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.     

Diet of the critically endangered blackchin guitarfish Glaucostegus cemiculus revealed using DNA metabarcoding

We present the first assessment of the diet of the blackchin guitarfish Glaucostegus cemiculus (Geoffroy Saint-Hilaire, 1817) for West Africa using DNA metabarcoding on stomach contents of individuals captured in the Bijagós Archipelago, Guinea-Bissau. The diet was dominated by crustaceans, particularly caramote prawn Penaeus kerathurus (frequency of occurrence [FO] = 74%, numerical frequency [NF] = 54%) and fiddler crab Afruca tangeri (FO = 74%, NF = 12%). Bony fishes were present in 30% of the stomachs. We highlight the importance of conservation action for intertidal habitats and their associated benthic invertebrates for the survival of the critically endangered blackchin guitarfish.     

Observations on the biology and ecology of the blue shark in the North-east Atlantic

Of 159 blue sharks Prionace glauca examined (59% female, 41% male) from oceanic waters SW of Britain and Ireland, all but two males were immature. Size-at-age and growth rate were similar to previous studies in the North Atlantic, while stomach contents included cephalopods, fish, cetaceans, and to a lesser degree, birds and crustaceans.     

Food habits and ontogenetic changes in the diet of the sandbar shark, Carcharhinus plumbeus, in Hawaii

The sandbar shark, Carcharhinus plumbeus, is a wide-ranging coastal species in tropical and temperate regions, and it is the most common species of shark in Hawaii, as in many locations where it occurs. Information on the diet and feeding habits of this species in the Pacific Ocean are extremely limited. For this study we quantified the diet of sandbar sharks in Hawaii based on records collected during the Hawaii Cooperative Shark Research and Control Program from 1967 to 1969. During this program a total of 565 stomachs were examined, of which 265 contained food. Sharks ranged in size from 59 to 190 cm total length. Teleosts were the most common prey group, but both cephalopods and crustaceans also occurred frequently. Ontogenetic changes in diet of sandbar sharks were apparent, with crustaceans forming a greater proportion of the diet of smaller sharks. Both cephalopods and elasmobranchs increased in importance with increasing shark size. Prey diversity also increased with size, with large, mobile, and reef prey species found more commonly in the diet of larger sharks. Mature male and female sharks appeared to segregate by depth, though major differences in the diet between the sexes were not apparent. However, there was some evidence of dietary differences between sharks caught in different depths and seasons. The results of this study suggest that sandbar sharks in Hawaii and throughout the world, are primarily piscivores, but also consume a variety of invertebrate prey, and that their diet varies with geographical location and stage of development.     

Feeding of the Brazilian sharpnose shark Rhizoprionodon lalandii (Müller & Henle, 1839) from southern Brazil

Stomach contents of 175 Brazilian sharpnose sharks, Rhizoprionodon lalandii, were examined to assess their feeding habits. Caught by artisanal fishers between June 2006 and July of 2007 at Ipanema Beach, on the central coast of the state of Paraná, southern Brazil, R. lalandii appears to be piscivorous (89.7% IRI), feeding mainly on families of Clupeidae (5.1% IRI) and Sciaenidae (3.7% IRI) and secondarily on squid Lolliguncula brevis (8.6% IRI). Diets were similar between sexes and seasons. However, there were ontogenetic changes in their diets. The major items for neonates were Penaeidae crustaceans (%IRI = 56.4) and Engraulidae fishes (%IRI = 29.3); for the juveniles, Sciaenidae (%IRI = 62.5) and Clupeidae (%IRI = 19.7), and for adults Clupeidae (%IRI = 45.8) and Sciaenidae (%IRI = 15.9). Only neonate sharks consumed crustaceans, whereas all size classes consumed cephalopods and teleosts. Neonates had the lowest trophic level (TR = 3.8), with the diet of juveniles and adults the highest (TR = 4.2). Given its abundance and diet, R. lalandii may be an important predator of demersal and pelagic prey in coastal waters of Brazil.     

