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8 pages, 4 figures, 2 tables.-- This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, This study documented the parasite faunas of the spiral valves of blue sharks Prionace glauca (L. 1758) and common thresher sharks Alopias vulpinus (Bonnaterre, 1788) caught in the California Current Large Marine Ecosystem (CCLME) north of the Mexican border. The spiral valves of 18 blue and 19 thresher sharks caught in the CCLME from 2009 to 2013 were examined for parasites. Seven parasite taxa were found in blue sharks and nine in threshers. The tetraphyllidean cestode Anthobothrium sp. (78% prevalence) was the most common parasite in blue sharks, and the phyllobothriid cestode Paraorygmatobothrium sp. (90% prevalence) was the most common in threshers. An adult nematode of the genus Piscicapillaria was found in threshers for the first time and may be a new species. Adult individuals of Hysterothylacium sp. were found in both shark species. The adult acanthocephalan Rhadinorhynchus cololabis and remains of the parasitic copepod Pennella sp. – both parasites of Pacific saury, Cololabis saira – were found in the intestines of threshers, indicating recent feeding on saury. This study paves the way for a more comprehensive examination, including more samples and a wider variety of shark species, to provide a greater understanding of shark feeding behaviour and possibly provide information on shark population biology, National Oceanographic Atmospheric Administration (NOAA)

Shark skin denticles (scales) are diverse in morphology both among species and across the body of single individuals, although the function of this diversity is poorly understood. The extremely elongate and highly flexible tail of thresher sharks provides an opportunity to characterize gradients in denticle surface characteristics along the length of the tail and assess correlations between denticle morphology and tail kinematics. We measured denticle morphology on the caudal fin of three mature and two embryo common thresher sharks (Alopias vulpinus), and we compared thresher tail denticles to those of eleven other shark species. Using surface profilometry, we quantified 3D-denticle patterning and texture along the tail of threshers (27 regions in adults, and 16 regions in embryos). We report that tails of thresher embryos have a membrane that covers the denticles and reduces surface roughness. In mature thresher tails, surfaces have an average roughness of 5.6 μm which is smoother than some other pelagic shark species, but similar in roughness to blacktip, porbeagle, and bonnethead shark tails. There is no gradient down the tail in roughness for the middle or trailing edge regions and hence no correlation with kinematic amplitude or inferred magnitude of flow separation along the tail during locomotion. Along the length of the tail there is a leading-to-trailing-edge gradient with larger leading edge denticles that lack ridges (average roughness = 9.6 μm), and smaller trailing edge denticles with 5 ridges (average roughness = 5.7 μm). Thresher shark tails have many missing denticles visible as gaps in the surface, and we present evidence that these denticles are being replaced by new denticles that emerge from the skin below.

Within the fields of biology and ecology, animal movement is arguably one of the most basic, and yet, often one of the most difficult areas of study. Where and why animals migrate, and what patterns can be derived from individual movements in order to make population-level inferences are key areas when attempting to define basic population dynamics. These questions are of equal interest to biologists and managers, with many species assessments identifying improvements in the understanding of population-level movement as a key research need. We aimed to improve our understanding of population level movement for common thresher sharks Alopias vulpinus by leveraging the largest satellite tagging dataset available for this species. Using a Bayesian approach specifically designed to address population-level questions with sparse telemetry data, we identified that A. vulpinus off the west coast of North America are partial migrators which conditionally migrate, based on a combination of fixed intrinsic states (size, sex) and variable extrinsic states (e.g. season, environment). Waters of the Southern California Bight were identified as an area where, seasonally, a large variety of sizes of A. vulpinus can be found. While smaller juveniles can be found throughout the year, larger sub-adults and adults often move out of the Bight during certain seasons (spring and winter). Knowledge of how A. vulpinus distribute along the coast, and that season, size, and to some extent sex, play important roles in where and what type of animals are likely to be found, are key pieces of information when attempting to accurately characterize basic biological parameters like age, growth, and reproduction, as well as understanding the effects of variable fishing pressures across the species’ range.

Alopias is a group of lamniform sharks characterized by a highly elongate caudal fin with three known extant species: Alopias pelagicus (pelagic thresher shark), Alopias superciliosus (bigeye thresher shark), and Alopias vulpinus (common thresher shark). Alopias pelagicus and A. vulpinus are considered fast swimmers and use their caudal fin to hunt for small schooling fish by stunning them, but this feeding behavior has never been directly observed for A. superciliosus. In this study, we examined four integumentary variables of selected fast swimming (e.g. A. pelagicus, A. vulpinus, and Lamna) and slow swimming (e.g. Mitsukurina and Megachasma) lamniform sharks to determine whether A. superciliosus is a fast swimmer or a slow swimmer. Our data indicate that A. superciliosus is a slow swimming lamniform, but it probably employs a simple laterally directed tail slap to capture its prey. Overall, our study points to an interpretation that A. superciliosus is an ambush predator, rather than an active prey-pursuing hunter. Mapping of scale data onto previously published phylogenetic trees indicate that slow swimming is a plesiomorphic condition in the order Lamniformes. Our work represents the most extensive comparative study of the morphology and variation of integumentary structures, especially placoid scales, conducted so far for Lamniformes.

Alopias vulpinus (Bonnaterre, 1788). Common Thresher Shark or Thresher Shark. To at least 5.73 m (18.8 ft) (Weigmann 2016), and possibly to 6.36 m (20.9 ft) TL (Ebert 2003). Circumglobal in warm waters; western Pacific Ocean north to Hokkaido Island, Japan (Yoshino and Aonuma in Nakabo 2002); west of Yakobi I., south-eastern Alaska (Bruce Wing, pers. comm. to M.L.) to Chile (Eschmeyer and Herald 1983), including Gulf of California (Smith et al. 2009). Coastal and oceanic epipelagic; depth: surface to 650 m (2,132 ft) (Weigmann 2016)., Published as part of Love, Milton S., Bizzarro, Joseph J., Cornthwaite, Maria, Frable, Benjamin W. & Maslenikov, Katherine P., 2021, Checklist of marine and estuarine fishes from the Alaska-Yukon Border, Beaufort Sea, to Cabo San Lucas, Mexico, pp. 1-285 in Zootaxa 5053 (1) on page 15, DOI: 10.11646/zootaxa.5053.1.1, http://zenodo.org/record/5578008, {"references":["Weigmann, S. (2016) Annotated checklist of the living sharks, batoids and chimaeras (Chondrichthyes) of the world, with a focus on biogeographical diversity. Journal of Fish Biology, 88, 837 - 1037. https: // doi. org / 10.1111 / jfb. 12874","Ebert, D. A. (2003) Sharks, Rays, and Chimaeras of California. University of California Press, Berkeley.","Nakabo, T. (Ed.). (2002) Fishes of Japan with Pictorial Keys to the Species. Tokai University Press, Tokyo.","Eschmeyer, W. N. & Herald, E. S. (1983) A Field Guide to Pacific Coast Fishes of North America from the Gulf of Alaska to Baja California. Houghton Mifflin, Boston.","Smith, W. D., Bizzarro, J. J. & Cailliet, G. M. (2009) The artisanal elasmobranch fishery of Baja California, Mexico: characteristics and management considerations. Ciencias Marinas, 35, 209 - 236. https: // doi. org / 10.7773 / cm. v 35 i 2.1534"]}

This study compared the concentration of essential (Co, Cr, Cu, Fe, Mn, Ni, Se, Zn) and nonessential (Ag, As, Cd, Hg, Pb) trace elements in the muscle tissue of a pregnant common thresher shark (Alopias vulpinus) to the concentration in the three embryos. With the exception of Ag, Cd, Cr, and Ni which were below the detection limit, all other elements accumulated in the embryo muscle tissue. The Se:Hg molar ratios in the embryos averaged 9.8, indicating that Se may have a protective role against Hg toxicity during this early life stage. Maternal transfer as a source of trace elements in sharks should not be overlooked and future studies need to focus on how reproductive strategy influences this process.

