Vulpinus Research Articles

Loss of Large Predatory Sharks from the Mediterranean Sea

Evidence for severe declines in large predatory fishes is increasing around the world. Because of its long history of intense fishing, the Mediterranean Sea offers a unique perspective on fish population declines over historical timescales. We used a diverse set of records dating back to the early 19th and mid 20th century to reconstruct long-term population trends of large predatory sharks in the northwestern Mediterranean Sea. We compiled 9 time series of abundance indices from commercial and recreational fishery landings, scientific surveys, and sighting records. Generalized linear models were used to extract instantaneous rates of change from each data set, and a meta-analysis was conducted to compare population trends. Only 5 of the 20 species we considered had sufficient records for analysis. Hammerhead (Sphyrna spp.), blue (Prionace glauca), mackerel (Isurus oxyrinchus and Lamna nasus), and thresher sharks (Alopias vulpinus) declined between 96 and 99.99% relative to their former abundance. According to World Conservation Union (IUCN) criteria, these species would be considered critically endangered. So far, the lack of quantitative population assessments has impeded shark conservation in the Mediterranean Sea. Our study fills this critical information gap, suggesting that current levels of exploitation put large sharks at risk of extinction in the Mediterranean Sea. Possible ecosystem effects of these losses involve a disruption of top-down control and a release of midlevel consumers.

Distribuição, abundância e uso de diferentes ambientes pela ictiofauna dominante na área de influência do reservatório de Itaipu

The aim of this paper is to characterize the structure of dominant ichthyofauna in the Itaipu reservoir and its area of influence. 85,160 individuals were collected during the period from November 1983 to October 1989 in 11 sample sites, or rather, in the dam area (Guaira, Santa Helena and Foz do Iguacu), in the tributaries of its left bank (the rivers Arroio Iguacu, Ocoi, Sao Francisco Falso and Sao Francisco Verdadeiro), in upstream and downstream Parana River, in the tributaries of the Parana River (Piquiri and Iguatemi). Results showed a great number of species with low frequency and few dominant species. Among the dominant species Auchenipterus nuchalis , Hypophthalmus edentatus , Iheringichthys labrosus , Loricariichthys sp, Parauchenipterus galeatus , Plagioscion squamosissimus , Prochilodus lineatus , Pterodoras granulosus , Rhaphiodon vulpinus and Steindachnerina insculpta are conspicuous. The places of the feeding, reproduction and initial development places to the dominant species were identified.

Plasma catecholamine levels as indicators of the post-release survivorship of juvenile pelagic sharks caught on experimental drift longlines in the Southern California Bight

Between 1983 and 2004, nearly 12 000 shortf in mako (Isurus oxyrinchus), common thresher (Alopias vulpinus) and blue (Prionace glauca) sharks were tagged in the Southern California Bight; however, only 1.97% of these have been returned. One possible reason for this low return rate could be post-release mortality caused by capture stress from the experimental longline. Plasma catecholamine levels were analysed to evaluate stress levels in longline-captured, rod-and-reel-captured and unstressed docile sharks. The mean catecholamine values determined for the three tag–release species ranged from 6539 to 22 079 pg mL–1. The level of adrenaline found in moribund I. oxyrinchus (94 807 pg mL–1) was much higher than in either P. glauca (46 845 pg mL–1) or A. vulpinus (36 890 pg mL–1). In contrast, blood obtained from sharks that were landed within minutes had lower catecholamine values (P. glauca, 889 and 1347 pg mL–1; I. oxyrinchus, 2960 and 3946 pg mL–1, adrenaline and noradrenaline respectively). Among the nine I. oxyrinchus specimens that were recaptured long after their longline capture and release, the highest adrenaline level measured just before release was 33 352 pg mL–1. Because these mako sharks survived sufficiently long to be recaptured, their time-of-release catecholamine levels provide a conservative estimate of ~80% viability on the longline-captured and released population.

