Artículos de revistas: "Hammerhead sharks"

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Barker, Amanda M., Douglas H. Adams, William B. Driggers, Bryan S. Frazier y David S. Portnoy. "Hybridization between sympatric hammerhead sharks in the western North Atlantic Ocean". Biology Letters 15, n.º 4 (abril de 2019): 20190004. http://dx.doi.org/10.1098/rsbl.2019.0004.

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Hybridization between closely related species has been documented across a wide range of taxa but has not been well studied in elasmobranchs. Hammerhead sharks have drawn global conservation concern because they experience some of the highest mortality rates among sharks when interacting with fisheries. Here we report on the detection of hybrids between the globally distributed scalloped hammerhead ( Sphyrna lewini ) and recently described Carolina hammerhead ( S. gilberti ) which are only known from the western Atlantic Ocean. Using a genomics approach, 10 first-generation hybrids and 15–17 backcrosses were detected from 554 individuals. The identification of backcrosses demonstrates hybrids are viable, and all backcrosses but one involved a scalloped hammerhead. All hybrids but one possessed Carolina hammerhead mtDNA, indicating sex-biased gene flow between species. Repeated hybridization and backcrossing with scalloped hammerheads could lead to the loss of endemic Carolina hammerheads.

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Alaudin, Alaudin, Jaliadi Jaliadi y Burhanis Burhanis. "SEBARAN UKURAN DAN PERTUMBUHAN HIU MARTIL (BY CATCH) YANG DIDARATKAN DI PANGKALAN PENDARATAN IKAN (PPI) UJONG BAROH MEULABOH". JURNAL PERIKANAN TROPIS 8, n.º 1 (3 de junio de 2021): 65. http://dx.doi.org/10.35308/jpt.v8i1.2595.

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Hammerhead shark is a type of predator shark belongs to the family of Sphyrnidae. This shark is so aggressive in hunting prey such as fish, squid, and shrimp. The hammerhead shark in Indonesia is included in Appendix II of CITES and has been a special concern in the field of capture fisheries. The aim of the study was to see the size spread, the number of catches, the first size caught, the age growth and the genital ratio of the hammerhead sharks caught with the base fish net. The study was conducted from October to December 2019. The shark measurement was performed once in 2 weeks. Sharks caught by the gills of the base (buttom gilt net) were measured using a roll meter. The collection of hammerhead sharks included total length (TL), number of catches and genital ratio. The analysis was done descriptively using the ELEFAN I existing on Sofwere FiSAT II. The results showed that the hammerhead sharks caught with an gill net of 65 tails from October to December 2019 were taken on the male genital. The total size spread of female malletic sharks were between 61.5-131.5 cm and male hammering sharks between 61.5-111.5 cm. The morphologically spread of the female hammerhead was relatively longer than the male shark. The male hammerhead shark was first captured at a length of 117.9 cm and a female hammerhead shark at a size of 106.2 cm. Hammerhead shark growth by following the curve of von Bertalanffy mallet were male Lt = 138,08 (1-exp (-0.480 (t + 0.0487)) and female mallet shark Lt = 138,08 (1-exp (-0.430 (t + 0.0434)). Such equations can be known by using the relationship curve model between the age and length of fish.

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Bahri, S., N. Hikmah y N. Fadli. "Relationship analysis of Scalloped Hammerhead (Sphyrna lewini) from West Aceh Waters using molecular genetics approach". IOP Conference Series: Earth and Environmental Science 1137, n.º 1 (1 de enero de 2023): 012016. http://dx.doi.org/10.1088/1755-1315/1137/1/012016.

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Abstract Hammerhead sharks are particularly vulnerable to fishing because of their slow growth rate and reproductive constraints. This type of sharks needs special attention due to its conservation status. This research was aimed to describe the relationships of the hammerhead sharks from West Aceh waters with the hammerhead sharks from other places. Samples of the shark were collected from Ujong Baroh Fish Port, West Aceh. The samples were analysed at the Laboratory of Department of Marine Science and Fisheries, Syiah Kuala University. The laboratory activity was started with extraction of DNA enhanced by Polymerase Chain Reaction method and visualized by an electrolytical. Analysis using BLAST showed that the first sample obtained 94%-95% cover query value and produced a 683 base pair length while the second sample obtained 98% per sample for a cover query value and produced a 658 base pair length. The average nucleotide values of the hammerhead shark were T=32.8, C=26.6, A=25.7 and G=14.9. The phylogenetic tree shows that the hammerhead sharks from the study area were more similar to the hammerhead sharks from Australia and Malaysia. Overall, based on the nucleotide composition, phylogenetic tree and genetic distance, the hammerhead sharks from the study area are unique compared to the populations from the other places.

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Anna, Zuzy, Purna Hindayani, Asep Agus Handaka Suryana, Yudi Nurul Ihsan y Asia Salsabila. "Sustainability Study of Scalloped Hammerhead Shark (Sphyrna lewini) in Indramayu Waters". Sustainability 12, n.º 24 (14 de diciembre de 2020): 10459. http://dx.doi.org/10.3390/su122410459.

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Hammerhead shark (Sphyrna lewini) population decline is a global problem experienced by various ocean basins worldwide, including Indramayu waters. As the regency known by its fishery barn that supplies 65% of captured fisheries in West Java, Indonesia, illegal fishing practices towards this protected species is inevitable. In 2017, 2869 tons of sharks were landed in Indramayu with the production value of IDR 44.01 billion, which hammerhead shark catch reaches 268 tons. This research aimed to observe the sustainability of hammerhead shark in Indramayu waters using a bio-economic model of Gordon Schaefer (GS) and Gompertz. The results showed the overfishing of hammerhead shark in Indramayu waters on actual conditions in 2012, 2014, 2015, 2016, 2017, and 2018, both in the GS and Gompertz models. The abundant number of hammerhead sharks started to deplete from 2015 to 2018, and the highest depletion was found in 2017, with a depletion value of 16 tons and depreciation value of IDR 164 million. The depletion rate suffered the most significant decline in 2011 to 2012 for all types of sharks, including hammerhead. The prohibition of consistent fishing and more pronounced law enforcement for hammered shark fishing are needed to maintain the sustainability of this resource.

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Piercy, Andrew N., John K. Carlson y Michelle S. Passerotti. "Age and growth of the great hammerhead shark, Sphyrna mokarran, in the north-western Atlantic Ocean and Gulf of Mexico". Marine and Freshwater Research 61, n.º 9 (2010): 992. http://dx.doi.org/10.1071/mf09227.

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The great hammerhead shark, Sphyrna mokarran, is a cosmopolitan species that is caught in a variety of fisheries throughout much of its range. The apparent decline of great hammerhead shark populations has reinforced the need for accurate biological data to enhance fishery management plans. To this end, age and growth estimates for the great hammerhead were determined from sharks (n = 216) ranging in size from 54- to 315-cm fork length (FL), captured in the Gulf of Mexico and north-western Atlantic Ocean. Growth curves were fitted using multiple models and evaluated using Akaike’s information criterion. The von Bertalanffy growth model was the best fitting model, with resulting growth parameters of L∞ = 264.2-cm FL, k = 0.16 year–1, t0 = –1.99 year for males, and L∞ = 307.8-cm FL, k = 0.11 year–1, t0 = –2.86 year for females. Annual band pair deposition was confirmed through marginal-increment analysis and a concurrent bomb radiocarbon validation study. Great hammerheads have one of the oldest reported ages for any elasmobranch (44 years) but grow at relatively similar rates (on the basis of von Bertalanffy k value) to other large hammerhead species from this region. The present study is the first to provide vertebral ages for great hammerheads.

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Kajiura, Stephen M. y Kim N. Holland. "Electroreception in juvenile scalloped hammerhead and sandbar sharks". Journal of Experimental Biology 205, n.º 23 (1 de diciembre de 2002): 3609–21. http://dx.doi.org/10.1242/jeb.205.23.3609.