Alopias vulpinus(Bonnaterre, 1788) Alopias vulpinus: Baranes & Darom, 1978 (Heb.); Golani, 1996; Golani, 2005; Golani, 2006. ORDER: CARCHARINIFORMES, Published as part of Golani, Daniel, 2021, An updated Checklist of the Mediterranean fishes of Israel, with illustrations of recently recorded species and delineation of Lessepsian migrants, pp. 1-108 in Zootaxa 4956 (1) on page 7, DOI: 10.11646/zootaxa.4956.1.1, http://zenodo.org/record/4691195, {"references":["Baranes, A. & Darom, D. (1978) On sharks and jaws. Mada, 22 (2), 61 - 68. [in Hebrew]"]}

Alopias vulpinus (Bonnaterre, 1788) Thresher Shark Squalus vulpinus Bonnaterre, 1788: 9. Types unknown according to Compagno (2001), type locality: Mediterranean Sea. Local synonymy: Alopias vulpes: Bleeker, 1860b: 58; Thompson, 1914: 147; Barnard, 1925: 34; Barnard, 1947: 14, fig. 3, pl. 2. Alopecias vulpes: G̹nther, 1870: 393 (Cape seas); Gilchrist, 1902: 164. Alopias vulpinus: Smith, 1949a: 47, fig. 22; Smith, 1965: 47, fig. 22; Bass et al., 1975c: 35, fig. 18, pl. 11; Compagno, 1984a: 232, fig.; Bass, 1986: 102, fig. 16.3; Cliff & Wilson, 1986: 13; Compagno et al., 1989: 42, pl.; Compagno et al., 1991: 44; Compagno, 1999: 118; Heemstra & Heemstra, 2004: 72; Compagno et al., 2005: 180, fig., pl. 29; Ebert et al., 2013 a: 223, fig., pl. 27; NPOA, 2013: 50; Ebert & Dando, 2014: 61, fig.; da Silva et al., 2015: 246; Ebert & van Hees, 2015: 145; Compagno, 2016: 1236; Weigmann, 2016: 849. Alopias pelagicus: D’Aubrey, 1964a: 18, pl. 5 (east coast of South Africa). South Africa voucher material: SAIAB 8654, SAIAB 26219, SAIAB 27024, SAIAB 75572, SAIAB 75573, SAIAB 99326. South African distribution: NC to KZN; less common on the east coast. Remarks: The most common of the three thresher species in South Africa, it is caught commercially in various fisheries (NPOA, 2013) and by anglers in the WC. Conservation status: VU (2019)., Published as part of Ebert, David A., Wintner, Sabine P. & Kyne, Peter M., 2021, An annotated checklist of the chondrichthyans of South Africa, pp. 1-127 in Zootaxa 4947 (1) on pages 42-43, DOI: 10.11646/zootaxa.4947.1.1, http://zenodo.org/record/4614567, {"references":["Bonnaterre, J. P. (1788) Tableau encyclopedique et methodique des trois regnes de la nature. Ichthyologie, Paris, 215 pp. https: // doi. org / 10.5962 / bhl. title. 11660","Compagno, L. J. V. (2001) Sharks of the World, an Annotated and Illustrated Catalogue of Shark Species Known to Date. Volume 2. Bullhead, Mackerel and Carpet Sharks (Heterodontiformes, Lamniformes and Orectolobiformes). FAO, Rome, 269 pp.","Bleeker, P. (1860 b) Zesde bijdrage tot de kennis der vischfauna van Japan. Acta Societatis Regiae Scientiarum Indo-Neerlandicae, 8 (1), 1 - 104. https: // doi. org / 10.5962 / bhl. title. 144153","Thompson, W. W. (1914) Catalogue of the fishes of the Cape Province (Pt 1). Marine Biological Report, Cape Town, 2 (8), 132 - 167.","Barnard, K. H. (1925) A monograph of the marine fishes of South Africa. Part I (Amphioxus, Cyclostomata, Elasmobranchii, and Teleostei-Isospondyli to Heterosomata). Annals of the South African Museum, 21, 1 - 418.","Barnard, K. H. (1947) A Pictorial Guide to South African Fishes. Marine and Freshwater. Maskew Miller Ltd, Cape Town, 226 pp.","Gilchrist, J. D. F. (1902) Catalogue of fishes recorded from South Africa. Cape of Good Hope, Department of Agriculture, Marine Investigations in South Africa, 1, 97 - 179.","Smith, J. L. B. (1949 a) The Sea Fishes of Southern Africa. South Africa Central News Agency Ltd., 550 pp.","Smith, J. L. B. (1965) The Sea Fishes of Southern Africa. 5 th Edition. Central News Agency Ltd., 580 pp.","Bass, A. J., D'Aubrey, J. D. & Kistnasamy, N. (1975 c) Sharks of the east coast of southern Africa. IV. The families Odontaspididae, Scapanorhynchidae, Isuridae, Cetorhinidae, Alopiidae, Orectolobidae and Rhiniodontidae. Investigational Report. Oceanographic Research Institute, Durban, 39, 1 - 102.","Compagno, L. J. V. (1984 a) FAO Species Catalogue. Sharks of the World. An Annotated and Illustrated Catalogue of Shark Species Known to Date. FAO Fisheries Synopsis. Vol. 4. No. 125. Part 1. Hexanchiformes to Lamniformes. FAO, Rome, pp. 1 - 250.","Bass, A. J. (1986) Families Chlamydoselachidae, Heterodontidae, Orectolobidae, Rhinicodontidae, Scyliorhinidae, Pseudotriakidae, Sphyrnidae, Lamnidae, Cetorhinidae, Alopiidae, Pseudocarchariidae, Squatinidae. In: Smith, M. M. & Heemstra, P. C. (Eds.), Smith's Sea Fishes. Macmillan, Johannesburg, pp. 47 - 48 + 64 - 66 + 87 - 102 + 103 + 107.","Cliff, G. & Wilson, R. B. (1986) Natal Sharks Board's Field Guide to Sharks and Other Marine Animals. Natal Sharks Board, Umhlanga Rocks, 57 pp.","Compagno, L. J. V., Ebert, D. A. & Smale, M. J. (1989) Guide to the Sharks and Rays of Southern Africa. Struik Publishers, Cape Town, 158 pp.","Compagno, L. J. V., Ebert, D. A. & Cowley, P. D. (1991) Distribution of offshore demersal cartilaginous fishes (class Chondrichthyes) of the west coast of southern Africa, with notes on their systematics. South African Journal of Marine Science, 11, 43 - 139. https: // doi. org / 10.2989 / 025776191784287664","Compagno, L. J. V. (1999) An overview of chondrichthyan systematics and biodiversity in southern Africa. Transactions of the Royal Society of South Africa, 54, 75 - 120. https: // doi. org / 10.1080 / 00359199909520406","Heemstra, P. C. & Heemstra, E. (2004) Coastal Fishes of Southern Africa. National Inquiry Service Centre and South African Institute for Aquatic Biodiversity, Grahamstown, 488 pp.","Compagno, L., Dando, M. & Fowler, S. (2005) Field Guide to the Sharks of the World. Harper Collins Publishers Ltd, London, 368 pp.","Ebert, D. A., Fowler, S. & Compagno, L. J. V. (2013) Sharks of the World: A Fully Illustrated Guide to the Sharks of the World. Wild Nature Press, Plymouth, 528 pp.","NPOA. (2013) National Plan of Action for the Conservation and Management of Sharks (NPOA-Sharks). Department of Agriculture, Forestry and Fisheries (DAFF), Rogge Bay, Cape Town, 63 pp.","Ebert, D. A. & Dando, M. (2014) On Board Guide for the Identification of Pelagic Sharks and Rays of the Western Indian Ocean. SmartFish Programme, FAO, Rome & Indian Ocean Commission, Port Louis, 109 pp.","da Silva C., Booth, A. J., Dudley, S. F. J., Kerwath, S. E., Lamberth, S. J., Leslie, R. W., McCord, M. E., Sauer, W. H. H. & Zweig, T. (2015) A description and updated overview of the status and management of South Africa's chondrichthyan fisheries. South African Journal of Marine Science, 37, 233 - 248. https: // doi. org / 10.2989 / 1814232 X. 2015.1044471","Ebert, D. A. & van Hees, K. E. (2015) Beyond jaws: rediscovering the \" Lost Sharks \" of southern Africa. African Journal of Marine Science, 37, 141 - 156. https: // doi. org / 10.2989 / 1814232 X. 2015.1048730","Compagno, L. J. V. (2016) Sharks. In: Carpenter, K. E. & De Angelis, N. (Eds.), The Living Marine Resources of the Eastern Central Atlantic. Vol. 2. Bivalves, Gastropods, Hagfishes, Sharks, Batoid Fishes, and Chimaeras. FAO Species Identification Guide for Fishery Purposes. FAO, Rome, pp. 1122 - 1336.","Weigmann, S. (2016) Annotated checklist of the living sharks, batoids and chimaeras (Chondrichthyes) of the world, with a focus on biogeographical diversity. Journal of Fish Biology, 88, 837 - 1037. https: // doi. org / 10.1111 / jfb. 12874","D'Aubrey, J. D. (1964 a) Preliminary guide to the sharks found off the east coast of South Africa. South African Association for Marine Biological Research, Oceanographic Research Institute, Investigational Report, 8, 1 - 95."]}