Embryos of common thresher shark Alopias vulpinus in southern Brazil, South Atlantic Ocean

Eight embryonic thresher sharks Alopias vulpinus (53·9–124 cm total length) were collected from two females caught by commercial longline off southern Brazil in September and November 2004. Morphometric measurements are provided.

The red muscle morphology of the thresher sharks (family Alopiidae)

A more medial and anterior position of the red aerobic myotomal muscle (RM) and the presence of a vascular counter-current heat exchange system provide the functional elements that facilitate regional RM endothermy in tunas, lamnid sharks and the common thresher shark (Alopias vulpinus). The convergent RM morphology among all species capable of RM endothermy suggests that RM position is a strong predictor of fish endothermic capacity. The present study investigated the comparative RM morphology of the other two thresher shark species (bigeye thresher, Alopias superciliosus, and the pelagic thresher, Alopias pelagicus), for which there is no information regarding their capacity for RM endothermy, and compared these data with published works on A. vulpinus. The digitization of transverse sections along the body of A. superciliosus and A. pelagicus enabled quantification of the relative amount of RM and the position and placement of the RM along the body. The RM in both A. superciliosus and A. pelagicus is positioned subcutaneously, along the lateral edges of the myotomes, and is distributed relatively evenly over the trunk of the body. The position of maximum RM area is at 50% fork length (FL) for A. superciliosus and at 75% FL for A. pelagicus. The amount of RM (mean +/- S.E.M.) is 2.31+/-0.11% and 3.01+/-0.10% in A. superciliosus and A. pelagicus, respectively. When compared with A. vulpinus, all three alopiid sharks have a similar amount of RM. However, A. superciliosus and A. pelagicus differ from A. vulpinus in that they do not possess the medial and anterior RM arrangement that would likely facilitate metabolic heat conservation (RM endothermy).

NOT ALL THRESHER SHARKS KEEP WARM

In the fish world, it's normal to be cold-bodied and take on the temperature of your surroundings. But there are exceptions to every rule;tunas and lamnid sharks are endothermic, managing to keep their bodies warmer than the waters they live in. The common thresher shark, a large alopiid shark with a formidable tail that roams temperate and deep tropical waters, is also warm-bodied. Since all tunas and all lamnid sharks are endothermic, it seemed fair to suppose that the two other known thresher shark species, bigeye and pelagic threshers, are also warm-bodied. But Chugey Sepulveda, Diego Bernal and their colleagues reveal that bigeye and pelagic thresher sharks are nothing like their warm-bodied common cousins(p. 4255).Most fish keep the red muscle that's used for swimming just beneath their skin and can't retain the heat their muscles produce, but tunas, lamnid sharks and the common thresher shark all keep their red muscles nestled deep inside their bodies, insulating their internal `furnace' from the cold water. If bigeye and pelagic thresher sharks also bury their red muscle deep inside their bodies, Sepulveda and Bernal reasoned, then it's likely that these sharks are also warm-bodied.Sepulveda and Bernal teamed up with Nick Wegner and Jeff Graham to find out if all threshers have the same red muscle distributions. Since live thresher sharks are very difficult to catch, the team bought some dead thresher sharks from commercial fisheries. They froze the sharks, sliced them into thin transverse sections and took a digital image of each slice. Reconstructing a 3D computer model of each species, the team visualized red muscle distribution all along the length of the sharks' bodies. But as soon as they cut open the first bigeye and pelagic threshers, the team spotted that these sharks are clearly nothing like their common cousin. The red muscle of both bigeye and pelagic threshers runs just beneath the skin and is mainly distributed towards the tail end of the body, while in the common thresher shark the red muscle runs along the backbone and is concentrated at the head end of the body. `We didn't expect to see such a big difference', Bernal recalls, `so our first thought was that the fisheries had sold us the wrong species.' But a DNA analysis soon confirmed that they really were inspecting the right species.The team also found another clear difference among the three thresher species. Tunas, lamnid and common thresher sharks retain the heat produced by their red muscles using vascular counter-current heat exchange systems that short-circuit heat loss to the environment. But when the team examined the bigeye and pelagic thresher sharks' vascular systems to look for these modifications, they found no evidence of such heat exchangers. This finding,together with the team's observation that bigeye and pelagic thresher sharks don't keep their red muscle near their body core, means that it's very unlikely that these two species are warm-bodied.The team concludes that the common thresher shark is the only thresher species with the anatomical specializations for red muscle endothermy. Why and how these specializations evolved in common threshers but apparently not in bigeye and pelagic threshers is a mystery that the team is now delving into.

