Reef fisheries are important activities that support the livelihoods of millions of people. Reef fisheries exploit different habitats and typically target a diversity of species caught with a matching diversity of fishing gears. However, previous studies of reef fisheries have generally lacked detailed information on the catch and effort by gear and habitat type. In this dissertation, the sustainability of a coral reef fishery at the Marine Protected Area Costa dos Corais, Northeastern Brazil is assessed. In 1,833 landing interviews with local fishers, 100 fished species were identified and the total catch in kilograms for each species, the size composition of captured individuals and the habitat type exploited were recorded. First, the dissertation explores how fishing gears selected for distinct functional traits. A low competitive interaction between different gears was noted. Gears used in reef habitats selected for sedentary and benthic species, while gears used in coastal lagoons targeted highly mobile and pelagic. Second, the dissertation assesses how different gear affected the catch rates of coral reef fishes. Gears used on coral reef habitats had a more negative effect on catch rates than those used in coastal lagoons. The three gear types that affected catch rates more severely were hook and line, gillnet and cast net. Based on the results it is argued that the effects of reef fisheries on catch rates were highly depended on the vulnerability of target species. Finally, the dissertation assesses the ability of the fishing-down concept to assess the sustainability of the local fishery; the fishing-down is used to describe the process of moving away from catching large fish to progressively targeting smaller fish. I found strong support for the fishing-down, as fisheries decreased the average size of the fish assemblage and affected more heavily the catch rates of fishes with higher index of vulnerability. Overall results show that fisheries management should focus on the conservation of vulnerable taxa that are responsible for key ecological processes in coral reefs such as herbivory and coral predation. The decision-making process on management measures must be based on clear discussions with all stakeholders involved. / Doctor of Philosophy / Coral reefs are one of the richest environments on the planet, but overfishing threatens their conservation. Reef fishers use many techniques, or fishing gears, such as hook and line and nets, to catch a high diversity of fish species. Reef fisheries are often unsustainable as fishers are allowed to employ high levels of effort. Thus, studies are needed to assess the sustainability of coral reef fisheries and determine which gears are more negative to reef fishes. In a series of three studies, I investigated how reef fisheries affected fish communities in Northeastern Brazil. I used a total of 1,833 interviews with fishers in which I recorded the total catch for each species, obtained size of fish individuals, and asked about the environment that was exploited, coral reefs or coastal lagoons. First, I evaluated how the different gears selected for groups of species with unique life-history characteristics, such as size, mobility and period of activity. I found that gears such as hook and line and harpoon selected for species with sedentary traits that live near the bottom of the ocean, whereas nets selected for very mobile species that inhabit surface waters. In general, fishers did not compete for the same resources with different gears. Second, I assessed how the different gears affected the relative abundance of coral reef fishes. The three gear types that affected more heavily the relative abundance of fishes were hook and line, gillnet and cast net. I argue that the negative effects occurred because these gears caught species with characteristics that made them vulnerable to exploitation, such as slow body growth. Third the dissertation assesses the ability of the fishing-down concept to assess the sustainability of the local fishery; the fishing-down is used to describe the process of moving away from catching large fish to progressively targeting smaller fish. I found strong support for the fishing-down as the studied fisheries impacted the size and the abundance of local fishes. My results suggest that fisheries management should focus on the conservation of vulnerable fish responsible for key ecological processes such as herbivory and coral predation. The decision-making process regarding fisheries management must also be based on clear discussions with all stakeholders involved.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/108368 |
| Date | 15 February 2022 |
| Creators | De Moraes Carvalho, Felipe |
| Contributors | Fish and Wildlife Conservation, Castello, Leandro, Padovani Ferreira, Beatrice, Frimpong, Emmanuel A., Orth, Donald J., Power, Michael |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf, application/pdf |
| Coverage | Brazil |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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