Diet of young-of-the-year bluefin tuna, Thunnus thynnus (Linnaeus, 1758), in the southern Tyrrhenian (Mediterranean) Sea

The diet of juvenile bluefin tuna (Thunnus thynnus) caught 2 to 8 miles off NE Sicily was investigated in order to improve knowledge of the species’ early life history. From 1998 to 2000, 107 specimens ranging from 63 to 495 mm (total length) were fished between July and November. Fishes were caught by trolling line or purse seine in a Fish Aggregating Devices (FADs) area 2 to 8 miles offshore and as by‐catch of the purse‐seine sardine fishery 2 to 4 miles offshore. Most frequently found items in the T. thynnus stomachs were fishes (84.5%), crustaceans (54.6%) and cephalopods (50.5%). The largest contribution in weight was provided by cephalopods (47.3%) and fishes (46.5%), while the most abundant items were fishes (51%), cephalopods (27.2%) and crustaceans (21.1%). These results suggest that young‐of‐the‐year tuna have an essentially piscivorous diet, although invertebrate prey provide a substantial contribution to the food array. Prey show little relationship with FADs, although one prey species (blue runner, Caranx crysos) is associated with FADs in the Mediterranean.     

Diet and scavenging habits of the smooth skate Dipturus innominatus

The diet of smooth skate Dipturus innominatus was determined from examination of stomach contents of 321 specimens of 29·3-152·0 cm pelvic length, sampled from research and commercial trawlers at depths of 231-789 m on Chatham Rise, New Zealand. The diet was dominated by the benthic decapods Metanephrops challengeri and Munida gracilis, the natant decapod Campylonotus rathbunae and fishes from 17 families, of which hoki Macruronus novaezelandiae, sea perch Helicolenus barathri, various Macrouridae and a variety of discarded fishes were the most important. Multivariate analyses indicated the best predictors of diet variability were D. innominatus length and a spatial model. The diet of small D. innominatus was predominantly small crustaceans, with larger crustaceans, fishes and then scavenged discarded fishes increasing in importance as D. innominatus got larger. Scavenged discards were obvious as fish heads or tails only, or skeletal remains after filleting, often from pelagic species. Demersal fish prey were most frequent on the south and west Chatham Rise, in areas where commercial fishing was most active. Dipturus innominatus are highly vulnerable to overfishing, but discarding practices by commercial fishing vessels may provide a positive feedback to populations through improved scavenging opportunities.     

Ontogenetic dietary shifts and feeding behavior of the tiger shark, Galeocerdo cuvier, in Hawaiian waters

Synopsis Stomach content data from 281 tiger sharks caught during shark control programs in Hawaii between 1967 and 1969, and during 1976 were analyzed to examine feeding habits and ontogenetic shifts in diet. As sharks increased in size, prey diversity and frequency of occurrence of large prey items increased. The percent occurrence of teleosts and cephalopods in stomachs decreased as sharks increased in length, while occurrence of elasmobranchs, turtles, land mammals, crustaceans, and undigestible items increased. Comparisons between the diets of tiger sharks from Hawaii and other locations indicate that ontogenetic shifts are universal in this species and that tiger sharks may be opportunistic feeders that prey heavily on abundant, easy to capture prey. Small tiger sharks may be spatially segregated from medium and large sharks and appear to be primarily nocturnal, bottom feeders. Large tiger sharks feed near the bottom at night, but also feed at the surface during the day. Prey, similar in size to humans, begin to occur in the diet of tiger sharks approximately 230 cm TL, and therefore sharks of this size and larger may pose the greatest threat to humans. Ontogenetic shifts in diet may be attributed to increased size of sharks, expanded range and exploitation of habitats of larger sharks, and/or improved hunting skill of larger sharks.Deceased 1974     

Feeding habits of alfonsino Beryx splendens

The diet of the alfonsino Beryx splendens was determined from examination of stomach contents of 287 specimens of 17 to 48 cm fork length (L_F) sampled by bottom trawl on the Chatham Rise to the east of New Zealand. Prey items were predominantly crustaceans and mesopelagic fishes. The most important prey species by mass was Sergestes spp. prawns, followed by the myctophid Lampanyctodes hectoris, and then Pasiphaea spp. prawns. Multivariate analyses indicated that small crustaceans (euphausiids and amphipods) were most important in the diet of smaller B. splendens (100–424 g, 17–26·5 cm), with larger prawn species and mesopelagic fishes most important for larger fish (425–2070 g, 27–46 cm). Moon phase and bottom temperature also explained some of the variability in diet, but the moon phase effect was difficult to explain, and the bottom temperature effect may have been confounded, to some extent, with L_F. The results indicated that B. splendens were moderately selective feeders that foraged primarily in the mesopelagic layers. The diet of New Zealand B. splendens is generally similar to those reported from other areas, i.e. dominated by mesopelagic crustaceans and fishes, and with a transition from small crustaceans to fishes with increasing predator size.     

