Percorrer por autor "Oliveira, Nuno"
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- Analysis of organic residues in the context of the middle bronze age in the northwestern Iberian Peninsula: the case of the Cova da Moura funerary monument (Viana do Castelo, nw Portugal)Publication . Oliveira, Nuno; Oliveira, César; Bettencourt, Ana M. S.; Costa, CláudiaThis paper presents and discusses the results of chromatographic analyses conducted on the contents of a ceramic pot recovered from Cova da Moura, a coastal funerary context located on the western slope of the Serra de Santa Luzia in Carreço, within the municipality and district of Viana do Castelo, Northwest Portugal. The site was excavated in 1931 by Abel Viana, who uncovered a monument beneath a tumulus that concealed a cluster of granite outcrops with numerous cavities (tafoni). Depositional activities in these cavities revealed several artifacts, including fragments of various ceramic containers, metal and glass objects, knapped and polished stone tools, animal remains, a diverse assemblage of plant-derived charcoal, and at least one anthropomorphic stele. The materials exhibit a wide chronological range, with the earliest occupation dating from the Late Middle Bronze Age (circa 15th-14th century BCE) and the most recent from the Late Iron Age. Among these finds was a fragmented ceramic pot containing organic residues at its internal base, dated from the regional Bronze Age. Chromatographic analysis of these residues identified traces of animal meat, possibly from monogastric species, and plant oils, both of which appear to have been exposed to high temperatures. This study represents the first application of organic chemical analysis to a ceramic vessel from a plausible Middle Bronze Age funerary context in Northwestern Portugal. The findings suggest the presence of commensal rituals or the deposition of prepared meat offerings as part of funerary practices.
- Diagnóstico social do concelho de São Brás de AlportelPublication . Sousa, Vanessa Duarte de; Biel, Filipa Capelo; Oliveira, NunoO presente documento introduz os principais elementos de diagnóstico social para o concelho de São Brás de Alportel.
- Experimental anthropogenic food restrictions drive short-term foraging and immuno-haematological changes in sympatric breeding gullsPublication . Pereira, Jorge M.; Ramos, Jaime A.; Domingues, Adriana; Almeida, Ana; Marçalo, Ana; Cascão, Catarina; Silva, Carlos; Rey, Daniel; Ceia, Filipe R.; Carvalho, Flávia; Santos, Ivo dos; Gonçalves, Jorge Manuel Santos; Cerveira, Lara R.; Frade, Magda; Laranjeiro, Maria I.; Oliveira, Nuno; Nascimento, Tânia; Paiva, Vítor H.; Norte, Ana C.Fishery discards and landfills provide major subsidies to scavenging seabirds, shaping their foraging behaviour and population dynamics. However, few studies have compared the behaviour and health of individuals with and without access to such predictable anthropogenic food subsidies (PAFS). We assessed the foraging behaviour and immuno-haematological condition of incubating Audouin's (Ichthyaetus audouinii) and yellow-legged gulls (Larus michahellis) in response to an experimental restriction of access to fisheries and landfill food subsidies in southern Portugal. In response to food restrictions, gulls from both species increased their foraging distance from the colony, likely relying on alternative prey, and/or foraging in association with other fishing fleets in Portuguese or nearby Spanish waters. This was supported by a decrease in the number of yellow-legged gulls observed at both the landfill and the Culatra fishing harbour during the food restriction trials. These changes were followed by alterations in the leucocyte profiles of yellow-legged gulls, characterised by a predominance of heterophils over lymphocytes, i.e. an indicator of physiological stress. Our findings show that limited access to PAFS can influence gulls' foraging behaviour and physiological condition, highlighting their reliance/dependence on these predictable subsidies. These short-term responses suggest that PAFS may function as ecological traps for opportunistic seabirds during the breeding period. Understanding such responses is critical to predict long-term ecological consequences and to develop waste and fisheries management policies aligned with EU strategies.
