Species-specific probe,based on 18S rDNA sequence,could be used for identification of the mucilage producer microalga <Emphasis Type="Italic">Gonyaulax fragilis</Emphasis> (Dinophyta)

Brook trout (Salvelinus fontinalis) in Appalachia experience prolonged periods of poor feeding conditions, particularly during summer and fall. To determine which prey organisms are important in sustaining brook trout populations, we monitored the feeding patterns of a population of brook trout over the course of 2 years with an emphasis on seasonal change. We employed a bioenergetics model to estimate whether or not each fish had obtained enough energy to meet daily metabolic demand. As a result, qualitative comparisons between fish feeding above maintenance ration (successfully feeding fish) and fish feeding below maintenance ration (unsuccessfully feeding fish) were possible. With the exception of winter, brook trout derived significantly more energy from terrestrial organisms than aquatic organisms. During each season, successfully feeding brook trout fed on greater proportions of specific prey types. Terrestrial Coleoptera and Lepidoptera consistently proved to be important prey during warmer seasons, while large organisms such as vertebrates and crayfish appeared to be important during winter. Our findings suggest that terrestrial organisms are more important than aquatic organisms in sustaining brook trout populations. Further, certain large and abundant terrestrial taxa are critical in providing energy to brook trout.     

Seasonality in Dietary Shifts in Size-Structured Freshwater Fish Assemblages in Three Reservoirs of Sri Lanka

We studied seasonal changes in feeding habits of size-structured fish assemblages in three freshwater reservoirs in Sri Lanka. We obtained fish samples for diet analysis from three reservoirs during the months of rising water level (RIWL) and receding water level (REWL). During RIWL, peripheral areas with terrestrial/semi-terrestrial macrophytes get inundated, which resulted in increased food availability for macrophyte feeding fish. During REWL, detrital food sources increase due to decaying terrestrial plant material, which has inundated. Based on the dietary habits of individual species in the three reservoirs during RIWL and REWL, it is evident that detritivorous and phytoplanktivorous fish species, which belong to low trophic levels do not show significant variation in dietary habits between the two seasons (e.g. Oreochromis mossambicus, Oreochromis niloticus and Amblypharyngodon melettinus). Stenophagous species such as benthic invertebrate predators (Puntius chola and Puntius dorsalis), macrophytophagous species (Etroplus suratensis and Tilapia rendalli) and zooplanktivorous Hemirhamphus limbatus do not exhibit significant variation in dietary habits between seasons. Also their feeding habits do not vary with body size. Euryphagous species such as Puntius filamentosus on the other hand, exhibit variations in dietary habits between seasons as well as with body size. Stenophagous species, which feed on detritus and phytoplankton and euryphagous species, which exhibit temporal dietary plasticity, are therefore abundant in fish assemblages of these reservoirs.     

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.     

The food and feeding habits of Eutropius niloticus (Ruppell), family Schilbeidae (Osteichthyes: Siluriformes) in Lake Kainji,Nigeria

Studies on the food and feeding habits of Eutropius niloticus in Lake Kainji, Nigeria revealed that the fish is omnivorous but fed more on insects than on any other food. The most important insects were Povilla adusta Navas nymphs and imagos and adults of the common grasshoppers. Fish, particularly the clupeids Sierrathrissa leonensis Thys Van den Audernaerde and Pellonula afzeliusi Johnels, also formed an important part of the diet. There was seasonal variation of organisms selected for food and there were variations in the dietary items selected by different age groups. Accumulation of fat was found to correlate with seasonal feeding intensity. E. niloticus serves as food for other fishes.     

