Lamna Nasus Research Articles

Virtual reconstruction of the skeletal labyrinth of two lamnid sharks (Elasmobranchii, Lamniformes).

The first virtual reconstruction of the skeletal labyrinth of the porbeagle shark Lamna nasus and the shortfin mako shark Isurus oxyrinchus is presented here using high-resolution micro-computed tomography. The results, in comparison with previously published information, suggest relationships between skeletal labyrinth morphology and locomotion mode in chondrichthyans, but also show that further studies are required to establish such connections. Nevertheless, this study adds to the knowledge of the skeletal labyrinth morphology in two apex elasmobranch species.

Transboundary movements, unmonitored fishing mortality, and ineffective international fisheries management pose risks for pelagic sharks in the Northwest Atlantic

The shortfin mako (Isurus oxyrinchus), porbeagle (Lamna nasus), and blue shark (Prionace glauca) are three frequently caught shark species in the northwestern Atlantic Ocean. Satellite tagging studies show that all three species range widely across many national boundaries but spend up to 92% of their time on the high seas, where they are largely unregulated and unmonitored. All are caught in large numbers by swordfish and tuna fishing fleets from a large number of nations, usually unintentionally, and all are unproductive by fish standards, which makes them particularly sensitive to fishing pressure. Landing statistics that grossly underrepresent actual catches, unreported discards that often exceed landings, and high discard mortality rates are threats to the populations and roadblocks to useful population monitoring. The influence of these threats is greatly magnified by inattention and ineffective management from the responsible management agency, the International Commission for the Conservation of Atlantic Tunas (ICCAT), whose prime focus is the more valuable swordfish and tuna stocks. Although practical management options are available, none will be possible if organizations like ICCAT continue to treat sharks like pests.

Concentrations of mercury and other trace elements in porbeagle shark Lamna nasus

Concentrations of 11 trace elements in three tissues of porbeagle shark Lamna nasus (n=33) were determined. The maximum observed concentrations of Cd and Pb in muscle were 0.04 and 0.01mgkg−1, respectively, and all muscle samples were below European seafood limits for these metals. Hg concentrations in either the red or white muscle that exceeded European regulations for seafood were observed in one-third of specimens. Hg concentration, however, increased with length, and all fish >195cm had concentrations >1.0mgkg−1, with a maximum observed value of 2.0mgkg−1. Concentrations of Fe and Cu were, on average, 9.7 and 10 times higher in red muscle than in nearby white muscle, respectively. Mn, Zn, As and Se were also found in significantly higher concentrations in red muscle than in white muscle.

Complete mitochondrial genome of the porbeagle shark, Lamna nasus (Chondrichthyes, Lamnidae)

We report for the first time, the complete mitochondrial genome sequence of the porbeagle shark, Lamna nasus, from a specimen collected from offshore waters of New England, USA in the western North Atlantic Ocean. The genome structure of this species is similar to the other reported shark mitogenomes. The genome sequence has a total length of 16,697 bases; similar in size to the mtDNA genomes reported for other lamnid species. A Bayesian phylogenetic tree was reconstructed for the Lamnidae family using mitogenome sequences available in the Genbank.

Discards, hooking, and post-release mortality of porbeagle (Lamna nasus), shortfin mako (Isurus oxyrinchus), and blue shark (Prionace glauca) in the Canadian pelagic longline fishery

Discards, hooking, and post-release mortality of porbeagle (<i>Lamna nasus</i>), shortfin mako (<i>Isurus oxyrinchus</i>), and blue shark (<i>Prionace glauca</i>) in the Canadian pelagic longline fishery

Homology of Lateral Cusplets in the Teeth of Lamnid Sharks (Lamniformes: Lamnidae)

Teeth are a potentially rich source of character data for phylogenetic studies of living and fossil sharks, but there are many uncertainties about the homologies of tooth loci as well as structural details of teeth in different taxa. Here, we provide new developmental data on the so-called lateral cusplets of the teeth in Lamniformes. We studied the five living species of Lamnidae (Lamna nasus, L. ditropis, Isurus oxyrinchus, I. paucus, and Carcharodon carcharias) and a more basal lamniform, the Sand Tiger Carcharias taurus, using light microscopy and micro-CT scanning. We also studied a single skeletal specimen of the smalltooth Sand Tiger, Odontaspis ferox. Structures in the teeth of juvenile White Sharks, C. carcharias, were interpreted as lateral cusplets in some previous studies, but we show that they develop differently from lateral cusplets in the teeth of Lamna and Carcharias. We conclude that the structures in Carcharodon are not homologous to the lateral cusplets of Lamna and Carcharias taurus a...