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SUMMARY The unique head morphology of sphyrnid sharks might have evolved to enhance electrosensory capabilities. The `enhanced electroreception' hypothesis was tested by comparing the behavioral responses of similarly sized carcharhinid and sphyrnid sharks to prey-simulating electric stimuli. Juvenile scalloped hammerhead sharks Sphyrna lewini and sandbar sharks Carcharhinus plumbeus oriented to dipole electric fields from the same maximum distance (approximately 30 cm) and thus demonstrated comparable behavioral-response thresholds (<1 nV cm-1). Despite the similarity of response threshold, the orientation pathways and behaviors differed for the two species. Scalloped hammerheads typically demonstrated a pivot orientation in which the edge of the cephalofoil closest to the dipole remained stationary while the shark bent its trunk to orient to the center of the dipole. By contrast, sandbars swam in a broader arc towards the center of the dipole. The different orientation patterns are attributed to the hydrodynamic properties of the cephalofoil, which enables the hammerheads to execute sharp turns at high speed. The greater trunk width of the sandbar sharks prevented them from demonstrating the same degree of flexibility. Therefore, although the sphyrnid head morphology does not appear to confer a greater sensitivity to prey-simulating dipole electric fields, it does provide(1) a greater lateral search area, which may increase the probability of prey encounter, and (2) enhanced maneuverability, which may aid in prey capture.

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Marcotte, Megan M. y Christopher G. Lowe. "Behavioral Responses of Two Species of Sharks to Pulsed, Direct Current Electrical Fields: Testing a Potential Shark Deterrent". Marine Technology Society Journal 42, n.º 2 (1 de junio de 2008): 53–61. http://dx.doi.org/10.4031/002533208786829133.

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To describe and contrast the behavioral responses of two species of sharks to an electrical deterrent, sharks were baited to a food odor source within a strong pulsed, direct current electrical field. A head twitch behavior was elicited in scalloped hammerhead (Sphyrna lewini) and leopard sharks (Triakis semifasciata) at mean voltage gradient thresholds of 4.16 ± 0.59 V/m (X ± SD) and 4.30 ± 0.78 V/m, respectively, and did not differ significantly. A shimmy behavioral response was elicited in some hammerhead sharks at a mean threshold of 5.54 ± 1.55 V/m. A retreat behavioral response occurred in hammerhead and leopard sharks at a mean, maximum threshold of 18.50 ± 13.27 V/m and 9.64 ± 10.28 V/m, respectively. The hammerhead sharks retreated at significantly stronger field strengths than the leopard sharks, suggesting that some species may require stronger electrical fields for effective deterrence. Both species of shark remained significantly further away and spent less time near the food odor source when the electrical field was on versus off. The maximum voltage gradient threshold required to cause the sharks to retreat was much higher than previously reported, and the electrical field was not 100% effective at excluding sharks. The sharks only retreated after involuntary muscle contractions were induced by the electrical field.

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Taylor, Stephen, Wayne Sumpton y Tony Ham. "Fine-scale spatial and seasonal partitioning among large sharks and other elasmobranchs in south-eastern Queensland, Australia". Marine and Freshwater Research 62, n.º 6 (2011): 638. http://dx.doi.org/10.1071/mf10154.

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Our understanding of the ecological role of larger elasmobranchs is limited by a lack of information on their spatial and seasonal abundance. Analysis of 14 years of gill-net catch data in south-eastern Queensland, Australia, revealed that the species composition of large sharks and other elasmobranchs significantly differed among beaches and seasons. Spinner sharks (Carcharhinus brevipinna) and hammerhead sharks (Sphyrna spp.) comprised nearly half the catch of all elasmobranchs. Although the distribution of these sharks overlapped, spatial variation existed in their abundance. Spinner sharks characterised the catch at Sunshine Coast beaches, whereas the catch at Gold Coast beaches was dominated by hammerhead sharks. Seasonal differences in elasmobranch community structure were also apparent, driven largely by a lower abundance of many species during the winter and the predominance of species such as spinner sharks and hammerheads in spring and summer. The present study provides the first quantitative data for numerous species of Carcharhiniformes in south-eastern Queensland and demonstrates that analysis of catch-rate data can improve our understanding of how larger sharks partition resources.

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9

Lowe, Christopher y Gwen Goodman-Lowe. "Suntanning in hammerhead sharks". Nature 383, n.º 6602 (octubre de 1996): 677. http://dx.doi.org/10.1038/383677a0.

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10

Bezerra, Natalia P. A., Bruno C. L. Macena, Paulo Travassos, Pedro Afonso y Fábio H. V. Hazin. "Evidence of site fidelity and deep diving behaviour of scalloped hammerhead shark (Sphyrna lewini) around the Saint Peter and Saint Paul Archipelago, in the equatorial Mid-Atlantic ridge". Marine and Freshwater Research 71, n.º 6 (2020): 708. http://dx.doi.org/10.1071/mf19029.

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Seven scalloped hammerhead sharks (Sphyrna lewini) were satellite tagged around the Saint Peter and Saint Paul Archipelago (SPSPA), located at the equatorial Mid-Atlantic ridge, to investigate their vertical and horizontal movements. All sharks remained in the surroundings of the SPSPA over the course of the 120-day monitoring period, suggesting a high degree of medium-term site fidelity. During this period, scalloped hammerhead sharks covered a wide extension of the water column, ranging from the mixed layer to the mesopelagic zone. All sharks remained in warm (>22°C) shallow layers most of the time, but also dove to depths greater than 150m, mostly at night, eventually reaching 728m (5.6°C) on two occasions. This study contributes important, novel information on the habitat use and movement patterns of scalloped hammerhead shark in Atlantic equatorial oceanic waters. It also highlights the potential of protecting key, large oceanic areas as a useful tool for the conservation of this endangered species.

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Bezerra, Natalia P. A., Bruno C. L. Macena, Paulo Travassos, Pedro Afonso y Fábio H. V. Hazin. "Corrigendum to: Evidence of site fidelity and deep diving behaviour of scalloped hammerhead shark (Sphyrna lewini) around the Saint Peter and Saint Paul Archipelago, in the equatorial Mid-Atlantic ridge". Marine and Freshwater Research 71, n.º 6 (2020): 719. http://dx.doi.org/10.1071/mf19029_co.

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Seven scalloped hammerhead sharks (Sphyrna lewini) were satellite tagged around the Saint Peter and Saint Paul Archipelago (SPSPA), located at the equatorial Mid-Atlantic ridge, to investigate their vertical and horizontal movements. All sharks remained in the surroundings of the SPSPA over the course of the 120-day monitoring period, suggesting a high degree of medium-term site fidelity. During this period, scalloped hammerhead sharks covered a wide extension of the water column, ranging from the mixed layer to the mesopelagic zone. All sharks remained in warm (>22°C) shallow layers most of the time, but also dove to depths greater than 150m, mostly at night, eventually reaching 728m (5.6°C) on two occasions. This study contributes important, novel information on the habitat use and movement patterns of scalloped hammerhead shark in Atlantic equatorial oceanic waters. It also highlights the potential of protecting key, large oceanic areas as a useful tool for the conservation of this endangered species.

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Dharmadi, Dharmadi, Mahiswara Mahiswara y Kamaluddin Kasim. "CATCH COMPOSITION AND SOME BIOLOGICAL ASPECTS OF SHARKS IN WESTERN SUMATERA WATERS OF INDONESIA". Indonesian Fisheries Research Journal 22, n.º 2 (24 de enero de 2017): 99. http://dx.doi.org/10.15578/ifrj.22.2.2016.99-108.

