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Contribution of estuarine nursery areas to the structure and biocontamination of stocks of commercially important fish species along the Portuguese coast. Tese de Doutoramento em Biologia,Especialidade de Biologia Marinha e Aquacultura.
No full textFlight Morphology and Foraging Behavior of Male and Female Cory's Shearwaters
No full textIn some seabirds sexually dimorphic in size, males and females segregate at sea or diverge in other aspects of foraging behavior. We examined factors influencing foraging strategies of Cory's Shearwater and compared the sexes' flight morphology and activity patterns. Trip duration, incubation-shift length, total mass gain, and rate of mass gain at sea of birds from our two study colonies differed. The colonies are situated in regions of contrasting oceanographic conditions: Selvagem Grande, a remote subtropical oceanic island, and Berlengas, an island on the Portuguese continental shelf. Although the wing loading and wing span of males and females breeding at Selvagem Grande differed significantly, sex did not consistently influence activity patterns of Cory's Shearwaters foraging at sea during the incubation period. Moreover, both sexes breeding at Selvagem Grande foraged in areas with similar sea-surface temperatures. Our study suggests that sexual differences in size and shape may be poor predictors of differentiation in the ways male and female pelagic seabirds use the marine environment
Modelação do crescimento de Sardina pilchardus (Walbaum, 1792) em duas zonas (oceanograficamente distintas) da costa portuguesa. Tese de Mestrado em Biologia Marinha.
No full textOccurrence and relative abundance of common\ud dolphins in three sites of the Portuguese shore
Get PDFThroughout the years some researchers have dedicated their efforts to the study of cetaceans’\ud
occurrence off Portugal mainland. However, it is still missing a systemic scientific methodology\ud
for studying the presence of coastal small cetaceans. This work is a recent approach to the\ud
occurrence and relative abundance estimative of cetaceans and especially common dolphins off\ud
the west central coast of Portugal. Boat-based visual surveys were conducted in three different\ud
geographic locations, resulting in the sighting of several species. In Nazaré we have only\ud
observed Delphinus delphis while in Peniche and Sesimbra a great diversity of species was\ud
recorded, including Tursiops truncatus, Stenella coeruleoalba, Phocoena phocoena and\ud
Balaenoptera acutorostrata. Most frequently sighted was common dolphin (62%). Occurrence\ud
of large groups of this species seems to take place along main ocean topographic features, like\ud
the Portuguese submarine canyons and we consider that great depths near shore are suitable\ud
habitats for more pelagic species of dolphins such as common dolphins. Total index of common\ud
dolphin abundance was of 2.198 individuals per surveyed hour. A much smaller APUE was\ud
found for Peniche than for the other two regions, where common dolphins show a similar\ud
relative abundance. Future studies using linear transects and continuous long-term approaches\ud
will give further insight to small cetaceans’ occurrence along Portugal mainland and its relation\ud
with different oceanographic features, particularly depths and distances to shore. On-going\ud
efforts in coming years added to this first approach will be required to obtain knowledge for the\ud
conservation of cetaceans
Historical accounts about the occurrence and capture\ud of common dolphins in Portugal mainland
Get PDFHistorical oral sources indicate that common dolphins (Delphinus delphis), locally known as\ud
“toninhas”, were observed and captured in large numbers at Portugal mainland during late 19th\ud
and 20th centuries. Historical occurrences given by naturalists and scientific surveys conducted\ud
by biologists indicate their regular presence with particular preference for certain areas. Also,\ud
recent observations of opportunity resulted in the same kind of accounts. Between 1976 and\ud
1978, a research for captured cetaceans in fish markets along the Portuguese shore was\ud
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\ud
captures were part of a local non industrial fishery, as they were not the main target, rather\ud
opportunistic catches or even by-catches of other fisheries. Delphinids were not protected by\ud
law at the time and were caught with hand harpoons or accidentally drowned in fish nets,\ud
sometimes sold at major fish markets such as Sesimbra, Peniche and Póvoa de Varzim. In\ud
geographic areas where recent cetacean sightings are rare and information is sparse, such as\ud
Portugal, it becomes important to recur to alternative sources of data. Our contribution towards\ud
the compilation of relevant “forgotten science”, such as historical naturalistic observations,\ud
whaling data and observations of opportunity, will add new data to the occurrence of common\ud
dolphins in a poorly studied region
Mysterious attendance cycles in Cory's shearwater, Calonectris diomedea: an exploration of patterns and hypotheses
