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Whistles of Bottlenose Dolphins (Tursiops truncatus) in the\ud Sado Estuary, Portugal: Characteristics, Production Rates,\ud and Long-Term Contour Stability
No full textThis study focuses on the whistle characteristics and\ud
production patterns of bottlenose dolphins (Tursiops\ud
truncatus) resident in the Sado Estuary, Portugal.\ud
Recordings and observations were conducted inside\ud
the estuary and in adjacent coastal waters using single\ud
hydrophones between 1987 and 2000. In the groups\ud
sampled, the mean number of whistles emitted per\ud
minute per animal was 0.28. The acoustic characteristics\ud
of a sample of 735 whistles were measured and\ud
compared with data from other Tursiops populations,\ud
showing that, in a pattern of overall similarity, the\ud
whistles recorded in the Sado are relatively long and\ud
the frequency range used is relatively wide. Mean\ud
peak frequency was 9.2 kHz. About 30% of the\ud
whistles were stereotyped, and remarkable stability\ud
was found in several contours over a 12-year period.\ud
No relation was found between dolphin group size\ud
and whistle rate, suggesting some restriction in production;\ud
and no relation was found between dolphin\ud
group size and the emission of different contours.\ud
Significant variation was found between episodes\ud
of simple travel and more aroused activities in terms\ud
of the production of whistles in general and also of\ud
different whistle contours
LARGE NUMBERS OF STAGING BALEARIC\ud SHEARWATERS PUFFINUS MAURETANICUS ALONG\ud THE LISBON COAST, PORTUGAL, DURING THE\ud POST-BREEDING PERIOD, JUNE 2004
No full textEm Junho de 2004 foi\ud
observado um número relactivamente elevado de Fura-buchos ao longo da costa de Lisboa, entre o\ud
Guincho e Cascais, indicando que esta zona é uma das principais áreas de alimentação desta espécie\ud
no período pós-nupcial. Nos dias 2, 3 e 4 de Junho foram observados respectivamente um mínimo de\ud
1294, 953, e 1177 Fura-buchos, ou seja, aproximadamente 14% da população desta ave marinha\ud
rara e globalmente ameaçada. Embora a maioria dos indivíduos se encontrasse a descansar em grupo\ud
(em média 59.7 %), foram também detectadas bandos de Fura-buchos em alimentação (o maior bando\ud
com cerca de 700 indivíduos, juntamente com 540 Alcatrazes Morus bassanus e com outras\ud
espécies). A maior proporção de Fura-buchos a descansar e o maior bando de aves (900 indivíduos) foi\ud
detectado a sul de Cascais, provavelmente porque a orientação Este-Oeste desta costa confere protecção\ud
contra os ventos dominantes de nordeste. As observações foram comparadas com dados do início dos\ud
anos noventa, numa altura em que esta espécie era mais abundante, e com dados recentes sobre a\ud
ocorrência desta espécie ao longo da costa portuguesa
Winter upper ocean circulation in the Western Iberian Basin—Fronts, Eddies and Poleward Flows: an overview.
Get PDFAn overview of the winter circulation and upper ocean structure offshore of Western Iberia is presented. The focus is on winter slope currents, fronts and mesoscale eddies, as well as on the connection of these local features to the largescale circulation of the region. Satellite sea surface temperature; sea surface elevation data from altimetry; cross-shore and meridional hydrological surveys and current meter observations, mainly obtained during winter periods, are used to illustrate features of the winter upper ocean structure and of the generation and evolution of the Iberia Poleward Current. A schematic/hypothetical model of winter upper ocean circulation on the scale of the Western Iberian Basin is given which attempts to systematize and resolve certain ambiguities in the existing circulation schemes and in the concepts and terminology used to describe observed features in the area
Trends in NE Atlantic landings (southern Portugal): identifying the relative importance of fisheries and environmental variables.