- Mitigation measures to reduce seabird's interactions with bottom-set nets in southern IberiaPublication . Frade, Magda; Carvalho, Flávia; Samel, Vighnesh Nilesh; Oliveira, Nuno; Andrade, Joana; Gonçalves, Jorge Manuel Santos; Marçalo, AnaBycatch poses a significant threat to seabird populations globally. On the southern coast of mainland Portugal, mitigation measures were tested to reduce seabird interactions with fishing vessels. Between 2021 and 2023, this study evaluated the effectiveness of a visual deterrent (a ’scarybird’ device), an acoustic deterrent (megaphone broadcasts), alongside modification in fisher’s behaviour discard management— avoiding discards during fishing operations to minimize seabird interactions. Observers monitored 166 fishing events, comparing control and experimental treatments. Discard management was the most effective deterrent, significantly reducing seabird abundance, particularly gulls (Larus spp.) and northern gannets (Morus bassanus). Model predictions indicated a 37 % and a 47 % reduction in the abundance of gulls and northern gannets, respectively, around commercial fishing vessels when discard management was used. This practice effectively kept a substantial proportion of birds away from the vessel during operations, thereby reducing their vulnerability to bycatch. The megaphone showed limited efficacy, with higher seabird abundance in treatment groups compared to controls. The scarybird device was largely ineffective in deterring gulls unless combined with discard management but showed potential in reducing interactions with northern gannets. Importantly, all mitigation measures did not negatively impact Landings Per Unit Effort (LPUE), which facilitated their acceptance among fishers. Our findings suggest that simple modifications in the fisher’s behaviour, such as retaining fish discards and viscera onboard, could serve as a promising bycatch mitigation measure, potentially eliminating the need for additional less effective mitigation devices that fishers may be reluctant to adopt.
- Modelling the impact of deep-water crustacean trawl fishery in the marine ecosystem off Portuguese Southwestern and South Coasts: I) the trophic web and trophic flowsPublication . Angeles Torres, Maria; Fonseca, Paulo; Erzini, Karim; Borges, Teresa C.; Campos, Aida; Castro, Margarida; Santos, Jorge Manuel Bastos; Costa, Maria Esmeralda; Marçalo, Ana; Oliveira, Nuno; Vingada, JoseThe concentration of the population in coastal regions, in addition to the direct human use, is leading to an accelerated process of change and deterioration of the marine ecosystems. Human activities such as fishing together with environmental drivers (e.g. climate change) are triggering major threats to marine biodiversity, and impact directly the services they provide. In the South and Southwest coasts of Portugal, the deep-water crustacean trawl fishery is not exemption. This fishery is recognized to have large effects on a number of species while generating high rates of unwanted catches. However, taking into account an ecosystem-based perspective, the fishing impacts along the food web accounting for biological interactions between and among species caught remains poorly understood. These impacts are particularly troubling and are a cause of concern given the cascading effects that might arise. Facing the main policies and legislative instruments for the restoration and conservation of the marine environment, times are calling for implementing ecosystem-based approaches to fisheries management. To this end, we use a food web modelling (Ecopath with Ecosim) approach to assess the fishing impacts of this particular fishery on the marine ecosystem of southern and southwestern Portugal. In particular, we describe the food web structure and functioning, identify the main keystone species and/or groups, quantify the major trophic and energy flows, and ultimately assess the impact of fishing on the target species but also on the ecosystem by means of ecological and ecosystem-based indicators. Finally, we examine limitations and weaknesses of the model for potential improvements and future research directions.
- Plano de desenvolvimento social de São Brás de Alportel 2006/2010 e Plano de Ação 2006/2007Publication . Sousa, Vanessa Duarte de; Biel, Filipa Capelo; Oliveira, NunoO presente documento apresenta os principais elementos de estratégia e de ação para o concelho de São Brás de Alportel. O Plano de Desenvolvimento Social é estruturado para o período de 2006/2010 e o plano de ação para o ano 2006/2007.
- Portuguese purse seine fishery spatial and resource overlap with top predatorsPublication . Wise, Laura; Galego, Catarina; Katara, Isidora; Marçalo, Ana; Meirinho, Ana; Monteiro, Silvia S.; Oliveira, Nuno; Santos, Jorge; Rodrigues, Pedro; Araujo, Helder; Vingada, Jose; Silva, AlexandraThe Portuguese purse seine fishery, with average annual catches of 70 000 tonnes, operates mainly in coastal areas and targets small pelagic fish (SPF). Potential competition for resources may occur between the fishery and some species of marine mammals and seabirds, as suggested by observed incidental catches. For those species directly affected by the fishery, the spatial distribution of marine taxa and the fishing fleet are key pieces of information for spatial planning and management. We analysed the spatial and resource overlap between the fishery's distribution and effort, and the distribution and abundance of 6 species of top predators -seabirds (n = 4) and marine mammals (n = 2) between 2010 and 2014. Estimates of annual consumption by top predators and the fishery catch within the distributional range of one of their main prey species (sardine Sardina pilchardus) were also determined. Spatial overlap between all considered species and the fishery was low (<0.221), and only 2 species (common dolphins Delphinus delphis and Cory's shearwaters Calonectris borealis) showed high resource overlap with the fishery (>0.7). Overall, values of consumption of SPF by the top predators were of the same order of magnitude as mean annual purse seine landings for the studied area. Our results can be used for marine spatial planning, including designation of Marine Protected Areas and the development of an ecosystem-based model for the effective management of the Portuguese purse seine fishery that takes into account the consumption of natural predators.