Moon phase influences the diet of southern Ray's bream Brama australis

Diet composition of the southern Ray's bream Brama australis was examined from stomach contents of 399 specimens sampled by bottom trawl on Chatham Rise to the east of South Island, New Zealand, over 3 years. Prey items were predominantly mesopelagic fishes and crustaceans. Multivariate analysis indicated that moon phase explained more of the diet variability than any other predictor examined. It appears likely that diet composition is influenced by a combination of changes in both tidal flows and illumination. Different combinations of prey were consumed by B. australis at different times of the lunar cycle. An influence of moon phase on feeding by fishes has rarely been reported, but it is likely that moon phase influences the diets of other species that specialize in mesopelagic prey. The most important prey group by mass for B. australis was Myctophidae (primarily Lampanyctodes hectoris), followed by Stomiiformes (primarily Maurolicus australis) and shrimps (Sergestes spp). An ontogenetic shift in diet was observed, from numerical dominance by small crustaceans including amphipods and euphausiids (with some fishes) in smaller (mass <1045 g) B. australis to pelagic teleost prey (with a few larger crustaceans) in larger (>1440 g) B. australis.     

Feeding habits of Lutjanus guttatus (Pisces: Lutjanidae) at Los Cóbanos and Puerto La Libertad, El Salvador

Abstract: A total of 175 spotted snapper Lutjanus guttatus were collected monthly in the Los Cobanos and Puerto La Libertad, El Salvador, from January to December 2000 to determine its feeding habits. The fishes studied ranged 9.8 - 58.0 cm in total length. Were collected using push-net and hook and line. This snapper is a bentonic opportunistic carnivorous predator. The total biomass of the stomach contents was 260.5 g. Crustaceans (Squillidae, Portunidae, Dynomenidae. Penaeidae, Sicyoniidae, Callianassidae), were the most abundant group: they accounted for 50.4% of the total biomass. Numerically, Portunus asper was the most abundant prey. Ontogenic differences were observed in the diet. In juveniles (16 cm TL). at any time of the year, the most frequent and abundant components were crustaceans and in adults were crustaceans, fishes and mollusks. The relative importance of different components of the diet was assessed with two indexes that combine. in different ways. percentage frequency of occurrence, percentage number and percentage weight of prey categories. The commercial use this resource and the absence of management strategies are discussed.     

东海北部大管鞭虾的食性

根据对2009年6月至2010年5月在东海北部采集到的720尾大管鞭虾胃含物的分析,对不同季节、性别、个体大小以及发育条件下大管鞭虾的摄食习性进行了研究.结果表明: 东海大管鞭虾的饵料生物共有43种(包含未鉴定种),甲壳类、有孔虫类和多毛类为其主要的摄食群类,在食物中所占的数量百分比分别为34.7%、29.4%和12.4%.大管鞭虾的饵料组成具有明显的季节波动,春季以有孔虫、藻类和无脊椎卵为主要食物;夏、秋季以有孔虫、鱼类和多毛类为主要食物;冬季则以多毛类和有孔虫类为主要食物.其摄食强度在春季和夏季较高,秋季较低.不同甲长的个体食性变化显著,小于24 mm的个体主食有孔虫类和藻类,24 mm以上的个体主食有多毛类和十足类;随着性腺发育雌性个体摄食等级呈现减弱的趋势,表明大管鞭虾摄食活动受到繁殖周期的影响.不同性别和不同季节大管鞭虾的食物重叠指数均较高,与栖息环境饵料资源的波动有关.大管鞭虾的营养级为2.67,属低级肉食性动物.     

Dietary habits of the polkadot skate <Emphasis Type="Italic">Dipturus chinensis</Emphasis> in the East China Sea

We investigated the dietary habits of the polkadot skate, Dipturus chinensis (Japanese name: Gangi-ei), in the East China Sea by analyzing the stomach contents of 529 individuals. Of these, 18 (3.40%) had empty stomachs. The mean and maximum fullness indices (FIs) were 0.67% and 6.12%, respectively. The mean FI of female skates > 500 mm in total length (TL) was higher than that of males and smaller females. The most dominant prey category was crustaceans, which included shrimps, crabs, and anomurans, followed by fishes. Cephalopods were additionally observed. Dipturus chinensis fed on a wide variety of crustacean taxa, and among them, Caridea and Galatheidae were particularly common. Fishes that could be identified were mostly demersal fishes, such as Callionymidae, Triglidae, and Rajidae. Some juvenile D. chinensis were also observed, indicating that cannibalism occurs in this species. Even though dental sexual dimorphism was observed in large size classes (mainly > 500 mm TL), the diet of males and females significantly overlapped. Size-related dietary shifts from small crustaceans, such as shrimps and anomurans, to relatively fast-swimming prey, such as fishes, crabs, and cephalopods, were observed in all seasons. The composition of these prey categories varied among seasons. Shannon–Wiener diversity indices calculated for each size class ranged from 2.01 to 2.51, indicating D. chinensis are generalist predators. As size increased, trophic level increased from 3.58 to 3.85, indicating that larger specimens are at a slightly higher trophic level than smaller specimens. These results suggest that D. chinensis are middle-trophic-level generalist predators that utilize diverse prey depending on their size and the season, and thus play an influential role in the demersal ecosystem of the East China Sea.     