No full textSeveral species of seabirds show cyclic patterns of attendance at their nesting colonies. We examined the patterns of variation in the numbers of Cory's shearwater at three colonies (two oceanic and one located on the continental shelf), including the world's largest, at Selvagem Grande, Madeira, Portugal and considered several hypotheses concerning their causal mechanisms. At Selvagem Grande, cycles were exceptionally marked and regular, with a periodicity ranging from 7.8 to 11 days, and involved both breeders and nonbreeders. In contrast, variation in numbers was aperiodic at a nearby and much smaller colony (Selvagem Pequena), and also at the colony located off the Portuguese coast (Berlenga Island). We found no relationships between number of birds ashore and environmental variables such as wind direction and speed or lunar cycle. Cycles did not seem to be driven by oscillations in food availability or accessibility, given that they did not correlate with daily chick growth rates (which were acyclic) or diet. Despite their regularity, cycles were slightly out of phase in different sectors of Selvagem Grande, which suggests that social interactions at the colony could act as an entrainment agent for an endogenous rhythm, and so cycles are probably more likely to occur in large and dense colonies. Observations are consistent with the hypothesis that cycles facilitate social interactions by maximizing the probability of encounters at the colony. However, the exact mechanisms through which these remarkable cycles are controlled are still completely unknown, and clearly further research is needed. (C) 2009 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved
Brood-guarding behaviour in Cory’s Shearwaters Calonectris diomedea
No full textBrood-guarding (or the continual attendance at\ud
the nest by one parent) has been relatively little studied in\ud
altricial birds. Parental investment in brood-guarding is\ud
often highly variable within a species, and the study of\ud
such variability may contribute to the understanding of the\ud
functions and regulation of this behaviour and of the tradeoffs\ud
involved in the choice between attending the nest and\ud
leaving to forage. In some colonial birds, it has been found\ud
that early nesting pairs attend their chick for longer than\ud
later nesting counterparts, giving rise to the synchronisation\ud
hypothesis that suggests that early pairs prolong broodguarding\ud
in order to reduce the probability of nest\ud
predation by a dilution effect. In this paper, for the first\ud
time we test the prediction that burrow-nesting colonial\ud
birds subject to little predation pressure should not display\ud
a seasonal decline in brood-guarding duration. The growth\ud
assistance hypothesis suggests that brood-guarding may\ud
allow the provision of frequent small meals and the efficient\ud
use of energy by chicks with poor homeothermic\ud
capabilities, resulting in improved early chick-growth.\ud
Finally, the chick-protection hypothesis predicts that chicks\ud
in more exposed nests should be brood-guarded for longer.\ud
Data collected at two Cory’s Shearwater Calonectris\ud
diomedea colonies situated in contrasting environments\ud
supported the synchronisation hypothesis, as there was no\ud
seasonal trend in brood-guarding duration. Contrary to the\ud
growth assistance hypothesis, chicks brood-guarded for\ud
longer periods did not have an improved growth (in one\ud
colony there was even a negative effect of brood-guarding\ud
on early chick development). Finally, we found no difference\ud
in brood-guarding between nests with contrasting\ud
levels of exposure to potential predators and weather.\ud
Despite confirming the prediction of the synchronisation\ud
hypothesis, more research is needed to identify the main\ud
factors underlying the variability of brood-guarding\ud
observed in this and other studies
Trace element concentrations in Proteocephalus macrocephalus (Cestoda) and Anguillicola crassus (Nematoda) in comparison to their fish host, Anguilla anguilla in Ria de Aveiro, Portugal
No full textThe use of some fish parasites as bioindicators of heavy metal pollution has been demonstrated as particularly adequate due to their capacity of bioconcentration. This study evaluated the effect of Proteocephalus macrocephalus on the accumulation of trace elements in the edible fish, Anguilla anguilla, in a contaminated area in Portugal (Ria de Aveiro). Also, the model P. macrocephalus/A. anguilla was assessed as a bioindicator system in the presence of the highly prevalent nematode Anguillicola crassus. Samples (kidney, liver, muscle, A. crassus and P. macrocephalus) of 20 eels harbouring A. crassus and another 20 harbouring both A. crassus and P. macrocephalus were selected for element analysis by ICP-MS. The highest concentrations of Cr, Ni and Zn were detected in P. macrocephalus. However, there was a higher liver and muscle Cr concentration in eels not infected by P. macrocephalus. Also, the nematode A. crassus presented higher Cr concentrations in those eels harbouring P. macrocephalus. Results suggest that P. macrocephalus individuals accumulate Cr and Ni while levels of Cr in eel livers and Ni levels in eel kidney are reduced. The system P. macrocephalus/A. anguilla yielded bioaccumulation factors for Cr, Ni, Pb and Zn, whereas bioaccumulation of Cu, Cr and Pb in A. crassus varied according to eel co-infection with P. macrocephalus, thus emphasising the possible role of cestode infection in metal metabolization/storage processes in host tissues. Results suggest that heavy metal pollution in Ria de Aveiro has been decreasing although it is still higher than in other contaminated areas in Europe. Nevertheless, eel consumption in Ria de Aveiro represents no risk for humans although they may represent a real contamination risk for wildlife. The system P. macrocephalus/A. anguilla is proposed as another promising bioindicator system to evaluate environmental Cr, Ni, Pb and Zn exposure in estuarine areas where both species co-occur