Alopias vulpinus (Bonnaterre 1788) ���Thintail thresher Taxonomy. New record from Lebanon, based on photos of an individual landed in Nakoura (2 June 2018). Recent unpublished record from Naqoura (2 July 2018). Distribution. Circumglobal in tropical through temperate seas (including Caribbean Sea, Mediterranean Sea, Black Sea, western Baltic Sea, North Sea). Conservation. IUCN: Global (VU: A2bd+3bd+4bd, 20 February 2007); Med. (EN: A2 bd, 25 March 2016); CITES Appendix II. Capture and threats: FIT, FIB, unknown. Occurrence: Very rare. Medium priority for conservation action., Published as part of Bariche, Michel & Fricke, Ronald, 2020, The marine ichthyofauna of Lebanon: an annotated checklist, history, biogeography, and conservation status, pp. 1-157 in Zootaxa 4775 (1) on pages 14-15, DOI: 10.11646/zootaxa.4775.1.1, http://zenodo.org/record/3983887

Elasmobranch species composition and spatiotemporal variability can often be characterized from landing surveys of local fisheries, with important management implications. In the present study, we describe the elasmobranch landing composition of 4 major artisanal fishing ports in northwestern Baja California, Mexico. Sampling was conducted opportunistically between 1995 and 2010 and included an effort of 684 fishing days. Species composition was gear-dependent and varied with the fishing area, with thresher sharks (Alopias vulpinus) and spiny dogfish (Squalus suckleyi) dominating the catches landed by coastal gill net fisheries, and blue sharks (Prionace glauca) and shortfin mako sharks (Isurus oxyrhinchus) dominating the catches landed by the offshore longline fishery. Size-structure analysis indicated that catches were composed primarily of juveniles for most species, although the catch of mature soupfin sharks (Galeorhinus galeus) increased in longline fisheries during the winter. The results indicate that minor regional differences in elasmobranch species composition occur along the Pacific coast of Baja California and are most likely related to regional oceanographic or habitat differences. The results of this study may form the basis for future efforts to monitor species composition changes over time, to more completely assess elasmobranch populations.

The common thresher shark (Alopias vulpinus) is an important fisheries species in the northeastern Pacific Ocean along California, USA and Mexico; yet genetic understanding of this species is incomplete. Using IonTorrent PGM generated metagenomic libraries constructed from the skin surface, we recovered the complete mitogenome of the common thresher shark. The length of the mitogenome was 16,712 basepairs and consisted of 22 tRNA, two rRNA, 13 protein coding sequences, a replication origin and a control region, similar to other Alopias spp. The median coverage across the mitogenome was 21 ×, ranging from 1 to 48 × coverage. The mean GC content of the mitogenome was 37.83%. Using the 13 protein coding genes of the mitogenome, we show phylogenetic placement of the common thresher shark with the pelagic thresher (Alopias pelagicus; a posterior probability of 1). In addition, the inclusion of this mitogenome increased certainty for the placement of the Lamniformes family with the Carcharhiniformes family (a posterior probability of 1), rather than with the Orectolobeformes family, as has been previously reported. The availability of the common thresher shark mitogenome will aid phylogenetic inference and population based studies of this important fisheries species.

Management and conservation of marine predator species relies on a fundamental knowledge of their movements and behaviour. Pop‐up satellite archival tags were used to investigate the vertical movement patterns of five blue sharks (Prionace glauca) and one thresher shark (Alopias vulpinus) within the southeastern Indian Ocean. Sections of similar depth distribution, identified using a split moving window analysis, were investigated in relation to the thermal structure of the water column and activity rates. Minimum horizontal displacement of between 66 and 5,187 km for blue sharks and 16 km for the thresher shark were recorded over 863 tracking days. Maximum depths ranged from 540 to 807 m for blue sharks and 144 m for the thresher shark. All sharks displayed plasticity in their depth distribution, with diel vertical movements and surface‐oriented movements the two most common patterns. Diel movement of prey is the most likely explanation for diel vertical movements of thresher and blue sharks. This study has improved our understanding of the vertical movement patterns of these pelagic predators and the relationship between their depth distribution, temperature, and activity.

A thresher shark poached by fishermen in the stretch of sea between the island of Ponza and the coast of Terracina (Lazio, Central Italy, Mediterranean Sea) and confiscated by the Italian health authorities was evaluated for the presence of chemical contaminants. Hg mean concentration of 2.1 mg kg−1 was found in muscle; speciation analysis confirmed it was almost in the toxic organic form of MeHg (2.0 mg kg−1). The Se:Hg molar ratio was

We have developed a set of tools that operate within an aquatic geographic information system to improve the accessibility, and usability of remote-sensed satellite and computer-modeled oceanographic data for marine science and ecosystem-based management. The tools form the Pelagic Habitat Analysis Module (PHAM), which can be applied as a modeling platform, an investigative aid in scientific research, or utilized as a decision support system for marine ecological management. Applications include fisheries, marine biology, physical and biological oceanography, and marine spatial management. The GIS provides a home for diverse data types and automated tools for downloading remote sensed and global circulation model data. Within the GIS environment, PHAM provides a framework for seamless interactive four-dimensional visualization, for matching between disparate data types, for flexible statistic or mechanistic model development, and for dynamic application of user developed models for habitat, density, and probability predictions. Here we describe PHAM in the context of ecosystem-based fisheries management, and present results from case study projects which guided development. In the first, an analysis of the purse seine fishery for tropical tuna in the eastern Pacific Ocean revealed oceanographic drivers of the catch distribution and the influence of climate-driven circulation patterns on the location of fishing grounds. To support management of the Common Thresher Shark (Alopias vulpinus) in the California Current Ecosystem, a simple empirical habitat utilization model was developed and used to dynamically predict the seasonal range expansion of common thresher shark based on oceanographic conditions.