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This study was conducted in western Sumatera and since October 2013 to June 2014. The sampling locations in Banda Aceh and Sibolga-North Sumatera which were the largest base of fisheries in western Sumatera region. Shark landing recorded by enumerators was used as sampling data daily . This research aim to describ sex ratio, size composition, catch composition of sharks, and length at first maturity. In Banda Aceh, the sharks as target fish collected by sorting the bycatch from tuna longlines and tuna handlines. In Sibolga, sharks is bycatch from fish net, bottom gillnet and purse seine. Overall, there were 20 species of shark caught in west Indian Ocean and landed at those fish landing sites, dominated by Spot tail shark (23%) and Silky shark (13%), whereas Hammerhead shark contributed about 10% and Oceanic whitetip shark was only less than 1%. Almost of Spot tail shark, Silky shark, and Scalloped hammerhead that caught in that area were immature, while for the almost part of Tiger shark and Pelagic thresher were matured. The sex ratios for Spot tail shark, Silky shark, Tiger shark, Pelagic thresher, and Scalloped hammerhead caught and landed at Lampulo and Sibolga fish landing sites were not balance. The length at first maturity for Spot tail shark was Lm=87,1 cm and Lm = 213,2 cm total length for Tiger shark.

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Hsu, Hua Hsun, Zahid Nazeer, Premlal Panickan, Yu-Jia Lin, Ali Qasem, Lotfi Jilani Rabaoui y Mohammad Ali Qurban. "Stomach Content Analysis for Juvenile Great Hammerhead Sharks Sphyrna mokarran (Rüppell, 1837) from the Arabian Gulf". Fishes 7, n.º 6 (29 de noviembre de 2022): 359. http://dx.doi.org/10.3390/fishes7060359.

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The stomach contents of 30 male and 43 female (age < 3 years; 74–236 cm total length) juvenile great hammerhead sharks (Sphyrna mokarran (Rüppell, 1837)) obtained from commercial fisheries operating in Saudi Arabian waters of the Arabian Gulf were analyzed for the first time. After exclusion of parasites and abiotics, a total of 31 prey items, including the remains of cephalopods, fish, crustaceans, and bivalve mollusks, were identified in the stomachs of 59 great hammerheads. Based on the index of relative importance, teleosts were their main prey, and Platycephalus indicus (Linnaeus, 1758) was the most important prey at the species level. Significant age-related dietary differences were noted (F = 1.57, p = 0.026), indicating that the prey of the hammerheads aged 0–3 years shifted from Platycephalidae to Myliobatidae. Levin’s niche overlap index was low (0.05–0.21), indicating that <3-year-old juvenile great hammerheads are specialized predators. The estimated trophic level was 4.40–5.01 (mean ± SD, 4.66 ± 0.45), indicating that the great hammerhead is a tertiary consumer.

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Moravec, F., KM Dalrymple, AS Galloway, AM Barker y I. de Buron. "First record of Piscicapillaria bursata (Nematoda: Capillariidae), a parasite of hammerhead sharks Sphyrna spp., in the western Atlantic Ocean". Diseases of Aquatic Organisms 138 (12 de marzo de 2020): 133–36. http://dx.doi.org/10.3354/dao03458.

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Examination of 32 spiral valves from neonate specimens of hammerhead shark Sphyrna spp. (Carcharhiniformes: Sphyrnidae) captured between June and August 2018 off the Atlantic coast of South Carolina, USA, revealed the presence of the capillariid nematode Piscicapillaria bursata (Capillariidae) in the Carolina hammerhead S. gilberti, the scalloped hammerhead S. lewini, and their hybrids. This is the second find of this parasite originally described from hammerhead sharks off Australia, its first record from the western Atlantic Ocean, and its first record in a new host species and in hybrids.

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Chapman, Demian D., Mahmood S. Shivji, Ed Louis, Julie Sommer, Hugh Fletcher y Paulo A. Prodöhl. "Virgin birth in a hammerhead shark". Biology Letters 3, n.º 4 (22 de mayo de 2007): 425–27. http://dx.doi.org/10.1098/rsbl.2007.0189.

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Parthenogenesis has been documented in all major jawed vertebrate lineages except mammals and cartilaginous fishes (class Chondrichthyes: sharks, batoids and chimeras). Reports of captive female sharks giving birth despite being held in the extended absence of males have generally been ascribed to prior matings coupled with long-term sperm storage by the females. Here, we provide the first genetic evidence for chondrichthyan parthenogenesis, involving a hammerhead shark ( Sphyrna tiburo ). This finding also broadens the known occurrence of a specific type of asexual development (automictic parthenogenesis) among vertebrates, extending recently raised concerns about the potential negative effect of this type of facultative parthenogenesis on the genetic diversity of threatened vertebrate species.

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ALGHOZALI, FAQIH AKBAR, DIAH PERMATA WIJAYANTI y AGUS SABDONO. "Short Communication: Genetic diversity of scalloped hammerhead sharks (Sphyrna lewini) landed in Muncar Fishing Port, Banyuwangi". Biodiversitas Journal of Biological Diversity 20, n.º 4 (29 de marzo de 2019): 1154–59. http://dx.doi.org/10.13057/biodiv/d200430.

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Abstract. Alghozali FA, Wijayanti DP, Sabdono A. 2019. Short Communication: Genetic diversity of scalloped hammerhead sharks (Sphyrna lewini) landed in Muncar Fishing Port, Banyuwangi. Biodiversitas 20: 1154-1159. The majority of sharks caught in Indonesian fisheries were bycatch products from the tuna longline fisheries, but some regions in Indonesia fish the sharks as their main target. One of these regions is located in Muncar, Banyuwangi, which fishes the endangered Scalloped Hammerhead sharks (Sphyrna lewini) as target species. This research aimed to study the genetic diversity of the endangered Scalloped Hammerhead sharks landed in Muncar Fishing Port, Banyuwangi. Genetic analysis was done through PCR (Polymerase Chain Reaction) amplification and sequencing of the mitochondrial DNA COI (Cytochrome Oxidase subunit I) gene. Out of the 37 samples collected, 30 were successfully amplified and sequenced.The results showed moderate haplotype diversity (Hd: 0,582 ± 0,079) and low nucleotide diversity (π: 0,00392± 0,0024) with five haplotypes (h) and 26 polymorphic sites (S). Tajima’s D neutrality model values indicated a population expansion event. Two different clades were determined through phylogenetic analysis and by GenBank sequences comparison. These results provided basic information and present status of the Scalloped Hammerhead sharks population genetically within the fishing ground (Makassar Strait-Kangean Islands).

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Lowe, C. "Kinematics and critical swimming speed of juvenile scalloped hammerhead sharks". Journal of Experimental Biology 199, n.º 12 (1 de diciembre de 1996): 2605–10. http://dx.doi.org/10.1242/jeb.199.12.2605.

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Kinematics and critical swimming speed (Ucrit) of juvenile scalloped hammerhead sharks Sphyrna lewini were measured in a Brett-type flume (635 l). Kinematic parameters were also measured in sharks swimming in a large pond for comparison with those of sharks swimming in the flume. Sharks in the flume exhibited a mean Ucrit of 65±11 cm s-1 (± s.d.) or 1.17±0.21 body lengths per second (L s-1), which are similar to values for other species of sharks. In both the flume and pond, tailbeat frequency (TBF) and stride length (LS) increased linearly with increases in relative swimming speed (Urel=body lengths traveled per second). In the flume, tailbeat amplitude (TBA) decreased with increasing speed whereas TBA did not change with speed in the pond. Differences in TBF and LS between sharks swimming in the flume and the pond decreased with increases in Urel. Sharks swimming at slow speeds (e.g. 0.55 L s-1) in the pond had LS 19 % longer and TBF 21 % lower than sharks in the flume at the same Urel. This implies that sharks in the flume expended more energy while swimming at comparable velocities. Comparative measurements of swimming kinematics from sharks in the pond can be used to correct for effects of the flume on shark swimming kinematics and energetics.

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Pepperell, JG. "Trends in the distribution, species composition and size of sharks caught by Gamefish Anglers off South-eastern Australia, 1961-90". Marine and Freshwater Research 43, n.º 1 (1992): 213. http://dx.doi.org/10.1071/mf9920213.

