Feeding habits of <Emphasis Type="Italic">Bathydraco marri</Emphasis> (Pisces,Notothenioidei, Bathydraconidae) from the Ross Sea,Antarctica

In comparison with other bathydraconids, all species of the genus Bathydraco are poorly known from an ecological perspective. The diet of juvenile Bathydraco marri Norman, 1938 was studied for the first time in specimens collected in the southwestern Ross Sea during summer 1998. Fish were collected in a single otter trawl catch at 330–340 m depth. The stomach content analysis showed that this species fed exclusively on crustaceans. Overall, 20 prey taxa were identified to genus or species level. Mysids, amphipods and copepods were the most important prey in decreasing order of importance. Other prey, such as Euphausia superba, isopods and tanaids were eaten occasionally and in very small amounts. A multivariate analysis was applied to feeding data to assess ontogenetic or sex-related changes in diet. No difference was detected between sexes, whereas diet of small and large fish differed in some degree. An ontogenetic shift from small and pelagic crustaceans such as copepods to benthic–benthopelagic prey such as amphipods and mysids was observed. Relating present results with published data on physiological characteristics of B. marri, it was possible to infer their feeding behaviour and mode of life. Like other bathydraconids, this species appeared to be an inactive and sluggish fish, which relied on more or less motile benthic or epibenthic prey adopting a “sit and wait” feeding strategy. On the other hand, smaller fish seem to be more active, feeding also on pelagic prey such as copepods that can be seasonally abundant, thus reducing the intraspecific competition for food.     

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

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

The role of copepods in the planktonic ecosystems of mixed and stratified waters of the European shelf seas

The European shelf seas can be divided into regions which have tidally mixed waters and thermally stratified waters. The tidally mixed near shore environments support zooplankton communities dominated by smaller copepods and having large meroplankton contributions. These small copepods (Centropages spp., Temora spp., Acartia spp., Paral Pseudo/Microcalanus spp.) together with the microzooplankton component form a different and more complex food web than the larger copepod/diatom link associated with thermally stratified waters. The copepods Calanus finmarchicus and C. helgolandicus account for over 90% of the copepod dry weight biomass in stratified waters. Although occurring in lower numbers in mixed waters they can still make significant contributions to the biomass. A 31 year time series from the European shelf shows the inter- and intea-annual variability of these species. The basic biology and food web that these two systems support, and the transfer of energy, can result in marked differences in quantity and quality of particulates available as food for fish larvae. Calanus dominated systems allow the primary production to be directed straight through the trophic food chain (diatoms/Calanus/fish larvae) while the near shore communities of smaller copepods limit the amount of energy being transferred to the higher trophic levels. Eighty-two Longhurst Hardy Plankton Recorder hauls were used as the data base for this study. In all cases the zooplankton was dominated by copepods both in numbers and biomass accounting for > 80% of total zooplankton dry weight in the Irish Sea, Celtic Sea, shelf edge of the Celtic Sea and the northern and southern North Sea in Spring.     

Planktonic cnidarian distribution and feeding of <Emphasis Type="Italic">Pelagia noctiluca</Emphasis> in the NW Mediterranean Sea

Pelagic cnidarians are important consumers of zooplankton and ichthyoplankton in the world’s oceans, and thus harm fisheries as competitors and predators of fish. This study examined the inshore-offshore distribution of pelagic cnidarians and the trophic ecology of Pelagia noctiluca ephyrae (<12 mm diameter) and larger medusae in late spring 1995 in the NW Mediterranean Sea. The distribution of pelagic cnidarians was closely related to the presence of the shelf-slope front with most species mainly concentrated close to the front. Meroplanktonic antho- and leptomedusae predominated in coastal waters and more holoplanktonic trachy- and narcomedusae occurred both in shelf and open sea waters. P. noctiluca was more abundant than other medusae, including hydromedusae. Siphonophores, particularly Muggiaea atlantica, outnumbered medusae at most stations. The diet of P. noctiluca ephyrae contained mainly copepods, but ~12% of the prey were fish larvae. P. noctiluca exhibited positive prey selection for chaetognaths and mollusc larvae in day and night samples, but fish larvae were positively selected only at night. These differences may be related to the diel vertical distributions of P. noctiluca and their prey. Most of the ingested fish larvae belonged to the family Myctophidae, but anchovy and sparid larvae also were found in the gastric pouches. The size of ingested fish larvae increased as ephyra diameter increased; however, in the larger medusae (>12 mm) the number of prey increased with medusa size rather than the size of the larvae. The temporal and spatial co-occurrence of P. noctiluca with early life stages of fish suggests that P. noctiluca may be an important predator on summer ichthyoplankton.     