Carnobacterium maltaromaticumis a well-known pathogen of bony fish. More recently,C. maltaromaticumhave been isolated from the brain and inner ear of disorientated and stranded common thresher (Alopias vulpinus) and salmon shark (Lamna ditropis). While thresher shark strandings are recent, salmon sharks have been stranding for decades, suggesting a long-term association betweenC. maltaromaticumand sharks. Interestingly, some strains ofC. maltaromaticumare used by the food industry for their probiotic and antimicrobial activity. Here, we sequenced the genome of 9C. maltaromaticumstrains (SK-isolates) from diseased common thresher and salmon sharks and compared them to otherC. maltaromaticumstrains in order to identify the genomic signatures that differentiate the disease-associated from the innocuousC. maltaromaticumisolates. SK strains formed a monophyletic clade, with a conserved gene repertoire, and shared a high degree of pseudogenization even though isolates were from different shark species, locations, and across years. In addition, these strains displayed few virulence associated genes and unique genomic regions, some resulting from horizontal gene transfer. The association of diseased sharks and SK strains suggests their role as potential pathogens. Although the high degree of pseudogenization suggests a transition to a host-adapted lifestyle, a set of conserved functional genes highlights the need of essential functions required for a host-independent life style. Globally, this work identifies specific genomic signatures ofC. maltaromaticumstrains isolated from infected sharks, provides the framework to elucidate the role of SK strains in the development of the disease in sharks, and further investigate the dissemination of SK strains in populations of wild fish.

The similarities between ichthyosaurs and sharks are a text-book example of convergence, and similarities in tail morphology have led many to theorize that they had similar swimming styles. The variation of ichthyosaur tail shapes is encompassed within the diversity of shark families. In particular early ichthyosaurs have asymmetrical tails like the heterocercal tails of carcharhinid sharks, while later occurring ichthyosaurs have lunate tails similar to those of lamnid sharks. Because it is not possible to measure ichthyosaur tail function, the goal of this study is to measure and compare the flexibility and stiffness of lunate and heterocercal shark tails, and to measure skeletal and connective tissue features that may affect tail flexibility. We measured flexibility in 10 species and focused on five species in particular, for dissection: one pelagic and one bottom-associated individual from each order, plus the common thresher shark (Die Ähnlichkeiten zwischen Ichthyosauriern und Haien ist ein Lehrbuchbeispiel für Konvergenz, und Ähnlichkeiten in der Schwanzflossenmorphologie haben zu der Theorie geführt, dass beide ähnliche Schwimmstile aufwiesen. Die Formvielfalt der Ichthyosaurier-Schwanzflossen findet ihre Entsprechung innerhalb der Diversität der Schwanzflossen von Haifamilien. Frühe Ichthyosaurier beispielsweise, zeigen asymmetrische Schwanzflossen ähnlich den heterocerken Schwanzflossen von Requiemhaien (Carcharhinidae), während später auftretende Ichthyosaurier lunulare Schwanzflossen aufweisen, ähnlich denen von Makrelenhaiartigen (Lamniformes). Da es unmöglich ist, die Schwanzflosse der Ichthyosaurier auf ihre Funktion hin zu untersuchen, besteht das Ziel dieser Studie darin, die Flexibilität und Steifheit von lunularen und heterocerken Hai-Schwanzflossen zu messen und zu vergleichen, sowie Merkmale von Skelett- und Bindegewebe zu bestimmen, die möglicherweise die Flexibilität der Schwanzflosse beeinflussen. Wir haben die Flexibilität bei 10 Arten bestimmt, wobei wir uns beim Sezieren auf fünf Arten konzentriert haben: ein pelagisches und ein bodenassoziiertes Individuum aus jeder Ordnung sowie den gemeinen Fuchshai (Alopias vulpinus), ein Spezialist für ‚tail-flapping‘(Einsetzen der Schanzflosse gegen Beutefische). Wie erwartet waren lunulare Schwanzflossen insgesamt weniger flexibel als heterocerke und wiesen eine höhere Biegesteifigkeit auf. Unsere Ergebnisse deuten darauf hin, dass das Querschnittsprofil des skelettgestützten des dorsalen Lobus die Biegesteifigkeit bedingt, wohingegen die Veränderung der Gewebezusammensetzung maßgeblich ist für die Biegesteifigkeit des ventralen Lobus. Zudem fanden wir strukturelle Unterschiede, die das Schwanzschlagverhalten (‚tail-flapping‘) des gemeinen Fuchshais ermöglichen könnten. Abschließend diskutieren wir unsere morphologischen Messungen im Vergleich mit Ichthyosaurier-Messungen aus der Literatur. Unter besonderer Berücksichtigung der Ähnlichkeiten in der funktionellen Morphologie als Stütze für die These, dass Haie ein gutes Analogon zum Verständnis der Ichthyosaurus-Schwimmbiomechanik sind. (By S. Kruppert)As semelhanças entre ictiossauros e tubarões são um exemplo clássico de convergência e semelhanças na morfologia da cauda levaram muitos a teorizar que eles tinham estilos de natação semelhantes. A variação das formas da cauda do ictiossauro é encontrada nas diversas famílias de tubarões. Em particular, os primeiros ictiossauros têm caudas assimétricas, como as caudas heterocercas dos tubarões carcharhinídeos, enquanto os ictiossauros, mais tarde, adquirem caudas semilunares semelhantes às dos tubarões lamnídeos. Como não é possível medir a função da cauda do ictiossauro diretamente, o objetivo deste estudo é medir e comparar a flexibilidade e a rigidez das caudas lunadas e heterocercas de tubarões e medir as características do tecido esquelético e conectivo que podem afetar a flexibilidade delas. Nós medimos a flexibilidade em 10 espécies e focamos em cinco delas para dissecação: um indivíduo pelágico e um indivíduo bentônico de cada ordem, além do tubarão-raposa (Alopias vulpinus), um especialista em chicoteio de cauda. Como esperado, as caudas semilunares eram geralmente menos flexíveis que as caudas heterocercas e tinham maior resistência à flexão. Nossos resultados sugerem que o perfil transversal do lobo dorsal com suporte esquelético determina a capacidade de flexão, mas que a alteração da composição do tecido determina a capacidade de flexão no lobo ventral. Também encontramos diferenças estruturais que podem possibilitar o comportamento de chicoteio na cauda do tubarão-raposa. Finalmente, discutimos como nossas medições morfológicas se comparam às dos ictiossauros encontradas na literatura, notando que similaridades na morfologia funcional sugerem que os tubarões podem ser um bom análogo para a compreensão da biomecânica da natação do ictiossauro. (By G. Sobral).इक्थियोसॉरस और शार्क के बीच समानताएं अभिसरण का एक पाठ्य-पुस्तक उदाऴरण ऴैं, और ईनकी पूंछ आकृति विज्ञान की समानता ने कई लोगों को यऴ सिद्ध करने के लिए प्रेरित किया ऴै कि ईनके पास समान तैराकी शैली थी। शार्क के परिवारों की विविधता के भीतर इचिथियोरस पूंछ की आकृतियों की विविधता को शामिल किया गया ऴै। विशेष रूप से शुरुआती इक्थियोसॉरस के पास विषम आकार की पूंछें ऴोती थी जैसे कि कार्सरिनिड शार्क की विषमकोणीय आकार की पूंछ, जबकि बाद में ऴोने वाले इक्थियोसॉरस के पास लैम्निड शार्क के समान लसीली (लूनेट) पूंछ ऴोती थी। क्योंकि इचिथियॉर्स की पूंछ के कृत्य को मापना संभव नऴीं ऴै, इस अध्ययन का लक्ष्य ऴै कि लूनेट और ऴेटेरोसेरेल शार्क की पूंछ के लचीलेपन और कठोरता की माप करना और तुलना करना, और कंकालीय संयोजी ऊतक विशेषताओं को मापना जो पूंछ के लचीलेपन को प्रभावित कर सकते ऴैं। ऴमने 10 प्रजातियों के लचीलेपन को मापा, और विशेष रूप से विच्छेदन के लिए पांच प्रजातियों पर ध्यान केंद्रित किया: एक पेलजिक प्रजाति, एक नीचे से जुड़ा ऴुआ प्रजाति, और साथ ऴी एक पूंछ-थप्पड़ विशेषज्ञ जैसे कि सामान्य थ्रेशर शार्क (एलोपियास वल्पिनस)। जैसी कि उम्मीद थी, कुल मिलाकर लूनेट शार्क की पूंछ ऴेटेरोसेरेल पूंछ की तुलना में कम लचीली थी और इसमें अधिक लचीली कठोरता थी। ऴमारे परिणामों से पता चलता ऴै कि कंकाल के समर्थित पृष्ठीय लोब का पार-अनुभागीय प्रोफ़ाइल फ्लेक्सुरल कठोरता को निर्धारित करता ऴै, लेकिन यऴ कि ऊतक संरचना को बदलने से वेंट्रल लोब में फ्लेक्सुरल कठोरता का निर्धारण ऴोता ऴै। ऴमने संरचनात्मक अंतर भी पाया जो सामान्य थ्रेशर शार्क के पूंछ के थप्पड़ व्यवऴार को सक्षम कर सकता ऴै। अंत में, ऴम चर्चा करते ऴैं कि ऴमारे आकृति विज्ञान के माप साऴित्य से इक्थियोसॉरस माप की तुलना कैसे करते ऴैं। अथार्थ कार्यात्मक आकृति विज्ञान में मौजूदा समानताएं बताती ऴैं कि शार्क इक्थियोसॉरस तैराकी की जैव यांत्रिकी को समझने के लिए एक अच्छा सादृश्य ऴो सकता ऴै। (By S. K. Ray).