Life in the open ocean: seasonal migration and diel diving behaviour of Southern Hemisphere porbeagle sharks (Lamna nasus)

A wide range of pelagic predators survive in the open ocean, yet little is known about how they use that environment. Much of the current information on these species comes from studies in shelf waters, and it is not clear how representative the results are of their oceanic lifestyle. We used pop-up satellite tags to explore the horizontal and vertical use of the open ocean by porbeagle sharks (Lamna nasus) in the south-west Pacific Ocean and to identify possible mitigation measures to reduce their bycatch in tuna longline fisheries. Ten porbeagle sharks were tracked in waters around New Zealand for 72–300 days (median 221 days). Sharks made horizontal movements of hundreds to thousands of kilometres, with a maximum estimated track length of almost 10,000 km. Mature females made seasonal latitudinal migrations from ~46–48°S in summer to ~35–38°S during winter–spring, where they are hypothesised to give birth to pups. Porbeagle sharks exhibited diel vertical migration, diving deeper during the day than at night. Dives generally began at dawn and finished at dusk and lasted 11–15 h depending on day length. Porbeagles feed mainly on mesopelagic fish and squid and appear to forage in the vertically migrating deep scattering layer. All sharks dived to at least 600 m with a maximum recorded depth of 1024 m. During the day, most of their time was spent at depths of 200–600 m in the open ocean. Porbeagle shark bycatch could be substantially reduced by limiting longline fishing to daylight hours when they are too deep to be caught. However, longliners currently set mainly at night to avoid seabird bycatch, which would increase unless other mitigation measures were implemented to protect them. A review of factors affecting the bycatch of various species, and the impact of mitigation measures on catches of target species, is required to identify an appropriate suite of management measures.

Identification of Shark Teeth (Elasmobranchii: Lamnidae) from a Historic Fishing Station on Smuttynose Island, Maine, Using Computed Tomography Imaging

Abstract - Two incomplete shark teeth were recovered during archaeological excavation of a historic fishing station on Smuttynose Island, ME. Specimens were identified to the species-level using non-destructive computed tomography (CT) imaging techniques. Their external and internal morphology is described and illustrated. Both teeth are from large sharks in the Order Lamniformes. The larger specimen is a developing tooth from the upper jaw of a Carcharodon carcharias (White Shark). The second specimen is a broken tooth from the lower jaw of a Lamna nasus (Porbeagle). The Smuttynose excavations provide an opportunity to examine faunal assemblages and the island's historic 17th-through 19th-century fisheries. Criteria for identifying teeth of common pelagic sharks of the Western North Atlantic are offered, and the role of sharks in the historic Gulf of Maine fishery is discussed.

A novel mini-DNA barcoding assay to identify processed fins from internationally protected shark species.

There is a growing need to identify shark products in trade, in part due to the recent listing of five commercially important species on the Appendices of the Convention on International Trade in Endangered Species (CITES; porbeagle, Lamna nasus, oceanic whitetip, Carcharhinus longimanus scalloped hammerhead, Sphyrna lewini, smooth hammerhead, S. zygaena and great hammerhead S. mokarran) in addition to three species listed in the early part of this century (whale, Rhincodon typus, basking, Cetorhinus maximus, and white, Carcharodon carcharias). Shark fins are traded internationally to supply the Asian dried seafood market, in which they are used to make the luxury dish shark fin soup. Shark fins usually enter international trade with their skin still intact and can be identified using morphological characters or standard DNA-barcoding approaches. Once they reach Asia and are traded in this region the skin is removed and they are treated with chemicals that eliminate many key diagnostic characters and degrade their DNA (“processed fins”). Here, we present a validated mini-barcode assay based on partial sequences of the cytochrome oxidase I gene that can reliably identify the processed fins of seven of the eight CITES listed shark species. We also demonstrate that the assay can even frequently identify the species or genus of origin of shark fin soup (31 out of 50 samples).

