Foraging interactions among three benthic fish in a Posidonia oceanica reef lagoon along the Tyrrhenian Coast

Three benthic predators Coris julis, Symphodus cinereus and Mullus surmuletus in a Posidonia oceanica reef lagoon of the Tyrrhenian coast had a broad diet, including hard-bodied invertebrates such as crustaceans and molluscs, but revealed consistent interspecific differences. Diet overlap was greater between C. julis and M. surmuletus in comparison to other combinations. All three species were diurnal feeders, but with diVerent daily patterns of foraging based on diVerent prey availability. There was a general spatio-temporal correlation in non-foraging activity among the three species, but foraging activity was correlated only between C. julis and the other two species, but not between S. cinereus and M. surmuletus .There was heterospecific aggregation during foraging between C. julis and M. surmuletus , and possibly a scrounger–producer relationship between them. Fights between C. julis specimens related to foraging activity were common, but not between species. These results support the view that diVerences in spatio-temporal organization of activity, and interactions during foraging, can contribute to resource partitioning among syntopic populations of fish belonging to the same trophic group.     

Behavioural response of Mullus surmuletus to habitat modification by the invasive macroalga Caulerpa taxifolia

Densities of red mullet Mullus surmuletus have declined since 1996 at Cap Martin, Alpes‐Maritimes, France, following colonization by Caulerpa taxifolia . Foraging M. surmuletus were rarely observed over C. taxifolia or the seagrass Posidonia oceanica , but were observed over bare sand and endemic macroalgae. Within colonized sites (where the mean cover of C. taxifolia was 30–100%), fish were concentrated on areas with low cover of C. taxifolia (<21%). A difference in the frequency of observations of foraging groups (17%) was observed between sites with and without C. taxifolia . The observed patterns were probably due to a physical barrier to foraging that is presented by meadows of C. taxifolia . Changes to habitat structure that occur when the substratum is colonized by C. taxifolia influence the accessibility to benthic food resources, and consequently the foraging activities of fish that feed on benthic invertebrates. The decline in density of M. surmuletus at Cap Martin could be the result of fish emigration from colonized sites (unfavourable to the species) to uncolonized sites.     

Niche separation between colonizing and indigenous goatfish (Mullidae) along the Mediterranean coast of Israel

The present study assesses the resource partitioning between two Red Sea colonizers, the goldband goatfish Upeneus moluccensis and the brownband goatfish U. pori , and the two indigenous Mediterranean goatfishes, the red mullet Mullus barbatus and the striped mullet M. surmuletus , along the Mediterranean coast of Israel.
Niche separation was studied along three axes: habitat selection, feeding habits and spawning season. Habitat selection is the most significant parameter separating the species. The two colonizing species occupy a shallow habitat, U. pori dominating the primarily sandy bottom at 20–30 m and U. moluccensis at 40–50 m, at which depth the sea bottom becomes increasingly silty. Of the two indigenous species, M. barbatus is dominant in depths below 55 m, while M. surmuletus appears at low abundance in all depths.
Niche separation by feeding habits is much less evident. All four species feed primarily on macrurid crustaceans and thus the values of diet overlap are rather high (0·666≤ T ≤0·928). Prey size is not an important factor in niche separation. Young fishes (S.L>,115 mm) of all four species feed upon prey of similar size (20–160 mg). Among older individuals (S.L.>115 mm) three species continue to feed upon the same size prey, while U. moluccensis feeds upon considerably larger prey (600–2200 mg).
The difference between the spawning seasons of the colonizing vs indigenous species and consequent timing of benthic settling may contribute to niche separation.
The results of this study suggest that success in colonization by Red Sea goatfish may be due to the existence of unexploited niches in the eastern Mediterranean ecosystem.     

Food niche variation of European and American mink during the American mink invasion in north-eastern Belarus

Understanding processes allowing the co-existence of ecologically similar species is important but difficult to study in community ecology. Introductions of alien species are unplanned experiments allowing investigation of co-adaptation of both native and invasive species over a short period. We analysed food niche differentiation between native European mink and alien American mink after invasion of the latter species in Belarus. European mink feed mainly on crayfish, frogs and fish whereas American mink prefer small mammals, fish and frogs. The diet of both species varied between seasons and during the period of alien mink invasion. Concurrent with the progress of American mink invasion, the European mink food niche has narrowed to feeding mainly on frogs, with the proportion of aquatic prey (fish and crayfish) in their diet drastically reduced. In contrast, the American mink food niche became wider during invasion. The breadth was stable but included a varied proportion of different prey categories: namely an increased proportion of aquatic prey and a decreased proportion of water vole and waterfowl. The increase in abundance of American mink saw a decrease in the proportion of larger prey in their diet. When American mink preyed more often on frogs, food niche overlap of both predators increased. This result suggests that arrival of an alien competitor reduced food abundance (exploitative competition) and caused a change in native mink diet.     

