Loading...
4 results
Search Results
Now showing 1 - 4 of 4
- Climate change vulnerability assessment of the main marine commercial fish and invertebrates of PortugalPublication . Bueno-Pardo, Juan; Nobre, Daniela; Monteiro, J. N.; Sousa, Pedro M.; Costa, Eudriano; Baptista, Vânia; Ovelheiro, Andreia; Vieira, Vasco; Chicharo, Luis; Gaspar, Miguel; Erzini, Karim; Kay, Susana; Queiroga, Henrique; Teodosio, Maria; Leitão, FranciscoThis is the first attempt to apply an expert-based ecological vulnerability assessment of the effects of climate change on the main marine resources of Portugal. The vulnerability, exposure, sensitivity, adaptive capacity, and expected directional effects of 74 species of fish and invertebrates of commercial interest is estimated based on criteria related to their life-history and level of conservation or exploitation. This analysis is performed separately for three regions of Portugal and two scenarios of climate change (RCP 4.5 and RCP 8.5). To do that, the fourth assessment report IPCC framework for vulnerability assessments was coupled to the outputs of a physical-biogeochemical model allowing to weight the exposure of the species by the expected variability of the environmental variables in the future. The highest vulnerabilities were found for some migratory and elasmobranch species, although overall vulnerability scores were low probably due to the high adaptive capacity of species from temperate ecosystems. Among regions, the highest average vulnerability was estimated for the species in the Central region while higher vulnerabilities were identified under climate change scenario RCP 8.5 in the three regions, due to higher expected climatic variability. This work establishes the basis for the assessment of the vulnerability of the human activities relying on marine resources in the context of climate change.
- Effect of bait type on the octopus fishery in Algarve, Southern PortugalPublication . Leitão, Francisco; Bueno-Pardo, Juan; Ovelheiro, Andreia; Monteiro, J. N.; Nobre, Daniela; Teodosio, MAIn Algarve, southern Portugal, a fishery regulation was established forbidding the use of live crab as bait for the octopus fishing. Such a regulation was not established under a scientific fundament. The objective of this work was to identify if using live crab as bait affects the octopus fishery. Time series (1989–2015) were analysed in order to calculate octopus catch rates (as Landing Per Unit Effort or LPUE) and revenues (as revenue per unit effort or RPUE) before and after the crab bait ban in 2009 and also by bait type (crab and fish) before ban. Overall, total annual fishing effort decreased as result of the decreasing number of boats and fishing days in the local and coastal fleets. After the ban both the LPUE and RPUE increased, with total landings showing no change through time but mean landings per boat increased. Between 1989 and 2009, the mean monthly fishing effort in the coastal fleet was higher when crab bait was used (3.88%) in comparison to using fish bait (0.3%). This result is superimposed by the large inter annual variability between the local and coastal fleets (39.11%). In consequence, no substantial evidence was found indicating that crab bait produced high octopus catch rates, while fishing effort indicated that such high octopus catch rate and revenue increase was due to the decline of number of boats and fishing effort, that was decreasing significantly regardless of the bait type and fleet before to crab ban, and not to the bait type used during this period.
- Supply and larval traits at metamorphosis of a coastal marine invertebrate with a bi-phasic life cycle under contrasting oceanographic conditionsPublication . Rey, Felisa; Silva Neto, Gina M.; Bueno-Pardo, Juan; Bispo, Regina; Calado, RicardoPatterns of larval supply and larval condition at metamorphosis play key roles in the structure and dynamics of marine populations. Hence, biological and environmental conditions driving the dispersion of larval individuals, shape early life phenotypes, and influence their survival and post-settlement success. We performed a study over two consecutive years at Ria de Aveiro (Portugal), a coastal lagoon influenced by upwelling regimens in the North-eastern Atlantic. This study assessed the effect of contrasting oceanographic conditions on larval supply and larval traits at metamorphosis of the green crab Carcinus maenas. Crab megalopae were daily sampled and monitored in the laboratory until metamorphosis. Environmental conditions experienced by larvae in the field were estimated considering their expected planktonic larval duration, which was calculated for each individual using the size at metamorphosis and the average water temperature during larval development. Presence/absence, megalopa supply, and larval size were posteriorly modelled using generalized linear mixed models. The analysis of the two consecutive years showed haphazard patterns, revealing that both larval supply and phenotypic traits changed during and between supply seasons. The lunar cycle and environmental conditions were identified as drivers of the presence and supply of megalopae. Settlement events with weak upwelling index were influenced by sea temperature, while intense and constant upwelling events conditioned megalopa supply and performance at metamorphosis. In 2013, megalopae invaded the coastal lagoon in a more advanced physiological stage than in 2012 and/or under better nutritional conditions, probably due to stronger and more constant upwelling events during their pelagic larval life. Our results show that oceanographic processes stimulating upwelling and secondary production are sources of phenotypic variation at settlement, influencing both early benthic performance and adult population dynamics of marine organisms with bi-phasic life cycles.
- Trends and drivers of marine fish landings in Portugal since its entrance in the European UnionPublication . Bueno-Pardo, Juan; Pierce, Graham J.; Cabecinha, Edna; Grilo, Catarina; Assis, Jorge; Valavanis, Vasilis; Pita, Cristina; Dubert, Jesus; Leitão, Francisco; Queiroga, HenriqueMarine landings in Portugal have decreased at a higher rate than fishing effort in the last 20 years. Identifying the variables driving the quantity and composition of landings is pivotal to understand the dynamics of the fisheries sector, which entails complex social and environmental aspects. In this study, we investigate the main drivers of marine fish landings in continental Portugal between 1989 and 2014. To identify common trends in time series, and quantify the importance of environmental factors, we applied a dynamic factor analysis considering four regions and three types of gear (trawling, purse-seine, and a multi-gear fishery). Our results show the importance of fishing effort as the most relevant factor driving marine landings in Portugal, both at the long and short terms. In addition, the effect of environmental factors such as the winter river discharge and the spring East Atlantic Teleconnection index should not be neglected, probably through mechanisms affecting coastal productivity. We provide a comprehensive amount of information that permits to improve our understanding of the trends of the most important commercial species in Portugal during the period of study.