This comparative study of the radial testes of sexually mature thresher sharks (Alopias vulpinus) and shortfin mako sharks (Isurus oxyrinchus) describes the histology of the three-tiered network of sperm-carrying ductules in the testis and the lymphomyeloid tissue associated with it, namely the epigonal organ. In both species, a testis → epigonal gradient was evident regarding the thickness of the ductule epithelial lining and subepithelial investment of connective tissue. Ductules straddling the testis-epigonal border often displayed luminal leukocytes and various signs of regression, including the progressive thickening of the ductule epithelial lining, dissolution of the cytoplasm, and loss of normal histoarchitecture. In Isurus, large amorphous areas formed due to the fusion of neighboring regressing ductules. The epigonal organ of Alopias additionally revealed circular degenerative sperm-containing, Hassall-like bodies with either a degenerate or cellular appearance, the latter the result of cell proliferative activity (as shown by proliferating cell nuclear antigen (PCNA) immunohistochemistry) in an expanding outer border comprising cells with intensely PCNA immunoreactive slender and oblong nuclei. The latter cells exhibited a periphery-to-center transformation of their nuclei, at which stage they were PCNA-negative and most likely in a terminally differentiated state as they phagocytized the cell debris in the degenerate core. Intermediate stages of these circular bodies were a rarity. The relationship between these degenerate bodies, and the common occurrence of blind pockets in the epithelial linings and non-apoptosis-related degenerate patches in the apical cytoplasmic regions of the irregular shaped ductules in Alopias is unclear, and needs further elucidation. Anat Rec, 299:1435-1448, 2016. © 2016 Wiley Periodicals, Inc.

Sharks are highly vulnerable species due to their biological characteristics. Productivity and Susceptibility Analysis (PSA) is a useful method to assess the vulnerability of shark populations to prioritize management strategies. Given that molecular and genetic tools have played an important role in the conservation of vulnerable populations and species, the objective of this study was to evaluate the ecological risk of Prionace glauca, Isurus oxyrinchus, and Alopias vulpinus in the Mexican Pacific by incorporating genetic information into PSA. We hypothesized that the integration of genetic variables such as genetic structure and diversity (Fst, h, and π ), in a PSA will allow us to discriminate species with the same vulnerability index. The results of PSA-1 indicated that I. oxyrinchus, and A. vulpinus were at high ecological risk with identical vulnerability values (v = 2.2). Our results suggest that PSA with the combination of genetic attributes could be a useful tool for the application of conservation strategies or management policies, making easier the interpretation of results when the productivity or susceptibility attributes do not provide enough variation to prioritize between species or populations analyzed. Nevertheless, more studies that combine fishery and genetic information of commercially important sharks are needed.

Large-sized pelagic sharks and teleost fish are vulnerable to overexploitation by professional fisheries but little is known about the species caught by recreational fishing. This study presents for the first time in the Mediterranean an evaluation of the catch of pelagic sharks and teleost fish being caught by recreational fishermen by analyzing publicly available videos posted on social media. The analysis reveals that several vulnerable species, including the blue shark Prionace glauca, the shortfin mako Isurus oxyrinchus, the thresher shark Alopias vulpinus, the sixgill shark Hexanchus griseus, the swordfish Xiphias gladius, and the Mediterranean spearfish Tetrapturus belone are caught by offshore recreational fishermen, with the blue shark and the swordfish being the most commonly caught species. The majority of individuals caught are juveniles that are mostly released back to sea, issues that are in agreement with field studies. New measures related to handling practices are proposed to protect these species.

Bomb radiocarbon dating was used to determine the periodicity of band pair formation in the vertebral centra of three common thresher sharks (Alopias vulpinus). The traditional interpretation of band pairs were accurate (i.e. annual) up to approximately 14 years of age. In older individuals, band pair counts underestimated age. A new maximum validated age was estimated to be 38 years (an increase of 18 years over the band count estimates). Previously reported length at age estimates for common thresher sharks up to 14 years were used in conjunction with the two older validated estimates to develop a revised growth curve for the species, which was described using the Schnute general model (sexes combined). Updated estimates of age at maturity remained the same for males (8 years) and increased by one year to 13 years for females. The primary finding was the increase in longevity for this species from a band pair count estimate of 24 years to a bomb radiocarbon validated estimate of 38 years, indicating this species lives much longer than previously thought.

Elasmobranchs are rapidly declining due to overfishing and bycatch, underlining the need for immediate protection. Critical baseline information on the diversity of targeted species is, however, often missing. Peru is a major country for shark fishery, an activity that has been under-regulated and poorly monitored, aggravated by the superficial taxonomic identifications at landing points across the country. Furthermore, most of the species landed by the shark fishery in Peru are listed as Vulnerable in the IUCN Red List. To assess the diversity of shark species targeted by fisheries in Peru we analyzed the variation of the cytochrome oxidase I (cox1) region of the mitochondrial DNA from 118 samples collected between 2004 and 2009, from six landing points. Our analysis revealed unambiguously that the 16 shark species classified by fishermen using meristic characters corresponded only to nine species. While some commonly landed species (e.g. Prionace glauca) were consistently correctly identified, for others species multiple inconsistent names were applied (e.g. Galeorhinus galeus). Our molecular characterization further allowed the identification of specimens with non-informative common names (i.e. “tiburon” = shark). In most cases the unknown specimens were Isurus oxyrinchus and P. glauca. Interestingly, all samples labeled as common thresher (Alopias vulpinus) were identified as pelagic thresher (Alopias pelagicus). Finally, one sample was equivocally identified as a dusky shark (Carcharhinus obscurus) and as a galapagos shark (Carcharhinus galapagensis) reinforcing the genetic similarity reported for these species. We generated a character-based identification library containing 26 of the 31 commercially important sharks landed in Peru and tested its performance as a species diagnostic. The library correctly identified 25 out of 28 barcodes tested, outperforming the distance-based approach. This is the first study sequencing barcodes of marine species in Peru and generated a genetic reference library of targeted shark species. We suggest that the molecular tools used are a quick and effective complement for the monitoring of the fishery of threatened shark species. A combined effort to obtain these data, by countries in the east Pacific region with an on-going shark fishery, would provide with the essential guiding information to promote the implementation of effective sustainable management plans.