Food of an endangered cyprinodont (Aphanius iberus): ontogenetic diet shift and prey electivity

Synopsis We studied the ontogenetic diet shift and prey electivity of an endangered cyprinodontid fish endemic to the Iberian Peninsula, the Spanish toothcarp (Aphanius iberus). The toothcarp’s diet was omnivorous, dominated by harpacticoid copepods (Mesochra lilljeborgi and Tisbe longicornis), copepod nauplii and detritus. Diet composition varied greatly among habitats, depending on prey availability. In a rarely inundated habitat (glasswort), there was more consumption of the isopod Protracheoniscus occidentalis and the harpacticoid copepod Mesochra lilljeborgi, while in algal mats another harpacticoid (Tisbe longicornis), chironomid dipterans and invertebrate eggs were more important in diet. Although a benthic feeding habitat has previously been suggested, in our study the diet was based rather on water column organisms for both glasswort and algal mat habitats. There was also an ontogenetic diet shift, with an increase of mean prey length with fish length, clearly linked to a microhabitat change. Smaller fish showed positive electivity and greater reliance on planktonic prey (e.g. copepod nauplii, the harpacticoid copepods Mesochra lilljeborgi and Tisbe longicornis, the rotifer Brachionus plicatilis, and ostracods), while larger fish elected and preyed on more benthic organisms (e.g. Canuella perplexa, Mesochra rapiens, and ephydrid dipterans).     

Does diet in Celtic Sea fishes reflect prey availability?

Feeding preferences of Celtic Sea fishes were investigated using a database of stomach content records, collected between 1977 and 1994. The diet of cod Gadus morhua, hake Merluccius merluccius, megrim Lepidorhombus whiffiagonis, whiting Merlangius merlangus and saithe Pollachius virens changed markedly as the animals grew larger, and although large predators generally chose larger bodied prey, the variability of prey sizes consumed also increased. Large predators continued to select small, low value, benthic prey (e.g. Callionymus spp. and Trisopterus spp.) which were easier to catch, rather than larger, more energy lucrative pelagic prey (e.g. mackerel Scomber scombrus), even though these pelagic prey‐fishes were nearly always available and were often very abundant. Stock estimates of the International Council for the Exploration of the Sea and U.K. groundfish survey catches were used as indices of prey abundance. Blue‐whiting Micromesistius poutassou and other small pelagic fishes (Argentina spp. and clupeoids) were identified as being particularly important, and were consumed by some predators more often than would be expected given the abundance of these prey in the environment. There was no evidence for density‐dependent feeding by predators on mackerel and only hake exhibited density‐dependent feeding on horse‐mackerel. Hake, cod and megrim consumed more blue‐whiting when this prey was at higher abundance in the environment. In choosing what prey to consume, predators must balance costs and benefits, considering the quality of prey and the energy expended during search, capture and handling.     

The role of notothenioid fish in the food web of the Ross Sea shelf waters: a review