No full textChanges in fisheries discard rates and seabird communities
No full textIt is clear that discards from commercial fisheries are a key food resource for many seabird species around the world. But predicting the response of seabird communities to changes in discard rates is problematic and requires historical data to elucidate the confounding effects of other, more 'natural' ecological processes. In the North Sea, declining stocks, changes in technical measures, changes in population structure and the establishment of a recovery programme for cod (Gadus morhua) will alter the amount of fish discarded. This region also supports internationally important populations of seabirds11, some of which feed extensively, but facultatively, on discards, in particular on undersized haddock (Melanogrammus aeglefinus) and whiting (Merlangius merlangus). Here we use long-term data sets from the northern North Sea to show that there is a direct link between discard availability and discard use by a generalist predator and scavenger—the great skua (Stercorarius skua). Reduced rates of discarding, particularly when coupled with reduced availability of small shoaling pelagic fish such as sandeel (Ammodytes marinus), result in an increase in predation by great skuas on other birds. This switching of prey by a facultative scavenger presents a potentially serious threat to some seabird communities
The use of separator panels and square mesh windows for by-catch reduction in the crustacean trawl fishery off the Algarve (South Portugal)
No full textThe utility of oblique separator panels combined with square mesh windows for reducing by-catch (mainly boarfish (Capros aper), blue whiting (Micromesistius poutassou) and horse mackerel (Trachurus trachurus)) was examined in the Algarve crustacean trawl fishery.\ud
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Three different panel/window mesh size combinations and the window alone were tested. The results suggest that the amount of blue whiting excluded was independent of the use of the separator panel, as well as the mesh sizes of the panel and the square mesh window. Between 67 and 71% of the total catch of this species was excluded. The window mesh size however, significantly affected the escape of boarfish, with the average escape percentage released rising from 10 to 44% as the mesh size increased from 70 to 100 mm.\ud
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The highest exclusion rates were obtained with the use of a 120 mm separator panel together with a 100 mm square mesh window. Under these conditions, the exclusion of by-catch was maximised while maintaining the catch for the target species(rose shrimp Parapenaeus longirostris, and Norway lobster, Nephrops norvegicus). In hauls where the square mesh window was used alone, only the escape rate of blue whiting was significant (67%), while boarfish escaped in much lower proportions and shrimp above the minimum landing size were lost. Despite the efficiency of these panels as by-catch excluders, their complex design is a major drawback to commercial adoption
Morphometric variation among anchovy (Engraulis encrasicolus, L.) populations from the Bay of Biscay and Iberian waters.
Get PDFFor management purposes, the European Atlantic anchovy is separated in two distinct stocks, one distributed in the Bay of Biscay (ICES Sub-Area VIII) and the other occupying mainly the southern part of ICES Division IXa (Bay of Cadiz). However, spatio-temporal irregularities in the dynamics of the Sub-Area VIII stock as well as scant knowledge on the IXa anchovy biology lead ICES to recommend more studies on population dynamics and possible relationships between areas. The present work describes morphometric differences between the two stocks based on the analysis of 10 samples collected within the area from Bay of Biscay to the Bay of Cadiz during two consecutive years (2000 and 2001). Distances on a “Truss Network” were computed from 2D landmark coordinates obtained from digitized images of each individual and corrected from the effect of fish size. Principal Component Analysis was applied to the shape data, as well as a Multidimensional Scaling to the squared Mahalonobis distances (D2) between every pair of sample centroids to visualise clustering. The significance of the computed D2 distances was also statistically tested. Finally, Artificial Neural Networks were applied to assess the robustness of sample groups highlighted in the previous analyses. Results indicate a separation between samples from the Bay of Biscay and those from Division IXa, which is stable over time, as well as a north-south cline along the Portuguese and Bay of Cadiz area. This variability is mainly caused by differences on the shape of the medium-posterior region of the body
Contribução para o conhecimento de alguns aspectos biológicos e económicos da arte xávega. Dissertação Apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para Obtenção do Grau de Mestre em Ecologia, Gestão e Modelação dos Recursos Marinhos.
No full textClimate change and abundance of the Atlantic-Iberian sardine (Sardina pilchardus)
No full textClimatic warming is affecting oceanic circulation patterns in coastal upwelling areas, but the impact of this climatic change on pelagic fish populations remains unclear. From juvenile landings collected over 38 years, the thresholds of environmental factors were determined that limited the optimal environmental window (OEW) for sardine (Sardina pilchardus recruitment success in the northwestern Iberian peninsula. The environmental factors considered were: water column stability in February, offshore water transport in March–April (QxMA), upwelling intensity in the preceding year from May to August (QxMJJA), and the winter North Atlantic Oscillation (NAO) index. From 1875 to the mid-1920s, the mean number of years within the OEW was relatively constant. However, since the mid-1920s, there have been oscillations and alternating decades with high and low number of years within the OEW, which were related to oscillations in sardine landings. From 1906 to 2000, there were four record, low sardine catches in the 1920s, 1950s, 1970s and 1990s, related to a high number of successive years with prevailing conditions out of the OEW. From 1875 to the present, a high year-to-year variation of the NAO, QxMJJA and water stability in February was observed, although with mean values usually within the OEW. The collapse in the 1950s was related, partly, to successive years with low QxMJJA. Successive years with high NAO values may be related to the collapse of the sardine fishery in the 1990s. QxMA has been the most significant factor controlling SRS in this area, being the factor related to the low catches observed in the 1920s, 1950s and 1970s. Water stability was not responsible for any of the collapses observed, but since the 1920s, there has been a significant trend toward decreasing water column stability before the onset of the spring bloom
Solar activity governs abundance of Atlantic\ud Iberian sardine Sardina pilchardus
No full textAnnual sardine Sardina pilchardus landings from 1906 to 2002 off the northwest\ud
coast of the Iberian Peninsula vary according to solar activity. When the solar cycle is short, there\ud
is a trend towards increasing water transport onshore, which favours larval retention in areas\ud
close to the coast and, hence, sardine catches increase. However, when the solar cycle is longer,\ud
the trend is toward increasing water transport offshore, carrying eggs and larvae into areas where\ud
there is not enough food to survive and, therefore, decreasing sardine catches. These findings\ud
reveal the potential importance of solar activity on all biological process affected by coastal\ud
upwelling, including pelagic fisheries