东海北部大管鞭虾的食性

根据对2009年6月至2010年5月在东海北部采集到的720尾大管鞭虾胃含物的分析,对不同季节、性别、个体大小以及发育条件下大管鞭虾的摄食习性进行了研究.结果表明: 东海大管鞭虾的饵料生物共有43种(包含未鉴定种),甲壳类、有孔虫类和多毛类为其主要的摄食群类,在食物中所占的数量百分比分别为34.7%、29.4%和12.4%.大管鞭虾的饵料组成具有明显的季节波动,春季以有孔虫、藻类和无脊椎卵为主要食物;夏、秋季以有孔虫、鱼类和多毛类为主要食物;冬季则以多毛类和有孔虫类为主要食物.其摄食强度在春季和夏季较高,秋季较低.不同甲长的个体食性变化显著,小于24 mm的个体主食有孔虫类和藻类,24 mm以上的个体主食有多毛类和十足类;随着性腺发育雌性个体摄食等级呈现减弱的趋势,表明大管鞭虾摄食活动受到繁殖周期的影响.不同性别和不同季节大管鞭虾的食物重叠指数均较高,与栖息环境饵料资源的波动有关.大管鞭虾的营养级为2.67,属低级肉食性动物.     

Feeding habits of the blue shark, Prionace glauca, and salmon shark, Lamna ditropis, in the transition region of the Western North Pacific

We describe the feeding habits of 70 blue sharks (Prionace glauca) and 39 salmon sharks (Lamna ditropis) caught at 0–7 m depth at night by research drift gillnets in the transition region of the western North Pacific during April–May of 1999 and 2000. Blue sharks of 50–175 cm total length fed on a large variety of prey species, consisting of 24 species of cephalopods and 16 species of fishes. Salmon sharks of 69–157 cm total length fed on a few prey species, consisting of 10 species of cephalopods and one species of fish. Important prey for the blue sharks were large, non-active, gelatinous, meso- to bathypelagic cephalopods (e.g., Chiroteuthis calyx, Haliphron atlanticus, Histioteuthis dofleini and Belonella borealis) and small myctophid fishes. Important prey for the salmon sharks were mid-sized, active, muscular, epi- to mesopelagic squids (e.g. Gonatopsis borealis, Onychoteuthis borealijaponica and Berryteuthis anonychus). Our results suggest that blue sharks feed on cephalopods mainly during the daytime when they descend to deep water. Salmon sharks may feed opportunistically with no apparent diurnal feeding period. Blue sharks and salmon sharks have sympatric distribution in the transition region in spring; they have different feeding habits and strategies that reduce competition for food resources.     

DIETS OF BAIRD'S BEAKED WHALES, BERARDIUS BAIRDII, IN THE SOUTHERN SEA OF OKHOTSK AND OFF THE PACIFIC COAST OF HONSHU, JAPAN

Stomach contents were analyzed from 127 Baird's beaked whales, Berardius bairdii , taken in coastal waters of Japan. During late July-August of 1985–1987, 1989, and 1991, 107 samples were collected from off the Pacific coast of Honshu. An additional 20 samples were collected from whales taken in the southern Sea of Okhotsk during late August—September of 1988 and 1989. Prey identification using fish otoliths and cephalopod beaks revealed the whales fed primarily on deep-water gadiform fishes and cephalopods in both regions. Prey species diversity and the percentage of cephalopods and fish differed between the two regions. Off the Pacific coast of Honshu the whales fed primarily on benthopelagic fishes (81.8%) and only 18.0% on cephalopods. Eight species of fish representing two families, the codlings (Moridae) and the grenadiers (Macrouridae), collectively made up 81.3% of rhe rotal. Thirty species of cephalopods representing 14 families made up 12.7%. In the southern Sea of Okhotsk, cephalopods accounted for 87.1% of stomach contents. The families Gonatidae and Cranchiidae were the predominant cephalopod prey, accounting for 86.7% of the diet. Gadiform fish accounted for only 12.9% of the diet. Longfin codling, Laemonema longipes , was the dominant fish prey in both regions. Depth distribution of the two commonly consumed fish off the Pacific coast of Honshu indicate the whales in this region fed primarily at depths ranging from 800 to 1,200 m.     