The Ross Sea, a large, high-latitude (72–78°S) embayment of the Antarctic continental shelf, averages 500 m deep, with troughs to 1,200 m and the shelf break at 700 m. It is covered by pack ice for 9 months of the year. The fish fauna of about 80 species includes primarily 4 families and 53 species of the endemic perciform suborder Notothenioidei. This review focuses on the diet and role in the food web of notothenioids and top-level bird and mammal predators, and also includes new information on the diets of artedidraconids and bathydraconids. Although principally a benthic group, notothenioids have diversified to form an adaptive radiation that includes pelagic and semipelagic species. In the southern Ross Sea, notothenioids dominate the fish fauna at levels of abundance and biomass >90% and are, therefore, inordinately important in the food web. Antarctic krill (Euphausia superba) and mesopelagic fishes are virtually absent from the shelf waters of the Ross Sea. Of the four notothenioid families, nototheniids show the most ecological and dietary diversification, with pelagic, cryopelagic, epibenthic and benthic species. Neutrally buoyant Pleuragramma antarcticum constitutes >90% of both the abundance and biomass of the midwater fish fauna. Most benthic nototheniids are opportunistic and feed on seasonally or locally abundant zooplanktonic prey. Artedidraconids are benthic sit-and-wait predators. Larger bathydraconids are benthic predators on fish while smaller species feed mainly on benthic crustaceans. Channichthyids are less dependent on the bottom for food than other notothenioids. Some species combine benthic and pelagic life styles; others are predominantly pelagic and all consume euphausiids and/or fish. South polar skuas, Antarctic petrels, Adélie and emperor penguins, Weddell seals and minke and killer whales are the higher vertebrate components of the food web, and all prey on notothenioids to some extent. Based on the frequency of occurrence of prey items in the stomachs of fish, bird and mammal predators, P. antarcticum and ice krill E. crystallorophias are the key species in the food web of the Ross Sea. P. antarcticum is a component of the diet of at least 11 species of nototheniid, bathydraconid and channichthyid fish and, at frequencies of occurrence from 71 to 100%, is especially important for Dissostichus mawsoni, Gvozdarus svetovidovi and some channichthyids. At least 16 species of notothenioids serve as prey for bird and mammal predators, but P. antarcticum is the most important and is a major component of the diet of south polar skua, Adélie and emperor penguins and Weddell seals, at frequencies of occurrence from 26 to 100%. E. crystallorophias is consumed by some nototheniid and channichthyid fish and can be of importance in the diet of emperor and Adélie penguins, although in the latter case, this is dependent on location and time of year.Unlike the linear phytoplanktonE. superbaconsumers of the E. superba food chain hypothesized for much of the Southern Ocean, the food web of the Ross Sea shelf is non-linear, with complex prey-predator interactions. Notothenioid fish play a key role: as predators, they occupy most of the trophic niches available in the ecosystem, relying on benthic, zooplanktonic and nektonic organisms; as prey, they are important food resources for each other and for most top predators living and foraging on the shelf. They also constitute the major link between lower (invertebrates) and higher (birds and mammals) levels of the food web. This is especially true for P. antarcticum. Along with E. crystallorophias, its ecological role in the Ross Sea is equivalent to that of myctophids and E. superba elsewhere in the Southern Ocean.     

Variation in the diet of Arctic Cod (<Emphasis Type="Italic">Boreogadus saida</Emphasis>) in the Pacific Arctic and Bering Sea

Arctic cod, Boreogadus saida (Lepechin, 1774), is a nodal species in Arctic marine foodwebs as an important prey of many birds, marine mammals, and other fishes, as well as an abundant predator of zooplankton and epibenthic fauna. We examined the summer diet of Arctic cod across a latitudinal gradient extending from the southern limit of their distribution in the eastern Bering Sea to the northern margins of the eastern Chukchi Sea (ECS) continental shelf. Specimens were collected from demersal and pelagic trawls conducted between 1999 and 2012, and across a range of predator sizes (3–26 cm). Arctic cod diets vary with body size and between regions within the study area, and appear to vary between years in the eastern Bering Sea, indicating opportunistic feeding habits. Constrained Analysis of Principal Coordinates was conducted on ECS demersal samples and revealed consumption of fish and decapod crustacea were positively correlated with Arctic cod length while consumption of euphausiids and copepods had the opposite relationship. The demersal Arctic cod diet in the northern latitudes of the ECS was dominated by copepod consumption (47% by weight, %W), but copepods were less important (12–26%W) in the central and southern latitudes of the ECS and in the northern and eastern Bering Sea—areas where diets were more varied in their composition. High levels of variation in the diet of Arctic cod highlights the need to monitor Arctic cod diets to identify consistently dominant prey types and potential future changes to trophic relationships related to climate change or increasing anthropogenic activity.     

The diet of the Weddell seal <Emphasis Type="Italic">Leptonychotes weddellii</Emphasis> at Laurie Island,South Orkney Islands

The diet of the Weddell seal Leptonychotes weddellii at the South Orkney Islands was investigated by the analysis of 44 and 26 faecal samples collected from the beaches of Laurie Island from May 1999 to January 2000 and from October to December 2001, respectively. The diet was diverse and both pelagic and benthic-demersal organisms were represented in the samples. Fish were the most frequent prey of the samples in both seasons, and fish and krill were the most numerous prey items. Octopods predominated by mass in 1999, whereas krill constituted the bulk of the diet in 2001, a fact that was not observed previously. Among fish, Gobionotothen gibberifrons was largely the species that contributed mostly to the diet, whereas pelagic fish could not be identified in the samples. The results are compared with information from other study areas and discussed in relation to the consumption of krill.     

