Browsing by Author "Prieto, Rui"
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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.
- Diet of mid-Atlantic Sowerby’s beaked whales Mesoplodon bidensPublication . Pereira, José N.; Neves, Verónica C.; Clarke, D. C.; Prieto, Rui; Silva, Mónica A.; Cascão, Irma; Oliveira, Cláudia I.; Cruz, Maria J.; Barreiros, João P.; Medeiros, J. V.The first mid-Atlantic diet of Mesoplodon beaked whales is presented, from ten Sowerby's Mesoplodon bidens stranded in the Azores region between 2002 and 2009. This doubles the worldwide number of stomachs sampled, and reveals new feeding habits for this species. The mean number of prey items per stomach was 85±89 (range: 12–238), with fish accounting for 99.3% and cephalopods contributing less than 1% of total prey. Fish otoliths from 15 families and cephalopod lower mandibles from three families were identified, representing 22 taxa. The diet consisted mainly of small mid-water fish, the most numerous being Diaphus sp., Lampanyctus sp. and Melamphaidae species. Myctophids were present in all stranded individuals, followed by Diretmidae, Melamphaidae and Opisthoproctus soleatus, while the remaining fish species were scarce or single occurrences. Consistency of diet in four different years reveals a divergence from all previous records in continental areas, where mainly neritic and shelf-break benthopelagic fish species have been reported. Mid-Atlantic Sowerby's beaked whales' showed dietary plasticity, feeding on the most abundant mid-water groups occurring between 0 and750 m. Trophic level from prey numerical frequency was estimated at 4.4±0.46.
- Revision of the occurrence of the long‐finned pilot whale Globicephala melas (Traill, 1809), in the AzoresPublication . Prieto, Rui; Fernandes, ManuelAlthough the expected distribution of the long-finned pilot whale in the Atlantic includes the Azores, overlapping with the known northern distribution of the short-finned pilot whale, the only documental references to the species in the archipelago are based on a single specimen captured in 1894. Moreover, a clear distinction between the two species of pilot-whales based on osteological grounds was only possible after 1971 and before that a great uncertainty existed about the phylogeny of the Genus. The long-finned pilot whale, thus, has never been confirmed by sightings at sea in the region and the extent of its occurrence to the South in the central North Atlantic has been, up to now, an open issue. Here we present evidence of the occurrence of the long-finned pilot whale in the Azores, based on two sightings made in different years.
- The role of Malcolm Clarke (1930–2013) in the Azores as a scientist and educationistPublication . Gomes-Pereira, José N.; Prieto, Rui; Neves, Verónica C.; Xavier, J.; Pham, Christopher K.; Gonçalves, João M.; Porteiro, Filipe M.; Santos, Ricardo S.; Martins, Helen R.Malcolm Roy Clarke (1930–2013) was a British teuthologist who made an important contribution to marine science in the Azores archipelago (Portugal). Malcolm started doing research in the Azores from 1980s onward, settling for residency in 2000 after retirement (in 1987). He kept publishing on Azorean cephalopods collaborating in 20% of the peer reviewed works focus- ing on two main areas: dietary studies; and the ecology of cephalopods on seamounts. Since his first visit in 1981, he was involved in the description of the dietary ecology of several cetaceans, seabirds, and large pelagic and deep-water fish. Using his own data, Malcolm revised the association of cephalopods with seamounts, updating and enlarging the different cephalopod groups according to species behaviour and ecology. Malcolm taught several students working in the Azores on cephalopods and beak identification, lecturing the Third International Workshop in Faial (2007). He empowered the recently established research community, by providing important contacts with foreign institutes and informal advice. He collaborated in the regional cetacean stranding network (RACA) and was an active member of the advisory board of the journal Arquipelago—Life and Marine Sciences. But the scientific role of Malcolm Clarke in the Azores went beyond his academic activities. In the last 10 years Malcolm and Dot Clarke dedicated themselves to building and running a museum on Pico Island, showing the biology of the sperm whale and its interaction with squid; a cultural and touristic legacy for future generations to enjoy.
- Trophic position of dolphins tracks recent changes in the pelagic ecosystem of the Macaronesian region (NE Atlantic)Publication . Bode, Antonio; Saavedra, Camilo; Álvarez-González, Miguel; Arregui, Marina; Arbelo, Manuel; Fernández, Antonio; Freitas, Luís; Silva, Mónica A.; Prieto, Rui; Azevedo, José M. N.; Giménez, Joan; Pierce, Graham J.; Santos, M. BegoñaDolphins play a key role in marine food webs as predators of mid-trophic-level consumers. Because of their mobility and relatively long life span, they can be used as indicators of large-scale changes in the ecosystem. In this study, we calculated the trophic position (TP) of 5 dolphin species from the Canary, Madeira and Azores Islands using bulk and compound-specific stable isotope ratios from muscle tissue to assess trophic adaptations to recent changes in the availability of feeding resources. Dolphin TP values were then compared with those of 7 other species of cetaceans from this region. Analysis of stable nitrogen isotopes in amino acids of the common dolphin indicated non-significant effects of changes in the basal resources of the food web and thus supported the use of bulk samples for TP estimations. Dolphins occupied an intermediate TP (mean: 3.91 to 4.20) between fin (3.25) and sperm whales (4.95). Species-specific TP were equivalent among islands. However, TP increased for the common dolphin and decreased for the bottlenose dolphin (the latter also becoming more oceanic) between 2000 and 2018 in the Canary Islands. These results suggest different impacts of recent changes in the oceanography and in the pelagic food web of the Macaronesian region on the trophic ecology of dolphin species.