Diet and feeding strategy of blackmouth catshark Galeus melastomus

Diet and feeding strategy of the blackmouth catshark Galeus melastomus in the deep waters of the eastern Ionian Sea were investigated. Sampling was carried out using experimental bottom longline fishing at depths ranging from 300 to 855 m in summer and autumn 2010. Diet variability with fish size, season, area, sex and depth zone was tested and only season was found to significantly affect the diet of the species. Of the 870 stomachs examined, only 1·4% were empty. Cumulative prey curves showed that the sample sizes were adequate to describe the main prey items of the diet for both seasons. Prey identified belonged primarily to three major groups: fishes, cephalopods and dendrobranchiatan and caridean shrimps. In autumn, the above three major groups were found as principal prey, whereas in summer cephalopods followed by fishes were the principal prey and shrimps were found as secondary prey. SIMPER analysis indicated high dissimilarity between seasons and highlighted that Sepiolidae, Myctophidae, fishes, cephalopods, shrimps and other crustaceans contributed to seasonal differences in the diet of G. melastomus. The prey diversity index was higher in autumn than in summer. A high dietary overlap was observed between the two seasons. Galeus melastomus behaved as an opportunistic predator with a variety of unimportant prey in its diet. Feeding strategy indicated that G. melastomus holds a generalist niche with a considerable specialization at the individual level. This strategy seems to be an adaptation to a food‐scarce environment, as typified in deep‐water habitats.     

PYGMY SPERM WHALES KOGIA BREVICEPS IN THE NORTHEAST ATLANTIC: NEW INFORMATION ON STOMACH CONTENTS AND STRANDINGS

Little is known about the feeding ecology of pygmy sperm whales ( Kogia breviceps ) in the Northeast Atlantic. Results are presented on the stomach contents of five whales stranded on the Galician coast (NW Spain) between 1995 and 2002 and seven whales stranded on the French Atlantic coast between 1984 and 2001. These results are compared with those obtained from the stomach contents of two pygmy sperm whales (a pregnant female and her calf ) stranded on the Scottish (UK) coast in 1999, the first records of the species in Scotland. In 13 out of 14 cases, food remains consisted almost entirely of cephalopod beaks, although some crustacean and fish remains were also present. In all the Spanish specimens, the identified prey were oceanic species: the cephalopods Histioteuthis reversa , H. bonnellii , Todarodes sagittatus , the viperfish Chauliodus sloani , and the giant mysid Gnatophausia sp. The same cephalopod species were found in the stomachs of the whales stranded in Scotland, although both whales had also consumed neritic cephalopod species such as Rossia macrosoma and other sepiolids. In the French specimens, almost all prey identified were oceanic cephalopods ( H. reversa , Brachioteuthis riseii , T. sagittatus , Taonius pavo , etc. ), but remains of crustaceans and a neritic squid ( Loligo forbesi ) were also found. One whale from France had eaten mainly Henslow's swimming crab ( Polybius henslowi ). Results from the present study are consistent with those found by other authors in the Azores and the Canary Islands in that pygmy sperm whales appear to be mainly teuthophagous, with histioteuthid squids forming an important part of the diet. Strandings records suggest that occurrence of pygmy sperm whales in the NE Atlantic may be seasonal, with most strandings occurring in autumn and winter.     

Food habits of the smooth dogfish, Mustelus canis, dusky shark, Carcharhinus obscurus, Atlantic sharpnose shark, Rhizoprionodon terraenovae, and the sand tiger, Carcharias taurus, from the northwest Atlantic Ocean

Diet and feeding habits of the smooth dogfish, Mustelus canis, Atlantic sharpnose, Rhizoprionodon terraenovae, dusky, Carcharhinus obscurus, and the sand tiger, Carcharias taurus sharks, were investigated through analysis of stomach contents. Diet in M. canis was relatively homogeneous and was dominated by crustaceans, consisting mostly of rock crabs, Cancer irroratus. Diet in R. terraenovae was more heterogeneous and consisted largely of crustaceans and teleosts, in similar levels of prey importance. Use of cumulative prey curves as a measure of precision indicated that data were insufficient to fully describe the diets of C. obscurus and C. taurus. Nonetheless, these data suggested that both species are generalized feeders and consume a variety of teleost and elasmobranch prey. Further studies are necessary to fully characterize diet in these two species.