Lentinellus ursinus & L. vulpinus make their first recorded appearance in Epping Forest

Lentinellus ursinus & L. vulpinus make their first recorded appearance in Epping Forest

Evidence for Temperature Elevation in the Aerobic Swimming Musculature of the Common Thresher Shark, Alopias vulpinus

<i>Ichthyology & Herpetology</i> (formerly <i>Copeia</i>) publishes work on the biology of fishes, amphibians, and reptiles, or work using those organisms as models for testing hypotheses of broad significance.

First Observations of Feeding on Thresher &lt;I&gt;(Alopias vulpinus)&lt;/I&gt; and Hammerhead &lt;I&gt;(Sphyrna zygaena)&lt;/I&gt; Sharks by Killer Whales &lt;I&gt;(Orcinus orca)&lt;/I&gt; Specialising on Elasmobranch Prey

Killer whale (Orcinus orca) predation on elasmobranchs (sharks and rays) is not often reported. In New Zealand waters, killer whales captured and ate thresher (Alopias vulpinus) and smooth-hammerhead (Sphyrna zygaena) sharks. Both species were not reported previously as prey of killer whales. These observations help support the idea that elasmobranchs are a main prey type for New Zealand killer whales; ten species of elasmobranchs are now recorded as prey for this population.

Stable isotopes from multiple tissues reveal diet switching in sharks

Food web relationships in marine systems have traditionally been defined through stomach content analysis, but biochemical techniques have recently emerged to validate and broaden temporal diet patterns. Stable isotope analysis has become a practical tool for evaluating these relationships in aquatic systems; however, routine sampling of muscle tissue captures only part of the trophic information available from each animal. We compared δ 15 N and δ 13 C values among liver, muscle and cartilage in the blue shark Prionace glauca, shortfin mako Isurus oxyrinchus, and common thresher Alopias vulpinus from the northwest Atlantic to show how multiple-tissue sampling captured feeding relationships which would have been invisible to muscle tissue alone. Specifically, we demonstrated evidence of a cephalopod to bluefish Pomatomus saltatrix diet switch in the short- fin mako in spring, and found that the blue shark and common thresher have consistent diets throughout the year. We concluded that consistency observed among stable isotope values in multi- ple tissues implied that the fish were in steady-state with the isotope ratios of their diet and that multiple tissues should be used in trophic assessments of large pelagic fishes. Further experiments to quantify the turnover of stable isotopes in different tissues and species are needed to improve the accuracy of stable-isotope analyses .

Role of polyols in thermal inactivation of shark ornithine transcarbamoylase.

The ability of activity modulators of ornithine transcarbamoylase (OCT) from the liver of the thresher shark Alopias vulpinus to stabilize the enzyme against thermal denaturation was investigated in the tri-buffer at pH 7.8, at temperatures ranging from 60 to 70 (o)C, in the presence of polyhydroxylic molecules such as glycerol and sugars. The study indicated that in the presence of 0.5 M sugars and 1.6 M glycerol in the preincubation medium the OCT activity increases. When trehalose is introduced directly in the reaction mixture in a range of concentration of 0.25-0.5 M, the activity is lower than that with maltose, glycerol and buffer alone. Kinetic data for carbamoyl phosphate and ornithine with and without maltose and glycerol are similar, whereas trehalose increases the kinetic values. Arrhenius plots show an increase of activation energy due to trehalose, whereas values obtained with maltose and glycerol are similar to the control.

