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1. In 2016, the UK government announced plans for a large-scale Marine Protected Area around Ascension Island, a UK Overseas Territory in the South Atlantic. 2. To improve baselines for marine life to support ambitious conservation and assess change over time, archives were searched for historical accounts of wildlife from Ascension's discovery in 1501 to the present. For more recent changes, 139 interviews with past and present inhabitants were conducted. 3. Ascension's marine life has, from first discovery to the present, been consistently remarked upon for its exceptional abundance. Historical sources indicate declines in seabird and turtle populations from human exploitation and introduction of rats and cats. They are recovering with good management, although still below pre-settlement abundance. 4. Interviews with residents indicate more recent changes, notably declines in catch per unit of fishing effort at popular shore angling sites, a decline in yellowfin tuna (Thunnus albacares) and increase in Galapagos sharks (Carcharhinus galapagensis). 5. What is very notable, however, based on the interviews, was that there was no temporal signal suggestive of recent systemic decline, in marked contrast to many parts of the world where recent wildlife declines have been pervasive and steep. Ascension represents a remarkable and immensely important centre of abundance in a sea of depletion and change, warranting full protection for all the island's waters.

Carcharhinus galapagensis (Snodgrass & Heller, 1905). Galapagos Shark. To at least 3.0 m (12.1 ft) TL and possibly to 3.7 m (14.1 ft) TL (Weigman 2016). Circumglobal in tropical waters; western Pacific Ocean north to Ogasawara Islands (Yoshino and Aonuma in Nakabo 2002); patchily distributed from central Baja California (Compagno et al. in Fischer et al. 1995), and Rocas Alijos, southern Baja California (Gotshall 1996), to Peru (Cornejo et al. 2015), and Easter Island (Chirichigno and V��lez 1998), including Gulf of California (Compagno et al. in Fischer et al. 1995) and Islas Gal��pagos (Grove and Lavenberg 1997). Depth: surface to 371 m (1,217 ft) (min.: Allen and Robertson 2015; max.: Weijerman et al. 2019). Possibly a synonym of Carcharhinus obscurus (Naylor et al. 2012). Pazmi��o et al. (2019) reported on a number of individuals that were hybrids of C. galapagensis and Carcharhinus obscurus (Lesueur, 1818) in the eastern Pacific Ocean., 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 18, DOI: 10.11646/zootaxa.5053.1.1, http://zenodo.org/record/5578008, {"references":["Nakabo, T. (Ed.). (2002) Fishes of Japan with Pictorial Keys to the Species. Tokai University Press, Tokyo.","Fischer, W., Krupp, F., Schneider, W., Sommer, C., Carpenter, K. E. & Niem, V. H. (1995) Guia FAO para la identificacion para los fines de la pesca. Pacifico centro-oriental. Volume II, Vertebrados, Parte 1. Volume III, Vertebrados, Parte 2. FAO, Rome.","Gotshall, D. W. (1996) Fishes of Rocas Alijos. In: Smeider, R. W. (Ed.). Rocas Alijos Scientific Results from the Cordell Expedition. Kluwer Academic, Dordrecht, pp. 347 - 354.","Cornejo, R., Velez-Zuazo, X., Gonzalez-Pestana, A., Kouri J., C. & Mucientes, G. (2015) An updated checklist of Chondrichthyes from the southeast Pacific off Peru. CheckList, 11, 1809. https: // doi. org / 10.15560 / 11.6.1809","Chirichigno, F. N. & Velez D, J. (1998) Clave para identificaticar los peces marinos del Peru (segunda edicion, revisada y actualizada). Instituto de Mar de Peru Publicacion Especial.","Grove, J. S. & Lavenberg, R. J. (1997) The Fishes of the Galapagos Islands. Stanford University Press, Stanford.","Robertson, D. R. and Allen, G. R. (2015) Shorefishes of the Tropical Eastern Pacific: an Information System. Version 2.0 (2008). Smithsonian Tropical Research Institute, Balboa. http: // biogeodb. stri. si. edu / sftep / en / pages","Weijerman, M., Gruss, A., Dove, D., Asher, J., Williams, I. D., Kelley, C. & Drazen, J. (2019) Shining a light on the composition and distribution patterns of mesophotic and subphotic fish communities in Hawai'i. Marine Ecology Progress Series, 630, 161 - 182. https: // doi. org / 10.3354 / meps 13135","Naylor, G. J. P., Caira, J. N., Jensen, K., Rosana, K. A. M., White, W. T. & Last, P. R. (2012) A DNA sequence-based approach to the identification of shark and ray species and its implications for global elasmobranch diversity and parasitology. Bulletin of the American Museum of Natural History, Number 367. https: // doi. org / 10.1206 / 754.1","Pazmino, D. A., van Herderden, L., Simpfendorfer, C. A., Junge, C., Donnellan, S. C., Hoyos-Padilla, E. M., Duffy, C. A. J., Huveneers, C., Gillanders, B. M., Butcher, P. A. & Maes, G. E. (2019) Introgressive hybridization between two widespread sharks in the east Pacific region. Molecular Phylogenetics and Evolution, 136, 119 - 127. https: // doi. org / 10.1016 / j. ympev. 2019.04.013"]}