The common thresher shark ( Alopias vulpinus ) is the focus of a popular southern California recreational fishery that targets individuals using multiple fishing gears and techniques. Despite increasing trends in the use of catch and release techniques in the recreational fishery for thresher sharks, a comprehensive estimate of post-release survival is not available for all modes of capture. This study focused on assessing post-release survival in two modes of capture routinely observed in the southern California recreational fishery: (1) sharks that are caught using caudal-based angling techniques and unintentionally released with trailing gear left embedded and (2) sharks that are caught and released using mouth-based angling techniques. Post-release survivorship was assessed using pop-up satellite archival tags programed for 10- and 90-day deployments, with the former used for mouth-caught sharks and the latter for individuals with trailing gear. Post-release survivorship estimates for the trailing gear studies were based on data from nine common thresher sharks (111-175 cm FL) while the mouth-based experiments utilized data from an additional seven sharks (125-187 cm fork length, FL). For the trailing gear studies, six sharks died within 5 days after release, one died after 81 days, and two sharks survived the deployment period for an overall survivorship rate of 22%. All seven mouth-hooked common thresher sharks survived the acute (∼10 days) effects of capture (100% survivorship). These results suggest that in the southern California recreational thresher shark fishery, caudal-based angling techniques, which often result in trailing gear left embedded in the shark, can negatively affect post-release survivorship. This work also reveals that mouth-based angling techniques can, when performed properly, result in high survivorship of released sharks.

Trophic pathways and size-based bioaccumulation rates of total mercury were evaluated among recreationally caught albacore tuna (Thunnus alalunga), yellowfin tuna (Thunnus albacares), shortfin mako shark (Isurus oxyrinchus), thresher shark (Alopias vulpinus), and dolphinfish (Coryphaena hippurus) from offshore southern New England waters of the northwest Atlantic Ocean between 2008 and 2011. Mercury concentrations were highest in mako (2.65 ± 1.16 ppm) and thresher sharks (0.87 ± 0.71 ppm), and significantly lower in teleosts (albacore, 0.45 ± 0.14 ppm; yellowfin, 0.32 ± 0.09 ppm; dolphinfish, 0.20 ± 0.17 ppm). The relationship between body size and mercury concentration was positive and linear for tunas, and positive and exponential for sharks and dolphinfish. Mercury increased exponentially with δ 15N values, a proxy for trophic position, across all species. Results demonstrate mercury levels are positively related to size, diet and trophic position in sharks, tunas, and dolphinfish, and the majority of fishes exhibited concentrations greater than the US EPA recommended limit.

Shark take, driven by vast demand for meat and fins, is increasing. We set out to gain insights into the impact of small-scale longline fisheries in Peru. Onboard observers were used to document catch from 145 longline fishing trips (1668 fishing days) originating from Ilo, southern Peru. Fishing effort is divided into two seasons: targeting dolphinfish (Coryphaena hippurus; December to February) and sharks (March to November). A total of 16,610 sharks were observed caught, with 11,166 identified to species level. Of these, 70.6% were blue sharks (Prionace glauca), 28.4% short-fin mako sharks (Isurus oxyrinchus), and 1% were other species (including thresher (Alopias vulpinus), hammerhead (Sphyrna zygaena), porbeagle (Lamnus nasus), and other Carcharhinidae species (Carcharhinus brachyurus, Carcharhinus falciformis, Galeorhinus galeus). Mean ± SD catch per unit effort of 33.6 ± 10.9 sharks per 1000 hooks was calculated for the shark season and 1.9 ± 3.1 sharks per 1000 hooks were caught in the dolphinfish season. An average of 83.7% of sharks caught (74.7% blue sharks; 93.3% mako sharks) were deemed sexually immature and under the legal minimum landing size, which for species exhibiting k-selected life history traits can result in susceptibility to over exploitation. As these growing fisheries operate along the entire Peruvian coast and may catch millions of sharks per annum, we conclude that their continued expansion, along with ineffective legislative approaches resulting in removal of immature individuals, has the potential to threaten the sustainability of the fishery, its target species, and ecosystem. There is a need for additional monitoring and research to inform novel management strategies for sharks while maintaining fisher livelihoods.

A low-cost and non-invasive survey technique focused on pelagic sharks was evaluated during an ecotourism cruise on two Sudanese reefs, Angarosh and Sha'ab Rumi, in the Southern Red Sea. The research technology was based on a set of small, underwater video recording cameras and a pair of laser pointers. Video footage provided insight into shark biodiversity on the two reefs, detecting five species, Alopias vulpinus, Sphyrna lewini, Triaenodon obesus, Carcharhinus amblyrhynchos and Galeocerdo cuvier, during 15.8 h of video recording. These recordings also provided preliminary information on aggregations of S. lewini. The laser pointers were used to measure the size of sharks, providing seven total length (TL) measurements for S. lewini (N = 2) and C. amblyrhynchos (N = 5), confirming the possibility of easily obtaining size parameters using this tool. These low-cost and user-friendly instruments provide ecotourism divers with an opportunity to become involved in marine research projects.

A putative mechanism for maternal transfer of organic contaminants and total mercury was empirically demonstrated in a near-term pregnant female common thresher shark (Alopias vulpinus). Contaminants were measured in the liver and muscle tissue of the mother and her four embryos, as well as the embryos’ stomach contents. Concentrations of organic contaminants and mercury were found to be lower in the embryos’ livers than in the mother’s and were clearly measurable in the embryo stomach contents, which consisted of consumed ovulated eggs. Presence of high concentrations of organic contaminants and mercury in embryos, prior to any exogenous exposure, provides clear evidence of maternal offloading in this species. In addition, the detection of these chemicals in the yolky stomach contents provides a mechanism by which oophagous elasmobranch females offload contaminants onto their young.

Reproductive organs from 130 male and 256 female Common Thresher Sharks Alopias vulpinus were examined to describe the reproductive characteristics and determine size at maturity and reproductive seasonality for the species in the western North Atlantic Ocean. Males ranged in size from 78 to 237 cm FL and females ranged from 62 to 263 cm FL. The onset of maturity in males was best described by an inflection in the relationship of clasper length to FL in combination with the degree of clasper calcification. Males matured between 181 and 198 cm FL, and estimated median size at maturity was 188 cm FL. In females, changes in the relationship between ovary and uterus length and width with FL were used to estimate the size at maturity. Females matured between 208 and 224 cm FL; the estimated median size at maturity was 216 cm FL. Litter sizes averaged 3.7 young. The period of parturition is protracted, spanning late spring to late summer (May–August). As in other Lamniformes, young are nourished throug...