Driftnet fishing and biodiversity conservation: the case study of the large-scale Moroccan driftnet fleet operating in the Alboran Sea (SW Mediterranean)

Illegal, large-scale driftnets are still used in several Mediterranean areas. According to international official sources, Morocco harbors the bulk of this fleet in the Mediterranean. To ascertain its biodiversity impact, 369 fishing operations (worth 4140 km of driftnets set) made by the driftnet fleet targeting swordfish ( Xiphias gladius) based in Al Hoceima (Alboran Sea) were monitored between December 2002 and September 2003. Parallel surveys were made in the main Mediterranean ports and in that of Tangiers, in the Gibraltar Straits, to estimate the total fishing effort. Results showed an active driftnet fleet conservatively estimated at 177 units. Estimated average net length ranges from 6.5 to 7.1 km, depending on the port, though actual figures are suspected to be much higher (12–14 km). Most boats perform driftnet fishing all year round, resulting in very high annual effort levels. A total of 237 dolphins (short-beaked common dolphin, Delphinus delphis, and striped dolphin, Stenella coeruleoalba), 498 blue sharks ( Prionace glauca), 542 shortfin makos ( Isurus oxyrinchus) and 464 thresher sharks ( Alopias vulpinus) were killed by the boats monitored during the sampling period, during the peak of the swordfish fishery, along with 2990 swordfish. Loggerhead turtle ( Caretta caretta) was also caught (46 individuals). Estimates for a 12-month period by the whole driftnet fleet yielded 3110–4184 dolphins (both species) and 20,262–25,610 pelagic sharks distributed in roughly equal proportions for P. glauca, I. oxyrinchus and A. vulpinus, in the Alboran Sea alone; further 11,589–15,127 dolphins and 62,393–92,601 sharks would be killed annually around the Straits of Gibraltar. Dolphins suffer from annual take rates exceeding 10% of their population sizes in the Alboran Sea; this unsustainable impact is particularly worrying for D. delphis, because its last remnant healthy population in the Mediterranean occurs in this area. Average catch rate for swordfish, the main target species, amounted to only 0.8 individuals/km net set. Pelagic sharks are actively targeted by a part of the fleet.

Predicting trophic position in sharks of the north-west Atlantic Ocean using stable isotope analysis

Trophic positions (TP) were estimated for the blue shark (Prionace glauca), shortfin mako (Isurus oxyrinchus), thresher shark (Alopias vulpinus), and basking shark (Cetorhinus maximus) using stable isotope ratios of carbon (δ13C) and nitrogen (δ15N). The basking shark had the lowest TP (3·1) and δ15N value (10·4‰), whereas the thresher shark had the highest values (4·5, 15·2‰). Mako sharks showed considerable variation in TP and isotopic values, possibly due to foraging from both inshore and offshore waters. Thresher sharks were significantly more enriched in δ15N than blue sharks and mako sharks, suggesting a different prey base. The δ13C values of thresher sharks and mako sharks varied significantly, but neither was significantly different from that of blue sharks. No statistical differences were found between our TP estimations and those derived from published stomach contents analyses, indicating that stable isotope data may be used to estimate the trophic status of sharks.

