Food habits of the sandpaper skate, Bathyraja kincaidii (Garman, 1908) off central California: seasonal variation in diet linked to oceanographic conditions

The stomachs of 130 sandpaper skates, Bathyraja kincaidii (Garman, 1908), were sampled from off central California to determine their diet composition. The overall diet was dominated by euphausiids, but shrimps, polychaetes and squids were also important secondary prey. A three-factor MANOVA demonstrated significant differences in the diet by sex, maturity status and oceanographic season using numeric and gravimetric measures of importance for the major prey categories. These three main factors explained more variation in diet than interactions between the factors, and season explained the most variance overall. A detailed analysis of the seasonal variation among the prey categories indicated that abundance changes in the most important prey, euphausiids, were coupled with seasonal changes in the importance of other prey. When upwelling occurred and productivity was great (Upwelling and Oceanic seasons), euphausiids were likely highly abundant in the study area and were the most important prey for B. kincaidii. As productivity declined (Davidson Current season), euphausiids appeared to decrease in abundance and B. kincaidii switched to secondary prey. At that time, gammarid amphipods and shrimps became the most important prey items and polychaetes, mysids and euphausiids were secondary.     

Feeding habits of ocellate spot skate,Okamejei kenojei (Müller & Henle, 1841), in coastal waters of Taean,Korea

The feeding habits of Okamejei kenojei were studied using 592 specimens collected in the coastal waters of Taean, Korea from April 2008 to March 2009. O. kenojei is a bottom‐feeding carnivore that consumes mainly shrimp, fishes, and crabs. Its diet also includes small quantities of amphipods, mysids, cephalopods, euphausiids, copepods, isopods, and polychaetes. The total length (TL) of individuals in this study ranged from 8.2 to 49.0 cm. Cluster analysis based on %IRI (index of relative importance) identified three size classes. Group A (< 20 cm TL) ate primarily caridean shrimp and amphipods; group B (20–30 cm TL) ate exclusively shrimp; and group C (> 30 cm TL) ate penaeoidean shrimp, fishes, and crabs. O. kenojei showed ontogenetic changes in feeding habits. Although shrimps were the primary food consumed by all size groups, the proportion of shrimp in the total diet decreased and the consumption of fishes and crabs gradually increased with the body size of O. kenojei. Size of the prey organisms also increased. Smaller individuals fed mainly on small prey, such as amphipods, mysids, and small shrimp, whereas larger individuals preferred larger prey, such as larger shrimp, fishes, and crabs. The size‐related diet breadth and the percentage of empty stomachs were significant; the diet breadth gradually increased with body size, whereas the percentage of empty stomachs decreased. Seasonal changes in the O. kenojei diet were not significant, but shrimp constituted 97.3% of the summer diet by %IRI. Seasonal changes in diet breadth and the percentage of empty stomachs were not significant.     

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.     

Diet composition of the Persian sturgeon <Emphasis Type="Italic">Acipenser persicus</Emphasis> at the coast of the Guilan Province,Caspian Sea

Sturgeons are one of the most important and valuable species in the Caspian Sea. This investigation (2000–2002) was aimed at determining the feeding habits and the main and secondary prey organisms consumed by the Persian sturgeon (Acipenser persicus Borodin, 1897) living at depths less than 10 m in the Caspian Sea (Guilan Province). The food spectrum of immature A. persicus was comprised of benthic invertebrates of seven genera and fishes of three genera. The main prey items of immature A. persicus were polychaete worms and the secondary prey were crustaceans. The study of stomach contents showed that polychaetes were the most important component of the diet of immature A. persicus of the length class up to 25 cm.     

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.     

Partitioning of food resources among Sillago japonica, Ditremma temmincki, Tridentiger trigonocephalus, Hippocampus japonicus and Petroscirtes breviceps in an eelgrass, Zostera marina, bed

We carried out dietary analysis on five numerically abundant fishes, Sillago japonica, Ditremma temmincki, Tridentiger trigonocephalus, Hippocampus japonicus and Petroscirtes breviceps in an eelgrass bed in Kwangyang Bay, Korea. Comparisons between species demonstrated that the dietary composition of each fish species was significantly different from that of every other species. Although gammarid amphipods and caprellid amphipods were consumed by all species, their individual contributions to each species' diet varied. Furthermore, polychaetes contributed to the diets of S. japonica and T. trigonocephalusand crab larvae were consumed byD. temmincki. Algae and eelgrass were not consumed by four fish species and made only a minimal contribution to the diet of P. breviceps. The diet of each fish species except H. japonicus underwent size-related changes; smaller fishes consumed gammarid amphipods, mysids and copepods, while larger fishes ate polychaetes, gastropods, isopods and other fishes. Differences in the prey organisms consumed of each individual species could be often related to differences in mouth length and width. S. japonica, D. temmincki, T. trigonocephalus, and P. breviceps underwent also a significant diel changes that could be related to differences in foraging behavior and/or prey availability. Thus, use of vision to detect prey would account for the greater daytime consumption of copepods by S. japonica and of crab larvae by D. temmincki, whereas the nocturnal emergence of gammarid amphipods, polychaetes and isopods from the substrate explained their greater consumption by S. japonica, D. temmincki, T. trigonocephalusand P. breviceps at night. Dietary breadth was greater for species with larger mouth dimensions.     

