Browsing by Author "Bolten, Alan B."
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- Hawksbill (Eretmochelys imbricata) and Green Turtle (Chelonia mydas) Nesting and Beach Selection at Príncipe Island, West AfricaPublication . Ferreira, Rogério L.; Martins, Helen R.; Bolten, Alan B.Hawksbills (Eretmochelys imbricata) and green turtles (Chelonia mydas) are the predominant nesting sea turtle species on the beaches of Príncipe Island in the Gulf of Guinea. The extent of nesting has been largely unknown, but such information is essential for management and conservation. Our study is the first island-wide nesting assessment. Results from the survey, conducted from 1 December 2009 to 18 January 2010 (during peak nesting season), show that the potential suitable nesting area (10 km) is scattered around the island’s 50 beaches. Sea turtles nested on 32 of the beaches (hawksbills, 20; green turtles, 28) and used 7.5 km of the suitable nesting habitat (hawksbills, 5.8 km; green turtles, 7.0 km). We estimated that 101 (95% CI = 86–118) clutches were deposited by 17-29 hawksbills and 1088 (95% CI = 999–1245) clutches were deposited by 166-429 green turtles on Príncipe from November 2009 to February 2010 (nesting season). Long-term green turtle nest count data collected from 2007/08 to 2015/16 suggest a positive trend. Analyses of clutch densities in relation to beach characteristics suggested that both species preferred areas where human presence is lower, which coincided with the most sheltered areas. These findings should be used to inform coastal planning and minimize impacts on nesting beaches, as Príncipe is currently targeted for tourism development. Overall, results highlight that Príncipe beaches are very important for the conservation of West African hawksbill and green turtle populations.
- Impact of swordfish fisheries on sea turtles in the Azores.Publication . Ferreira, Rogério L.; Martins, Helen R.; Silva, Alexandre A.; Bolten, Alan B.The surface longline fishery around the Azores targets swordfish (Xiphias gladius). Bycatch from this fishery includes loggerhead sea turtles (Caretta caretta) and occasionally leatherback sea turtles (Dermochelys coriacea) that are either hooked or entangled in the lines. Hooks are generally set at depths of 15-50 m and baited with squid, mackerel, or sometimes with shark meat. The size classes of loggerhead sea turtles caught ranged from 41.3 to 65.4 cm curved carapace length and constitutes the largest size class of loggerheads occurring in the Azores. The impact on this size class affects the survival of the southeastern United States (SEUS) population of loggerheads because the loggerheads from the Azores are primarily from SEUS rookeries. For one commercial longline boat, we observed that the mean capture of turtles per 1000 hooks by month ranged between a minimum of 0.04 in May and a maximum of 0.79 in July with a weighted mean catch of 0.27. October and November also registered high catch rates. Of 60 turtles recorded, 54 were hooked in the mouth, 3 in the esophagus, 1 in the eye, 1 in the flipper, and one was undetermined. The turtles that were caught were physically strong, except one that was weak and another dead. Total capture of loggerhead sea turtles is estimated to be 4190 for the entire fleet fishing in the Exclusive Economic Zone of the Azores during the swordfish season (May to December) of 1998. We strongly recommend that observer programs be continued because capture rates may vary among years and among fishing boats.
- Sea turtles : University of Florida – University of the Azores connection 1984 – present. A reviewPublication . Martins, Helen R.; Bjorndal, Karen A.; Ferreira, Rogério L.; Parra, Hugo Alexandre Esteves; Pham, Christopher K.; Rodríguez, Y.; Santos, M. R.; Vandeperre, Frederic; Bolten, Alan B.The loggerhead (Caretta caretta) is the most common sea turtle in the Azores. Since they do not nest in the area, a tagging program was started in the 1980’s to try to discover their origin. The result based on size distribution, suggested that they mainly are coming from beaches in SE United States. A collaboration between University of Florida and the University of the Azores began in 1984 in order to proceed with further research.
- Size distribution of pelagic-stage loggerhead sea turtles (Caretta caretta) in the waters around the Azores and MadeiraPublication . Bolten, Alan B.; Martins, Helen R.; Bjorndal, Karen A.; Gordon, JonathanAs tripulações de navios atuneiros marcaram e mediram 731 tartarugas-caretas (Caretta caretta) durante as safras de 1990, 1991 e 1992. Os comprimentos curvos das carapaças das tartarugas variaram de 10 a 82 cm. A distribuição interanual de tamanhos não foi significativamente diferente. O tamanho médio de 45 tartarugas marcadas na Madeira foi significativamente maior do que o das tartarugas dos Açores. Os resultados deste trabalho suportam a hipótese de as pequenas tartarugas pelágicas desta espécie derivarem da população reprodutora existente no Sudeste dos E.U.A. O espectro de tamanhos de tartarugas-caretas que vivem nas águas envolventes dos Açores foi aumentado.