A revision of F. R. Irvine's Ghanaian marine fishes in the collections of The Natural History Museum, London

Some 180 species of marine fish were reported from Ghana in F. R. Irvine's The Fishes and Fisheries of the Gold Coast, an important milestone in West African ichthyology published in 1947. Although the book has been a major source of records for subsequent workers, the underpinning collections have been largely ignored. Two hundred and ninety-two specimens from 139 species collected by Irvine and colleagues were located within The Natural History Museum collections and are reported here with notes on their zoogeography. These were re-identified in the light of the intervening half century of research and have allowed us to examine the basis for most of Irvine's records by matching Irvine's collection numbers (referred to in his book) to BMNH registration numbers. In addition to registered material some 26 jars of unregistered material containing 46 specimens were discovered. About 20% of the species were found to have been misidentified. Six of the marine species collected by Irvine were described by J. R. Norman as new species between 1930 and 1935. These remain valid as: Rhinobatos albomaculatus Norman, 1930; Rhinobatos irvinei Norman, 1931; Serranus accraensis (Norman, 1931); Spicara nigricauda (Norman, 1931); Branchiostegus semifasciatus (Norman, 1931) and Pontinus accraensis Norman, 1935. A further nine species collected by Irvine were at the time unknown to science and have since been described by others as new species. Of particular interest is a specimen of Panturichthys isognathus Poll, 1953 which appears to be only the second adult specimen reported. Most of the 39 species for which material could not be located represented uncontentious records. However, there were eight species listed by Irvine, for which no voucher specimens could be located, which are unlikely to occur off Ghana, and a further two species (Carcharodon carcharias and Alopias vulpinus) for which Irvine's records cannot be considered a basis for a Ghana record. Five species (Conger conger, Umbrina cirrosa, Scorpaena scrofa, Chaetodon striatus and Liza ramada) are considered as doubtful records based on misidentifications. Three other species (Dentex macrophthalmus, Sphyrna zygaena and S. tudes) appear unlikely records for Ghana but cannot be totally dismissed. Inter alia this study demonstrates the critical importance of voucher specimens in museum collections to support biodiversity research.

Pelagic shark fisheries along the west coast of the United States and Baja California, Mexico

Fisheries targeting elasmobranch resources have experienced a dramatic growth during the past two decades. World-wide elasmobranch landings exceed 600 000 metric tons (mt) annually and have clearly made a significant impact on portions of that resource. In the eastern north Pacific catches of common thresher, shortfin mako and blue sharks may exceed 15 000 mt annually. Nearly 90% of all sharks taken within this area are immature. Like most sharks, these pelagics have low rates of increase which make them quite vulnerable to modern day fishing pressure. Clearly, the removal of large segments of juveniles from any population has the potential to decrease the adult population to unsustainable levels. The ability of populations to recover from over-exploitation depends not only on initial stock size, natural mortality, and migration rates, but also upon reducing total fishing mortality. Regulations enacted by special interest groups benefiting only one segment of the resource users, combined with the lack of biological information, have slowed progress towards achieving rational management.

Blood supply to the eyes and brain of lamniform sharks (Lamniformes)

AbstractThe arterial supply to the eyes and brain of the common thresher shark, Alopias vulpinus, was examined and compared with that of five other lamniform shark species. Temperatures of the eyes and brain in two of these species were shown in previous studies to be higher than ambient. This was considered to be correlated with the presence of an orbital rete mirabile derived from the hyoidean efferent and pseudobranchial arteries. This study shows that the pseudobranchial artery forms a rete in only one of the two species previously shown to be warm, indicating that the brain of the other species is warmed by a non‐retial vessel. This finding raises the possibility of brain and eye warming in Alopias vulpinus, which lacks an orbital rete mirabile.

A Note on the Occurrence of the Thresher Shark, Alopias Vulpinus from South-Western Black Sea

On 8 November 1996, a female thresher shark (Figure 1) was caught in a purse seine full of bluefish (Pomatomus saltator), off Şile (41°15′24″N 29°35′30″E). The shark was photographed and tooth samples from lower and upper jaws were removed, and placed in the personal collection of the author. The total length of the shark was 453 cm.Alopias vulpinus (Bonnaterre, 1788) is one of the three species of the family Alopiidae (Compagno, 1984). The thresher shark occurs worldwide, usually far offshore in temperate to tropical oceans, but where there are schools of bluefish, mackerel and squid, it may come close to the shore in pursuit. It is one of the most common shark species in the Mediterranean Sea (Quero, 1984). According to Devedjian (1926), Rhasis Erazi (1942) and Slastenenko (1955–1956) thresher sharks occur in the Sea of Marmara, the Bosphorus and the Black Sea, however, over the last 40 years there have been no reports of this species in these areas (Ak§iray, 1987).