A record of the Porbeagle, Lamna nasus, in coastal waters of Buenos Aires (Argentina) confirmed by DNA barcoding

AbstractA record of a juvenile Porbeagle, Lamna nasus, in the coastal waters of Argentina is confirmed by DNA barcoding, since the specimen lacked some external diagnostic features. We discuss the occurrence of this species in the coastal waters of Argentina, its molecular affinity with conspecifics from a broad range of the species, and relevant conservation issues.

Predation of pop-up satellite archival tagged albacore (Thunnus alalunga)

Three out of eight albacore (Thunnus alalunga) tagged with pop-up satellite archival tags (PSATs) in the greater Bay of Biscay area of the North East Atlantic were predated as indicated by missing light level data, sudden increases in temperature, and substantial changes in depth profiles. Recorded stomach temperatures and differences between stomach and ambient water temperatures were consistent with shortfin mako (Isurus oxyrinchus) and porbeagle (Lamna nasus) sharks. Vertical behavior in the form of diel migrations, deep dives and extensive periods spent close to the surface during day and night time was again consistent with Lamnid sharks. The observed predation rate was considered to be elevated due to irregular post-release behavior as opposed to symptomatic of natural mortality.

Organohalogen contaminants and trace metals in North-East Atlantic porbeagle shark (Lamna nasus)

The North-East Atlantic porbeagle (Lamna nasus) population has declined dramatically over the last few decades and is currently classified as ‘Critically Endangered’. As long-lived, apex predators, they may be vulnerable to bioaccumulation of contaminants. In this study organohalogen compounds and trace elements were analysed in 12 specimens caught as incidental bycatch in commercial gillnet fisheries in the Celtic Sea in 2011. Levels of organohalogen contaminants were low or undetectable (summed CB and BDE concentrations 0.04–0.85mgkg−1wet weight). A notably high Cd concentration (7.2mgkg−1wet weight) was observed in one mature male, whereas the range observed in the other samples was much lower (0.04–0.26mgkg−1wet weight). Hg and Pb concentrations were detected only in single animals, at 0.34 and 0.08mgkg−1wet weight, respectively. These contaminant levels were low in comparison to other published studies for shark species.

Large pelagic predators could jeopardize the recovery of endangered Atlantic salmon

Long-term population viability of Bay of Fundy Atlantic salmon (Salmo salar) is threatened by high levels of marine mortality during migration. Pop-up satellite archival tags on repeat spawners provide direct evidence of extensive natural mortality of migrating salmon in coastal zones attributed to predation by large pelagic fish and no evidence of fishing mortality. Ingested tags show that salmon with a coastal migration are eaten by porbeagle shark (Lamna nasus) inside the Bay of Fundy, whereas distant migrants are consumed by Atlantic bluefin tuna (Thunnus thynnus) and other apex predators along the Scotian Shelf. Mortality is clustered in a few zones because of similar predator–prey habitat preferences and overlapping migration paths. The extent of predation in salmon populations with different migration strategies can account for observed decline rates in neighbouring populations with different life histories. The impact on endangered salmon populations that rely on multiple repeat spawners for population stability may be sufficient to hamper ongoing recovery efforts.

Distribution and trend in abundance of the porbeagle (Lamna nasus) in the southern hemisphere

Knowledge of a species’ distribution is an important element in its effective management and conservation. The porbeagle (Lamna nasus) is a common by-catch shark in the tuna longline fishery in the southern hemisphere, but its distribution and abundance are largely unknown. The investigation of observer data from the tuna longline fishery and other fishery survey data has revealed that (1) porbeagles are distributed in the pelagic waters across the oceans of the southern hemisphere, (2) juveniles and adults are distributed in cooler environments than are neonates, (3) pregnant females occur in the pelagic waters of the Indian Ocean and the Tasman Sea, most being frequently recorded around the Cape of Good Hope between June and July and (4) the standardised catch per unit effort (CPUE) based on tuna longline fishery (1994–2011) and driftnet survey (1982–1990) data indicate no continuous decreasing trend in the abundance of the southern porbeagle, contrary to the declining trend reported in a limited region in the South Atlantic. Considering its circumglobal distribution, stock status of this population should be assessed using information from the areas of its major distribution, including pelagic waters, and international coordination across oceans is necessary for the effective management of this population.