To determine trends over time in the relative abundance of species prioritized in the Malpelo Fauna and Flroa Sanctuary Management Plan, underwater visual censuses were done from April 2009 to August 2019. Data were collected for five species of bonefish: bluefin trevally (Caranx melampygus), longfin yellowtail (Seriola rivoliana), yellowfin tuna (Thunnus albacares), leather bass (Dermatolepis dermatolepis) and sailfin grouper (Mycteroperca olfax), and six cartilaginous fish: spotted eagle ray (Aetobatus laticeps), silky shark (Carcharhinus falciformis), Galapagos shark (Carcharhinus galapagensis), whitetip reef shark (Triaenodon obesus), whale shark (Rhincodon typus) and scalloped hammerhead shark (Sphyrna lewini). A negative non-significant trend in abundance through time was observed for most of the evaluated species, except A. laticeps and T. obesus, which showed positive non-significant trends. The hammerhead shark (S. lewini) was the only species that showed a statistically significant decrease in abundance over time. The results of this study highlight the urgent need to establish more effective fisheries management and regulation measures that promote the conservation of important fish species, not just inside the sanctuary but also within the Tropical Eastern Pacific. RESUMEN Con el objetivo de determinar tendencias en la abundancia relativa a través del tiempo para especies priorizadas dentro del Plan de Manejo del Santuario de Fauna y Flora Malpelo, se realizaron censos visuales submarinos (CVS) entre abril de 2009 y agosto de 2019. Se colectaron datos para cinco especies de peces óseos: jurel azul (Caranx melampygus), bravo (Seriola rivoliana), atún aletiamarillo (Thunnus albacares), cherna (Dermatolepis dermatolepis) y mero (Mycteroperca olfax), y seis especies de peces cartilaginosos: raya águila (Aetobatus laticeps), tiburón sedoso (Carcharhinus falciformis), tiburón de Galápagos (Carcharhinus galapagensis), tiburón aletiblanco de arrecife (Triaenodon obesus), tiburón ballena (Rhincodon typus) y tiburón martillo (Sphyrna lewini). En términos generales, se observó una tendencia negativa no significativa en la abundancia relativa a través del tiempo para la mayoría de las especies evaluadas, exceptuando A. laticeps y T. obesus, las cuales mostraron tendencias positivas no significativas. El tiburón martillo (S. lewini) fue la única especie que mostró una disminución estadísticamente significativa de su abundancia a través del tiempo. Los resultados de este estudio evidencian la necesidad apremiante de establecer medidas más eficientes de manejo y de regulación pesquera, que promuevan la conservación de especies importantes de peces no sólo dentro del santuario sino a lo largo del Pacífico Oriental Tropical.

Reef fishes are an important component of marine biodiversity, and changes in the composition of the assemblage structure may indicate ecological, climatic, or anthropogenic disturbances. To examine spatial differences in the reef fish assemblage structure around Easter Island, eight sites were sampled during autumn and summer 2016–2017 with baited remote underwater video systems. To determine seasonal changes, quarterly (seasonal) sampling was conducted at five of those eight sites. Fifteen pelagic species of fishes were recorded during this study, some of which have not previously been recorded in scuba surveys, including the Galapagos shark (Carcharhinus galapagensis, Snodgrass & Heller, 1905) and tunas (Scrombidae). Significant spatial and seasonal differences were found in the fish assemblage. Fish assemblages from the south coast differed significantly from those along the west and east coasts, mainly due to the occurrence of top predators. Winter differed from other seasons, especially along the south coast where the island is more exposed to large oceanic swells and winds from Antarctica. Owing to the variety and high relative abundance of species recorded during this survey, baited remote underwater video systems seemed to be an effective method for studying top predators at Easter Island. The identification of priority zones for the protection of top predator species represents an important contribution of this study, in order to develop management and conservation strategies to be implemented in the newly created Rapa Nui multiple uses coastal marine protected areas.

Long-distance movements of sharks within and between islands pose substantial challenges for resource managers working with highly migratory species. When no-take zones do not cover the critical areas that sharks use as part of their lifecycle, exposure to fishing activities can be significant. Shark movements between the Marine Protected Areas (MPAs) of the Eastern Tropical Pacific (ETP) have been studied for several years, however little is known about the strength of connectivity between these islands. We analyzed the extensive MigraMar ultrasonic telemetry dataset to assess how Galapagos sharks (Carcharhinus galapagensis) and silky sharks (Carcharhinus falciformis) use different islands as stepping-stones during their migrations within the Revillagigedo National Park and other ETP islands. Of the 66 sharks monitored, 63.5% moved within the same island, 25.4% between two islands or more and only 10.1% across different MPAs. A C. falciformis tagged in Roca Partida Island, Revillagigedo, travelled to Clipperton Atoll and another one tagged in Darwin Island travelled to the atoll on two different years. The largest movement of C. galapagensis was accomplished by a shark tagged at Socorro Island, Revillagigedo, later detected at Clipperton and finally recorded in Darwin Island, Galapagos. This last path was in fact, one of the longest movements ever recorded for the species. Although long-distance dispersion was not common, our results highlight the need for co-operation between different countries to ensure adequate protection for sharks in the form of swimways and other conservation tools in the ETP.

Made available in DSpace on 2020-12-10T17:03:16Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-12-20 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundacao Estadual de Amparo a Pesquisa do Estado do Espirito Santo PROTRINDADE Here we present records of sharks obtained using baited remote underwater stereo-video systems (stereo-BRUVS) at two Brazilian oceanic islands. Fourteen of the 60 deployments recorded 19 sharks in Trindade Island. In Saint Peter and Saint Paul Archipelago (SPSPA), two pelagic and two demersal deployments recorded two and one shark, respectively, including the locally extinct Galapagos shark Carcharhinus galapagensis. Stereo-BRUVS should be considered as adjuncts to other non-invasive methods to monitor shark populations. Univ Fed Espirito Santo, Dept Oceanog, Programa Posgrad Oceanog Ambiental, Vitoria, ES, Brazil Univ Fed Fluminense, Dept Biol Marinha, Niteroi, RJ, Brazil Univ Estadual Paulista, Inst Biociencias, Sao Paulo, SP, Brazil Curtin Univ, Sch Mol & Life Sci, Perth, WA, Australia Univ Fed Para UFPA, Nucleo Ecol Aquat & Pesca Amazonia, Aquat Ecol Grp Lab, Belem, Para, Brazil Univ Estadual Paulista, Inst Biociencias, Sao Paulo, SP, Brazil CNPq: 441241/2016-6 CNPq: 441243/2016-9 CAPES: 001 PROTRINDADE: 405426/2012-7