Occurrence and Morphological Comparisons of Campula oblonga (Digenea: Campulidae), including a Report from an Atypical Host, the Thresher Shark, Alopias vulpinus

New host records for Campula oblonga Cobbold, 1858 from the common dolphin, Delphinus delphis L., and from the thresher shark, Alopias vulpinus (Bonnaterre), are reported herein. Campulids have not been reported previously from a host that was not a marine mammal. The excellent condition and small size of the gravid specimen and the diet and natural history of the thresher shark lead us to conclude that the digene was acquired from the consumption of infected fish. Specimens of C. oblonga from these 2 hosts and from harbor porpoises, Phocoena phocoena (L.), and from Dall's porpoises, Phocoenoides dalli (True), are compared, and a wide variation in ranges and values for characters is noted. The synonymy of Campula folium Ozaki, 1935 with C. oblonga is further supported by the apparent effect of the host on the size of the trematodes. Due to the degree of variation in measurements and the numerous factors that may impact these values, we recommend the use of qualitative morphologic characters for the identification of C. oblonga.

Paraorygmatobothrium barberi n. g., n. sp. (Cestoda: Tetraphyllidea), with amended descriptions of two species transferred to the genus

Paraorygmatobothrium n.g. (Cestoda: Tetraphyllidea) differs from all other phyllobothriid genera in having serrated microtriches on the proximal bothridial surfaces, two dorsal and two ventral scutes on the neck, and the presence of very small (<500 nm) triangular structures on the surface of the neck. No single light microscopical feature is sufficient to distinguish the new genus from other phyllobothriid genera. Phyllobothrium prionacis from Prionace glauca and Anthobothrium exiguum from Alopias vulpinus are transferred to the new genus and their descriptions are amended. Paraorygmatobothrium barberi n. sp. from Triakis semifasciata is also described, and can be distinguished from the other two species in being longer, having a greater number of segments, longer and wider mature segments, a greater number of testes, a longer cirrus-sac, a longer and wider ovary, a wider ovicapt, and a greater number of rows of dorsal and ventral vitelline follicles than the other two species. It also differs in the shape of the egg-shell and in the possession of a circular band of sub-tegumentary muscles in the middle third of each bothridium. Two of the species placed in the new genus have microtriches resembling an “ear of corn” on the distal bothridial surface. These microtriches are similar to structures reported for Phyllobothrium squali from the Squalus acanthias and Orygmatobothrium musteli from Mustelus henlei; this similarity in microtriche structure potentially indicates a systematic relationship between members of Paraorygmatobothrium and these two species.

The storage of spermatozoa in the oviducal glands of western North Atlantic sharks

Spermatozoa stored in oviducal glands of sharks sampled off the North American east coast were revealed by viewing stained tissue sections using light microscopy. Of eleven species surveyed, sperm were found in nine:Alopias vulpinus, Lamna nasus, Carcharhinus obscurus, Carcharhinus plumbeus, Galeocerdo cuvieri, Prionace glauca, Rhizoprionodon terraenovae, Sphyrna lewini andSphyrna tiburo. Three insemination patterns are proposed to account for differences noted in these findings: (1) non-storage/immediate insemination for sharks such asLamna nasus; (2) short-term storage/delayed insemination as found in sharks in which ovulation is prolonged over weeks or months such asRhizoprionodon terraenovae, and (3) long-term storage/repeated insemination, a characteristic of nomadic sharks such asPrionace glauca andCarcharhinus obscurus which can store sperm in specialized tubules for months to years.