Age and growth estimates were generated for the Common Thresher Shark Alopias vulpinus in the western North Atlantic (WNA) using vertebral centra from 173 females and 135 males ranging in size from 56 to 264 cm FL. Assuming that vertebral band pairs were deposited annually, we estimated ages up to 22 years (228 cm FL) for males and 24 years (244 cm FL) for females. The growth of both sexes was similar until approximately age 8 (185 cm FL), after which male growth slowed. The growth of females slowed at a later age (∼age 12) than that of males. Relative goodness of fit for all candidate models supported the separate modeling of sexes. For males, von Bertalanffy growth parameters generated from the vertebral data using a set size at birth (81 cm FL) provided the best fit for the band counts (asymptotic length [L∞ ] = 225.4 cm FL; growth coefficient [k] = 0.17). For females, the standard three-parameter von Bertalanffy growth model provided the best fit to the band counts (L∞ = 274.5 cm FL; k = 0.09...

Organic contaminant and total mercury concentrations were compared in four species of lamniform sharks over several age classes to examine bioaccumulation patterns and gain insights into trophic ecology. Contaminants found in young of the year (YOY) sharks were assumed to be derived from maternal sources and used as a proxy to investigate factors that influence maternal offloading processes. YOY white (Carcharodon carcharias) and mako (Isurus oxyrinchus) sharks had comparable and significantly higher concentrations of PCBs, DDTs, pesticides, and mercury than YOY thresher (Alopias vulpinus) or salmon (Lamna ditropis) sharks. A significant positive relationship was found between YOY contaminant loads and maternal trophic position, suggesting that trophic ecology is one factor that plays an important role in maternal offloading. Differences in organic contaminant signatures and contaminant concentration magnitudes among species corroborated what is known about species habitat use and may be used to provide insights into the feeding ecology of these animals.

The health of sharks is linked with emergent properties of its microbiome. Most marine organisms have mucus overlying the skin, but shark have dermal denticles that protrude above the mucus. We characterized the microbiome from the skin of the common thresher shark (Alopias vulpinus) to investigate the structure and composition of the skin microbiome. An average of 618,812 reads per metagenomic library contained open reading frames (80.9% ± S.D. 0.44%), and 7.6 to 12.8% matched known protein sequences. Genera distinguishing the A. vulpinus microbiome from the water column included, Pseudoalteromonas (12.8% ± 4.7 of sequences), Erythrobacter (5. 3% ± 0.5), Limnobacter (4.1% ± 1.4), and Idiomarina (4.2% ± 1.2) and gene pathways included, cobalt, zinc, and cadmium resistance (2.2% ± 0.1); iron acquisition (1.2% ± 0.1); ton/tol transport (1.3% ± 0.08); and n-Phenylalkanoic acid degradation (0.9% ± 0.08). Taxonomic β-diversity of the shark (77.6) was higher than the water column (70.6) and a reference host microbiome (algae: 71.5), and functional β-diversity of the shark (87.4) was similar to water (82.9) and algae (87.5). We conclude the A. vulpinus skin microbiome is influenced by filtering processes, that include biochemical and biophysical components of the shark skin and result in a highly structured microbiome, confirmed by high β-diversity. This article is protected by copyright. All rights reserved.

Morphological features of coronary arteries and incidental lesions are reported from hearts in five species of sharks, the shortfin mako shark, Isurus oxyrhinchus Rafinesque, thresher shark Alopias vulpinus (Bonaterre), blue shark, Prionace glauca L., the smooth dogfish, Mustelus canis (Mitchill), and spiny dogfish, Squalus acanthias L. Sharks were collected from the northwestern Atlantic between June and August from 1996 to 2010. They were necropsied dockside and the hearts were preserved in buffered formalin. Routine sections including ventricle/conus arteriosus and the atrio-ventricular junctions were embedded in paraffin, stained with common histological and immunohistochemical methods and examined by brightfield microscopy. Myointimal hyperplasia, medial myo-myxomatous hyperplasia and bifurcation pads were observed commonly, and medial muscle reorientation and epicardial myeloid tissues were rare. All the above features differed in severity, prevalence and distribution depending on anatomical site and shark species/size. Morphometric analysis indicated that myomyxomatous hyperplasia is associated with luminal narrowing of blood vessels. As suggested previously, the described morphological features are most likely physiological responses to blood flow characteristics. Vascular and cardiac lesions were uncommon and included, granulomatous proliferative epicarditis with fibroepitheliomas, myxomatous epicardial expansions, medial arterial vacuolation, myocardial fibrosis, acute ventricular emboli and parasitic granulomas. The lesions of embolism, proliferative and granulomatous epicarditis and myocardial fibrosis were in all sharks associated with capture events including retained fishing hooks. The significance and aetiopathogenesis of medial vacuolation and epicardial myxomatous expansions remains unclear.

The common thresher shark (Alopias vulpinus) is a pelagic species with medially positioned red aerobic swimming musculature (RM) and regional RM endothermy. This study tested whether the contractile characteristics of the RM are functionally similar along the length of the body and assessed how the contractile properties of the common thresher shark compare with those of other sharks. Contractile properties of the RM were examined at 8, 16 and 24 °C from anterior and posterior axial positions (0.4 and 0.6 fork length, respectively) using the work loop technique. Experiments were performed to determine whether the contractile properties of the RM are similar along the body of the common thresher shark and to document the effects of temperature on muscle power. Axial differences in contractile properties of RM were found to be small or absent. Isometric twitch kinetics of RM were ~fivefold slower than those of white muscle, with RM twitch durations of about 1 s at 24 °C and exceeding 5 s at 8 °C, a Q(10) of nearly 2.5. Power increased approximately tenfold with the 16 °C increase in temperature, while the cycle frequency for maximal power only increased from about 0.5-1.0 Hz over this temperature range. These data support the hypothesis that the RM is functionally similar along the body of the common thresher shark and corroborate previous findings from shark species both with and without medial RM. While twitch kinetics suggest the endothermic RM is not unusually temperature sensitive, measures of power suggest that the RM is not well suited to function at cool temperatures. The cycle frequency at which power is maximized appeared relatively insensitive to temperature in RM, which may reflect the relatively cooler temperature of the thresher RM compared to that observed in lamnid sharks as well as the relatively slow RM phenotype in these large fish.

This study describes the feeding ecology of three pelagic shark species in the California Current: shortfin mako (Isurus oxyrinchus); blue (Prionace glauca); and thresher (Alopias vulpinus) sharks. Stom- ach contents of sharks collected from 2002 to 2008 were identified to the lowest taxonomic level and analyzed using univariate and multivariate methods. Of 330 mako sharks sampled (53 to 248 cm fork length (FL)), 238 stomachs contained 42 prey taxa, with jumbo squid (Dosidicus gigas) and Pacific saury (Cololabis saira) representing the most important prey based on the geometric index of importance (GII). In addition, 158 blue sharks were sampled (76 to 248 cm FL) and 114 stomachs contained 38 prey taxa, with jumbo and Gonatus spp. squids representing the most important prey. Lastly, 225 thresher sharks were sam- pled (108 to 228 cm FL) and 157 stomachs contained 18 prey taxa with northern anchovy (Engraulis mor- dax) and Pacific sardine (Sardinops sagax) identified as the most important prey. Overall, mako sharks had the most diverse diet based upon Simpson's diversity index (1/D) (8.43±1.16), feeding on many species of teleosts and cephalopods, followed by blue sharks (6.20±2.11) which consumed a wide range of prey (primarily cephalopods), while thresher sharks were most specialized (2.62±0.34), feeding primarily on coastal pelagic teleosts. Dietary overlap was lowest between blue and thresher sharks (Sorensen similarity index00.321 and Simplified Morisita Horn index0 0.006), and seasonal variability in diet was greatest for blue sharks (Simplified Morisita Horn index0 0.260, Analysis of Similarity (ANOSIM) p