Diet and condition of three fish species (Characidae) of the Andean foothills in relation to deforestation

Synopsis I studied effects of deforestation on diet and condition of three characid species; Astyanax zonatus, Knodus gamma, and Prionobrama filigera in small streams in the Ecuadorian Amazon. The best condition of K. gamma was found at sites with low canopy cover, while the best condition of P. filigera was found at sites with high canopy cover. Deforestation changed population structure of A. zonatus by decreasing mean size of individuals, but this was not associated with lower fish condition. A. zonatus was omnivorous, and fed equally on invertebrate and plant food. A. zonatus increased feeding on aquatic food items (filamentous algae and fish scales) in the deforested sites (43%) compared to the forested sites (16%). K. gamma was an omnivorous species with preference for invertebrates. K. gamma was mainly feeding on terrestrial food sources in the forested sites, but switched to equal feeding between terrestrial and aquatic food sources in the deforested sites. P. filigera was an terrestrial insectivore feeder, and no differences in the overall food categories was found between stream groups. In contrast, there were no pronounced difference in the composition of invertebrate taxa in the stomachs of K. gamma between stream groups. However, less empty stomachs were observed among K. gamma in the deforested sites. The stomach contents of P. filigera showed great changes in composition of the predominating prey taxa between stream groups and less empty stomachs were observed among P. filigera in the forested sites. Food availability and utilisation seemed to be of main importance for the condition of these fish. Deforestation seems to favour species with high availability to utilise aquatic food items. In contrast, deforestation seems to have negative effects on species that are specialised on terrestrial invertebrates, and have low capacity to switch between aquatic and terrestrial food items.     

THE FEEDING HABITS OF THE WHITEWINGED BLACK TERN ON LAKE KARIBA

Bego, G. W. 1973. The feeding habits of the Whitewinged Black Tern on Lake Kariba. Ostrich 44: 149–153.

The stomach contents of 33 Whitewinged Black Terns were examined over the period 26 August 1971 to 6 January 1972. The most important single food item was the sardine, Limnothrissa miodon. This sheds new light on the habits of this fish. The terns fed primarily during calm weather. Sardines are caught by hovering and diving. Fishes of the genera Haplochromis and Synodonlis, also appeared in the stomach contents. Terns taken from marginal localities appear not to feed on fish. Of the insects eaten Odonata are the most important aquatic source of food, while many terrestrial insects are eaten (Orthoptera, Hemiptera, Coleoptera, Isoptera). Such insects could have been found drifting on mats of Salvinia on which the terns rest, otherwise insects are either hawked or skimmed from the surface of the water.     

The feeding ecology of the European Water shrew

This review examines our knowledge of the feeding ecology of the European Water shrew, Neomys fodiens. It describes and discusses the different methods which have been used to study the diets of Water shrews, from the first casual observations to the discovery of food caches and food remains in the wild, and the analysis of stomach contents and faecal pellets of trapped animals. These studies have revealed that Water shrews feed on a variety of invertebrate and vertebrate prey from tiny freshwater dip-teran larvae to sizable fish and frogs. Although aquatic prey are seen to be the major dietary component in most studies, terrestrial prey are also important and may be eaten in an equal proportion. Laboratory studies have increased our knowledge of the foraging behaviour of Water shrews but there is still much to be learnt, especially about underwater prey location.     

Egg-feeding in the freshwater piscicolid leech Cystobranchus virginicus (Annelida, Hirudinea)

Abstract. Leeches are common terrestrial and aquatic annelids, parasitizing or feeding on a wide range of host taxa. Here we report evidence for an unusual feeding behavior of egg‐feeding in the piscicolid leech Cystobranchus virginicus. We identified distended specimens of C. virginicus in the nests of at least 4 different fish species: Campostoma anomalum, Moxostoma carinatum, Moxostoma sp. (either M. anisurum and/or M. breviceps), and Nocomis leptocephalus. We collected a total of 41 leeches from the nests of these host species and documented at least 1 leech in 19 of 55 nests (35%), with many sites containing multiple leeches. Individuals of C. virginicus were not identified feeding on any of the 41 adult specimens of Moxostoma spp. or the 635 adult specimens of Nocomis leptocephalus examined, and were never found in the absence of active host spawning (26 sites). These results are consistent with individuals of C. virginicus being an opportunistic or possibly even an obligate egg‐feeder, potentially timing their own reproductive activities with the spawning of their fish hosts. The current distribution of C. virginicus has been expanded to include North Carolina, South Carolina, and Tennessee. The potential for leech species to induce mortality in developing fish eggs could be a concern for fish conservation and merits further investigation.     