The application of genome-wide cytonuclear molecular data to identify management and adaptive units at various spatio-temporal levels is particularly important for overharvested large predatory organisms, often characterized by smaller, localized populations. Despite being “near threatened”, current understanding of habitat use and population structure of Carcharhinus galapagensis is limited to specific areas within its distribution. We evaluated population structure and connectivity across the Pacific Ocean using genome-wide single-nucleotide polymorphisms (~7200 SNPs) and mitochondrial control region sequences (945 bp) for 229 individuals. Neutral SNPs defined at least two genetically discrete geographic groups: an East Tropical Pacific (Mexico, east and west Galapagos Islands), and another central-west Pacific (Lord Howe Island, Middleton Reef, Norfolk Island, Elizabeth Reef, Kermadec, Hawaii and Southern Africa). More fine-grade population structure was suggested using outlier SNPs: west Pacific, Hawaii, Mexico, and Galapagos. Consistently, mtDNA pairwise Φ(ST) defined three regional stocks: east, central and west Pacific. Compared to neutral SNPs (F(ST) = 0.023–0.035), mtDNA exhibited more divergence (Φ(ST) = 0.258–0.539) and high overall genetic diversity (h = 0.794 ± 0.014; π = 0.004 ± 0.000), consistent with the longstanding eastern Pacific barrier between the east and central–west Pacific. Hawaiian and Southern African populations group within the west Pacific cluster. Effective population sizes were moderate/high for east/west populations (738 and 3421, respectively). Insights into the biology, connectivity, genetic diversity, and population demographics informs for improved conservation of this species, by delineating three to four conservation units across their Pacific distribution. Implementing such conservation management may be challenging, but is necessary to achieve long-term population resilience at basin and regional scales.

We use a genomic sampling of both nuclear and mitochondrial DNA markers to examine a pattern of genetic admixture between Carcharhinus galapagensis (Galapagos sharks) and Carcharhinus obscurus (dusky sharks), two well-known and closely related sharks that have been recognized as valid species for more than 100years. We describe widespread mitochondrial-nuclear discordance in which these species are readily distinguishable based on 2152 nuclear single nucleotide polymorphisms from 910 independent autosomal regions, but show pervasive mitochondrial admixture. The species are superficially morphologically cryptic as adults but show marked differences in internal anatomy, as well as niche separation. There was no indication of ongoing hybridization between the species. We conclude that the observed mitochondrial-nuclear discordance is likely due to historical mitochondrial introgression following a range expansion.

The Galapagos shark (Carcharhinus galapagensis) is one of over thirty shark species inhabiting the Galapagos Marine Reserve (GMR), where it is a priority species for conservation. Identifying stock structure and effective population size for species-specific management and effective conservation of this top predator is important. We examined stock structure, connectivity and effective population size of Galapagos sharks among GMR locations using genome-wide neutral Single Nucleotide Polymorphism (8103 SNP) and mtDNA markers. Potential historical gene flow and/or sex-biased dispersal were also examined using the mitochondrial control region (997 bp). Cluster analyses of neutral SNPs revealed two differentiated stocks in the GMR—a western (Isabela Island) and eastern (San Cristobal and Santa Cruz Islands) stock. Effective population size (Ne) estimates of approximately 200 suggest these populations are susceptible to ongoing natural and anthropogenic stressors and are of concern for long term resilience of populations. Mitochondrial DNA failed to identify distinct stocks, with AMOVA analyses indicating most genetic variation occurs within, rather than among locations. This pattern of genome-wide nuclear (but not mtDNA) discrimination among neighbouring islands either points to possible sex-biased dispersal by females or identifies limitations of the single organelle mtDNA marker at such small spatial scales. Regional differences across the archipelago or in behaviour may be implicated in the observed population structure. Further research focusing on a larger, Pacific wide analysis of population connectivity and effective population size at a broader spatial scale is required, to estimate the extent of discreteness and potential local adaptation. Potential adaptive units (AUs) in Galapagos sharks should ultimately be identified to leverage adaptive management and fisheries forensics applications.

The Galapagos shark, Carcharhinus galapagensis (Snodgrass & Heller, 1905) is a large circumtropical species mostly found around oceanic islands. In Brazil, commercial fishing in the Saint Peter and Saint Paul Archipelago (SPSPA), located in the equatorial Mid-Atlantic Ridge, resulted in a drastic reduction in the number of carcharhinid sharks, and the once very abundant Galapagos shark was then considered locally extinct. In opposition to this premature conclusion, however, this study provides records of the species, as well as its abundance trends and patterns of distribution in the SPSPA from the period of supposed disappearance to nowadays. Results are based on fishermen interviews, video footage and catch data obtained during the shark monitoring program conducted in the archipelago from 2010 to 2019. Galapagos shark was the second most caught shark in SPSPA, showing that this species is not only still present but is also becoming again one of the most common shark species in the archipelago. No significant difference was observed in sex ratio and in the size frequency distribution of males and females. An apparent recovery of carcharhinid sharks was attested by all fishermen interviewed. This recovery was mainly noticed after the complete ban on elasmobranch fishing, in 2012, emphasizing the vulnerability of these species to fishing pressure. Further research on the biology, ecology, behavior, and distribution patterns of Galapagos sharks will greatly aid future decision-making regarding the management and conservation of the species, not only in SPSPA, but in all insular ecosystems.