Shark Predation on Migrating Adult American Eels (Anguilla rostrata) in the Gulf of St. Lawrence

In an attempt to document the migratory pathways and the environmental conditions encountered by American eels during their oceanic migration to the Sargasso Sea, we tagged eight silver eels with miniature satellite pop-up tags during their migration from the St. Lawrence River in Québec, Canada. Surprisingly, of the seven tags that successfully transmitted archived data, six were ingested by warm-gutted predators, as observed by a sudden increase in water temperature. Gut temperatures were in the range of 20 to 25°C—too cold for marine mammals but within the range of endothermic fish. In order to identify the eel predators, we compared their vertical migratory behavior with those of satellite-tagged porbeagle shark and bluefin tuna, the only endothermic fishes occurring non-marginally in the Gulf of St. Lawrence. We accurately distinguished between tuna and shark by using the behavioral criteria generated by comparing the diving behavior of these two species with those of our unknown predators. Depth profile characteristics of most eel predators more closely resembled those of sharks than those of tuna. During the first days following tagging, all eels remained in surface waters and did not exhibit diel vertical migrations. Three eels were eaten at this time. Two eels exhibited inverse diel vertical migrations (at surface during the day) during several days prior to predation. Four eels were eaten during daytime, whereas the two night-predation events occurred at full moon. Although tagging itself may contribute to increasing the eel's susceptibility to predation, we discuss evidence suggesting that predation of silver-stage American eels by porbeagle sharks may represent a significant source of mortality inside the Gulf of St. Lawrence and raises the possibility that eels may represent a reliable, predictable food resource for porbeagle sharks.

Evaluation of Hook and Bait Type on the Catch Rates in the Western North Atlantic Ocean Pelagic Longline Fishery

Research was conducted in 2002 and 2003 by noaa's national Marine fisheries service, southeast fisheries science center, to investigate changes in hook design and bait type to reduce the bycatch of sea turtles on pelagic longlines in the western north atlantic ocean. The effectiveness of 18/0-20/0 circle hooks and 10/0 Japanese tuna hooks with squid (Illex spp.) and mackerel bait (Scomber scombrus linnaeus, 1758) was evaluated against the industry standard 9/0 J-hooks with squid bait with respect to reducing sea turtle and shark interactions while maintaining swordfish (Xiphias gladius linnaeus, 1758) and tuna (Thunnus spp.) catch rates. In total, 973,734 hooks were deployed during the study. Individually, circle hooks and mackerel bait significantly reduced both loggerhead [Caretta caretta (linnaeus, 1758)] and leatherback [Dermochelys coriacea (vandelli, 1761)] sea turtle bycatch. The combination of 18/0 circle hooks with mackerel bait was even more effective for loggerhead sea turtles and had a significant increase in swordfish catch by weight. The combination 18/0 circle hooks with squid bait resulted in a significant decrease in the swordfish catch and a significant increase in the catch rate of blue shark [Prionace glauca (linnaeus, 1758)] , bluefin tuna [Thunnus thynnus (linnaeus, 1758)], and albacore tuna [Thunnus alalunga (bonnaterre, 1788)]. With all hook types, mackerel bait resulted in a significant decrease in blue shark, bigeye tuna [Thunnus obesus (lowe, 1839)], and albacore tuna, but significantly increased the catch of porbeagle [Lamna nasus (bonnaterre, 1788)] and shortfin mako (Isurus oxyrinchus rafinesque, 1810).

Comparative morphology of rostral cartilages in extant mackerel sharks (Chondrichthyes, Lamniformes, Lamnidae) using CT scanning

A comparative study of rostral morphology of extant mackerel sharks (Lamniformes, Lamnidae) is presented. Based oncomputed tomography (CT) scans of fresh specimens, 3D reconstructions, dried museum chondrocrania and the availableliterature, detailed morphological descriptions of the rostral cartilages are provided for the type species of all three extantlamnid genera, namely Carcharodon carcharias (Linnaeus, 1758), Isurus oxyrinchus Rafinesque, 1810 and Lamna nasus(Bonnaterre, 1788), and compared with those of I. paucus Guitart Manday, 1966 and L. ditropis Hubbs &amp; Follett, 1947.Despite intraspecific variation, the rostral cartilages of all extant lamnids present significant differences that allow genus-and species-level identification, which is especially of use to identify fossil rostral nodes of these particular taxa. The maindifferences were found to be in overall calcification of the rostrum (Lamna &gt; Isurus &gt; Carcharodon), general configura-tion of the rostral open space, position of the base of the lateral rostral cartilages, (non-)abutting lateral cartilages, (absent)rostral keels and shape of the rostral node. In cross section, the base of the rostral node is rounded in Lamna, Y-shaped in Isurus and uncalcified in juvenile and subadult Carcharodon (tesserae absent).

