Browsing by Author "Burgess, George H."
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- Microsatellite loci in the tiger shark and cross-species amplification using pyrosequencing technologyPublication . Mendes, Natalia J.; Cruz, Vanessa P.; Ashikaga, Fernando Y.; Camargo, Samia M.; Oliveira, Claudio; Piercy, Andrew N.; Burgess, George H.; Coelho, Rui; Santos, Miguel N.; Mendonca, Fernando F.; Foresti, FaustoThe tiger shark (Galeocerdo cuvier) has a global distribution in tropical and warm temperate seas, and it is caught in numerous fisheries worldwide, mainly as bycatch. It is currently assessed as near threatened by the International Union for Conservation of Nature (IUCN) Red List. In this study, we identified nine microsatellite loci through next generation sequencing (454 pyrosequencing) using 29 samples from the western Atlantic. The genetic diversity of these loci were assessed and revealed a total of 48 alleles ranging from 3 to 7 alleles per locus (average of 5.3 alleles). Cross-species amplification was successful at most loci for other species such as Carcharhinus longimanus, C. acronotus and Alopias superciliosus. Given the potential applicability of genetic markers for biological conservation, these data may contribute to the population assessment of this and other species of sharks worldwide.
- A new map of the tiger shark (Galeocerdo cuvier) genetic population structure in the western Atlantic Ocean: Hypothesis of an equatorial convergence centrePublication . Carmo, Camila B.; Ferrette, Bruno L.S.; Camargo, Sâmia M.; Roxo, Fábio F.; Coelho, Rui; Garla, Ricardo C.; Oliveira, Claudio; Piercy, Andrew N.; Bornatowski, Hugo; Foresti, Fausto; Burgess, George H.; Mendonça, Fernando F.The tiger shark (Galeocerdo cuvier) is a common widespread coastal–pelagic shark species whose population genetic structure has only recently been the object of genetic studies. In this study, the tiger's shark mitochondrial DNA control region was sequenced for a sample of 172 individuals from the western Atlantic and from Australia's east coast in the Pacific Ocean. The results show a moderate variation in genetic diversity (h = 0.615 ± 0.038, π = 0.00184 ± 0.00021) with a strong population structure between Atlantic areas (ΦST = 0.28141, P = 0.00001). The maternal lineage has high site fidelity, which paradoxically is coupled with connectivity across open ocean stretches to Fernando de Noronha Archipelago, which is identified as an important hotspot for this species. These results help with the understanding of what drives the displacement of this shark, at intra‐ and/or inter‐ocean basins levels, and can help inform the implementation of future conservation and management measures. We recommend that the conservation of genetic diversity should be maintained at a global level and its maintenance should be pursued diligently in all populations of tiger shark. As the Fernando de Noronha region in the western Atlantic appears to contain the largest global genetic diversity of the species, this area should be treated as a marine reserve or ecological refuge for the tiger shark.
- Status and the potential for extinction of the largetooth sawfish Pristis pristis in the Atlantic OceanPublication . Fernandez-Carvalho, Joana; Imhoff, Johanna L.; Faria, Vicente V.; Carlson, John K.; Burgess, George H.1. Sawfishes currently are among the most threatened elasmobranchs in the world. Only two species inhabit Atlantic waters: the largetooth sawfish (Pristis pristis) and the smalltooth sawfish (Pristis pectinata), both having suffered dramatic declines in their ranges. 2. The goal of this study was to evaluate the status of P. pristis in the Atlantic, and estimate local extinction risk based on historical and recent occurrence records. In order to accomplish these goals, a thorough search for historical and recent records of P. pristis in the Atlantic was conducted, by reviewing scientific and popular literature, museum specimens, and contacting regional scientists from the species’ historical range. 3. In total, 801 P. pristis records (1830–2009) document its occurrence in four major regions in the Atlantic: USA (n =41), Mexico and Central America (n =535), South America (n=162), and West Africa (n =48). Locality data were not available for 15 records. 4. Historical abundance centres were the Colorado-San Juan River system in Nicaragua and Costa Rica (and secondarily Lake Izabal of Guatemala), the Amazon estuary, and coastal Guinea-Bissau. 5. Currently, the species faces drastic depletion throughout its entire former range and centres of abundance. It appears to have been extirpated from several areas. The probability of extinction was highest in the USA, northern South America (Colombia to Guyane), and southern West Africa (Cameroon to Namibia). 6. Currently, the Amazon estuary appears to have the highest remaining abundance of P. pristis in the Atlantic, followed by the Colorado–San Juan River system in Nicaragua and Costa Rica and the Bissagos Archipelago in Guinea Bissau. Therefore the protection of these populations is crucial for the preservation and recovery of the species.
- Use of encounter data to model spatio-temporal distribution patterns of endangered smalltooth sawfish, Pristis pectinata, in the western AtlanticPublication . Waters, John D.; Coelho, Rui; Fernandez-Carvalho, Joana; Timmers, Amy A.; Wiley, Tonya; Seitz, Jason C.; Mcdavitt, Matthew T.; Burgess, George H.; Poulakis, Gregg R.1. Sawfishes are among themost threatened fish species globally,with only the smalltooth sawfish (Pristis pectinata) currently regularly observed in the westernAtlantic. TheNational Sawfish EncounterDatabase (NSED) documents reported encounters with sawfishes in the western Atlantic and contains 4945 reports of 8773 individual P. pectinata (1782–2011). 2. Statistical modelling (generalized linear models and generalized additive models) and kernel density analyses were used to (1) identify spatio-temporal patterns among encounter reports, including range reduction in the western Atlantic; (2) determine current distribution to identify areas and time periods where conservation and recovery efforts could be focused; and (3) identify and describe spatio-temporal distribution patterns of large juveniles and adults. 3. Pristis pectinata were found to be year-round residents of Florida but showed relatively consistent spatial and temporal trends by life stage throughout the year. Although the historical range in the western Atlantic included coastal waters from North Carolina to Brazil, the current geographic range of the species was limited to Florida from 2001 through 2011, with occasional reports in neighbouring states, the Bahamas, and Cuba. 4. Seasonally, encounters of all life stages peaked fromMarch through July and annual recruitment of juveniles was apparent during the study period. Spatial hotspots based on increased numbers of encounters of large juveniles (201–340 cm) and adults (>340 cm) were identified in southern Charlotte Harbor, the Ten Thousand Islands, Florida Bay, theAtlantic side of the FloridaKeys, and off St. Lucie in south-east Florida. The analyses presented herein provide evidence of range reduction in the western Atlantic, provide an important tool for resource managers to focus research, monitoring, and conservation efforts, and may provide a framework to model and predict habitat use of other species.