Feeding habits of juvenile <Emphasis Type="Italic">Trematomus newnesi</Emphasis> (Pisces,Nototheniidae) at Potter Cove,South Shetland Islands,Antarctica

The dietary composition of juvenile Trematomus newnesi, trawled at Potter Cove, South Shetland Islands, in the summers 2004–2005 and 2005–2006 was analysed using frequency of occurrence (F%) and dietary coefficient Q (%) methods. The samples consisted exclusively of immature specimens in the range 4–15.4 cm (total length) and are complementary to those of larger fish from the same site, including adults, which were analysed in previous work. Benthic-demersal organisms such as gammaridean amphipods and harpacticoid copepods were the main (coefficient Q) and most frequent (F%) prey. The importance of the smaller and larger main prey diminished and increased, respectively, during ontogeny. Pelagic krill, being negligible in the diet of the small and medium size fish categories, became secondary food, but only for fish larger than 12 cm. Other taxonomic groups occurred scarcely and constituted occasional food. They were mostly benthic, such as gastropods, bivalves, isopods, cumaceans, and algae, with the exception of an insignificant number of pelagic ostracods and calanoid copepods. Unlike the more pelagic/planktivorous mode of life known for late juvenile-adult stages of T. newnesi, including cryopelagy, present results indicate that early juvenile fish remain sheltered among macroalgae beds preying on the associated community of demersal-benthic organisms.     

The diets of polar cod (Boreogadus saida) from August 2008 in the US Beaufort Sea

Polar cod (Boreogadus saida) play an integral part in the Arctic ecosystems linking the upper and lower trophic levels. Though their estimated biomass is considerable, recent knowledge of their diets in the US Beaufort Sea is sparse. Collections of polar cod from the US Beaufort Sea were made during August 2008 using demersal and pelagic trawls. Polar cod diet composition was quantified as percent prey weight, percent prey count, and frequency of occurrence of prey. The diet composition between the demersal- and pelagic-captured cod showed differences in all these categories. Polar cod captured in the demersal nets primarily fed on fish (by weight), and pelagic cod primarily fed on copepods (frequency of occurrence) and euphausiids (by weight). In general, these dominant preys are different than what has been reported in other studies describing polar cod diets.     

Summer and spring trophic niche of larval and juvenile <Emphasis Type="Italic">Pleuragramma antarcticum</Emphasis> in the Western Ross Sea,Antarctica

The aim of this paper is to contribute to the knowledge on the feeding habits of larvae and juvenile Pleuragramma antarcticum in the western Ross Sea. In summer, the diet of P. antarcticum postlarvae (8–17 mm) was dominated by calanoid eggs (35.5%), Limacina (32.1%) and tintinnids (17.6%), while the principal food of juveniles consisted mainly of copepods (98.2%), with Oncaea curvata being the most abundant (85.1%) and the most frequently consumed prey. The food composition of P. antarcticum postlarvae (24–29 mm), collected in spring, suggest that they fed actively under the sea ice. Stephos longipes, Harpacticus furcifer and Paralabidocera antarctica sea ice copepods represent, in all their different developmental stages, the most abundant biomass food in Terra Nova Bay in this period. Our results therefore suggest that the diet of younger Pleuragramma specimens shifted in prey composition from the first summer to the following spring. This study draws attention to the key role of the copepod, P. antarctica, in the food web of Terra Nova Bay. This article belongs to a special topic: Five articles coordinated by L. Guglielmo and V. Saggiomo appear in this issue of Polar Biology and are a result of a workshop on Sea-ice communities in Terra Nova Bay (Ross Sea) held in August 2007 in Capo Calavà, Messina, Italy.     

Diet of the invasive piscivorous fish <Emphasis Type="Italic">Fistularia commersonii</Emphasis> in a recently colonized area of the eastern Mediterranean

The composition of the diet of the Indo-Pacific cornetfish Fistularia commersonii from the SE Aegean Sea is described. The stomach contents of 245 specimens collected between September 2004 and March 2005 were examined. Dietary comparisons were made reflecting the relationship between diet composition, time of year, and fish size. Correlation between predator length and prey length was significant. The diet of the blue cornetfish consists of 96% by number and 99.95% by weight of fish. Size classification and habitat of prey groups (benthic, supra-benthic, and pelagic) showed that with increased body length the blue cornetfish extended its diet to larger prey and more generalist feeding. Spicara smaris, Boops boops, and Mullidae spp. were the most abundant prey by weight whereas a variety of small benthic fish (especially gobiids) and newly hatched fish constituted the largest number of prey items. Length–weight relationships for the cornetfish were investigated.     