Diel feeding habits of juveniles of Mullus surmuletus (Linneo 1758) in the lagoon of the Stagnone di Marsala (Western Sicily, Italy)

Diet composition, feeding rhythm, gastric evacuation rate and daily ration were investigated in juvenile Mullus surmuletus (Linneo 1758). Fish were collected in the lagoon of the Stagnone di Marsala in western Sicily, in July 1995, during a 24 h sampling period. Copepoda, Polychaeta, Amphipoda and Tanaidacea were shown to be the most frequent prey items. The feeding index values showed two different daily feeding times. A unimodal trend in the daily rhythm of food consumption was derived, with a peak in feeding between 1200 and 2000 h. Gastric evacuation in juvenile M. surmuletus is best described by an exponential model, with a gastric evacuation rate R  = 0.66 g h⁻¹ ( r = 0.88) ( T  = 24.45 ± 0.64°C). The amount of food consumed daily, calculated according to the Elliott and Persson model, was 0.079 g, equal to about 8% of the average dry weight of the fish.     

Ecomorphological comparisons of sagittae in Mullus barbatus and M. surmuletus

For both Mullus barbatus and M. surmuletus , the relationship between sagitta area (O), sulcus acusticus area (S) throughout postlarval growth was characterized by their negative allometric growth. The adjusted mean S: O ratio differed between the two species. This may be associated with the difference in size and shape of the sagittae, a difference in somatic growth, and differences in food and spatial niches. The inner ear of Mullus cannot be considered as specialized and the interaction of stimuli detected by the sensory barbels and the inner ear together could be a compensatory mechanism that helps in the food search.     

山东近海三种底层鱼类的摄食生态与食物竞争

研究根据2016—2017年在山东近海进行的四个季节的渔业资源底拖网调查和胃含物分析数据, 应用分类树和生态位重叠指数法等, 研究了该海域高眼鲽(Cleisthenes herzensteini)、黄鮟鱇(Lophius litulon)和小眼绿鳍鱼(Chelidonichthys spinosus)3种主要底层鱼类的食物组成及其营养-空间二维生态位的重叠情况, 并分析环境因素对其摄食习性的影响, 旨在为该海域渔业资源的可持续利用和科学管理提供基础资料。研究发现, 这3种底层鱼类均主要以虾类和鱼类为食, 属于底栖动物食性。3种鱼类的摄食习性存在一定的差异, 可以通过构建分类树将其进行区分。通过CCA分析发现, 这3种鱼类的摄食习性受不同的环境因素影响, 其中高眼鲽的摄食习性主要与其体长有关, 随着体长的增加, 高眼鲽会摄食更多的鱼类和虾类; 小眼绿鳍鱼的摄食主要与季节有关, 不同季节小眼绿鳍鱼摄食鱼类和虾类的比例不同; 而黄鮟鱇的摄食主要受空间分布的影响, 高纬度的黄鮟鱇摄食更多的虾类, 而随着经度的增加, 黄鮟鱇会摄食更多的鱼类。黄鮟鱇的营养生态位和空间生态位宽度均最高, 而其余两种鱼的营养和空间生态位宽度相对较小。山东近海这3种鱼类的营养生态位重叠指数都较高, 但是空间生态位重叠指数较小, 在一定程度上可以缓和它们之间的种间竞争。     

An experimental study of body size and food size relations in crucian carp,Carassius carassius

Synopsis In dense, single-species assemblages of crucian carp, competition is intense and results in populations of stunted fish. To explore mechanisms underlying this competition, we measured handling times, return rates, and prey choice for five sizes of crucian carp feeding on six sizes of a standardized food. Handling times increased with prey size and decreased with fish size. Return rates (dry mass ingested per unit handling time) increased dramatically with fish size, and generally decreased with increasing prey size, especially for small fish. Patterns of return rates among size-classes suggested that one or more size-related shifts in feeding efficiency exist for crucian carp; combined with physiological stresses related to winter anoxia, the inability of fish to make these shifts may contribute to size structures observed in high-density populations. Comparisons of relations among fish size, prey size, and return rates for crucian carp and bluegill, Lepomis macrochirus, suggest that similar intraspecific competitive relations exist between generalist species with size-structured populations. Despite differences in return rates among prey sizes, the extent of food selectivity based on prey size exhibited by crucian carp in two types of choice trials was less than predicted. Crucian carp commonly take in several items before mechanically processing food with their pharyngeal apparatus; this multiple prey processing may contribute to disparities between observed choice patterns and those predicted based on return rates for single prey.     