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Records of shark captures were extracted from the archives of 10 of the major New South Wales gamefishing clubs that operate from ports located between latitudes 33�s and 37�s. Although organized game fishing began off eastern Australia in 1936, the majority of catches were made after 1960. Data normally recorded by these clubs included common name of shark, whole weight, locality of capture, boat name and angler. Recognized single species of sharks recorded by these clubs were blue (Prionace glauca), tiger (Galeocerdo cuvier), white (Carcharodon carcharias), shortfin mako (Isurus oxyrinchus) and grey nurse (Carcharias taurus). Species identified only to generic level, and recorded by clubs, were whalers or requiem sharks (Carcharhinus spp.), hammerheads (Sphyrna spp.) and threshers (Alopias spp.). Analysis of catch records indicated that the mako shark was the most common species caught overall, although whaler sharks dominated the catch in the northern part of the study area and hammerhead sharks dominated the catch in the south. Grey nurse and white sharks were relatively rare in the southern part of the study area. Whaler sharks dominated the catch in the 1960s, and the proportions of blue and tiger sharks in the catch increased in the 1980s. Size ranges and distributions of some species also varied through time and by area. Some of the observed changes could be attributed to changed fishing practices, particularly the increasing popularity of tag-and-release and an increasing tendency to fish further from the coast. A marked decline in the number and proportion of white sharks in the catch since the 1970s gives cause for some concern regarding the status of that species off south-eastern Australia.

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Galindo, E., A. Giraldo y AF Navia. "Feeding habits and trophic interactions of four sympatric hammerhead shark species reveal trophic niche partitioning". Marine Ecology Progress Series 665 (29 de abril de 2021): 159–75. http://dx.doi.org/10.3354/meps13681.

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Knowledge of the ecological roles of species within food webs and how their trophic interactions affect food web structure is critical to model management and conservation scenarios for species that are suffering high levels of anthropogenic pressure, such as hammerhead sharks. In this paper, we analyze the diet and trophic relationships of 4 sympatric hammerhead shark species using a combination of stomach content and stable isotope analyses. These species showed trophic similarities by sex and trophic dissimilarities by maturity stage. We found that the trophic niche of hammerhead species tends to be more similar within species than among them. This suggests that competitive interactions are more likely to occur between conspecifics than between congeneric individuals and highlights the potential different roles that these species can play within the food web structure. The intermediate to high trophic positions observed in Sphyrna corona, S. media, S. tiburo and S. lewini juveniles indicate mesopredator roles, whereas S. lewini subadults could be considered top predators. Our findings revealed multiple trophic interactions between hammerhead sharks and prey from different trophic levels, which could be critical for the structure and function of marine food webs.

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McComb, D. M., T. C. Tricas y S. M. Kajiura. "Enhanced visual fields in hammerhead sharks". Journal of Experimental Biology 212, n.º 24 (27 de noviembre de 2009): 4010–18. http://dx.doi.org/10.1242/jeb.032615.

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Chodrijah, Umi y Bram Setyadji. "SOME BIOLOGICAL ASPECTS OF SCALLOPED HAMMERHEAD SHARKS (Sphyrna lewini Griffith & Smith, 1834) CAUGHT FROM COASTAL FISHERIES IN THE EASTERN INDIAN OCEAN". Indonesian Fisheries Research Journal 21, n.º 2 (31 de diciembre de 2015): 91. http://dx.doi.org/10.15578/ifrj.21.2.2015.91-97.

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Indonesia has the largest chondrichthyan fishery in the world, with a reported of 105,000 and 118,000 tonnes landed in 2002 and 2003 respectively. Scalloped hammerhead shark was either targeted or by-catch from this fishery, mostly for its fins. Despite of the growing concern around the world, the availability of biological data of this species, especially in the Eastern Indian Ocean is still lacking. The objectives of this paper are to present some biological information (size composition and sex ratio) of the scalloped hammerhead, from coastal fisheries in Eastern Indian Ocean. The data used for the analysis comprised of two components, i.e. survey data in 2010 (February, March, June, August, October and December) and data from daily monitoring shark landing in 2013 (January to December). Substantially lower mean size, more immature sharks and more frequent of female caught over years showed that scalloped hammerhead shark in the Eastern Indian Ocean are facing intensive fishing pressure which could lead to overfishing. This could harm the sustainability of scalloped hammerhead shark resource in the long run. The relationship between clasper length and total length was positively correlated where every 5 cmTL increment on clasper length adding 51 cmTL on total length.

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Hsu, Hua Hsun, Zahid Muhammed Nazeer, Yu Jia Lin, Premlal Panickan, Khaled Al-Abdulkader, Ronald Loughland y Mohammad Ali Qurban. "Biological aspects of juvenile great hammerhead sharks Sphyrna mokarran from the Arabian Gulf". Marine and Freshwater Research 72, n.º 1 (2021): 110. http://dx.doi.org/10.1071/mf19368.

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The life history of the critically endangered great hammerhead Sphyrna mokarran was examined using samples collected from commercial fisheries operating in Saudi Arabian waters of the Arabian Gulf. In all, 105 specimens (47 males, 58 females), with a total length (TL) ranging from 67.0 to 236.0cm, were examined between April 2016 and November 2019. All individuals were immature. A neonate measuring 67.0cm TL caught in early June suggested the parturition period of this species was during May and June. Vertebrae under the first dorsal fin from 69 individuals (30 males, 39 females) were processed. Three age groups, from 0+ to 2+ years old, were identified by vertebrae analysis. Based on the relationship between vertebral central diameter and TL, the Fraser–Lee approach was used to back-calculate the growth history of TL. A two-parameter von Bertalanffy growth function provided the best fit to describe early growth of great hammerheads during 0–2.9 years of age based on observed and back-calculated length-at-age data. The asymptotic lengths and k values were estimated to be 256.8cm TL and 0.449 year–1 respectively. This study provides the first life history information of great hammerhead sharks in the north-western Indian Ocean.

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Wongsopatty, Karto, Luky Adrianto, Zairion Zairion, Irfan Yulianto, Hollie Booth y Andi Zulfikar. "Contingent Valuation in Measuring Fishermen’s Willingness to Pay for the Conservation of Hammerhead Shark (Sphyrna spp) Resources in Tanjung Luar, East Lombok". Economic and Social of Fisheries and Marine Journal 010, n.º 01 (30 de octubre de 2022): 90–101. http://dx.doi.org/10.21776/ub.ecsofim.2022.010.01.08.

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The hammerhead shark has high economic value, but its population is highly threatened due to its high exploitation. This study aims to calculate the level of preference of shark fishermen on the value of willingness to pay for the conservation of hammerhead shark resources. This research was conducted from November to December 2020 in Tanjung Luar Village, East Lombok Regency. The method used is observation and in-depth interviews with a sample of 150 shark fishermen. The analysis used is binary logit regression analysis using the R studio 4.1.2 tool. The results of this study indicate that (1) the total price of willingness to pay from all Tanjung Luar shark fishermen is IDR 9,654,000, and the average monthly value is IDR 53,633 per person; (2) factors that are quite influential on respondents' willingness to pay are age, education level, number of family members, and monthly income. The conservation of hammerhead shark resources needs to be considered because it has been included in the CITES Appendix II red list with a critically endangered status towards extinction. Suggestion there is a need for educational steps from various parties to fishermen regarding the importance of the existence of hammerhead sharks in the ecosystem so that they can reduce the high level of fishing activity in nature.

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24

Liu, Kwang-Ming, Lung-Hsin Huang, Kuan-Yu Su y Shoou-Jeng Joung. "Vulnerability Assessment of Pelagic Sharks in the Western North Pacific by Using an Integrated Ecological Risk Assessment". Animals 11, n.º 8 (21 de julio de 2021): 2161. http://dx.doi.org/10.3390/ani11082161.

