Detalhes bibliográficos
| Ano de defesa: |
2021 |
| Autor(a) principal: |
LIRA, Alex Souza
 |
| Orientador(a): |
FRÉDOU, Flávia Lucena |
| Banca de defesa: |
MORAIS, Luis Tito de,
ANGELINI, Ronaldo,
SEVERI, Wiliam,
HARMELIN-VIVIEN, Mireille |
| Tipo de documento: |
Tese
|
| Tipo de acesso: |
Acesso aberto |
| Idioma: |
eng |
| Instituição de defesa: |
Universidade Federal Rural de Pernambuco
|
| Programa de Pós-Graduação: |
Programa de Pós-Graduação em Recursos Pesqueiros e Aquicultura
|
| Departamento: |
Departamento de Pesca e Aquicultura
|
| País: |
Brasil
|
| Palavras-chave em Português: |
|
| Área do conhecimento CNPq: |
|
| Link de acesso: |
http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/9529
|
Resumo: |
The shrimp fishery is responsible for one of the main anthropogenic impacts on the seabed and associated communities. In Northeast Brazil, this fishery is of small scale, characterized mainly by weak or completely absence of management; and by a high socio-economic importance for many people that depend on this activity as source of income and food. The overall aim of this thesis is to assess the current and potential future impact of fishing and environmental changes from the multiple methods adapted to data-limit framework under the scope of Ecosystem Approach to Fishery (EAF) in Sirinhaem, Pernambuco, using, as study case, a small-scale shrimp trawling in Northeastern Brazil. Firstly, an integrative view of the fishery was carried out encompassing the characteristics of environment and fishing aspects, and the dynamics of the target and bycatch species (Chapter 1). The importance of crustaceans, especially the target species (shrimps) in the support to coastal food-web was accessed using two complementary tools (stomach content and stable isotope) (Chapter 2). A temporally dynamic model (Ecosim) was built to evaluate the potential isolated and combined effects of different fishing effort control policies and environmental changes on marine resources and ecosystem (Chapter 3). Finally, a semi-quantitative risk analysis – PSA (Productivity and Susceptibility Analysis) adapted to regional conditions, was developed in order to evaluate, for the first time, the vulnerability and the potential risk (low, moderate and high) of the target and non-target species exploited by the trawl fishing in the north-eastern Brazil. Shrimp fishing occurs in shallow waters at depth varying from 10 to 20 m associated to mud zones. The abundance and catches of target and non-target species are positively correlated to the rainfall season. Penaeidae shrimps are the main targets, particularly the seabob shrimp (Xiphopenaeus kroyeri) the most abundant, and the pink shrimp (Penaeus subtilis) and white shrimp (Penaeus schmitti) with the high market-values. These species, together with other invertebrates (e.g., worms and crabs), are extremely important preys for the fish fauna, highlighting their importance in the food web. Potential decreasing the abundance of these preys, including shrimps, due to cumulative effects of trawling in the area, may lead to intense changes in the trophic structure of the ecosystem affecting the food web and the sustainability of the fishery. Considering the target species, although the traditional stock assessment carried out in the region do not indicate overexploitation, the pink shrimp (P. subtilis) is o more affected by the increasing of effort than P. schmitti and X. kroyeri. However, considering the particularities of our case study and without accounting for the effect of environmental changes, not adopting effort control measures for the current trawling conditions do not appear to cause major losses for target species in terms of biomass and catches. Amongst the fish bycatch, the Scianidae and Pristigasteridae families were the most important species in terms of abundance and biomass, with most of them being consumed by the local community and classified as the moderate risk, given its high resilience (e.g., Pellona harroweri, Isopisthus parvipinnis, Chirocentrodon bleekerianus). However, Elasmobranchs and catfish, often discarded or consumed; hakes and croakers’ fishes, usually commercialized; were assigned as high vulnerable, mainly given the low productivity (medium to long life-span and low spawning potential reproduction, for elasmobranchs and catfish) and/or the high capture rates of young individuals and overlap with the fishing areas (mainly for the hakes and croakers). Considering the integrated results here observed, we evaluated the possible regulation which would be adapted to our study case. Given its reduced extension of the fishing grounds, spatial management approaches (e.g., Marine Protect Area – MPA or no-fishing zones) maybe not very effective as a possible regulation in the region. In addition, large effort reductions or the definition of size and gear limitations did not appear to be necessary measures, considering that, according to the traditional stock assessment, the target species are being exploited at biologically accepted levels. However, the controlled decrease of the trawling effort up to 10% were promising, with better fishing management performance than the closed season, which did not present significant improvements in terms of ecosystem functioning. Considering that several bycatch fish species are also potentially vulnerable to bottom trawling, given its biology, ecology and importance for other fleets, associated to the lack of studies, they should be assigned as priority for management and data collection. The use of Bycatch Reduction Devices (e.g., fisheye, grid and square mesh) to exclude bycatch may be one alternative however, given crucial role of the bycatch to food security on small-scale fisheries, as in our case, its viability needs to be better evaluated in terms of the socio-economic aspects. Finally, regardless of what fishery regulation may be applied in the management of small-scale shrimp fisheries in Sirinhaém, Northeastern Brazil, we found clear evidence that environmental changes (e.g., rainfall, primary productivity), consequence of the climate changes, cause significant adverse impacts in the ecosystem. These effects should be considered in any eventual regulatory measure, since the cumulative effect environment changes and fishery, considerably threat the ecosystem, and consequently, the sustainability of the activity. |