Stomach contents of the Antarctic Silverfish Pleuragramma antarcticum from the southern and eastern Weddell Sea (Antarctica)

Summary The stomach contents of 142 Pleuragramma antarcticum from the southernmost part of the Weddell Sea (Gould Bay: 77°19S) and from the eastern coast (72°–74°S) were analyzed. The fish were collected in February 1983 and stored frozen. Size range of the investigated specimens was from 6.4 cm SL (7.3 cm TL) to 21.9 cm SL (24.1 cm TL). The fish were caught by bottom trawl (Gould Bay) and Agassiz Trawl and pelagic RMT-m net in the upper 300 m layer at the eastern coast, respectively. Thirty-six stomachs were empty or contained sand only. The most important prey in terms of biomass were euphausiids, which occurred in 49 stomachs at a mean number of 2. Their dry weight was estimated to be 15–50 times that of the next important food items, which were copepods, gastropods and gammarids. Krill (Euphausia superba) constituted up to 14% of the euphausiids in the diet of fish caught in the eastern Weddell Sea. The rest was usually made up by Euphausia crystallorophias. This species was taken with preference even when the abundance of E. superba in accompanying plankton catches was 16 times higher. In the Gould Bay, gastropods were frequently eaten despite high numbers of copepods in the plankton, whereas in the eastern Weddell Sea, copepods were abundant both in plankton and in the stomach content. The almost complete absence of the early stages of fish in the diet of Pleuragramma antarcticum in the southern and eastern Weddell Sea is due to a pronounced vertical segregation of fish of different sizes. This distribution pattern is thought to be an adaptive mechanism to avoid intraspecific predation, as 90% of the ichthyoplankton in that area is Pleuragramma antarcticum.     

Feeding patterns of post-larval and juvenile notothenioids in the southern Weddell Sea (Antarctica)

Summary The food of 163 juvenile specimens of 13 species of notothenioid fishes collected in the southern Weddell Sea (Antarctica) was analyzed. Investigated fish size range was 3–13 cm SL. Principal food items were calanoid copepods Metridia gerlachei, Calanoides acutus, and Calanus propinquus; all developmental stages of Euphausia crystallorophias, and post-larval nototheniid fish Pleuragramma antarcticum. Diet of juvenile channichthyids is limited to few species of euphausiids and fish in the size > 10 mm, but does not include significant numbers of copepods. Pelagic stages of nototheniids feed on copepods and/or larval euphausiids smaller than 10 mm. At similar size, nototheniids and bathydraconids take smaller prey items than channichthyids.     

Ontogenetic diet shifts of rough scad Trachurus lathami in the North Patagonian shelf (south-west Atlantic Ocean)

Rough scad Trachurus lathami is a key pelagic fish in the Argentinean continental shelf (ACS, south-west Atlantic Ocean), with recent increases in abundance. It is a main prey of fishes and marine mammals, and shares the environment with commercially relevant pelagic species (Engraulis anchoita and Scomber colias), playing an important role linking lower and upper trophic levels in the ecosystem. This study aims to determine the ontogenetic changes in the diet composition, feeding strategy, trophic niche breadth and trophic level of T. lathami in the North Patagonian Shelf (43°–45°30′S). The stomach contents of adult fish (n = 238) were analysed. The results suggest a clear ontogenetic shift in the diet at a size of ~190 mm. Smaller individuals (160–190 mm) were specialized on misidaceans, and showed the highest trophic level, while larger T. lathami (221–230 mm) consumed decapods (Peisos petrunkevitchi) and teleosts (eggs and larvae). Trophic niche breadth was higher at the medium-sized class (191–220 mm), which mainly preyed on copepods (Calanoides carinatus) and chaetognaths (Sagitta spp.), evidencing a more diverse diet and a rather generalist strategy. Updated information on the trophic ecology of T. lathami evidences its extremely plastic feeding behaviour, being able to adapt its trophic niche to the most readily available food items from the mesopelagic community.     