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The vulnerability of 11 pelagic shark species caught by the Taiwanese coastal and offshore longline fisheries in the western North Pacific were assessed by an ecological risk assessment (ERA) and 10 of the 11 species was assessed by using an integrated ERA developed in this study. The intrinsic rate of population growth was used to estimate the productivity of sharks, and the susceptibility of sharks was estimated by the multiplication of the catchability, selectivity, and post-capture mortality. Three indices namely, the IUCN Red List category, the body weight variation trend, and the inflection point of population growth curve coupled with ERA were used to conduct an integrated ERA. The results indicated that the scalloped hammerhead is at the highest risk (group 1), followed by the silky shark, and the spinner shark at high risk (group 2). The bigeye thresher, and sandbar shark fall in group 3, the smooth hammerhead falls in group 4, and the shortfin mako, pelagic thresher, oceanic whitetip, and dusky shark fall in group 5. Rigorous management measures for the species in groups 1 and 2, setting total allowable catch quota for group 3, and consistent monitoring schemes for groups 4 and 5 are recommended.

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25

Bramasta, Rizaldi Cahya, Elok Faiqoh, I. Gede Hendrawan, Andrianus Sembiring y Ni Luh Astria Yusmalinda. "Identifikasi Hiu yang Diperdagangkan di Bali Menggunakan Metode DNA Barcoding dan Analisis Filogenetik". Journal of Marine and Aquatic Sciences 7, n.º 1 (2 de noviembre de 2021): 84. http://dx.doi.org/10.24843/jmas.2021.v07.i01.p12.

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Sharks are one of the keys for ecosystems balance in the ocean. Sharks as top predators have an important role to maintain the stability of the food chain in the ocean. The loss of sharks will have a major impact on the marine ecosystem, so the presence of sharks in the ocean must be protected from extinction. However, there are some activities such as sharks hunting and trading going on because of the high demand of sharks processed products. Bali is one of the locations of shark fishing and trading activities. The problem is the trade-in sharks have gone through the finning process, leaving only the body parts or fins which resulted in the difficulty of morphological identification process. An alternative method that can be used if molecular identification cannot be done is DNA Barcoding. DNA Barcoding means identifying all the animal species with an effective molecular approach applied to identify species. The identification results of DNA Barcoding of shark’s trade in Bali shows that there are four species of sharks have been sold, which is hammerhead sharks (Sphyrna lewini), thresher sharks (Alopias pelagicus), big eye thresher shark (Alopias superliciosus), silky sharks (Carcharinus falciformis). These sharks registered in the IUCN red list, Sphyrna lewini classified as threatened species, while the others (Alopias pelagicus, Alopias superciliosus and Carcharinus falciformis) classified as vulnerable species. In the international trade regulations on CITES, these four species come under the Appendix II. In national regulations, Alopias pelagicus, Alopias superciliosus, Sphyrna lewini have been regulated by the Ministerial regulations, while for Carcharinus falciformis, there are no national regulations yet.

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26

Febrianti, Isrina, Rini Puspitaningrum y Rusdi Rusdi. "IDENTIFIKASI FRAGMEN DNA MIOGLOBIN SEPANJANG 114PB PADA BEBERAPA JENIS HEWAN LAUT YANG MAMPU HIDUP PADA ZONA MINIMUM OKSIGEN". BIOMA 11, n.º 2 (9 de mayo de 2017): 194. http://dx.doi.org/10.21009/bioma11(2).9.

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ABSTRACT Myoglobin is a hemoprotein that contributes to intracellular oxygen storage and facilitates diffusion oxygen into mitochondria. Myoglobin production will increase as low levels of environmental oxygen called hypoxia. When oxygen in tissue is low, the body will respond by forming myoglobin in some tissues, such as muscle tissue. The aims of this study was to detect DNA fragments of myoglobin along 114pb in muscle tissue of marine animals are capable to live in the oxygen minimum zone, such as the green turtle, mackerel tuna and hammerhead sharks. The oxygen minimum zone is zone of oceans which have low dissolved oxygen levels at > 1,4μLO2L-1, the oxygen levels can be categorized as hypoxic conditions. This study was conducted in the Biochemistry laboratory, State University of Jakarta. This study used descriptive method by PCR and electrophoresis. The results indicated that myoglobin found in muscles of marine animals were capable live in oxygen minimum zone such as the green turtle, mackerel tuna and hammerhead shark. This information can be used as the basic that the tissue able to make adaptation strategy towards low oxygen environmental levels by increasing formation of myoglobin in muscle tissue. Kata kunci: Myoglobin DNA, Green Turtle, Mackerel Tuna and Hammerhead Sharks

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27

RASALATO, ERONI, VICTOR MAGINNITY y JUERG M. BRUNNSCHWEILER. "Using local ecological knowledge to identify shark river habitats in Fiji (South Pacific)". Environmental Conservation 37, n.º 1 (marzo de 2010): 90–97. http://dx.doi.org/10.1017/s0376892910000317.

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SUMMARYLocal ecological knowledge (LEK) and traditional ecological knowledge (TEK) have the potential to improve community-based coastal resource management (CBCRM) by providing information about the presence, behaviour and ecology of species. This paper explores the potential of LEK and TEK to identify shark river habitats in Fiji, learn how locals regard and use sharks, and capture ancestral legends and myths that shed light on relationships between these animals and local people. Interviews with representatives from 22 villages, communities and fishing settlements associated with seven riverine areas on Viti Levu and Vanua Levu confirmed the presence of sharks in estuaries and rivers on Fiji. Hammerhead sharks (Sphyrna spp.) and larger sharks were reported being close to the river mouths, whereas an unknown species of small size with a rounded snout was reported up to >30 km upriver. Local people consume shark meat as a source of protein, but sharks also have a rich background in ancestral stories and play an important part in Fijian myths and legends, resulting in the support of conservation measures by local villagers.

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Holland, KN, CG Lowe, JD Peterson y A. Gill. "Tracking Coastal Sharks with small boats: Hammerhead Shark Pups as a case study". Marine and Freshwater Research 43, n.º 1 (1992): 61. http://dx.doi.org/10.1071/mf9920061.

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Acoustic telemetry techniques have been adapted for use with small boats to facilitate tracking of nearshore reef species. In addition to permitting tracking in areas where manoeuvrability and quick responses are required, the system has modest operating costs that make tracking experiments a viable option for a wide range of researchers. Tracking and communication equipment can be powered for several days by a single 12-V 8D truck battery. Current topics in shark biology that are amenable to these tracking techniques are discussed. For instance, hammerhead pups have been tracked on their natal grounds for periods of up to 13 days. Their daytime movements appeared to be restricted to a well defined 'core area' where a school of sharks hovered between 1 and 3 m off the lagoon floor. At night, the sharks became more active, expanding their range of movements before returning to the core area the next morning.

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29

Monteforte, Kim I. P., Paul A. Butcher, Stephen G. Morris y Brendan P. Kelaher. "The Relative Abundance and Occurrence of Sharks off Ocean Beaches of New South Wales, Australia". Biology 11, n.º 10 (4 de octubre de 2022): 1456. http://dx.doi.org/10.3390/biology11101456.

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There is still limited information about the diversity, distribution, and abundance of sharks in and around the surf zones of ocean beaches. We used long-term and large-scale drone surveying techniques to test hypotheses about the relative abundance and occurrence of sharks off ocean beaches of New South Wales, Australia. We quantified sharks in 36,384 drone flights across 42 ocean beaches from 2017 to 2021. Overall, there were 347 chondrichthyans recorded, comprising 281 (81.0%) sharks, with observations occurring in <1% of flights. Whaler sharks (Carcharhinus spp.) had the highest number of observations (n = 158) recorded. There were 34 individuals observed for both white sharks (Carcharodon carcharias) and critically endangered greynurse sharks (Carcharias taurus). Bull sharks (Carcharhinus leucas), leopard sharks (Stegostoma tigrinum) and hammerhead species (Sphyrna spp.) recorded 29, eight and three individuals, respectively. Generalised additive models were used to identify environmental drivers for detection probability of white, bull, greynurse, and whaler sharks. Distances to the nearest estuary, headland, and island, as well as water temperature and wave height, were significant predictors of shark occurrence; however, this varied among species. Overall, we provide valuable information for evidence-based species-specific conservation and management strategies for coastal sharks.

