Peixes de recifes de coral, pescarias e conservação no Antropoceno

Abstract

Coral reefs contribute to climate regulation on planet at different spatial scales and participate in promoting the resilience of coastal and marine areas. The set of reef biodiversity promotes the maintenance of immaterial and material goods and Ecosystem Services (SEs), which are preponderant for guaranteeing food security, promoting individual and collective well-being, sense of place, and socioeconomic benefits of millions of people. However, climate change, overfishing trends, lack of marine spatial planning, unmanaged tourism activities, contribute to pollution, and accelerate the degradation of these environments. Synergistically, these stressors contribute to the alteration of ecosystems, by modifying the population structure, biomass, and diversity of trophic groups of fish in reef communities. The effects of these changes trigger a decrease in stony coral cover areas, and a gradual increase and replacement by macroalgae, resulting in phase shifts. In the reef food web, groups of carnivorous, piscivorous and herbivorous reef fish promotes the balance between primary productivity and consumption, but overfishing weakens interactions inducing trophic cascades accelerating changes. The general objective of this thesis was to investigate how scientific knowledge about herbivorous reef fish has advanced in Brazil, including the human perception for the conservation of marine biodiversity and ecosystem processes performed by reef fish. In the first chapter, a scientometric analysis showed that in more than fifty years, multidisciplinary scientific knowledge has advanced in the Southwest Atlantic (SWA), including the most studied environments and taxon sampling methodologies, components, and ecosystem processes. The evidenced gaps pointed to the need to identify the anthropic stressors that degrade coral reefs, the occurrence of phase shifts in the SWA, and the importance of using the Local Ecological Knowledge (LEK) of fishers in research to identify the SEs related to the fish, fisheries and proposing practical solutions for conservation and local management. In the second chapter, we use the LEK of fishers to fill in the gaps identified in the first chapter, and we test the hypothesis of the occurrence of the Shifting Baseline Syndrome (SBS) in the catches of trophic groups of carnivorous, piscivorous, and herbivorous fish, among different generations of fishermen on a tropical island. We presume that decreasing trends in stocks of different trophic groups and the co-occurrence of stressors trigger phase shifts. From 1952 to 2022, fish and fisheries are SEs that promote food, jobs, and income for people. However, the increase in the quantity and the multiplicity of fishing gear being increased over time, the reports on the decrease in catches of larger species of all trophic groups in the shallow zone, the decline in biomass reported by fishermen, indicates a gradual increase in the fishing effort suggesting that there is a depletion of the stock. We detected a shift in perception across generations, which was evidenced by observing the increase in stock and changing targets in the experienced category; aligned with the perception of decline in stock, acceptance of rarity, and lack of knowledge of large carnivorous and herbivorous species by the beginners; while the beginner considered parrotfish and snappers species not to grow much as a common pattern. Overfishing, habitat degradation, and unmanaged tourism were identified as the main anthropogenic stressors. The solutions pointed out were the reduction of low selectivity gear in coral reefs such as gill nets, management (e.g.: selectivity in capture), aligned with the effective inspection of fisheries, together with the monitoring of tourism activities. A proposal that includes ecosystem-based fisheries management, and coastal and marine spatial planning associated with the adoption of multilevel governance in collaborative networks can minimize stressors, and consist of alternatives that can promote coping, in addition to mitigating phase shifts.