The feeding habits of a group of herbivorous rock-dwelling cichlid fishes (Cichlidae: Perciformes) from Lake Malawi,Africa

Synopsis The feeding; habits of a group of tropical herbivorous rock-dwelling cichlid fishes from Lake Malawi, Africa, are investigated using stomach content analyses. The various species fed selectively on the periphyton of the rocky shores. Blue-green alga of the genus Calothrix was the most common item ingested by the group. Diatoms (Chrysophyta) also were abundant food items. Discriminant analysis showed that dietary items were good variables to identify species. Interspecific dietary differences showed a continuum from those species feeding primarily on Calothrix to those feeding primarily on diatoms. Algal resources exhibit distinct patterns of spatial variation. Diet was correlated with foraging behavior and trophic morphology. Interspecific differences in diet could possibly facilitate ecological coexistence among various species. Such coexistence would contribute to the maintenance of the high diversity fish faunas characteristic of the Great Rift Lakes of Africa.     

Interactions of Adult Stoneflies (Plecoptera) with Riparian Zones II. Diet

The diets of three species of gripopterygid stonefly adults (Acroperla trivacuata, Zelandoperla decorata and Zelandobius furcillatus) from New Zealand were investigated using field studies and laboratory experiments. Guts of female stoneflies were generally fuller than those of males, suggesting that terrestrial feeding was particularly important for females. Adult A. trivacuata and Z. decorata collected from riparian vegetation had fuller guts than those collected from rocks, indicating that adults may move towards riparian vegetation to feed after emergence. Fungi and pollen formed the core food categories found in the guts of adult stoneflies collected from riparian vegetation. Stable isotope analyses of stoneflies and potential food sources collected from the near-stream riparian zone indicated that adult body carbon was derived primarily from autochthonous sources and/or from lichen growing on exposed stream channel rocks. The absence of mature females in our near-stream field collections may explain the lack of congruence between results of gut content and stable isotope analyses, as there would be a time lag between feeding following emergence and incorporation of any terrestrial carbon into body tissue. Assays for the presence of fructose were typically negative, even though pollen and sooty mould fungi were often ingested, probably because nectar or honeydew was rapidly assimilated after ingestion. Laboratory feeding trials indicated that adult Z. decorata lived significantly longer when fed a dilute sucrose solution than when fed a yeast extract solution or water. Our results demonstrate that terrestrial food sources are consumed by these adult gripopterygid stoneflies and that feeding is important for longevity. The provision of dietary requirements for the completion of adult aquatic insect life cycles may be an important consideration in riparian vegetation management. Dietary and assimilation studies of mature females which may move deep into riparian zones are required to resolve the strength of these linkages.     

The use of integrated constructed wetlands (ICW) for the treatment of separated swine wastewaters

Haplochromine cichlids used to be the main prey of the introduced Nile perch, Lates niloticus, in Lake Victoria. After depletion of the haplochromine stocks at the end of the 1980s, Nile perch shifted to the shrimp Caridina nilotica and to a lesser degree to its own young and the cyprinid Rastrineobola argentea. In the present study, we investigated the Nile perch diet in the northern Mwanza Gulf after resurgence of some of the haplochromine species and compared it with data collected in the same area in 1988/1989. It became clear that haplochromines are again the major prey of Nile perch. The dietary shift from invertebrate feeding (shrimps) to feeding on fish (haplochromine cichlids) occurs at a smaller size than it did when Nile perch were taking primarily dagaa and juvenile Nile perch as their fish prey. The apparent preference for haplochromines as prey has reduced the degree of cannibalism considerably, which may have a positive impact on Nile perch recruitment.     

Humpback whale (Megaptera novaeangliae) and killer whale (Orcinus orca) feeding aggregations for foraging on herring (Clupea harengus) in Northern Norway

Aggregations of predators on food patches have been documented for both terrestrial and marine animals. Here, we documented for the first time, and investigated, non-predatory aggregations occurring between humpback whales (Megaptera novaeangliae) and killer whales (Orcinus orca) while feeding on wintering Norwegian spring spawning herring (Clupea harengus) in Andfjord, northern Norway. Observational data were collected during 109 opportunistic surveys through three seasons 2013–2016. Killer whales were observed feeding on 59 occasions, with one to three humpback whales involved in 47 of these feeding events (79.7%), and there was an increased probability of finding feeding humpback whales when feeding killer whales also were observed. With killer whales identified as the initiating species in 94.4% of the feeding aggregations for which the first species was known, and with humpback whales joining and feeding on the fish ball afterwards, we suggest that humpback whales may benefit more from these aggregations than the opposite.     