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30

Jerome, J. M., A. J. Gallagher, S. J. Cooke y N. Hammerschlag. "Integrating reflexes with physiological measures to evaluate coastal shark stress response to capture". ICES Journal of Marine Science 75, n.º 2 (2 de noviembre de 2017): 796–804. http://dx.doi.org/10.1093/icesjms/fsx191.

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Abstract In both commercial and recreational fisheries, sharks are captured and released alive to comply with regulations or due to low economic value or voluntary conservation ethic. As a result, understanding the physiological and behavioural responses of sharks to capture stress is important for determining subsequent effects of fisheries interactions on a species-specific basis, as well as for identifying factors that influence mortality. Here, we employed a suite of conventional blood physiology endpoints (glucose, lactate, and haematocrit) integrated with assessments of reflex impairment on blacktip (Carcharhinus limbatus), great hammerhead (Sphyrna mokarran), nurse (Ginglymostoma cirratum) and sandbar sharks (Carcharhinus plumbeus) captured via experimental drumline gear. We documented a wide range of species-specific differences in all parameters assessed, with nurse sharks consistently having the lowest relative levels of physiological disturbance and reflex impairment; and with great hammerheads exhibiting the highest level of physiological disturbance and reflex impairment, suggesting higher vulnerability to fishing. In general, increases in lactate were positively associated with hook time and correlated with reflex impairment assessment. Moreover, reflex indices showed significant impairment with hook time, with the “jaw” reflex emerging as the most potential predictor of disturbance. Our study results connect previously reported species-specific at-vessel and post-release mortality rates to their physiological disturbance and reflex impairment.

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Sentosa, Agus Arifin, Dharmadi Dharmadi y Didik Wahju Hendro Tjahjo. "PARAMETER POPULASI HIU MARTIL (Sphyrna lewini Griffith & Smith, 1834) DI PERAIRAN SELATAN NUSA TENGGARA". Jurnal Penelitian Perikanan Indonesia 22, n.º 4 (27 de enero de 2017): 253. http://dx.doi.org/10.15578/jppi.22.4.2016.253-262.

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Hiu martil (Sphyrna lewini Griffith & Smith, 1834) merupakan salah satu target tangkapan bagi perikanan artisanal di Indonesia. Dengan status konservasi masuk dalam Appendix II CITES, pengelolaan terhadap hiu martil telah menjadi perhatian khusus di bidang perikanan tangkap. Penelitian ini bertujuan untuk mengkaji beberapa aspek parameter populasi hiu martil yang tertangkap di perairan selatan Nusa Tenggara pada periode Januari – Desember 2015. Data ukuran panjang dan jenis kelamin diperoleh di Tempat Pendaratan Ikan Tanjung Luar, Lombok Timur, Nusa Tenggara Barat. Analisis dilakukan secara deskriptif menggunakan perangkat lunak FiSAT II. Hasil penelitian menunjukkan bahwa dari 634 ekor hiu martil yang tertangkap didominasi oleh jenis kelamin betina dengan sebaran ukuran panjang total berkisar antara 81 – 320 cm (rerata 211,2 cm) dan jenis kelamin jantan berkisar antara 91 – 310 cm (rerata 176,9 cm). Dominasi kelompok hiu muda yang belum matang kelamin berpotensi terjadinya recruitment overfishing. Hiu martil mampu mencapai panjang asimtot 399 cm. Laju pertumbuhan dan mortalitas jenis hiu jantan lebih tinggi dibandingkan jenis betina. Populasi hiu martil telah mengalami kondisi tangkap lebih sehingga perlu adanya regulasi dan pengelolaan agar pemanfaatannya tetap lestari. The scalloped hammerhead sharks (Sphyrna lewini Griffith & Smith, 1834) is one of the main target fishing for artisanal shark fisheries in Indonesia. By the conservation status of Appendix II CITES, its management had been concerned in capture fisheries. This research aimed to assess some aspects of scalloped hammerhead shark population parameters caught in the southern of Nusa Tenggara in the period from January to December 2015. Fish length and sex was obtained in Tanjung Luar landing site, East Lombok, West Nusa Tenggara. The analysis was done descriptively used FiSAT II software. The results showed that 634 individuals of hammerhead shark caught dominated by female with a total length size distribution ranging between 81-320 cm (mean 211.2 cm) and male ranged between 91-310 cm (mean 176.9 cm). The dominance catch of juvenile sharks with immature was potential to recruitment overfishing. Sphyrna lewini was capable of reaching 399 cm asymptotic length. The growth rate and mortality of male sharks was higher than female. The population of S. lewini had been overfished so that the regulation and management are needed in order to maintain their sustainability of the population.

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32

Braccini, Matias, Brett Molony y Nick Blay. "Patterns in abundance and size of sharks in northwestern Australia: cause for optimism". ICES Journal of Marine Science 77, n.º 1 (10 de octubre de 2019): 72–82. http://dx.doi.org/10.1093/icesjms/fsz187.

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Abstract Reliable information for population assessments is rare for sharks. We quantified patterns in catch rates and mean size for numerous tropical and subtropical species from 15 years of fishery-independent surveys (2002–2017) in northwestern Australia. This study region represents an area of ~0.8 million km2 which was closed to commercial shark fishing from 1993 or 2005 onward due to the very high State-wide catches of sandbar (Carcharhinus plumbeus) and dusky (Carcharhinus obscurus) sharks. A total of 43 shark and ray species were sampled, with sandbar shark being the most commonly caught species, followed by milk (Rhizoprionodon acutus), spot-tail (Carcharhinus sorrah), tiger (Galeocerdo cuvier), blacktip (Carcharhinus limbatus and Carcharhinus tilstoni), dusky and sliteye (Loxodon macrorhinus) sharks, and scalloped hammerhead (Sphyrna lewini). For sandbar shark, catch rates increased between 2008 and 2017 whereas for other taxa catch rates were mostly stable (albeit fluctuating). Mean size at capture fluctuated across years with no particular trends. Unlike for other parts of the world, catch rates and mean size of northwestern Australian sharks have been stable or increased in recent years. Though most shark species have conservative life histories, when science, management and enforcement work synergistically, sustainable resource use, recovery and conservation outcomes can all be achieved.

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MOORE, ALEC B. M., ROBERT D. WARD y RICHARD PEIRCE. "Sharks of the Persian (Arabian) Gulf: a first annotated checklist (Chondrichthyes: Elasmobranchii)". Zootaxa 3167, n.º 1 (20 de enero de 2012): 1. http://dx.doi.org/10.11646/zootaxa.3167.1.1.

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The first evidence-based checklist of sharks of the Persian (Arabian) Gulf is presented based on appraisal of primary lit-erature and new data, including identifications verified by COI barcoding. Evidence of the occurrence of 26 species in theGulf is presented, and the possible presence of a further 17 species is discussed. Carcharhinidae is the most species-richfamily (16 species) present. The first substantiated Gulf records of the spinner shark Carcharhinus brevipinna, blacktipreef shark C. melanopterus¸ and scalloped hammerhead Sphyrna lewini are provided, along with a new record of the rarelyreported grey nurse shark Carcharias taurus. The diversity of the Gulf’s shark fauna, and possible influences on it, are briefly discussed.

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34

Jennings, Randy D. "Seasonal Abundance of Hammerhead Sharks off Cape Canaveral, Florida". Copeia 1985, n.º 1 (11 de febrero de 1985): 223. http://dx.doi.org/10.2307/1444814.