With just a handful of documented cases of hybridisation in cartilaginous fishes, shark hybridisation remains poorly investigated. Small amounts of admixture have been detected between Galapagos (Carcharhinus galapagensis) and dusky (Carcharhinus obscurus) sharks previously, generating a hypothesis of ongoing hybridisation. We sampled a large number of individuals from areas where the species co-occur (contact zones) across the Pacific Ocean and used both mitochondrial and nuclear-encoded SNPs to examine genetic admixture and introgression between the two species. Using empirical analytical approaches and simulations, we first developed a set of 1873 highly informative SNPs for these two species to evaluate the degree of admixture between them. Overall, results indicate a high discriminatory power of nuclear SNPs (FST = 0.47, p 0.05), which failed to differentiate these species. We identified four hybrid individuals (∼1%) and detected bi-directional introgression between C. galapagensis and C. obscurus in the Gulf of California along the east Pacific coast of the Americas. We emphasize the importance of including a combination of mtDNA and diagnostic nuclear markers to properly assess species identification, detect patterns of hybridisation, and better inform management and conservation of these sharks, especially given the morphological similarities within the genus Carcharhinus.

The dusky shark Carcharhinus obscurus risks excessive fisheries exploitation worldwide due to its low productivity. Genetic monitoring is an effective way of resolving species stock structure, genetic diversity, and forensically identifying processed animals. Here we present the first C. obscurus species-specific microsatellite loci. Twenty-one di- to tetra-nucleotide loci with between 2 and 20 alleles per locus were developed. Observed heterozygosity ranged from 0.28 to 0.91 with only one locus slightly deviating from Hardy–Weinberg equilibrium. No significant evidence for null alleles or linkage disequilibrium was detected. These loci were cross-amplified in three related species. Seventeen, twelve, and eighteen loci exhibited polymorphism in sandbar shark Carcharhinus plumbeus, spinner shark Carcharhinus brevipinna, galapagos shark Carcharhinus galapagensis, respectively. Investigations into C. obscurus will benefit from these loci which possess attributes suitable for population-scale and individual-scale analyses. Additionally locus cross-amplification will facilitate research for these species with few existing microsatellites and similarly vulnerable life-histories.

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.

Conservation of vulnerable shark species that are also heavily exploited, such as the sandbar shark Carcharhinus plumbeus is a pressing issue, and molecular genetics is an increasingly important population monitoring and species identification tool. Here we present 19 C. plumbeus microsatellite loci with a broad range of alleles per locus (3–22), and observed heterozygosities (0.17–0.95). Null alleles were not apparent and if present, were at frequencies

Detecting and determining the validity of local extinctions is an important conservation measure in order to uncover management failures. There are quantitative and qualitative methods that estimate extinction probability based on past sighting records. However, because current baselines about species’ abundances and distributions in the sea were mostly established after humans had started affecting marine populations, researchers must often rely on historical data to elucidate past environmental conditions. We review early historical records from the Archipelago of Saint Paul’s Rocks, together with data from recent expeditions, with the aim of testing the hypothesis that reef sharks (Carcharhinus spp.) have become extinct there. Our analyses are based on non-parametric probabilistic tests for extinction and on a qualitative framework to examine and judge as objectively as possible the likelihood of local extinction. Until the mid-20th century, visitors to St. Paul’s Rocks invariably commented on the remarkable number of sharks around the Archipelago. These observations contrast with those of expeditions carried out during the last decade, which report no carcharhinid reef sharks while scuba diving in the archipelago, despite many more hours of underwater fieldwork than previous expeditions. All quantitative and qualitative methods conclude that the reef shark Carcharhinus galapagensis is locally extinct at St. Paul’s Rocks after a sharp decrease in abundance that took place following the commencement of fishing. However, the persistence of occasional individuals of the once locally common Carcharhinus falciformis in the vicinity of the Archipelago, as a result of constant immigration of this oceanic species from outside the area, suggest that the population might recover if the present fishing pressure was removed.

Sharks possess anterior electrosensory pores (ampullae of Lorenzini), which allow them to detect very weak electromagnetic fields. Powerful magnetic fields may overwhelm this sense, and repel sharks, even in the presence of an attractant. Using underwater video, we tested seven rare earth magnet configurations, two ferrite magnet configurations and two rare earth electropositive metals as means to reduce the rate at which Galapagos sharks ( Carcharhinus galapagensis ) depredated baited lines. Configurations of three 50 mm diameter rare earth magnet discs showed the most potential, with a vertical configuration of magnets alongside the bait reducing depredation by 50%, and a stacked configuration of the same magnets above the bait also producing significantly more aborted investigations of the bait prior to depredation. No other magnetic or electropositive metal configuration produced significant reductions in depredation rates, time taken to strike, or number of prior investigations. Our study showed that the overriding factor determining Galapagos shark behaviours towards baits was conspecific density. The number of sharks present increased as trials progressed, with a corresponding decrease in their time to depredate baits. This effect was particularly apparent when three or more animals were present. These higher shark densities diminished the effectiveness of our experiments as individuals engaged in non-selective “mob” rushes towards the closest bait. Although our results showed that social interactions between sharks outweighed individual responses to depredation-mitigation devices, magnetic deterrents have high potential for reducing shark bycatch for species that occur in lower densities, or which interact less vigorously with conspecifics than Galapagos sharks.