Feeding ecology of the critically endangered Valencia letourneuxi (Valenciidae)

Valencia letourneuxi is a critically endangered freshwater fish in urgent need of targeted conservation. Little information is however available on its life history and feeding ecology; therefore, food resource utilization by V. letourneuxi was studied in its most abundant known Greek population of Chiliadou stream. The diet of this population appears to be dominated by microcrustaceans, Dipteran larvae, Acari, and Mollusca. Its feeding is highly dependent on seasonal prey availability and diversity, with niche overlap being low only between winter and the rest of the seasons, indicating that only during winter its diet differs significantly in relation to the other seasons. There are no significant sex- and size-related dietary shifts. This V. letourneuxi population is characterized by a generalist feeding strategy and appears to consist mostly of individuals with broad niches. Its generalist feeding pattern and dietary flexibility permits it to fully exploit this very diverse and rich habitat and may account for the high local abundance of this population.     

Piscivory does not cause pansteatitis (yellow fat disease) in Oreochromis mossambicus from an African subtropical reservoir

相似文献   

Feeding Habits and Interspecific Feeding Associations of Caranx Latus (Carangidae) in a Subtropical Reef

I studied the feeding behavior and diet of the carangid jack Caranx latus in a subtropical reef at Búzios Island on the southeastern Brazilian coast. Caranx latus foraged alone or in small groups of up to three individuals during daytime employing two main feeding styles: searching for prey while swimming in mid-water and following individuals of other fish species which disturbed the substrate while foraging among the rocks. The labrid wrasse Bodianus rufus was the main fish species followed by the jack. The jack feeds on crustaceans and fishes some of which are benthic rocky bottom dwellers and are caught during following. The behavioral flexibility of C. latus enables this fish to consume both crustaceans from the water column and benthic rocky dweller fishes. There is little dietary overlap between C. latus and the followed B. rufus. The interspecific feeding associations could be regarded as advantageous for C. latus allowing access to a broader range of prey categories and increasing the food intake through the consumption of large benthic fish prey     

Food habits of fishes on an exposed sandy beach at Fukiagehama,South-West Kyushu Island,Japan

To clarify the feeding habits and major food sources of sandy beach fishes, the gut contents of 55 fish species collected on a sandy beach at Fukiagehama, South-West Kyushu Island, Japan, were examined. Ontogenetic changes in food preference were recognized in nine species (Hypoatherina valenciennei, Lateolabrax japonicus, Trachurus japonicus, Sillago japonica, Sphyraena japonica, Paralichthys olivaceus, Heteromycteris japonica, Paraplagusia japonica, and Takifugu niphobles). A cluster analysis based on dietary overlaps showed that the sandy beach fish assemblage comprised six trophic groups (mysid, amphipod, zooplankton, juvenile fish, terrestrial insect, and mollusk feeders). Of these, the first three groups were the most abundantly represented, whereas the last two were represented by only a single species. These results indicated that epibenthic macrofauna, such as mysids and gammaridean amphipods, and zooplankton, were important food resources for the fish assemblage at the study site, but infaunal macrobenthos, such as polychaetes and bivalves, being relatively unimportant.     

The influence of sulphur,molybdenum and cadmium exposure on the growth of goat,cattle and pig

A three factorial designed feeding experiment with common carp (Cyprinus carpio L.) was carried out in an intensive experimental rearing system. Fish (initial body weight 200 g) were fed on two different levels of dietary energy (16 and 18 MJ DE/kg DM), two different levels of protein (320 and 420 g CP/kg DM) and also two different feeding intensities (100% and 75% of the maximum intake). The experiment was terminated when fish reached a mean body weight of 1300 g.

