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Observações a bordo da pescaria do cerco: padrão de actividade, composição das capturas, rendimentos de pesca e interacções com cetáceos em 2010.
Get PDFPopulation trends of Cory’s Shearwaters Calonectris diomedea borealis breeding at Berlengas Islands, Portugal
No full textAs colónias das Cagarras Calonectris diomedea são muito difíceis de recensear com precisão e, consequentemente, são escassos os dados fiáveis acerca das tendências populacionais. No arquipélago das Berlengas, costa ocidental\ud
portuguesa, a maior parte dos ninhos é acessível e fácil de inspeccionar, possibilitando a monitorização de tendências\ud
populacionais. Em Junho de 2005, foi realizado um censo que permitiu estimar a população reprodutora em 850 casais, representando um aumento notável relativamente à estimativa\ud
anterior mais recente, de ca. 200 casais, no ano de 1987. Os\ud
resultados sugerem que, nos últimos 25 anos, a população nidificante na Berlenga tem crescido a uma taxa anual média\ud
de 10,1%. A tendência populacional é discutida em função\ud
das ameaças e de acções de conservação anteriores
Using historical accounts to assess the occurrence and distribution of small cetaceans in a poorly known area
No full textHistorical science may play an important role in helping understanding and shaping the future of the world’s oceans and to\ud
comprehend present day effects and conditions. Regarding cetaceans, historical accounts may be extremely useful to add new\ud
data to their occurrence and distribution in poorly studied regions. In Portugal, historical sources indicate that toninhas\ud
(possibly common dolphins Delphinus delphis) were observed since the 13th Century and were captured in large numbers\ud
during the late 19th and 20th Centuries. Historical occurrences given by naturalists and scientific surveys conducted by\ud
biologists indicate their regular presence with particular preference for certain areas. Also, recent observations of opportunity\ud
resulted in the same kind of accounts. Between 1976 and 1978, a study on captured cetaceans along the Portuguese shore\ud
found at fish markets was conducted and resulted in a total count of 45 cetaceans. Most captures were of small cetaceans\ud
(87% common dolphins), even though four baleen whales were registered. These cetacean captures were part of a local nonindustrial\ud
fishery, as they were not the main target, but rather opportunistic catches or even by-catches of other fisheries.\ud
Delphinids were not protected by law at the time and were caught with hand harpoons or accidentally drowned in fish\ud
nets, sometimes sold at major fish markets such as Sesimbra, Peniche and Po´voa de Varzim. In geographical areas where\ud
recent cetacean sightings are rare and information is sparse, such as Portugal, it becomes important to take advantage of\ud
alternative sources of data. Our contribution towards the compilation of relevant historical and ‘forgotten’ science such as\ud
old natural observations, whaling data and observations of opportunity stresses the relevance of using historical data to\ud
access past occurrence and distribution of cetaceans
Cetaceans’ occurrence off the west central Portugal coast: a compilation of\ud data from whaling, observations of opportunity and boat-based surveys
Get PDFThroughout the years some researchers have dedicated their\ud
efforts to the study of cetaceans’ occurrence off Mainland\ud
Portugal. However, it is still missing a systemic scientific\ud
methodology for studying the presence of coastal dolphins and\ud
whales. This work intends to be a first approach on the occurrence\ud
of cetaceans off the west central coast of Portugal. Our\ud
objective was to contribute towards the compilation of relevant\ud
“forgotten science” such as whaling data and observations of\ud
opportunity, together with two years of boat-based surveys.\ud
We found 1313 occurrences of great whales captured off\ud
Setúbal and Sesimbra (1925-1927 and 1944-1951) and a total\ud
of 45 cetaceans in non-directed captures between 1976 and\ud
1978. We accounted 45 dolphins and whales in sea-sightings\ud
as a result of observations of opportunity, from 2002 to 2008.\ud
In 2007 and 2008 a total of 63 boat-based visual surveys were\ud
conducted from three different geographic locations, Nazaré,\ud
Peniche and Sesimbra, and as a result 45 independent sightings\ud
of cetaceans were recorded. The most frequent small dolphin\ud
off the Portuguese mainland coast is the common dolphin\ud
(Delphinus delphis) as shown by the three distinct approaches\ud
used in this study. Regarding whales the most common species\ud
is the fin whale (Balaenoptera physalus) as shown by whaling\ud
records. Overall, the small delphinid community along the\ud
central coast of Portugal is similar to the one that can be found\ud
along the Iberia shore. [JMATE. 2009;2(1):10-13
Using positional data from vessel monitoring systems to validate the logbook-reported area fished and the stock allocation of commercial fisheries landings.
No full textCatches of target species and bycatches of an artisanal fishery: The case study of a trammel net fishery in the Portuguese coast
No full textn this work we studied an artisanal fishery targeting mainly soles (Solea senegalensis and Solea solea) and cuttlefish (Sepia officinalis) with trammel nets. Catches of target species, bycatches and discards were studied from October 2004 until August 2005 in the west coast of Portugal. A total of 37 sampling surveys onboard commercial fishing vessels were conducted. The number and weight of individuals of all species caught were registered, as well as the amount discarded and retained by fishermen. A total of 112 species were identified: Scomber japonicus, Chelidonichthys obscura and Callioynimus lyra were the most discarded fishes, corresponding to 28% in weight and 36% in number of discards. Discards represented 22%, in weight, of the total catches, while the amount retained by fishermen for consumption or direct selling was 12%, also in weight. The overall estimate of the annual discards value due to this fishery was ca. 170 tonnes, comprising near 45 fishing vessels. Inconsistencies between the catches recorded onboard and the official landings were detected for the main target species. Some bycatches of species under recovery plans were also found
Estimating fish abundance from acoustic surveys: calculating variance due to acoustic backscatter and length distribution error.
No full textMoult strategies of Cory’s Shearwaters Calonectris diomedea\ud borealis: the influence of colony location, sex and individual\ud breeding status
No full textThe replacement of old feathers is essential for birds, but it is also an energy-demanding task. As moult usually does not coincide with other stressful events in its annual cycle, such as reproduction and migration, the bird can optimise its use of time and energy allocated to different activities. There are very few studies comparing the moult strategies of populations with similar breeding calendars but occurring in areas of different habitat quality. Cory’s Shearwaters Calonectris diomedea have a partial moult–breeding overlap, an unusual phenomenon among pelagic seabirds. We have compared the moult schedules in Cory’s Shearwater colonies located in distinct environments (pelagic vs. coastal) and show that moult–breeding overlap is less extensive on Selvagem Grande, situated in deep oceanic waters, than on Berlenga, situated on the continental shelf. Colony attendance of failed breeders, most of which were moulting, was lower at Selvagem Grande than at Berlenga, which suggests that the feeding areas of birds from the former site are more distant from the colony. Failed breeders started to moult earlier than individuals still raising a chick, and breeding status had a stronger influence on determining the onset of wing-feather moult than colony location. Despite published evidence that internal circannual rhythms and external cues, such as variation in daylength, are important factors regulating moult schedules, it is clear that birds retain a considerable flexibility that allows them to respond to external factors in order to strategically manage time and energy in a way that is thought to maximise their fitness