Prey selection by flounder, Platichthys flesus, in the Douro estuary, Portugal

Prey selection by the flounder, Platichthys flesus (Linnaeus, 1758), in an estuarine nursery was investigated and the major factors influencing food choice by this species were assessed. Diet breadth was narrow, reflecting the low prey diversity observed in the benthos. A gradual ontogenetic shift from small prey such as amphipods to larger prey like polychaetes and bivalves was observed. Amphipods had positive electivity values in the upper estuary and negative values in the lower estuary.Polychaetes showed the inverse pattern. Bivalve electivity values were always positive. Differential selectivity throughout the estuary was mainly related to spatial segregation of flounders according to size, with the smaller individuals concentrating in the upper estuary and larger individuals concentrating in the lower estuary. Amphipods such as Corophium spp. play a crucial role in the flounder diet because of their small size, low mobility and diel activity pattern. As prey, the polychaete value increases throughout flounder ontogeny since the flounder size range is compatible with the larger mouth gapes and detection ability of larger fish. Bivalve electivity values for flounder are mainly related to high calorific values. The absence of Crangon crangon (Linnaeus, 1758) in the diet may be due to low water temperature since the cost–benefit involved in the capture of highly mobile prey is too high at low temperatures. It was concluded that flounder must use several sensory features to detect and capture prey in turbid estuarine waters and that field studies provide important background information on the actual predator preferences under natural conditions.     

Diet overlap among flatfish species in the southern North Sea

The diets of two non-commercial flatfish species (solenette Buglossidium luteum and scaldfish Arnoglossus laterna) and two commercial flatfish species (dab Limanda limanda and plaice Pleuronectes platessa) were compared in a study area in the German Bight (southern North Sea) to investigate prey-resource partitioning between these species. The diets of A. laterna and B. luteum mainly comprised crustaceans (harpacticoids, amphipods, cumaceans and decapods), whereas the diet of L. limanda and P. platessa consisted mainly of polychaetes. The Schoener index, calculated for different fish size classes between these flatfish species, showed a biologically significant diet overlap between small-sized L. limanda and P. platessa and B. luteum and A. laterna, using similar prey resources of smaller prey (e.g. amphipods, harpacticoids and juvenile bivalves). In contrast, with increasing body size, a change in the diet of L. limanda and P. platessa towards larger prey occurred (e.g. polychaetes and decapods), resulting in low diet overlap values with B. luteum and A. laterna. Due to these size-related differences in resource use, it is assumed that there is reduced interspecific competition for prey between larger L. limanda and P. platessa and both non-commercial flatfishes, probably facilitating resource partitioning within the same area. In contrast, smaller L. limanda and P. platessa may compete directly for the same prey resources with B. luteum and A. laterna. Furthermore, prey availability of most important prey items of the studied flatfishes was relatively low in the study area. Therefore, increasing abundances of B. luteum and A. laterna in the southern North Sea since the late 1980s, owing to fishing effects and climate change, might affect the population dynamics of L. limanda and P. platessa.     

Comparative Feeding Ecology of Two Sympatric Greenling Species, <Emphasis Type="Italic">Hexagrammos otakii</Emphasis> and <Emphasis Type="Italic">Hexagrammos agrammus</Emphasis> in Eelgrass <Emphasis Type="Italic">Zostera marina</Emphasis> Beds