- Roman-indigenous interaction in the Salas River valley (Northwest Iberia): the Roman camp of Alto da Raia and its archaeological landscape.Publication . Fonte, João; Tereso, João Pedro; Vaz, Filipe Costa; Rodrigues, Ana Luísa; Dias, Maria Isabel; Marques, Rosa; Russo, Dulce; Monteiro, Patrícia; Rodrigues, Mariana Costa; Pereiro, Tiago; Carvalho, José; Raimundo, Francisco; Cardoso, Vanessa; Jorge, Carlos; García Sánchez, Jesús; Gago, Manuel; Gonçalves, José Alberto; Meunier, Emmanuelle; Oliveira, Nuno; Oltean, IoanaThis paper discusses the archaeological research and historical contextualisation of the Alto da Raia enclosure located on the border between northern Portugal and Galicia, identified as a possible Roman camp, following an interdisciplinary and multi-proxy approach. This included archaeological excavation, remote sensing and geophysical survey, as well as sample collection for archaeobotanical and geochemical studies by means of chemical and mineralogical analyses and absolute dating using radiocarbon and luminescence protocols. The results seem to indicate that this site was a Roman camp probably built and occupied between the 1st century BC and the 1st century AD, when major changes occurred in Northwest Iberia driven by the expansion of the Roman State. The camp overlaps with previous prehistoric occupations possibly dating back to the Bronze Age and Iron Age.
- Seasonal variation in seabird abundance and bycatch at artisanal bottom-set net fisheries in the southern Iberian Atlantic coastPublication . Pereira, Jorge M.; Ramos, Jaime A.; Almeida, Ana; Marçalo, Ana; Carvalho, Flávia; Fagundes, Isabel; Gonçalves, Jorge Manuel Santos; Frade, Magda; Oliveira, Nuno; Nascimento, Tânia; Paiva, Vitor H.Bycatch is a major cause of seabird mortality, yet most studies focus on industrial fisheries, with limited knowledge on artisanal fisheries. This study investigates the seasonal abundance of seabirds off the southern-eastern coast of mainland Portugal, their attendance at artisanal bottom-set net fisheries, and observed bycatch, using onboard observations and fishermen interviews. From March 2020 to November 2022, 24,643 seabirds were observed attending fishing vessels in 183 daily fishing trips (98.4 % of 186 trips), spanning 20 species across 7 families, with 25 seabirds recorded as bycatch. Lesser black-backed and Yellow-legged gulls (Larus fuscus and Larus michahellis) were the most abundant species, followed by Audouin's gulls (Ichthyaetus audouinii), Great shearwaters (Ardenna gravis), and Northern gannets (Morus bassanus). During summer, the abundance of Yellow-legged and Audouin's gulls (local breeders) and Lesser black-backed gulls (non-breeding species) increased with fishery catch per unit effort. Great shearwaters were more affected by gear type, exhibiting higher attendance and bycatch in trammel nets during autumn. 65 % of Great shearwater bycatch occurred during a single fishing event, probably from fishermen cleaning nets and discarding fish and viscera during net setting. Fishermen interviews identified Northern gannets and Great cormorants (Phalacrocorax carbo) as the most frequently bycaught species, particularly in winter when onboard observations were limited. These findings underscore the impact of artisanal fisheries on seabird populations and highlight the importance of combining onboard data with fishermen interviews to improve bycatch estimates and inform conservation efforts. Our study also suggests that fishermen behaviour during fishery operations significantly influence seabird bycatch.
- Sistema de informação do concelho de São Brás de AlportelPublication . Sousa, Vanessa Duarte de; Biel, Filipa Capelo; Oliveira, NunoO documento apresenta os resultados da monitorização do território, através de um conjunto de quadros de bordo construídos a partir de um conjunto de dimensões analíticas que nos permitem aferir dos múltiplos elementos de diagnóstico social do concelho de São Brás de Alportel.