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35

Kajiura, Stephen M. y Timothy P. Fitzgerald. "Response of juvenile scalloped hammerhead sharks to electric stimuli". Zoology 112, n.º 4 (julio de 2009): 241–50. http://dx.doi.org/10.1016/j.zool.2008.07.001.

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36

Lowe, C. "Metabolic rates of juvenile scalloped hammerhead sharks (Sphyrna lewini)". Marine Biology 139, n.º 3 (septiembre de 2001): 447–53. http://dx.doi.org/10.1007/s002270100585.

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37

Mara, Kyle R., Philip J. Motta, Andrew P. Martin y Robert E. Hueter. "Constructional morphology within the head of hammerhead sharks (sphyrnidae)". Journal of Morphology 276, n.º 5 (13 de febrero de 2015): 526–39. http://dx.doi.org/10.1002/jmor.20362.

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38

Kotas, JE, V. Mastrochirico y M. Petrere Junior. "Age and growth of the Scalloped Hammerhead shark, Sphyrna lewini (Griffith and Smith, 1834), from the southern Brazilian coast". Brazilian Journal of Biology 71, n.º 3 (agosto de 2011): 755–61. http://dx.doi.org/10.1590/s1519-69842011000400022.

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Age and growth studies for the scalloped hammerhead shark, Sphyrna lewini (Griffith and Smith, 1834) caught along the southern Brazilian coast, were based on ring measurements of vertebrae sections of 115 males, 116 females and 14 unknown sexed sharks between 48 and 344 cm total length (TL). The von Bertalanffy growth models were best fit using back-calculated data. The growth parameters obtained for males, were L∞ = 266 cm; K = 0.05/year; L0 = 47 cm. For females, L∞ = 300 cm; K = 0.05/year; L0 = 51 cm. An adult female reached 217 cm TL and was 31.5 years old. On the other hand, an adult male was 29.5 years old and measured 234 cm TL. Longevity estimate for males and females was 55 years. Therefore, S. lewini is a long-lived fish. Ageing precision, based on the IAPE index, was 5.6%. Marginal Increment analysis based on MIR index from hammerheads smaller than 105 cm, compared with the percentual of opaque and hyaline bands found per month ageing whole vertebrae, showed an annual ring formation, i.e., in winter.

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39

Kajiura, Stephen M., Jesica B. Forni y Adam P. Summers. "Maneuvering in juvenile carcharhinid and sphyrnid sharks: the role of the hammerhead shark cephalofoil". Zoology 106, n.º 1 (enero de 2003): 19–28. http://dx.doi.org/10.1078/0944-2006-00086.

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40

Reid, D. D., W. D. Robbins y V. M. Peddemors. "Decadal trends in shark catches and effort from the New South Wales, Australia, Shark Meshing Program 1950 - 2010". Marine and Freshwater Research 62, n.º 6 (2011): 676. http://dx.doi.org/10.1071/mf10162.

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The New South Wales (NSW) government has operated a program of netting beaches for the protection of swimmers and surfers against shark attack since 1937 in Sydney, and since 1949 in Newcastle and Wollongong. The scope and directives of the Shark Meshing Program have remained constant since its inception, with operational modifications in net specifications in 1972, changes in spatial deployment in 1972, 1987 and 1992, and the elimination of winter netting since 1989. This markedly increased meshing effort in 1972, and again in 1987. In the present study, we examine the trends in catch and effort for the period from 1950–1951 to 2009–2010 over this 200-km section of the NSW coast. Significant temporal trends in species, size and sex composition are described herein. Catches were consistently dominated by three shark taxa, hammerhead sharks (Sphyrna spp.), whaler sharks (Carcharhinus spp.) and Australian angel sharks (Squatina australis), although their relative contributions to catches varied over time. Catch per unit effort has significantly declined for five of the most abundant shark taxa over the study period, increasing only for a single taxon, the sevengill shark (Notorynchus cepedianus). Catches of larger, potentially dangerous white sharks (Carcharodon carcharias) and tiger sharks (Galeocerdo cuvier) saw fewer large animals being caught over time. This pattern was not observed across other taxa. Four different monthly trends were observed in landings of the most abundant eight taxa, reflecting differences in the biology of the catch species. The current study also provides useful information on catches and sizes of grey nurse (Carcharias taurus) and white sharks before and after their protection in NSW waters in 1984 and 1998, respectively.

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Wilga, C. D. y P. J. Motta. "Durophagy in sharks: feeding mechanics of the hammerhead Sphyrna tiburo". Journal of Experimental Biology 203, n.º 18 (15 de septiembre de 2000): 2781–96. http://dx.doi.org/10.1242/jeb.203.18.2781.

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This study investigates the motor pattern and head movements during feeding of a durophagus shark, the bonnethead Sphyrna tiburo, using electromyography and simultaneous high-speed video. Sphyrna tiburo feeds almost exclusively on hard-shelled crabs, with shrimp and fish taken occasionally. It captures crabs by ram feeding, then processes or reduces the prey by crushing it between molariform teeth, finally transporting the prey by suction for swallowing. The prey-crushing mechanism is distinct from that of ram or bite capture and suction transport. This crushing mechanism is accomplished by altering the duration of jaw adductor muscle activity and modifying jaw kinematics by the addition of a second jaw-closing phase. In crushing events, motor activity of the jaw adductor muscles continues (biting of the prey occurs as the jaws close and continues after the jaws have closed) throughout a second jaw-closing phase, unlike capture and transport events during which motor activity (biting) ceases at jaw closure. Sphyrna tiburo is able to take advantage of a resource (hard prey) that is not readily available to most sharks by utilizing a suite of durophagous characteristics: molariform teeth, a modified jaw protrusor muscle, altered jaw adductor activity and modified jaw kinematics. Sphyrna tiburo is a specialist feeder on crab prey as demonstrated by the lack of differences in kinematic or motor patterns when offered prey of differing hardness and its apparent lack of ability to modulate its behavior when feeding on other prey. Functional patterns are altered and coupled with modifications in dental and jaw morphology to produce diverse crushing behaviors in elasmobranchs.

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42

Quattro, J. M., D. S. Stoner, W. B. Driggers, C. A. Anderson, K. A. Priede, E. C. Hoppmann, N. H. Campbell, K. M. Duncan y J. M. Grady. "Genetic evidence of cryptic speciation within hammerhead sharks (Genus Sphyrna)". Marine Biology 148, n.º 5 (13 de diciembre de 2005): 1143–55. http://dx.doi.org/10.1007/s00227-005-0151-x.

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43

Fischer, AF, FHV Hazin, F. Carvalho, DL Viana, MG Rêgo y C. Wor. "Biological aspects of sharks caught off the Coast of Pernambuco, Northeast Brazil". Brazilian Journal of Biology 69, n.º 4 (noviembre de 2009): 1173–81. http://dx.doi.org/10.1590/s1519-69842009000500023.

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One hundred seventeen specimens of sharks were caught along the coast of Pernambuco State, Northern Brazil, between May 2004 and May 2007, among which 86 were blacknose sharks, Carcharhinus acronotus, enabling a more detailed study of the species. Blacknose sharks were caught in the 2 study areas along the Boa Viagem/Piedade and Paiva beaches, accounting for the highest relative abundance among the species caught (73.5% of total). Potentially dangerous sharks, tiger and bull sharks, were also caught in the same areas, whereas hammerhead and blacktip sharks were only captured off Boa Viagem/Piedade. Concerning the blacknose shark, the total length (TL) ranged from 39.0 to 180.0 cm. Among the 38 females analysed, 32 were juveniles, 11 were maturing, 2 were pre-ovulatory and 21 were pregnant. Sexing was possible for 75 of the 83 embryos, 38 of which were males and 37 were females, with a sex proportion of 1:0.9 and total length ranging between 6.4 and 63.5 cm. Ovarian fecundity ranged from 5 to 10 and uterine fecundity from 1 to 3, with an estimated gestational period of 9 months. Among the 48 males, 6 were juveniles and 42 were adults. Both males and females seem to reach sexual maturity at about 105.0 cm TL. Among the 86 stomachs analysed, only 22.1% had contents, with teleosts as the most frequent item.