Food partitioning among carnivores within feeding guild structure of fishes inhabiting a mudflat ecosystem of Indian Sundarbans

The present study was aimed to determine dietary composition and feeding guild structure of the fishes inhabiting mudflat habitat of Indian Sundarbans. In addition, partitioning of food resources by the fish species belonging to the carnivorous feeding guild was also performed to understand the survival strategies of fish in a mudflat estuarine habitat. Seventeen prey categories were isolated from the stomachs of 31 studied fish species. Overall, five feeding guilds (viz. plankti-benthivore: 12 species, herbivore: one species, detritivore: three species, omnivore: one species and carnivore: 14 species) were identified on the basis of the prey abundance within their stomachs, considering 64 % Bray–Curtis similarity. Among the carnivorous, maximum trophic richness was obtained for Uroconger lepturus followed by Ophichthus apicalis. Teleost and decapods were the main animal prey items preferred by majority of the carnivorous fishes. However, O. apicalis and Terapon jarbua showed their preference toward maximum number of prey categories among carnivores, which was also ratified by the high values for standardized niche breadth presented by them. The maximum degree of interspecific dietary overlap was found between Uropterygius marmoratus and Pseudapocryptes elongatus as both of them were recognized as cranci-piscivore. The lowest was observed between Hyporhamphus limbatus and Coilia neglecta. As food resources are not limiting in the mudflats of Indian Sundarbans, the general patterns of resource partitioning and niche differentiation in resident ecological communities will improve the understanding of the mechanisms underlying species coexistence and community structure.     

The food, feeding habits and feeding structures of the whiting species Sillago sihama (Forsskål) and Sillago analis Whitley from Townsville, North Queensland, Australia

The diet, feeding habits and feeding structures of 519 Sillago sihama and 493 S. analis specimens collected from beaches and estuaries in the Townsville region are described. The species are carnivores on a wide range of benthic, epibenthic and planktonic prey. Both undergo size related dietary shifts; S. sihama from predominantly planktonic crustaceans in fish of less than 80 mm t.l . to polychaetes, penaeid and brachyuran crustaceans and molluscs at larger sizes; S. analis from a mixture of small Mesodesma eltanae and amphipods at sizes of less than 80 mm t.l . to predominantly M. eltanae and small quantities of penaeids and brachyuran crabs in larger fish. The dietary shift was not associated with migration from a nursery area.
While the species showed considerable overlap in the types of prey utilized, there were significant differences in the relative importance of shared components in their diets. The major difference was in the relative importance of the bivalve mollusc, M. eltanae. This was the dominant food of S. analis but of secondary importance in S. sihama. Associated with this basic difference in diet was a specialization of the pharyngeal dentition in S. analis to molariform crushing plates and a reduction of the gill rakers to vestigial knobs. In S. sihama , the pharyngeal teeth are sharp and pointed and the gill rakers normal.
The feeding activity of S. analis , but not S. sihama , is limited by the tidal cycle, a factor which may be a form of temporal partitioning.     

Diet, food resource partitioning and feeding periodicity of two riffle-dwelling fish species in a New Zealand river

The diets and feeding periodicities of two small, riffle-dwelling fish, the torrentfish, Cheimarrichthys fosteri , and the bluegilled bully, Gobiomorphus hubbsi , were investigated in an unstable, braided New Zealand river from May 1985 to April 1986. Aquatic insect larvae dominated diets of all fish and dietary overlap between species was high in 10 of 12 months. Nevertheless, the relative importance of prey items, as assessed by the index of relative importance (IRI), differed between species. Gobiomorphus hubbsi fed almost exclusively on larval Deleatidium (Ephemeroptera), whereas C. fosteri consumed a greater variety of prey items, with Deleatidium and trichopteran, elmid and chironomid larvae numerically dominant. A dietary switch from Deleatidium to chironomid larvae occurred in both species during December 1985, when total and relative abundances of mayfly and other benthic macroinvertebrate larvae were severely reduced by two consecutive floods. A diel sampling programme indicated that the feeding periodicity of the two species differed: C. fosteri was a nocturnal feeder, whereas G. hubbsi exhibited a strong crepuscular peak in feeding activity. Overall, the two fish partition their food resource weakly by consuming prey items in different proportions and sizes and more strongly by utilizing the food resource at different times.     