Synopsis Feeding ecology was compared between sympatric greenling species, Hexagrammos otakii and H. agrammus in the eelgrass beds in Jindong Bay, Korea, from January to December. These two species had similar diets composed of crustaceans, polychaetes, gastropods and fishes; both species consumed primarily crustaceans throughout study periods. H. otakii, however, fed a greater proportion of polychaetes and fishes than H. agrammus. H. agrammus had a greater proportion of gastropods in their diets. The diet of both species underwent size-related changes; smaller individuals of H. otakii and H. agrammus consumed amphipods (gammarid amphipods and caprellid amphipods), while larger individuals of H. otakii ate polychaetes and fishes and those of H. agrammus fed mainly on gastropods and crabs. The diet of H. otakii underwent seasonal changes; H. otakii consumed mainly polychaetes and fishes during January and February 2002 but amphipods during March and May 2002. H. agrammus, however, ate mainly gastropods and crabs all seasons. H. otakii underwent also a significant diel changes that could be related to difference of prey availability. Thus the nocturnal emergence of gammarid amphipods, polychaetes and fishes explained their greater consumption by H. otakii. Dietary breadth of both species was lower in the smallest individuals (<5 cm SL) and in March and April 2002. This was due to the disproportionate dry mass attributable to the consumption of amphipods by both H. otakii and H. agrammus. Dietary overlap of both species was relatively moderate to high, in particular in <9.9 cm SL (0.62 – 0.71) from May to July 2002 (0.63 – 0.71). This is coincident with higher abundances of crabs, caridean shrimps and polychaetes in the study area, and it was assumed that these prey species were not limited resources. Higher dietary overlap was correlated with an abundance of a shared resource and did not indicate the interspecific competition between H. otakii and H. agrammus.     

Diet selectivity of juvenile blue crabs (Callinectes sapidus) in Chesapeake Bay

Shallow coves in Chesapeake Bay have abundant food and serve as nursery grounds for juvenile blue crabs. In this study, we examined the relationships between the diet of very small (4-40?mm CW) juvenile blue crabs and the benthic infauna in shallow, unvegetated nursery coves. We compared infauna in benthic samples with gut contents of juvenile blue crabs from six shallow coves in each of two sub-estuaries (Rappahannock and York Rivers) in Chesapeake Bay, Virginia, USA. Benthic communities differed depending on river and location, with abundant clams in upriver regions and abundant polychaetes in downriver regions. Juvenile crabs, like adults, appeared to be opportunistic feeders, with gut contents including clams, amphipods, polychaetes, small crustaceans, plant matter, and detritus. There was a positive relationship between polychaetes in the benthic samples and in crab guts, suggesting that juvenile crabs are opportunistic feeders on polychaetes in the benthos. Moreover, Ivlev's electivity index and foraging ratio showed that clams and polychaetes were selectively eaten at all locations. Alternatively, crabs selectively rejected amphipods. Crab densities corresponded positively with polychaete densities, which suggests that there may be bottom-up control of crab distributions and that food resources are important in nursery habitats.     

Diet of the Antarctic starry skate Amblyraja georgiana (Rajidae, Chondrichthyes) at South Georgia (Southern Ocean)

Stomach contents were identified from 206 Antarctic starry skate (Amblyraja georgiana) that were collected during three groundfish surveys (September 2007, April 2008 and January 2009) at South Georgia, Southern Ocean. The diet of A. georgiana varied with skate size and between years. Preferred prey included fish (particularly for larger individuals) and Antarctic krill, Euphausia superba, as well as amphipods, polychaetes and other benthic fauna. The skate A. georgiana appears to be an opportunistic predator, and the clear presence of Antarctic krill in this demersal predator’s diet may indicate a benthic habit of this euphausiid species, which has hitherto mainly been considered as occupying a purely pelagic niche.     

Variation of diet and food consumption of the scaldfish Arnoglossus laterna(Walbaum, 1792)

Although Arnoglossus laterna (Walbaum, 1792) is a common benthic fish in Portugal, several aspects of its feeding ecology remain incomplete. In this study, diet was examined and the food consumption estimated on inshore waters in the central coast of Portugal. The diet of the scaldfish included mainly mysids, amphipods and polychaetes, while the decapod Philocheras bispinosus Hailstone was the most frequent prey. Variation in the diet according to fish size (two size‐classes), sex and spawning/non‐spawning seasons was examined. Significant differences in diet composition were found between seasons, whereby the most frequently consumed prey in the non‐spawning season were crustaceans, while polychaetes and nemerteneans comprised most of its diet in the spawning season. The average value of the vacuity index was very similar between seasons (24.7% non‐spawning season and 25.0% spawning season). Diet overlap between size‐classes and sexes was high, but low between the two seasons. Food consumption of A. laterna was estimated based on diet characterization and evacuation rate. The estimate of the daily food consumption was 1.15 mg dry weight for the non‐spawning season and 1.67 mg dry weight for the spawning season. Significant differences in consumption rates were found between size‐classes and sexes. Larger individuals showed a higher consumption rate than smaller individuals. Females consumed more food than males in the non‐spawning season, while in the spawning season males consumed more than females.     