On the by-catch of two porbeagle sharks Lamna nasus in the central Adriatic Sea

In July 2010 and August 2011 a subadult and an adult porbeagle shark Lamna nasus were respectively caught as by-catch by an artisanal fishery boat using a gill net in the central Adriatic Sea. The specimens, a mature 200 and a maturing 150 cm total length male, were photorecorded, measured and identified on the basis of meristic traits. Such two occurrences are discussed in the context of recent and historical information available on the presence of this species in the Mediterranean Sea. Overall, data confirmed on the one hand the rarity of the porbeagle shark in the Adriatic Sea also, and, on the other hand, they suggested some relation between the density of the findings for this species and the presence of a pit zone in the central part of the Adriatic Sea.

The taxonomic value of rostral nodes of extinct sharks, with comments on previous records of the genus Lamna (Lamniformes, Lamnidae) from the Pliocene of Lee Creek Mine, North Carolina (USA)

ABSTRACT Mollen, F.H. and Jagt, J.W.M. 2012. The taxonomic value of rostral nodes of extinct sharks, with comments on previous records of the genus Lamna (Lamniformes, Lamnidae) from the Pliocene of Lee Creek Mine, North Carolina (USA). Acta Geologica Polonica, 62 (1), 117-127. Warszawa. Shark rostral nodes from the Yorktown Formation (Zanclean, early Pliocene) of Lee Creek Mine, North Carolina (USA), previously assigned to the genus Lamna Cuvier, 1816, have been reinterpreted using a preliminary identification key for extant Lamniformes based on rostral morphology. In addition, the fossil rostral nodes have been compared in detail with Recent material of both the porbeagle, Lamna nasus (Bonnaterre, 1788) and the salmon shark, Lamna ditropis Hubbs &amp; Follet, 1947. Despite the fact that the rostra compared relatively well with those of Recent Lamna, the Lee Creek Mine specimens proved to differ significantly in having near-parallel lateral rostral cartilages that join the rostral node individually, instead of abutting ones. Based on this observation, we here propose to strike the genus Lamna from the Lee Creek Mine faunal list, so long as no other diagnostic material is forthcoming. These partially preserved rostra are likely to have belonged to extinct taxa within the families Lamnidae or Otodontidae, both of which have been documented from the Yorktown Formation on the basis of isolated teeth of at least three species, Cosmopolitodus hastalis (Agassiz, 1838), Megaselachus megalodon (Agassiz, 1835) and Parotodus benedenii (Le Hon, 1871).

Larval parasite gene sequence data reveal cryptic trophic links in life cycles of porbeagle shark tapeworms

The lack of information on marine tapeworm life cycles can be addressed with knowl- edge derived from trophic interactions in marine environments. These trophically transmitted para- sites exploit transmission routes involving predator-prey interactions. Porbeagle sharks Lamna nasus are apex predators feeding on a wide range of organisms, including teleosts and cephalopods. Although the biology of this shark species is relatively well studied, there is a surprising lack of infor- mation about the trophic interactions involving this species that lead to the acquisition of tapeworms. Recently, the use of molecular tools, combined with phylogenetics, has proven useful in identifying trophic links involved in the transmission of marine tapeworms. In the present study, we used sequence data from the D2 domain of the large subunit ribosomal DNA to link adult tapeworms of the species Clistobothrium cf. montaukensis and Dinobothrium sp. parasitising porbeagle sharks to lar- vae recovered from the squid Doryteuthis gahi. To the best of our knowledge, it is the first to provide empirical evidence for a trophic link between porbeagle sharks and D. gahi as a definitive route for the successful transmission of these tapeworms. Furthermore, our data suggest an ontogenetic shift in diet away from squid. Parasite abundance data in D. gahi indicate that the abundance of porbea- gle sharks can be significant in some years.