We equipped individual tiger (Galeocerdo cuvier Peron and Lesueur, 1822) and Galapagos (Carcharhinus galapagensis Snodgrass and Heller, 1905) sharks with both acoustic and satellite transmitters to quantify their long-term movements in the Papahanaumokuakea Marine National Monument (Northwestern Hawaiian Islands). Tiger sharks exhibited two broad patterns of behavior. Some individuals were detected at French Frigate Shoals (FFS) year round, whereas others visited FFS atoll in summer to forage on fledging albatross, then swam thousands of kilometers along the Hawaiian chain, or out into open ocean to the North Pacific transition zone chlorophyll front, before returning to FFS in subsequent years. These patterns suggest tiger sharks may use cognitive maps to navigate between distant foraging areas. Different patterns of spatial behavior may arise because cognitive maps are built up through individual exploration, and each tiger shark learns a unique combination of foraging sites. Galapagos shark detections were all associated with FFS, suggesting these sharks may be more resident around oceanic islands. Both Galapagos and tiger sharks primarily used the mixed layer (

Prototype acoustic 'business card' (BC) tags were deployed on 4 free-swimming Gala- pagos sharks Carcharhinus galapagensis associated with a shark ecotourism operation near Haleiwa, Hawaii, USA. These transmitter/receiver tags employed mobile peer-to-peer (MP2P) technology that allowed the tagged sharks to exchange codes among each other and to detect other sharks implanted with standard one-way coded acoustic transmitters. Two tags were recovered (after 20 and 132 d); both tags had multiple detections of all other BC tags, and a comparison of detections made by these tags to those made by a fixed array of standard VR2 receivers indicated that the BC tags accurately captured the 'presence-absence' patterns of the other tagged sharks. Importantly, the BC tags detected sharks that were beyond the range of the fixed receiver array. The results indicate that the BC tag/MP2P approach can elucidate important inter-and intra-specific interactions among individ- uals in areas remote from traditional fixed receiver arrays.

SUMMARYShark cage diving is both popular and controversial, with proponents citing educational value and non-extractive use of natural resources and opponents raising concerns about public safety and ecological impacts. Logbook data collected 2004–2008 from two Oahu (Hawaii) shark cage diving operations were analysed to determine whether such voluntary records provide useful insights into shark ecology or ecotourism impacts. Operators correctly identified common shark species and documented gross seasonal cycles and long-term trends in abundance of Galapagos (Carcharhinus galapagensis), sandbar (Carcharhinus plumbeus) and tiger sharks (Galeorcerdo cuvier). Annual cycles in shark abundance may indicate seasonal migrations, whereas long-term trends suggest gradual exclusion of smaller sandbar sharks from cage diving sites. Numerically dominant (> 98%) Galapagos and sandbar sharks are rarely implicated in attacks on humans. Negligible impact on public safety is supported by other factors such as: (1) remoteness of the sites, (2) conditioning stimuli that are specific to the tour operations and different from inshore recreational stimuli and (3) no increase in shark attacks on the north coast of Oahu since cage diving started. Tracking studies are required to validate logbook data and to determine whether sharks associated with offshore cage diving travel into inshore areas used for in-water recreation.

The Sultanate of Oman has a long established traditional shark fishery, which has experienced increased demand in recent years due to the shark fin trade. Despite the long history of the fishery in Oman and neighbouring countries, few studies have been undertaken to determine the biological characteristics of the fishery or its ability to withstand this increased exploitation. The present study was undertaken as a first step to remedying this situation. A total of 47 species was confirmed from Oman's coastal waters, of which 44 occurred in commercial landings. However, landings were dominated by eight species—Rhizoprionodon acutus, Iago omanensis, Carcharhinus sorrah, Loxodon macrorhinus, C. macloti, C. limbatus, Sphyrna lewini and C. falciformis. The species composition of landings varied along the coast and also with season. Brillouin Index values indicated that species diversity was greatest in the Muscat area, followed closely by Musandam. The Al-Wusta region displayed the lowest diversity. The occurrence of two uncommon shark species, Chaenogaleus macrostoma and Echinorhinus brucus, was of interest, as was the recording of a juvenile Carcharhinus galapagensis, extending its northern range in the Indian Ocean considerably.

Competition and predation are both important in structuring the distribution of marine organisms; however, little is known about how competition and predation influence the distribution of elasmobranch fishes. We used data collected from shark control programs conducted between 1967 and 1980, throughout the Hawaiian island chain, to examine the distribution and dietary over- lap of the 4 most abundant carcharhinid sharks. Tiger sharks Galeorcerdo cuvier and Galapagos sharks Carcharhinus galapagensis were caught at all islands, but were more abundant in the north- western Hawaiian Islands (NWHI) than in the main Hawaiian Islands (MHI). Gray reef sharks Carcharhinus amblyrhynchos and sandbar sharks Carcharhinus plumbeus showed an inverse rela- tionship in distribution, with sandbar sharks abundant in the MHI, but virtually absent throughout the NWHI, and gray reef sharks only sporadically found throughout the MHI, but abundant in the NWHI. Dietary overlap was high between gray reef and sandbar sharks, and between sandbar and Galapagos sharks. Tiger sharks had low dietary overlap with all other species, except for large Gala- pagos sharks. The data analyzed in our study support the hypothesis that interspecific competition influences the distribution of carcharhinid sharks throughout the Hawaiian Archipelago.