Feeding ecology of the Bay Goby (Pisces: Gobiidae). Effects of behavioral,ontogenetic, and temporal variation on diet

The ontogenetic, diel, seasonal, and yearly variations in gut fullness, diet, and prey diversity for a California estuarine gobiid (Lepidogobius lepidus Girard) were examined. Also the feeding behavior of this species was described.Small (<50 mm, SL) and large (? 50 mm, SL) gobies consumed similar prey types in different proportions. Major prey items were polychaetes, harpacticoid copepods, gammarid amphipods, molluscs, and other crustaceans. Diets of large and small gobies were not significantly correlated, and larger fish had a more diverse diet. Small fish fed at all times while larger gobies fed primarily at night. Changes in diet may be related to differential prey preferences, feeding chronologies, and increases in fish size.Both large and small gobies displayed seasonal differences in diet and prey diversity. Year-to-year changes in diet also were noted for both size classes. The bay goby uses different feeding behaviors to capture sedentary and motile prey and appears to forage opportunistically. This behavior is probably advantageous in an environment which fluctuates drastically.     

The contrasting diet of Harpagifer antarcticus (Notothenioidei, Harpagiferidae) at two localities of the South Shetland Islands, Antarctica

The diet of Harpagifer antarcticus was studied at two localities of the South Shetland Islands, Antarctica. The analysis of the stomach contents of specimens collected in tide pools at Potter Cove, King George Island, indicated that gammarid amphipods (mainly Gondogeneia sp.) were the main prey of this fish, followed by polychaetes, gastropods and isopods. By contrast, the specimens from Harmony Point, Nelson Island, which were recovered from stomach contents of Antarctic shags Phalacrocorax bransfieldensis feeding at depths of 46–110 m, preyed almost exclusively on the Antarctic krill Euphausia superba. These results are discussed and compared with previous studies. Received: 27 August 1997 / Accepted: 17 November 1997     

On the diet of the rock sole <Emphasis Type="Italic">Lepidopsetta polyxystra</Emphasis> off the eastern coast of the northern Kuril Islands and the southern extremity of Kamchatka

The bulk of diet of the rock sole Lepidopsetta polyxystra in waters of the eastern coast of the northern Kuril Islands and the southern extremity of Kamchatka from September to October 1997 was formed by polychaetes and amphipods (36.8 and 35.1% of the food bolus weight, respectively), which is typical of the feeding of this species, on the whole. The dominant consumption by L. polyxystra of polychaetes is recorded from February to June and of amphipods, from August to December. Polychaetes dominated in the diet of individuals with a length of 16–45 cm and amphipods, in the diet of individuals 46–55 cm long. The feeding migration of L. polyxystra in the study area took place at sites with an increased biomass of the accessible food benthos.     

On the food of the European eel, Anguilla anguilla (L.), in the upper zone of the Tagus estuary, Portugal

The estuarine food habits of the European eel, Anguilla anguilla (L.), in the upper zone of the Tagus estuary have been studied through the analysis of 210 specimens collected during 1988. Eels, measuring from 136 to 627 mm in total length, fed on prey organisms ranging from 2.0 to 76.0 mm in length. Amphipods and the shore crab, Carcinus maenas (L.), were the most important food items found. In more saline muddy bottom areas polychaetes, bivalves and shrimp increased their importance as prey, replacing the amphipods as preferential food. Fish were always a secondary, although significant, prey item. The occurrence of seasonal variations in eels' diet could be attributed to fluctuations in prey densities. There was evidence of a close relationship between the quantity of prey organisms in the benthos and the composition of eels' stomach contents, but a certain degree of food selection based on size, concealment capacity and motility of prey, was found.     

Diet composition of smooth-hound shark, Mustelus mustelus (Linnaeus, 1758), in the Gulf of Gabès, southern Tunisia

The diet of the smooth-hound shark, Mustelus mustelus , from the Gulf of Gabès (southern Tunisia, central Mediterranean Sea) was investigated with respect to fish size and season. Stomach contents were analyzed from 540 specimens with total lengths ranging from 34 to 158.5 cm. Of the total number of stomachs examined, 63 were empty (11.67%). Smooth-hound shark fed mainly on crustaceans, fishes and cephalopods. Sipunculids, polychaetes and echinoderms were occasional preys. No differences were found between the diets of males and females. Ontogenetic changes in diet of M. mustelus were apparent, with crustaceans forming a greater proportion of the diet of smaller sharks. Both teleosts and molluscs increased in importance with increasing shark size. Consumptions of polycheates, sipunculids and echinoderms were not related to predator size. Prey diversity also increased with size, with large and mobile prey species found more commonly in the diet of larger sharks. The limited overlap in the dietary compositions of juveniles, subadults and adults suggests the possibility of resource partitioning. Seasonality in food habits was in accordance with the dynamics of the predator and the prey species.     