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Jaiteh, Vanessa F., Adrian R. Hordyk, Matías Braccini, Carol Warren y Neil R. Loneragan. "Shark finning in eastern Indonesia: assessing the sustainability of a data-poor fishery". ICES Journal of Marine Science 74, n.º 1 (7 de noviembre de 2016): 242–53. http://dx.doi.org/10.1093/icesjms/fsw170.

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For over two decades, Indonesia has reported higher average shark landings than any other nation, but very little local information exists on the fishery and life histories of targeted species. This poses severe challenges to shark sustainability and conservation in this vast archipelago. We draw on diverse sources of data to evaluate the sustainability of the shark fishery in eastern Indonesia, a particularly data-poor region where sharks are primarily targeted for their fins. Shark fishers from three coastal communities were interviewed on their perceptions of catch trends over the past twenty years and asked to collect fishing data during fishing trips in the Seram, Arafura and Timor Seas. For the most frequently harvested species, we estimated maximum intrinsic rates of increase (rmax) to predict their resilience to fishing pressure. Our results indicate that shark fishing practices in the region are likely to be unsustainable. The catches of several species largely comprised of immature individuals and most fishers attributed observed declines in shark numbers, size and species diversity to overfishing. Hammerhead sharks have relatively high intrinsic resilience but are nevertheless at risk of local extinction due to their availability to the fishery and the value of their fins. Sandbar, dusky and grey reef sharks have lower resilience and are frequently caught but not managed. We recommend a composite management approach, including consistent implementation of existing trade restrictions, fisheries research and opportunities for fishers’ livelihood diversification, to stem shark harvests in eastern Indonesia.

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Arifin, Yusuf Nur. "Analysis of Law Enforcement Against Criminal Action on Illegal Fishing (Case Study of MV Hai Fa)". Hang Tuah Law Journal 4, n.º 1 (10 de junio de 2020): 14. http://dx.doi.org/10.30649/htlj.v4i1.146.

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The MV Hai Fa case has taken the public's attention for almost the last 5 years after the court ruling was issued by the Ambon Court. MV Hai Fa was declared proven to have captured 15 tons of spike shark (Carcharhinus spp) and hammerhead shark (Sphyrna lewini) which are some of the protected species of marine animals as stated in the Minister of Maritime Affairs and Fisheries Regulation Number 59 of 2014 concerning Prohibition of Fish Expenditures Cowboy sharks (Carcharhinus spp) and hammerhead sharks (Sphyrna lewini) outside the territory of the Republic of Indonesia and violating Article 100 in conjunction with Article 7 paragraph (2) letter m law No. 45 of 2009 concerning amendments to Law No.31 of 2004. This study uses normative legal research methods with a case, concept, law and comparison approach with the aim of knowing and analyzing the law enforcement process against illegal fishing cases by MV Hai Fa in Indonesian waters as well as analyzing comparative reviews of national law and international law in MV Hai Fa case and the government system owned by Vietnam and Australia. The results of the study concluded that the need for a government institution which is appointed by the President could carry out full coordination and supervision until the judicial process and that the revision of fisheries law which has more severe sanctions were adjusted to international law and the material and immaterial losses caused by the crime.

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46

Kotas, Jorge Eduardo, Miguel Petrere Jr, Roberta Aguiar Dos Santos, Ajax Bustamante, Celso Fernandes Lin, Antônio Alberto Da Silveira Menezes y Elizabethe Lobão Veras Micheletti. "The horizontal migration of hammerhead sharks along the southern Brazilian coast, based on their exploitation pattern and considerations about the impact of anchored gillnets activities on these species". Revista CEPSUL - Biodiversidade e Conservação Marinha 3, n.º 1 (25 de marzo de 2014): 45–68. http://dx.doi.org/10.37002/revistacepsul.vol3.32245-68.

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Between 1995-2009 hammerhead sharks were sampled from the landings ofthe industrial fleets based in the harbours of Itajaí and Navegantes, SC State,and Ubatuba, SP State, Brazil. In this case, fishing boats which operated with gillnetslonglines and trawls along the southern Brazilian Economic Exclusive Zone and internationaladjacent waters were targeted. A total of 2483 and 353 S. lewini and S. zygaena carcasses respectively were sexed, measured and converted to total lengths (LT). Additionallyinformation about, year, season, latitude/longitude and local depth (m) from the catches,by fishing category, were obtained. During the considered period, intense fishing mortalityover pups was caused by gillnets and trawls operating on shallow waters (≤20m) and overjuveniles along the continental shelf (>20m and ≤200m). Additionally, adults were exploitedby driftnets and longlines along the shelf border and slope (>200m). Therefore,both hammerhead species are exploited at all life-stages and throughout their migratory circuit.This includes during their inshore-offshore migration while they are growing from pupsto juveniles and as the offshore-inshore migration of pregnant females to pupping areas inshallower waters. This apparently unsustainable exploitation pattern, over different sizeclasses (newborns-juveniles-adults), and the economic pressure caused by the internationalfin market, is one of the reasons for population declining of these two species in southernBrazil. Non fishing zones for the hammerheads, protecting their migratory circuit, which isdriven by their growth pattern and reproduction, are necessary. Additionally, fishing effortreduction and a control over the international fin market are recommended.

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47

Krogh, M. "Spatial, seasonal and biological analysis of sharks caught in the New South Wales protective beach meshing programme". Marine and Freshwater Research 45, n.º 7 (1994): 1087. http://dx.doi.org/10.1071/mf9941087.

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Data for the catches of sharks at each beach meshed in New South Wales are presented for the period from October 1972 to December 1990. High catch rates of sharks were observed at a number of these beaches. Comparison of the catches of sharks at each beach by means of hierarchical clustering and nonmetric multidimensional scaling revealed regional associations as well as some unusual relationships. Beaches at either end of each netted region (i.e. Newcastle, Sydney or Wollongong) tended to have higher catches than did beaches in the centre of each region. Hammerhead sharks (Sphyrna spp.) had significantly higher catch rates on long open beaches. Significantly higher catches of whaler (Carcharhinus spp.), white (Carcharodon carcharias), and tiger (Galeocerdo cuvier) sharks occurred when deeper water was closer to the beach. Limited biological and seasonal data are also presented for the 11 species or species groups: Sphyrna spp., Carcharhinus spp., Squatina austmlis, Heterodontus spp., Carcharodon carcharias, Galeocerdo cuvier, Carcharias taurus, Notorynchus cepedianus, Alopias spp., Isurus oxyrinchus and Orectolobus spp.

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48

Nakaya, Kazuhiro. "Hydrodynamic Function of the Head in the Hammerhead Sharks (Elasmobranchii: Sphyrnidae)". Copeia 1995, n.º 2 (3 de mayo de 1995): 330. http://dx.doi.org/10.2307/1446895.

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49

Raoult, Vincent, Matt K. Broadhurst, Vic M. Peddemors, Jane E. Williamson y Troy F. Gaston. "Resource use of great hammerhead sharks ( Sphyrna mokarran ) off eastern Australia". Journal of Fish Biology 95, n.º 6 (23 de octubre de 2019): 1430–40. http://dx.doi.org/10.1111/jfb.14160.

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50

Couto, Ana, Nuno Queiroz, James T. Ketchum, Eduardo Sampaio, Miguel Furtado, André A. Cid, Joana Castro y Rui Rosa. "Smooth hammerhead sharks (Sphyrna zygaena) observed off the Portuguese southern coast". Environmental Biology of Fishes 101, n.º 8 (8 de junio de 2018): 1261–68. http://dx.doi.org/10.1007/s10641-018-0773-8.

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