The thresher sharks comprise a single family (Alopiidae) of pelagic sharks most easily recog- nized by the elongate dorsal lobe of their caudal fin. De- spite morphological similarities among the alopiids, the common thresher (Alopias vulpinus) is unique in that its red, aerobic myotomal muscle (RM) is medially posi- tioned (i.e., closer to the vertebrae), its systemic blood is supplied through a lateral circulation which give rise to counter-current heat exchanging retia, and it is capable of regional RM endothermy. Despite this information, it remains unknown if the other two alopiid species (bigeye thresher, Alopias superciliosus and pelagic thresher, Alo- pias pelagicus) also possess some or all of the character- istics related to regional RM endothermy. Thus, this study aimed to 1) document the presence of vascular specializations necessary for heat retention and RM endothermy and 2) measure the in vivo muscle tempera- tures of all three alopiid species. Laboratory dissections of the thresher species showed that only A. vulpinus possesses the lateral branching of the dorsal aorta giv- ing rise to a lateral subcutaneous circulation and retial system, and that RM temperatures are elevated relative to ambient temperature. By contrast, both A. pelagicus and A. superciliosus have a similar systemic blood circulation pathway, in which the dorsal aorta and postcardinal vein form the basis for the central cir- culation and in vivo RM temperature measurements closely matched those of the ambient temperature at which the sharks were captured. Collectively, the vas- cular anatomy and in vivo temperature data suggest that only one species of thresher shark (A. vulpinus) possesses the requisite vascular specializations (i.e., lateral subcutaneous vessels and retia mirabilia )t hat facilitate RM endothermy. J. Morphol. 272:1353-1364

The species composition and extent of large elasmobranch bycatch in the Sardinian tuna trap fisheries have received minimal attention in the primary literature. The Sardinian Large Elasmobranch Database (SLED), a non-governmental project, contains records from direct observations, fishing industry sources and reviews from the literature regarding the extent and composition of large elasmobranch bycatch from the only six tuna traps at six fishing sites (Saline; Capo Testa; Carloforte; Portoscuso; Calasetta; and Portopaglia) from the period of 1990 to 2009. During this time period, 42 bycatch events were documented that were comprised of the incidental capture of 15 Mobulid rays and 27 large sharks representing ten species and seven families (23% of the total elasmobranch species previously reported in Sardinian waters). Even though the low number of collective elasmobranchs captured (n = 42) in this study does not pose a conservation concern several bycatch species considered rare and/or depleted in this region were among the species observed. Mobula mobular was the most abundant elasmobranch species caught, with Alopias vulpinus the most commonly caught shark species. There were differences in the catch per unit effort between the six sites with the highest CPUE occurring in Saline, Carloforte and Porto Paglia. Although the sheer volume and conservation impact of traditional tuna traps on large elasmobranchs is exceeded by other fishing gears in Mediterranean waters, small scale (long term) bycatch monitoring programs are vital when evaluating the presence, biodiversity and conservation of elasmobranchs in previously unstudied areas.

This paper reports on a survey carried out in waters near Marshall Islands and on the analysis of catch rates of bigeye thresher shark, Alopias superciliosus, and thresher shark, Alopias vulpinus. The optimum swimming depth, water temperature, salinity and dissolved oxygen range of bigeye thresher sharks were identified as 240–360 m, 10–16°C, 34.5–34.7 and 3.0–4.0 ml/l, respectively, while for thresher sharks they were 160–240 m, 18–20°C, 34.5–34.8 and 1.0–1.5 ml/l, respectively, during daytime. The bigeye thresher shark and thresher shark were widely distributed in areas where the dissolved oxygen was higher than 0.5 ml/l. Some mitigation measures were recommended to reduce the bycatch of bigeye thresher shark and thresher shark, including avoiding fishing in peak areas and periods of shark abundance, using fish as bait and using nylon monofilament leaders. Furthermore, the hook depth data could be input into the ‘habitat model’ to standardise the shark catch per unit effort (CPUE).

The common thresher shark (Alopias vulpinus) is a secondary target species of the California drift gillnet fishery (CA-DGN) and supports a growing recreational fishery in California waters. This study used archival tags to examine the movement patterns and habitat preferences of common threshers of the size range captured in the CA-DGN (>120 cm fork length). Depth and temperature-logging archival tags were deployed on 57 subadult and adult common threshers in the Southern California Bight. Tags from five individuals (8.8%) were recovered, and 154 days of data were successfully obtained from four of these. By night, shark movements were primarily limited to waters above the thermocline, which ranged in depth from 15 to 20 m. Sharks were significantly deeper by day, and daytime vertical distribution consisted of two distinct modes: a ‘shallow mode’ (wherein sharks occupied only the upper 20 m of the water column) and a ‘deep mode’ (characterized by frequent vertical excursions below the thermocline). This modal switch is interpreted as relating to regional differences in abundance of surface-oriented prey and prey in deeper water. Maximum dive depth was 320 m, greatest dive duration was 712 min, minimum temperature experienced during a dive was 9.1°C, and dive descent rate was significantly greater than ascent rate. Sharks inhabited waters corresponding to a sea surface temperature range of 16 to 21°C. The nocturnal depth distribution of common threshers has implications for management of drift gillnet deployment depths in the CA-DGN.

The common thresher shark ( Alopias vulpinus ) is the focus of a popular southern California recreational fishery that typically captures individuals by hooking them in the caudal fin. This technique reduces the ability for forward locomotion and the capacity for ram ventilation. This study assessed the post-capture survivorship of tail-hooked adult and sub-adult common thresher sharks using pop-up satellite archival tags (PSATs) and quantified physiological indicators of capture stress in the blood. Survival of the acute effects of capture was determined from the depth and temperature records of 10-day PSAT deployments. Survivorship estimates were based on 19 common thresher sharks [160–221 cm fork length (FL); ∼67–151 kg] captured in southern California from 2007 to 2009 using recreational stand-up tackle (36 kg). Five mortalities were observed over the course of the study resulting in an overall post-release mortality estimate of 26%. All mortalities occurred in large individuals (≥180 cm FL) with fight times ≥85 min. The archived depth and temperature data from surviving sharks resembled those of previous common thresher movement studies with a diel depth distribution predominantly within the uniformed temperature surface layer. Capture induced stress parameters measured from the blood of eight additional common thresher sharks that were not tagged revealed plasma lactate and hematocrit levels that were significantly elevated with increased fight time. Similarly, all thresher sharks showed heightened heat shock protein 70 ( hsp 70 ) values relative to those obtained from blood that was allowed to recover in vitro for 24 h. Collectively, our findings indicate that large tail-hooked common thresher sharks with prolonged fight times (≥85 min) exhibit a heightened stress response which may contribute to an increased mortality rate. These results suggest that for larger individuals the current caudal-based capture methods used in the California recreational fishery may not be suitable for an effective catch-and-release based conservation strategy.

We investigated the potential use of open coastal habitat over the continental shelf as a nursery area for the common thresher shark Alopias vulpinus. Seven juvenile threshers were tracked using acoustic telemetry to determine their movement patterns and nursery habitat in the Southern California Bight (SCB). Tracked sharks occupied waters over the continental shelf 87% of the time. These waters had an average (± SD) sea surface temperature of 18.8 ± 1.6°C and chlorophyll concen- trations that were an order of magnitude higher than in adjacent waters offshore of the continental shelf. Tracked sharks had a mean rate of movement of 1.63 ± 0.56 km h -1 , and some sharks exhibited high site fidelity. The vertical distribution of juvenile threshers was generally limited to the upper 20 m of the water, and most sharks showed diel depth distribution patterns, with daytime depths significantly greater than nighttime depths. An analysis of SCB commercial fishery observer data confirms that juvenile common threshers are most frequently captured over the continental shelf. This region appears to provide juvenile threshers with ample food resources and reduced predation risk relative to adult habitat, and partially satisfies more quantitative nursery area criteria recently established in the literature.