Do Inactivated Microbial Preparations Improve Life History Traits of the Copepod <Emphasis Type="Italic">Acartia tonsa</Emphasis>?

We have tested a microbial preparation with probiotic effects (PSI; Sorbial A/S DANISCO) on the calanoid copepod Acartia tonsa (Dana) development time and reproduction effectiveness in culture. The hypotheses were that PSI increases the productivity and quality of copepods in culture (increased egg production and hatching success, HS). This was carried out because the use of copepods as live prey in aquaculture could increase the number of fish successfully raised through their entire life cycle. However, the availability of copepods is limited by their difficulty to be effectively raised. Our results show that the addition of PSI to the algal food increased the individual size of the adult females and their egg production. The PSI, together with Rhodomonas salina, also increased the HS of the eggs produced by PSI-treated females. These effects were observed despite that the biochemical analysis of the PSI revealed that it is a nutritionally poor food lacking essential fatty acids, and hence it cannot be used alone to raise copepods but instead as a food additive. This is the first demonstration that the effectiveness of copepod culturing can be improved using microbial preparations as a food additive.     

Species composition,distribution, and specific features of feeding of Fish Larvae,and fry in the Sea of Okhotsk from October to December 2007

Ichthyoplankton of the Sea of Okhotsk from October to December 2007 comprised larvae and fry of eight fish species belonging to five families. The larvae of lord Hemilepidotus gilberti, white-spotted greenling Hexagrammos stelleri, and Atka mackerel Pleurogrammus monopterygius were the most widespread and numerous in the study period. Fish larvae from October to December 2007 were seined over the vast water area of the Sea of Okhotsk, maximum catches were made in waters of western Kamchatka. The food spectrum of larvae of five fish species (H. gilberti, Hexagrammos octogrammus, H. stelleri, P. monopterygius, and Bathymaster signatus) included approximately 20 plankters. Irrespective of species belonging, copepods Pseudocalanus minutus and Oithona similis, eggs and nauplii of copepods, as well as juveniles of pteropods were common food items for all fish. Larvae of all considered fish species in the Sea of Okhotsk fed mainly during the light hours of the day.     

Body size, sex ratio and diet composition of Arctogadus glacialis (Peters, 1874) (Pisces: Gadidae) in the Northeast Water Polynya (Greenland)

Little is known about the biology and feeding ecology of Arctogadus glacialis (Peters, 1874), an endemic gadid fish species occurring circumpolarly in both ice-free and ice-covered Arctic seas. In this study we analysed specimens sampled from bottom trawl and Agassiz trawl catches conducted at eight stations in water depths from 115 to 490 m in the Northeast Water Polynya off Greenland in August 1990. Size composition and sex ratios were assessed for 585 fish with standard lengths ranging from 7.8 to 34.5 cm. Median fish sizes at the stations ranged between 8.6 and 18.8 cm. Quantitative stomach content analyses of a subsample of 175 specimens revealed that in the Northeast Water A. glacialis fed almost exclusively on pelagic prey. Truly benthic organisms were not found in the stomachs, and sympagic species were rarely recorded. Overall, calanoid copepods were the major prey in terms of numbers. However, stomach contents varied considerably between fish size groups. In terms of prey biomass, copepods dominated the diet of small fish (<12 cm), primarily occurring at shallow stations (115–250 m), whereas amphipods and mysids were relatively more important for larger fish (>16 cm), which dominated the catches at deep stations (360–480 m). The broad variety of diet composition indicated an opportunistic pelagic feeding pattern. Received: 6 November 1997 / Accepted: 11 May 1998     

Temporal variations in the diet of pearly razorfish Xyrichtys novacula (Osteichthyes: Labridae)

The diet of pearly razorfish Xyrichtys novacula, caught monthly along the shores of the Island of Lampedusa, appeared to be mainly composed of crustaceans, followed by colonial ascidians, molluscs and polychaetes. Among prey, sand dwellers and phanerogam‐associated species were recorded. In winter months, the diet was characterized by a small number of prey items, dominated by colonial ascidians, while in spring and summer a wider prey array was recorded. Dietary indices show that X. novacula do not strictly exploit benthic prey but also pelagic organisms, such as copepods. This feeding behaviour reached its peak in March and October, when the abundance of primary consumers was at its highest after phytoplankton blooms. Furthermore, X. novacula caught prey organisms according to their availability and seasonal patterns during their life cycles, irrespective of fish size.