Growth, feed utilization and nutrient composition of the whole body and fillet were observed. The highest growth was obtained when the fish were fed on the diet containing high dietary energy and high dietary protein with satiation feeding. High dietary energy, high dietary protein and restriction of feed intake improved feed conversion ratios. High dietary energy, low dietary protein and restrictive feeding increased energy utilization. Low dietary protein and restrictive feeding resulted in better protein utilization.

Fish fed with high dietary energy contained more fat and less protein in their carcasses. A lower fat content but higher protein and higher ash content in fish carcasses was shown when fish were fed with a diet high in protein and fed restrictively.     

Differences in the behavior and diet between shoaling and solitary surgeonfish (Acanthurus triostegus)

Variation in behavior within marine and terrestrial species can influence the functioning of the ecosystems they inhabit. However, the contribution of social behavior to ecosystem function remains underexplored. Many coral reef fish species provide potentially insightful models for exploring how social behavior shapes ecological function because they exhibit radical intraspecific variation in sociality within a shared habitat. Here, we provide an empirical exploration on how the ecological function of a shoaling surgeonfish (Acanthurus triostegus) may differ from that of solitary conspecifics on two Pacific coral reefs combining insight from behavioral observations, stable isotope analysis, and macronutrient analysis of gut and fecal matter. We detected important differences in how the social mode of A. triostegus affected its spatial and feeding ecology, as well as that of other reef fish species. Specifically, we found increased distance traveled and area covered by shoaling fish relative to solitary A. triostegus. Additionally, shoaling A. triostegus primarily grazed within territories of other herbivorous fish and had piscivorous and nonpiscivorous heterospecific fish associated with the shoal, while solitary A. triostegus grazed largely grazed outside of any territories and did not have any such interactions with heterospecific fish. Results from stable isotope analysis show a difference in δ15N isotopes between shoaling and solitary fish, which suggests that these different social modes are persistent. Further, we found a strong interaction between social behavior and site and carbohydrate and protein percentages in the macronutrient analysis, indicating that these differences in sociality are associated with measurable differences in both the feeding ecology and nutrient excretion patterns. Our study suggests that the social behavior of individuals may play an important and underappreciated role in mediating their ecological function.     

Field observation of predation on a horsehair worm (Gordioida: Chordodidae) by a diving beetle larva Cybister brevis Aubé (Coleoptera: Dytiscidae)

Diving beetles (Coleoptera: Dytiscidae) are carnivorous in both the larval and adult stages; larvae are exclusively predatory, whereas adults also scavenge for food. They are known to prey on zooplankton, insects, gastropods, fish, amphibians and reptiles. However, there have been no previous reports detailing direct predation on adult Gordioida by Dytiscidae in the field. This study represents the first observation of a diving beetle larva, Cybister brevis Aubé (Coleoptera: Dytiscidae), predating on an adult horsehair worm (Gordioida: Chordodidae). This might be the first report of predation on horsehair worms by insects.     

The diet and digestive energetics of an Australian short-necked turtle, Emydura macquarii

We described the diet of Emydura macquarii, an omnivorous turtle from south-eastern Australia, compared its digestive performance on diets of fish or plants at two temperatures, and related how both diet and temperature affect its food selection in nature. Filamentous algae constituted 61% of the stomach content of E. macquarii. The turtles rarely fed on motile prey, but selected carrion from the lagoon bottom and terrestrial insects (Diptera, Hymenoptera and Coleoptera) trapped on the surface of the water. Digestive efficiency of E. macquarii was affected little by body temperature, in contrast to consumption rates and rates of passage which were strongly influenced by both temperature and diet. In combination, these responses resulted in a slower rate of digestion at 20°C than at 30°C. Digestive efficiency of E. macquarii on a herbivorous diet at 30°C (49%) was about half that of turtles on a carnivorous diet (91%), but they had longer transit times (118 h on the plant diet versus 70 h). Lower consumption rates and longer mean retention times in turtles fed plants compared those fed fish relate to slower digestive processing of the plant. Rapid processing and higher consumption rates of fish by E. macquarii resulted in higher energy gains compared to turtles consuming plants (almost 100 times more energy at 30°C). The laboratory results suggest that fish carrion and aquatic and terrestrial invertebrates are probably essential dietary items of E. macquarii in the wild, because its metabolic requirements cannot be met from aquatic macrophytes alone.