□ Carcharhinus galapagensis (Snodgrass & Heller, 1905) – Galapagos shark; Tubarão-dos-Galápos ②, ③ According to Ebert & Stehmann (2013), the species Carcharhinus obscurus is very closely related to this species (C. galapagensis) and they are difficult to distinguish from each other. Recent molecular studies suggest that these two species may in fact be a single one, with one of the two forms being found far from landmasses (C. galapagensis) and the other one (C. obscurus) occurring in association with continental shelves and upper slopes (G. Naylor, pers comm. in Ebert & Stehmann 2013). Studies are currently ongoing to determine the relationship between these two species., Published as part of Carneiro, Miguel, Martins, Rogélia, Landi, Monica & Costa, Filipe O., 2014, Updated checklist of marine fishes (Chordata: Craniata) from Portugal and the proposed extension of the Portuguese continental shelf, pp. 1-73 in European Journal of Taxonomy 73 on page 11, DOI: 10.5852/ejt.2014.73, http://zenodo.org/record/3866515, {"references":["Ebert D. A. & Stehmann M. F. W. 2013. Sharks, batoids, and chimaeras of the North Atlantic. FAO Species Catalogue for Fishery Purposes no. 7, Food and Agriculture Organization, Rome."]}

Catch records from the Hawai'i Cooperative Shark Research and Control Program, which operated in Hawai'i from 1967–1969, were examined and data on the Galapagos shark,Carcharhinus galapagensis were analyzed. A total of 304 Galapagos sharks was caught, predominantly with longlines. More female sharks were caught than males, and the catch was skewed geographically. On the island of O'ahu the highest catch rates occurred along the north and south coasts. High catch rates also occurred near points of land, where longshore currents converge. Average depth of capture was greater for juveniles (45.1 m) and mature males (60.2 m), than for subadults (38.8 m) and mature female sharks (34.2 m). Males appear to reach maturity between 205 and 239 cm total length, and females between 215 and 245 cm. Litter size ranged from 4 to 16 pups, with an average of 8.7. In Hawaiian waters Galapagos sharks are born at just over 80 cm total length. Mating and parturition apparently occur early in the year, and gestation is estimated to be about 12 months. Stomach contents consisted mainly of teleosts and benthic prey, and ontogenetic changes in diet occurred as sharks increased in size. Sharks consumed a smaller proportion of teleosts and more elasmobranchs with increasing size. Dietary diversity also increased with increasing size of shark.

Although primarily a coral reef species the grey reef shark Carcharhinus amblyrhynchos has been recorded from a number of subtropical oceanic islands and reefs in the Southwest Pacific Ocean. Examination of all nominal C. amblyrhynchos voucher material collected from Lord Howe Island, Elizabeth and Middleton Reefs and Norfolk Island resulted in the re-identification of these specimens as Galapagos sharks, C. galapagensis . As C. amblyrhynchos superficially resembles C. galapagensis visual records of C. amblyrhynchos from Elizabeth and Middleton Reefs and the Kermadec Islands cannot be substantiated without voucher material. Carcharhinus amblyrhynchos therefore appears to be confined to waters north of about 25 o S in the Southwest Pacific. Precaudal vertebral counts should be used to confirm the identification of nominal C. amblyrhynchos specimens that have an interdorsal ridge.

Empirical data on the abundance and habitat preferences of coral reef top predators are needed to evaluate their ecological impacts and guide management decisions. We used longline surveys to quantify the shark assemblage at French Frigate Shoals (FFS) atoll from May to August 2009. Fishing effort consisted of 189 longline sets totaling 6,862 hook hours of soak time. A total of 221 sharks from 7 species were captured, among which Galapagos (Carcharhinus galapagensis, 36.2%), gray reef (Carcharhinus amblyrhynchos, 25.8%) and tiger (Galeocerdo cuvier, 20.4%) sharks were numerically dominant. A lack of blacktip reef sharks (Carcharhinus melanopterus) distinguished the FFS shark assemblage from those at many other atolls in the Indo-Pacific. Compared to prior underwater visual survey estimates, longline methods more accurately represented species abundance and composition for the majority of shark species. Sharks were significantly less abundant in the shallow lagoon than adjacent habitats. Recaptures of Galapagos sharks provided the first empirical estimate of population size for any Galapagos shark population. The overall recapture rate was 5.4%. Multiple closed population models were evaluated, with Chao M(h) ranking best in model performance and yielding a population estimate of 668 sharks with 95% confidence intervals ranging from 289-1720. Low shark abundance in the shallow lagoon habitats suggests removal of a small number of sharks from the immediate vicinity of lagoonal islets may reduce short-term predation on endangered monk seal (Monachus schauinslandi) pups, but considerable fishing effort would be required to catch even a small number of sharks. Additional data on long-term movements and habitat use of sharks at FFS are required to better assess the likely ecological impacts of shark culling.

Coral reef habitats in the Papahānaumokuākea Marine National Monument (PMNM) are characterized by abundant top-level predators such as sharks and jacks. The predator assemblage is dominated both numerically and in biomass by giant trevally (Caranx ignobilis) and Galapagos sharks (Carcharhinus galapagensis). A lower diversity of predatory teleosts, particularly groupers and snappers, distinguishes the PMNM from other remote, unfished atolls in the Pacific. Most coral reef top predators are site attached to a “home” atoll, but move extensively within these atolls. Abundances of the most common sharks and jacks are highest in atoll fore reef habitats. Top predators within the PMNM forage on a diverse range of prey and exert top-down control over shallow-water reef fish assemblages. Ecological models suggest ecosystem processes may be most impacted by top predators through indirect effects of predation. Knowledge gaps are identified to guide future studies of top predators in the PMNM.

