice, crabs (4.8 mm CW) preferred smaller conch (2.0 mm SL) to larger (3.7 mm SL), suggesting that 1 week of additional growth in shell length is advantageous to survivorship. Proportional mortality decreased as conch density increased when crabs were offered conch at seven different densities (two to 96 individuals). Crabs proved to be effective predators regardless of the amount of seagrass structure provided in a microcosm experiment, and could consume two conch in 10 s. The high densities of xanthid crabs that occur in the wild, their effectiveness as predators, and their large appetites point to the important role that small predators may potentially play in structuring the population dynamics of their small prey immediately after settlement.     

Food of the roughhead grenadier, Macrourus berglax, Lacepede in North Norwegian waters

Over 30 different prey species were found in the stomachs of roughhead grenadiers, Macrourus berglax , caught at depths of approximately 700 m off the coast of northern Norway. Crustaceans and fish were the principal prey categories and large, mature grenadiers are classified as being generalist feeders taking predominantly benthopelagic organisms. There is evidence for an ontogenetic shift in dietary composition, with a change from benthic prey to an increased reliance on benthopelagic prey as the fish increase in size and this results in reduced intraspecific competition for food.     

Prey ‘handling time’ and its importance in food selection by the 15-spined stickleback, Spinachia spinachia (L.)

The time taken to manipulate and swallow a prey item, termed ‘handling time’, increases with decreasing hunger in Spinachia spinachia (L.), Handling time is also dependent upon the size of the prey in relation to the size of the mouth. Estimates of the optimum prey size, defined as that prey which minimizes the value of the ‘cost/benefit’ ratio of handling time/mg dry weight of prey, agrees closely with the mean prey sizes of wild fish. Optimum prey size was found to be approximately half the maximum swallowing capacity of the mouth. The nature of the relationship between the cost/benefit ratio and prey weight was used to explain the facts that the size range of prey eaten is dependent upon fish length and that decreasing hunger results in fish becoming increasingly selective with respect to prey size.     

Feeding changes for three Sphoeroides species (Tetraodontiformes: Tetraodontidae) after Isidore hurricane impact in Carbonera Inlet, Southeastern Gulf of Mexico

The coexistence of ecologically similar species may occur because of resources distribution, such as prey and habitat type and segregation time, that minimizes the interspecific competition. The changes brought about by Hurricane Isidore in the distribution of food resources by three coexisting fish species of the family Tetraodontidae (Sphoeroides nephelus, S. spengleri and S testudineus), were analyzed at the Carbonera Inlet. Sphoeroides spp. based their food on benthic organisms; principally, they consume mussels (Brachidontes sp.), barnacles (Balanus sp.) and gastropods (Crepidula sp). Before hurricane impact, the three species share the available food resources in different proportions (bivalves, gastropods, barnacles and decapods), according to different strategies that enabled them to coexist and reduce interspecific competition. After the impact, the abundance of available prey decreased and the interespecific competition for food increased, leading to S. testudines and S. nephelus change their trophic spectrum (xiphosurans, amphipods, isopods and detritus) and displacing S. splengleri of the inlet. The distribution of food resources was conditioned by the abundance and diversity of prey, as well as the adaptive response of each species.     

Food and feeding habits of pearly razorfish, <Emphasis Type="Italic">Xyrichtys novacula </Emphasis>(Linnaeus, 1758), in the southern Tyrrhenian Sea: variation by sex and size

We collected pearly razorfish, Xyrichtys novacula (Labridae), from a sandy bottom of Capo dOrlando (Tyrrhenian Sea) to study their feeding habits. We caught fish by hand-lines and seine nets and identified, counted and weighed food items in their stomachs. We evaluated the importance of the different prey types by calculating the frequency of occurrence, abundance and mass. We used these values to calculate the index of relative importance (IRI) for each taxonomic category and a modified index (MI) which did not incorporate %N into the formula. Gammarideans were dominant food items in terms of %F but showed a very low MI value; the bivalve Acanthocardia tubercolata was the dominant species in terms of %W and MI value. The prey items were mostly benthic organisms belonging to the assemblage of fine, well-sorted sands showing that X. novacula is a benthic feeder. Despite the large number of prey taxa found, few species accounted for most of the prey consumed, indicating specialist feeding, as confirmed by the low value of the Levins standardised index. We found significant differences in prey distribution among size classes, with the highest prey diversity recorded in 120–140 mm TL size classes. Correspondence analysis showed a trend of increasing predator size classes among prey items, with small prey, such as copepods and amphipods, in the smallest predator size classes and bigger prey in the larger ones. Prey caught by larger predators differed significantly in weight from those taken by smaller specimens. There was a significant positive correlation of fish length with bivalves, decapods and echinoids, and a negative one with copepods, ostracods, caprellids, gammarideans. There were no significant differences between males and females of overlapping sizes. Juveniles are able to exploit only small, vulnerable prey, while adults take few, large prey, thereby avoiding competition with juveniles.     

Seasonal, diel and ontogenetic variation in feeding patterns of small yellow croaker in the central Yellow Sea

Stomach contents of 1603 small yellow croaker Pseudosciaena polyactis , sampled from seasonal bottom trawl surveys in the central Yellow Sea between March 2001 and January 2002, were examined. The results showed that small yellow croaker was a carnivorous predator and >30 prey species were identified from stomach contents analysis. Crustaceans (mainly euphausiids and decapods) were the most important prey, occurring in 93·1% of the stomachs containing food, and accounting for 77·6% of the total food by mass. Feeding activity was highest in autumn and lowest in spring and winter. Decapods were more important in summer, whereas euphausiids were more important during other seasons. Ontogenetic differences were found in the diet composition and feeding activity within the range of size (standard length, L _S) studied. The importance of fishes and decapods increased with L _S, whereas euphausiids, copepods and amphipods decreased in importance with L _S. Dietary breadth increased markedly for adults. A positive relationship was found between L _S and prey size. In each season the maximum diel feeding activity occurred at 0800 and 2400 hours, indicating that there was crepuscular and nocturnal feeding by small yellow croaker.