Variation in the diet of Genypterus blacodes(Ophidiidae) around the Falkland Islands

The diet change with size, season and area was investigated using the stomachs of 496 kingclip Genypterus blacodes collected around the Falkland Islands (south‐west Atlantic) between August 2001 and September 2002. The key prey species were rockcod Patagonotothen spp., benthic isopods and Patagonian grenadier Macruronus magellanicus . Kingclip <50 cm total length ( L _T) fed mainly on crustaceans and small fishes. With size the diet shifted away from crustaceans towards Patagonotothen spp. in kingclip 50–100 cm L _T, and finally towards larger fishes such as M. magellanicus and Micromesistius australis australis in kingclip >100 cm L _T. The niche breadth was highest in fish >100 cm L _T and the lowest in fish <50 cm L _T. The larger kingclip generally selected larger individuals of the same prey species, with the exception of the Patagonian squid Loligo gahi , where all ingested squid were of similar size, regardless of the predator length. The importance of the main prey species varied substantially between five consequent seasons studied, and appeared to follow the seasonal abundance and availability of prey. The spatial variability in the diet was found in kingclip caught in regions occupied by transformed temperate and sub‐Antarctic waters. The rockcod, which is available throughout the year around the Falkland Islands, was the most important prey in the kingclip diet. Kingclip takes advantage of other seasonally abundant prey species during their seasonal migrations ( e.g . L. gahi ) and also scavenge on discards from fishing vessels when available.     

Spatial variation in abundance of prey and diet of trumpeter (Pelates sexlineatus: Teraponidae) associated with Zostera capricorni seagrass meadows

Abstract The diet of juveniles of Pelates sexlineatus was examined at six estuaries, separated by tens to hundreds of kilometres, and two sites within each estuary, separated by hundreds of metres to kilometres. Fish were collected in Zostera capricorni seagrass meadows along the coast of New South Wales (Australia). Spatial variability in diet was compared with the abundance of prey. Pelates sexlineatus had a broad diet (27 different prey) but generally preferred crustaceans (harpacticoid copepods, gammarid amphipods, ostracods and tanaids), although at some sites other prey items were important (e.g. polychaetes, nematodes and foraminiferans). Composition of the diet varied among estuaries and between sites. Proportional representation of the different size of prey eaten by the three sizes of juveniles (40‐ 54 , 55–74 and 75–94 mm standard length) was similar. Fish generally preferred prey smaller than 1 mm. Abundance of prey also varied at both spatial scales. At five of the 12 sites, there was a significant correlation between abundance of prey in the seagrass meadows and abundance of prey in the diet. Variation in the composition of the diet was partly explained by spatial variation in abundance of prey. When crustaceans were not abundant in the seagrass, P. sexlineatus had a broad diet, taking both benthic and planktonic prey items. It is concluded therefore that trophic linkages between P. sexlineatus and benthic invertebrates may vary greatly with spatial scales from hundreds of metres to hundreds of kilometres, and are strongly related to availability of prey in seagrass habitats.     

Feeding ecology and growth of age 0 year Platichthys flesus(L.) in a vegetated and a bare sand habitat in a nutrient rich fjord

A study was carried out to investigate the diet and feeding strategies of age 0 year juvenile flounder Platichthys flesus in two different micro‐tidal habitats in the nutrient enriched Mariager Fjord on the Danish east coast. Juvenile flounder and benthic macrofauna were sampled monthly from June to October 1999 in a bare sand habitat and a habitat covered by filamentous and mat forming macroalgae. The presence of the 'opportunistic' macroalgae created a shift in the dominance of surface dwelling prey such as epifaunal amphipods to more infaunal groups such as oligochaetes and polychaetes. The diet of the flounder varied considerably between the two habitats mainly reflecting prey availability relative to their abundance, prey spatial distribution, habitat structure and ontogenetic prey shifts as a function of total length. Flounder in the vegetated site fed on a diverse diet of copepods, polychaetes and oligochaetes, whereas those caught in the bare sand site fed primarily on the amphipod Corophium volutator which was numerically dominant at this site. During the growth season, two diet shifts were observed: from copepods early in the season to macrofauna organisms and, later in the season, the inclusion of more hyperbenthic prey such as Mysidea spp; Idotea spp. and the common goby Pomatoschistus microps .