Immunoglobulin molecules from diverse vertebrate species were examined, using an enzyme-linked immunosorbent assay (ELISA), for the expression of determinants detectable by rabbit antisera to VHa allotypes. The data indicate that immunoglobulins of elasmobranchs, teleosts, amphibians and birds express determinants cross-reactive with those specified by the a1, a2 and a3 alleles in the domestic rabbit. We localize VHa cross-reactive specificity to the denatured heavy chain of a primitive vertebrate, the Galapagos shark (Carcharhinus galapagensis). Furthermore, the N-terminal amino acid sequence of the shark heavy chain shows significant homology with rabbit heavy chains of known VHa type at positions where allotype-correlated differences have been implicated. VHa-related determinants are shared by immunoglobulins of a wide range of vertebrates from sharks to man and thus seem to be epitopes which have been conserved during vertebrate evolution. The determinants detected on immunoglobulins of lower vertebrates by rabbit anti-VHa allotype sera most probably are VH-subgroup rather than allotypic markers. Their distribution demonstrates a strong phylogenetic conservation of VH-regions.

Isolated light chains of IgM-type immunoglobulins of carcharhine sharks were analyzed by serological and biochemical means. When analyzed by isoelectric focusing analysis, light chains of the tiger shark (Galecerdo cuvieri), the galapagos shark (Carcharhinus galapagensis) and the sandbar shark (Carcharhinus plumbeus) showed a broad, but patterned, spectrum of bands ranging from pI 5.0 to 7.7 in which discrete families were observed. Serologically, light chains of the galapagos shark cross-reacted with rabbit antibodies against mouse immunoglobulin and a synthetic peptide corresponding to the J segment of T cell receptor beta chain. The latter cross-reaction is shared among light chains and T cell receptors. Although there was considerable heterogeneity in isoelectric focusing analysis, the light chains were homogeneous on the basis of apparent mass (23 kDa) and those of tiger shark and galapagos shark had relatively homogeneous dominant N-terminal sequences representing the first framework. The N-terminal sequences of these two shark light chains, were strongly homologous to one another and showed 75% identity to certain V kappa sequences of man and dog. Homology was also shown to V lambda sequences, but the degree of identity was approximately 50%. Following cleavage of the tiger shark light chain with o-iodosobenzoic acid which cleaves at tryptophanyl residues, a constant region peptide was isolated by gel filtration. It was possible to identify the homolog of this peptide within the constant regions of mammalian kappa and lambda chain, but the relationship to C kappa chain was stronger. The degree of identity among the corresponding C region peptides of mammalian, avian and elasmobranch species was much less than that observed for the framework 1 sequence of the light chain variable region. These data support the concept that variable and J region sequence have been conserved in the evolution of placoderm-derived vertebrates, but that constant regions show much greater phylogenetic variation.

To study primitive vertebrate recognition molecules we have purified the immunoglobulins of three species of carcharhine sharks. The tiger (Galeocerdo cuvieri), the sandbar (Carcharhinus plumbeus) and the galapagos sharks (Carcharhinus galapagensis) possess 18S high molecular weight and 7S low molecular weight immunoglobulin forms. Both within and between species these forms closely resemble each other in polypeptide chain composition, heavy chain mass, carbohydrate content, amino acid composition, antigenic character and amino terminal sequence. These carcharhine species are separated by at least 30 million years of evolutionary time and it is remarkable that so little diversification of immunoglobulin structure has occurred during their evolution. By several criteria carcharhine immunoglobulins most closely resemble mammalian IgM. Studies of serological cross-reactions indicate that some immunoglobulin determinants have been conserved over a broad phylogenetic range of vertebrate classes; most notably JH and VHa-related markers are shared between forms as diverse as sharks and mammals.

The immunoglobulins of three carcharhine sharks were isolated from serum by means of salt precipitation and gel chromatography. The Galapagos shark (Carcharhinus galapagensis), the sandbar shark (Carcharhinus plumbeus) and the tiger shark (Galeocerdo cuvieri) each contained high molecular weight (18S) and low molecular weight (7S) IgM-like molecules as the major serum immunoglobulins. Both within and between species 18S and 7S immunoglobulins closely resemble each other in antigenic character, polypeptide chain composition, chain mass, amino acid composition, carbohydrate content and amino-terminal sequence. These results suggest that the immunoglobulins of carcharhine sharks have undergone little structural divergence during their evolution.

Sharks have declined worldwide and remote sanctuaries are becoming crucial for shark conservation. The southwest Indian Ocean is a hotspot of both terrestrial and marine biodiversity mostly impacted by anthropogenic damage. Sharks were observed during surveys performed from April to June 2013 in the virtually pristine coral reefs around Europa Island, a remote Marine Protected Area located in the southern Mozambique Channel. Observation events comprised 67 1-hour scientific dives between 5 – 35m depth and 7 snorkeling inspections, as well as 4 dinghy-based observations in the shallow lagoon. In a period of 24 days, 475 sharks were tallied. Carcharhinus galapagensis was most encountered and contributed 20% of the abundance during diving, followed by C. albimarginatus (10%). Both species were more abundant between 11-14h, and on the exposed sides of the island. Numbers of Sphyrna lewini were highest with 370 individuals windward and leeward, mostly schooling. S. lewini aggregations in the area are hypothesized to be attracted to the seamount archipelago offering favorable conditions for deep incursions and of which Europa Island forms part. C. amblyrhynchos, Galeocerdo cuvier and S. mokarran were uncommon, while there was an additional observation of Rhincodon typus. The lagoon of Europa was a nursery ground for C. melanopterus where it was the only species present. A total of 8 species was recorded, contributing to the shark diversity of 15 species reported from Europa since 1952 in the scientific and gray literature. Overall, with the occurrence of several species of apex predators in addition to that of R. typus, large schools of S. lewini, fair numbers of reef sharks and a nursery of C. melanopterus, Europa’s sharks constitute a significant reservoir of biodiversity, which contributes to preserve the functioning of the ecosystem. Our observations highlight the relevance of Europa Island for shark conservation and the need for shark-targeted management in the EEZ of both Europa and Bassas da India.

