Browsing by Author "Gordon, Jonathan"
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- An Atlantic cetacean survey using yachtsmen : a pilot study.Publication . Boisseau, Oliver; Prieto, Rui; Nicholson, Desmond; Gordon, JonathanIn the summer of 1998, yachtsmen sailing from the Caribbean to the Azores were encouraged to take part in an Atlantic cetacean survey. The principle aim of this project was to evaluate the potential of using regular seafarers as sources of data on cetacean distribution. Identification guides and sighting forms were distributed and participants were asked to record any cetacean sightings as well as to conduct routine set-effort watches. A secondary aim of the project was to investigate reports of illegal whaling in the Atlantic. Data collected from the yachtsmen reveal a concentration of sightings along the mid- Atlantic ridge, perhaps corresponding to an increase in productivity in this area. No further reports of whaling activity were made. Although this work only involves a small data set, it illustrates how useful yachtsmen can be in assisting research in otherwise inaccessible regions. Future involvement of yachtsmen in cetacean surveying should be encouraged, as long-term data sets gathered in this way can be invaluable in revealing offshore trends.
- A first assessment of operator compliance and dolphin behavioural responses during swim-with-dolphin programs for three species of Delphinids in the AzoresPublication . Cecchetti, Arianna; Stockin, K. A.; Gordon, Jonathan; Azevedo, José M. N.The popularity of swim-with wild dolphin programs around the world is fast growing, with the studies required to investigate their impact lagging behind. In the Azores, species targeted include the short-beaked common (Delphinus delphis), the bottlenose (Tursiops truncatus) and the Atlantic spotted dolphin (Stenella frontalis). To evaluate the effects of this activity on local dolphin populations, and thus provide support for management decisions, dolphin response data were collected onboard commercial boats off São Miguel Island between 2013 and 2015. All three species revealed high degree of neutral and avoidance behaviours, and very low approach rates. Tursiops showed higher frequency of neutral responses than Delphinus, while Stenella both avoided and approached more frequently than the other species. When boats intersected the path of dolphin groups, avoidance responses were more likely and the duration of swims was shorter. Swims were also shorter when animals were resting and travelling, and when groups were smaller. The operators generally complied with the legislation, except in respect to the number of swim attempts per dolphin group, which was higher than the legal maximum. Improvement of the current legislation and concurrent reinforcement of controls is essential to avoid detrimental long-term effects of this activity on dolphin populations in the Azores.
- Long-Range Longitudinal Movements of Sperm Whales (Physeter macrocephalus) in the North Atlantic Ocean Revealed by Photo-IdentificationPublication . Mullin, Keith D.; Steiner, Lisa; Dunn, Charlotte; Claridge, Diane; González García, Laura; Gordon, Jonathan; Lewis, TimThis article summarises a sperm whale photo-id match from the Gulf of Mexico to the Azores, another match from the Bahamas to the Azores and a match from the Gulf of Mexico to the Bahamas.
- Observations of fin whales (Balaenoptera physalus L., 1758) around the central north Atlantic islands of the Azores and MadeiraPublication . Gordon, Jonathan; Steiner, Lisa; Martins, Helen R.Referem-se os avistamentos de rorquais comuns a partir de um navio de investigação e vigias em terra ao largo das ilhas dos Açores e Madeira. Apesar de raros, os rorquais comuns estão presentes nas águas dos Açores entre Abril e Junho, e ausentes de Julho a Outubro. Não existe informação disponível acerca da sua ocorrência entre Outubro e Abril. Para a Madeira a informação sobre a abundância desta espécie é ainda mais escassa. Contudo apresentam-se algumas observações interessantes sobre uma concentração de rorquais em alimentação no mês de Maio.
- Sei whales (Balaenoptera borealis) encountered in the Azores : a new record for the regionPublication . Gordon, Jonathan; Steiner, Lisa; Gonçalves, João M.A baleia sardinheira ou rorqual de Rudolphi é pela primeira vez referido para as águas dos Açores. Cinco indivíduos foram observados no canal entre as ilhas de São Jorge e Pico a 16 de Julho de 1989, dirigindo-se para Norte, o que não está de acordo com os actuais conhecimentos sobre o comportamento migratório desta espécie. Não é provável que estas baleias visitem o arquipélago para se alimentarem.
- 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.