Feeding habits and diet overlap of marine fish larvae from the peri-Antarctic Magellan region

The Magellan region is a unique peri-Antarctic ecosystem due to its geographical position. However, the knowledge about the distribution and feeding ecology of fish larvae is scarce. Since this area is characterized by low phytoplankton biomass, we hypothesize that marine fish larvae display different foraging tactics in order to reduce diet overlap. During austral spring 2009–2010, two oceanographic cruises were carried out along southern Patagonia (50–56°S). Larval fish distribution and feeding of the two most widely distributed species were studied, the smelt Bathylagichthys parini (Bathylagidae) and black southern cod Patagonotothen tessellata (Nototheniidae). Larvae of B. parini showed a lower increase in the mouth gape at size, primarily feeding during daytime (higher feeding incidence during the day) mostly on nonmotile prey (invertebrate and copepod eggs, appendicularian fecal pellets, diatoms). They showed no increase in feeding success (number, total volume of prey per gut and prey width) with increasing larval size, and the niche breadth was independent of larval size. Larvae of P. tessellata showed a large mouth gape at size, which may partially explain the predation on motile prey like large calanoid copepods (C. simillimus) and copepodites. They are nocturnal feeders (higher feeding incidence during night) and are exclusively carnivorous, feeding on larger prey as the larvae grow. Nonetheless, niche breadth was independent of larval size. Diet overlap was important only in individuals with smaller mouth gape (<890 μm) and diminished as larvae (and correspondingly their jaw) grow. In conclusion, in the peri-Antarctic Magellan region, fish larvae of two species display different foraging tactics, reducing their trophic overlap throughout their development.     

Food habits and trophic status of Limanda sakhalinensis (Pleuronectidae) on the western Kamchatka shelf in the summer period

Based on materials of expeditions of TINRO-Center on the western Kamchatka shelf in July 2005, 2008, and 2010, we analyze data on feeding of Sakhalin flounder. Sakhalin flounders are consumers of euphausiids, copepods, amphipods, polychaetes, and juvenile fish. The calculated values of the trophic levels are 3.58–3.95. Consumption of maturing and mature Sakhalin flounder primarily plankton prey leads to divergence of ecological niches with morphologically close yellowfin sole, extends prey species, and apparently provides the basis for the dominance of the western Kamchatka shelf community. Mature and maturing Sakhalin flounders feed predominantly on plankton prey, which leads to a divergence of their ecological niche with morphologically close yellowfin sole and expanding food supply and apparently is the basis of the dominance of flatfish community of the western Kamchatka shelf.     

Food niche overlap and ecological separation in a multi-species community of shrews in the Siberian taiga

An investigation of the feeding habits and prey availability in a community of seven species of shrew (Insectivora: Soricidae) inhabiting the taiga of Central Siberia was carried out with the aim of quantifying levels of niche overlap and elucidating modes of ecological separation amongst these coexisting species. All species took a wide range of invertebrate prey, and overlap in the numbers of shared prey taxa was high, but differences in dietary composition of certain taxa reduced overlap between most species. Small species fed almost exclusively on small arthropods, mostly Araneae, Chilopoda and Coleoptera, while medium and large-sized species took high proportions of oligochaetes. Prey were mostly taken in proportions approximately equal to their availability, although certain prey appeared to be selected. All shrews took prey in a range of sizes, and the high dietary occurrence of small invertebrates reflected their availability and high encounter rate in field samples. Dietary occurrence of small prey was negatively correlated, and large prey positively correlated, with body size of shrew. Smaller shrews were predominantly ground-surface foragers while larger species were more subterranean, with body size and dietary occurrence of soil prey being positively correlated. Differences in prey size and foraging mode reduced niche overlap between shrew species of widely differing sizes. Each shrew species did not occupy a separate, well-defined food niche. Instead, the community was sub-divided into three functional groups: large and small species which tended towards specialization with relatively low levels of overlap, and intermediate, generalist species with higher levels of overlap.     