Attachment of Dermophthirius carcharhini is described using light, scanning electron, and transmission electron microscopy. Adult worms place a cup-shaped opisthohaptor over the proximal dorsal surface of a placoid scale and are firmly attached by means of a cement composed of an acellular, tyrosine-rich lipoprotein. Adhesion is further enhanced by a scale-like topography of the cement and by longitudinal furrows on the ventral opisthohaptoral surface that are complementary with the surface structures and pattern of the host's placoid scale. Perhaps a reduced pressure within the opisthohaptoral cup, sealed by a parenchymatous rim, also contributes to attachment. The opisthohaptor depresses and erodes host epidermis and ruptures goblet cells in the area of attachment, presumably making the scale more susceptible to detachment by the worm. Dermophthirius is a genus of microbothriid monogenean parasites of sharks. Dermophthirius nigrelli Cheung & Ruggieri, 1983 and D. carcharhini MacCullum, 1926 are serious pathogens of captive sharks of several species in aquaria (see Cheung et al., 1982; Overstreet, 1978). Heavy infections result in loss of placoid scales at sites of attachment, in formation of skin ulcers which become secondarily infected with bacterial pathogens such as Vibrio (see Cheung et al., 1982), and eventual host death if untreated. That species of Dermophthirius can detach placoid scales from host skin is remarkable because each scale is securely rooted into the dermis by a basal plate. There are several studies on the morphology of species of Dermophthirius (Cheung & Ruggieri, 1983; MacCullum, 1926; Price, 1938), but none provide either anatomical details of the opisthohaptor or the means by which it is attached to the host. How this monogenean detaches host scales is unknown. Large numbers of D. carcharhini MacCullum, 1926 on Galapagos sharks, Carcharhinus galapagensis (Snodgrass & Heller, 1905) which were maintained at the Bermuda Aquarium, Natural History Museum and Zoo, are the subject of the present study. We investigated the microanatomy and morphology of the ventral surface of the opisthohaptor of D. carcharhini and the histochemistry of the opisthohaptoral secretion. The manner by which this monogenean parasite attaches to C. galapagensis and the possible functions of the opisthohaptoral secretion are discussed. 1 We thank Drs. D. K. Cone and D. H. Williamson of Saint Mary's University and Dr. C. M. Morrison of Fisheries and Oceans, Halifax Laboratory, Nova Scotia, Canada, for providing research facilities, helpful advice and generous hospitality. We acknowledge the help of Dr. J. R. Lichtenfels, Curator, National Parasite Collection, U.S.D.A., Beltsville, Maryland for arranging the loan to us of the paratype material. This work was supported by National Research Council of Canada Grant No. 25503. TRANS. AM. MICROSC. Soc., 105(2): 158-169. 1986. ? Copyright, 1986, by the American Microscopical Society, Inc. This content downloaded from 207.46.13.145 on Wed, 27 Apr 2016 05:38:56 UTC All use subject to http://about.jstor.org/terms VOL. 105, NO. 2, APRIL 1986 MATERIALS AND METHODS Four Galapagos sharks, lightly infected with Dermophthirius carcharhini, were caught by hook and line during 1981 and 1982 in coastal Bermudian waters and transported alive to a 127,000-liter tank, reserved for sharks, at the Bermuda Aquarium, Natural History Museum and Zoo. Within three months of capture, the fish became infected heavily with this monogenean. Therefore, hosts were removed from the display tank, killed with an intracerebral injection of absolute alcohol, and autopsied. Detached worms and excised pieces of infected shark skin were fixed in 10% formol-saline. Skin tissues were decalcified in either 25% EDTA or 8% formic acid (see Roberts, 1978, p. 238). All tissues studied by light microscopic (LM) techniques were dehydrated in an ethanol series, cleared briefly in xylene, embedded in Paraplast-Plus, and sectioned at 6-7 tum. Sections were stained using techniques described by either Bancroft (1975) or Humason (1972) as follows: Mayer's hematoxylin and eosin; Brown & Brenn Gram stain for microorganisms; aqueous periodic acid-Schiff (PAS) for detection of muco-polysaccharides; Gomori's Millon reaction for tyrosine; Sakaguchi's reaction for arginine; ninhydrin-Schiff reaction for alpha amino acids; Sudan IV for bound lipids; and acid hematin for phospholipids. Sections also were stained with malachite green for ortho-dihydroxyphenols (Smyth, 1951). Material examined by scanning electron microscopy (SEM) was dehydrated in an acetone series, critical-point dried by carbon dioxide substitution, coated with gold in an Edwards IBT 200 sputtering unit and viewed in a JEOL JXA35 microscope operated at 25 kV. For transmission electron microscopy (TEM), specimens were post-fixed overnight in a 0.1 M phosphate buffer, pH 7.3, containing 4% formaldehyde and 1% glutaraldehyde, then in 1.5% Os04 in 0.1 M phosphate buffer for 1.5 h. This material was dehydrated in acetone, embedded in TAAB resin; and sectioned, either with a Reichart UM2 ultra-microtome or a LKB Ultratome. Thick sections (0.5 ,um) were stained with 1% toluidine blue in a sodium borate solution. Thin sections (70-120 nm) were post-stained with 25% uranyl acetate in methanol (Stempack & Ward, 1964) and chelated lead citrate (Reynolds, 1963); the sections were examined and photographed in a Hitachi HS9 microscope. Our specimens were identified as D. carcharhini after examining wholemounted specimens and comparing them to the paratypes of D. carcharhini MacCallum, 1926 (USNM No. 35687) and D. maccallumi Watson & Thorson, 1967 (USNM No. 71466), and after consulting the recent description of D. nigrelli given by Cheung & Ruggieri (1983).