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Publications

Publications by Manuela Maria Oliveira

2015

The phycotoxins' impact on the revenue of the Portuguese artisanal dredge fleet

Authors
Oliveira, MM; Camanho, AS; Gaspar, MB;

Publication
MARINE POLICY

Abstract
The bivalve dredge fleet, considered as one of the most important artisanal fleets due to the high value of the catches, is by far the most extensively studied among the Portuguese artisanal segment. Acknowledging the growing presence of marine phycotoxins in the waters, the present study explores their impact on the revenue of the fleet that operates along the coast of mainland Portugal. The results obtained using stochastic frontier analysis models enlighten the harmful impact of algae blooms on the activity of the artisanal dredge fleets. In particular, it was observed that in the Algarve region, where the frequency and the intensity of these episodes is higher, the sustainability of the dredge fishing activity is seriously compromised by the phycotoxins.

2013

The influence of catch quotas on the productivity of the Portuguese bivalve dredge fleet

Authors
Oliveira, MM; Camanho, AS; Gaspar, MB;

Publication
ICES JOURNAL OF MARINE SCIENCE

Abstract
Among the Portuguese artisanal fishing fleets, the bivalve dredge fleet is one of the most profitable. In the last decade, after the implementation of a quotas system, the management of this fishery has been largely focused on adjusting catch to the conservation status of the resources exploited. The present work aims to understand how changes in the amount of quota attributed to each vessel each year and shifts in the quota regime affected vessel productivity. Boostrapped Malmquist indices, complemented with an efficiency assessment using a directional distance function, were used to quantify productivity changes between 1999 and 2011 for the fleets operating in two areas along the Portuguese coast (northwest and southwest). The results showed that the implementation of a weekly quota, as opposed to a daily quota, led to a significant improvement in productivity. This was mainly due to the decrease in fishing days and fuel consumption. It is predicted that the implementation of weekly quotas in the south area would lead to an overall reduction of about 12% in fishing days and fuel consumption, even though the variation in fuel consumption may be affected by the status of the resources. The results achieved provide important insights for future management actions and showed the potential advantages of applying this type of management to other fisheries worldwide, mainly those using active gear.

2014

A novel and simple approach to define artisanal fisheries in Europe

Authors
Garcia Florez, L; Morales, J; Gaspar, MB; Castilla, D; Mugerza, E; Berthou, P; Garcia de la Fuente, LG; Oliveira, M; Moreno, O; Jose Garcia del Hoyo, JJG; Arregi, L; Vignot, C; Chapela, R; Murillas, A;

Publication
MARINE POLICY

Abstract
Although the importance of the social, economic, environmental and traditional importance of artisanal fisheries is widely accepted, there is no single internationally accepted definition for this activity, since its characteristics differ among countries. Notwithstanding, it is also generally accepted that artisanal fisheries comprises a group of characteristics that clearly differ from those of the industrial fishing. In the present paper, an objective, simple and easy to use methodology is presented for the segmentation of fishing fleets by using a group of descriptors currently available in the European Union datasets. The numerical descriptors approach (NDA) is a score-based methodology that was applied to several EU fishing fleets from the Atlantic Area. The results obtained allow a more realistic segmentation of the European fishing fleet into artisanal (both coastal artisanal and small-scale fisheries) and non-artisanal than the current limit of 12 m vessels overall length. The procedure can be, and should be, refined and improved by the addition of new descriptors (e.g. operational range of the vessels and fishing effort, time spent at sea as well as other socio-economic indicators) when the necessary information becomes available for the entire European fishing fleet. The NDA represents a flexible tool that could be used at any geographical scale by adapting the final score and/or the numerical ranges of each descriptor.

2015

A system dynamics model to support the management of artisanal dredge fisheries in the south coast of Portugal

Authors
Martins, J; Camanho, A; Oliveira, M; Gaspar, M;

Publication
INTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH

Abstract
This paper presents a management model developed to promote the sustainability of artisanal fisheries, considering socioeconomic and environmental dimensions. The management of artisanal fisheries faces many challenges, including the lack of appropriate tools to support policy makers and stakeholders in the decision-making process. The model presented in this study is based on system dynamics and allows the simulation of the behavior of the artisanal dredge fishery on the south coast of Portugal, including four main species and two fleets. Two scenarios were simulated to assess the impact of regulatory measures on the system sustainability: scenario 1 simulated a permanent reduction of fishing effort, returning an improvement of biologic and economic sustainability; scenario 2 simulated the closure of one species for a period of one year to allow its recovery. It was found that although the revenue of fisheries decreases in that year, the system is able to return to the average levels of revenue three years after the closure. The study aimed to guide decision makers in the selection of the most appropriate measures toward the preservation of marine ecosystems and socioeconomic stability of fishing communities. The developed system dynamics model, combining available data with knowledge of fisheries experts, proved to be a useful scientific tool to identify management policies and organizational structures leading to greater success. This technique can be applied to the study of other fishery systems worldwide.

2016

Portfolio efficiency analysis with SFA: the case of PSI-20 companies

Authors
Ferreira, NB; Oliveira, MM;

Publication
APPLIED ECONOMICS

Abstract
This study aimed to assess the technical efficiency (TE) of individual companies and their respective sectors that are traded on the Portuguese stock market. We accomplished this by combining the internal input variables (e.g., market value and return') with exogenous variables (e.g., interest income', depreciation', cost of goods', employees' and net sales') into a Stochastic Frontier Analysis (SFA) model. The TE of the PSI-20 (Portuguese Stock Index) was estimated using factors that affect efficiency variability. The main advantage of using the SFA approach is its potential to discriminate between measurement error and systematic inefficiencies in the estimation process. The results demonstrated that TE is higher for enterprises in the industrial, construction and distribution sectors, whereas the commercial banking sector has the lowest TE scores. The employees' and depreciation' are the variables which most contribute to stock market inefficiency.

2014

Nonlinearities in the EU sovereign debt crisis

Authors
Ferreiraa, NB; Oliveira, MM;

Publication
INTERNATIONAL WORK-CONFERENCE ON TIME SERIES (ITISE 2014)

Abstract
Sights of sovereign debt crisis spread among financial players started in late 2009 as a result of the rising private and government debt levels worldwide. In 2010 news developments concerning Spain and Italy lead European nations to implement several financial support measures such as the European Financial Stability Facility. In an established crisis context, it was searched for evidence of nonlinearities, structural breaks and cointegration between interest rates and stock market prices in order to evaluate the impact effect analysis of the European markets contamination by sovereign debt. Four European markets under stress were examined using the United States of America as benchmark. It was found evidence in the crisis regime especially for Portugal, obtaining the greatest nonlinear threshold adjustment between interest rates and stock market returns. Moreover, significant structural breaks were found at the end of 2010 and the null hypothesis of no cointegration was consistently rejected.

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