Trophic ecology of the emerald notothen <Emphasis Type="Italic">Trematomus bernacchii</Emphasis> (Pisces,Nototheniidae) from Terra Nova Bay,Ross Sea,Antarctica

The trophic ecology of the emerald notothen Trematomus bernacchii was investigated using a sample of 284 specimens collected in the coastal waters of Terra Nova Bay (Ross Sea) during the summer season 1990–1991. The stomach-content analysis provided data on feeding habits and trophic niche breadth. Overall, 72 taxa of food items were identified; the most important as prey were infaunal and epifaunal polychaetes, amphipods and molluscs. Food of secondary importance comprised isopods, pycnogonids, fish and fish eggs. Several other taxa, such as euphausiids, mysids, decapods, echinoids, holothurians, priapulids and thaliaceans constituted food eaten in very small amounts and only occasionally. On the basis of their diet, T. bernacchii can be considered generalized feeders, with a wide niche breadth composed almost exclusively of benthic organisms. A cluster analysis was conducted to compare stomach-content data of subsamples selected on the basis of fish size and sampling depth, aiming to determine diet diversity and niche breadth, as well as factors involved in reducing intraspecific competition for food resources. Diet was different for fish sampled in shallow (90 m depth) and deeper waters (>90 m depth): while the first group fed mostly on bivalves (Adamussium colbecki) and amphipods, the latter preferred infaunal-epifaunal polychaetes. Conversely, fish size did not contribute significantly to diet diversification. According to our data and published data on feeding behaviour and sensory ecology, we conclude that in this species the intraspecific competition for food is reduced, either through habitat heterogeneity or different foraging strategies.     

Carnivorous and detritivorous feeding of Mesocyclops leuckarti Claus (Cyclopoida Copepoda)

Food preference of M. leuckarti was experimentally analysed in relation to different species of live and dead crustaceans. Also their possibility of using detritus from bottom sediments as a source of food was tested.It has been found that M. leuckarti readily feed on dead organisms, and detritus from bottom sediments is sufficient for their survival.On the basis of experimental results the feeding strategy of M. leuckarti in lakes is discussed. It seems that the availability of different species of live prey depends on the mode of their swimming and on their body cover, while the availability of dead prey depends only on the body cover. Detritus may be an important source of food, particularly when the live prey are scarce in the pelagic zone, or not easily available.     

Trophic complexity of small fish in nearshore food webs

Small nearshore fishes are an important part of lacustrine and functional diversity and link pelagic and benthic habitats by serving as prey for larger nearshore and offshore fishes. However, the trophic complexity of these small nearshore fishes is often unrecognized and detailed studies of their role in food webs are lacking. Here, we examined niche space patterns of small nearshore fish species using Bayesian analyses of carbon and nitrogen stable isotope data in nine freshwater lakes that are among the largest lakes in Minnesota. We found considerable variability in niche areas within species and high variability in niche overlap across species. At the assemblage level, niche overlap (average diet overlap of all species pairs at a lake) decreased as whole-lake species richness increased, possibly indicating a greater degree of resource specialization in more speciose lakes. Overall fish niche space was weakly but significantly related to niche space of their invertebrate prey. Although nearshore benthic resources contributed to fish diets in all lakes, all fish species also had non-negligible and variable contributions from pelagic zooplankton. This inter- and intraspecific variability in trophic niche space likely contributes to the multi-level trophic complexity, functional diversity, and potentially food web resilience to ecosystem changes.

     

Feeding ecology of the endangered Valencia toothcarp,Valencia hispanica (Actinopterygii: Valenciidae)

Patterns of food resource utilisation by Valencia toothcarp were studied in a small coastal lagoon in the Iberian Peninsula, its most northern population. Emphasis was placed on feeding activity, diet composition, seasonal and intraspecific variation in diet and feeding strategy. Important features of the overall feeding pattern of the Valencia toothcarp are decreased feeding activity during winter, concentration on benthic invertebrates and narrow dietary breadth, with a focus on gammarid amphipods. The feeding of V. hispanica was independent of seasonal variation in food availability, because its main prey were much the same throughout the year. There were no differences in seasonal niche width and niche overlap between seasons was high. There are also no differences in diets between sexes, although diet composition, niche width and niche overlap differ between juvenile and adult fish. The Valencia toothcarp population from Santes Creus lagoon was formed by specialist individuals, with narrow niche widths, that fed on four preferential prey types, but also consumed some occasional prey.     

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.