Banca de DEFESA: JULIANA SILVA SOUZA LUZ

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : JULIANA SILVA SOUZA LUZ
DATE: 30/03/2026
TIME: 09:00
LOCAL: Google Meet (https://meet.google.com/oap-gjkc-ddy)
TITLE:

Trophic relationships on the beaches of Fernando de Noronha: occurrence of lemon shark (Negaprion brevirostri)s associated with sardines (Harengula sp.) and local ecological knowledge on coastal predation

 

KEY WORDS:

coastal interactions; ethnoecology; oceanic islands; participatory monitoring; trophic ecology

PAGES: 105
BIG AREA: Ciências Biológicas
AREA: Ecologia
SUMMARY:

Trophic relationships play a fundamental role in structuring marine ecosystems by regulating energy flow between lower and higher trophic levels. In shallow coastal environments and surf zones, characterized by high hydrodynamic energy, medium- and large-bodied predators exploit prey aggregations as a foraging strategy. Among these predators, the lemon shark (Negaprion brevirostris), classified as Vulnerable, on the IUCN Red List, stands out as a species that uses the Fernando de Noronha Archipelago, an oceanic island located approximately 350 km off the northeastern coast of Brazil, throughout its entire life cycle. Within the archipelago, the scaled sardine (Harengula sp.) is the main pelagic fish species recorded and forms dense schools in shallow waters and surf zones. In addition to its ecological relevance as an intermediate link in energy transfer across trophic levels, this species holds socioeconomic importance, being widely used as bait in artisanal fisheries. The concentration of sardine schools near the shoreline creates favorable conditions for multispecies predation events that spatially and temporally overlap with human activities such as artisanal fishing, surfing, and tourism, thus configuring a complex socioecological system. This study aimed to identify the main shallow-water use areas and periods of occurrence of the lemon shark in Fernando de Noronha, evaluating its relationship with the presence of scaled sardines and environmental variables, as well as investigating local community perceptions regarding the dynamics of coastal predation associated with these events. The research was structured into two complementary chapters. In the first chapter, the spatial–temporal occurrence of the lemon shark was analyzed using citizen-science data obtained from the Tubarões e Raias de Noronha Project. After filtering and standardization procedures, 348 records of subadult and adult individuals (2021–2024) were analyzed and integrated with independent sardine occurrence data (8,772 records) and environmental variables, including rainfall, swell intensity and wave period (high-energy oceanic wave events), and spatial beach groupings. Hierarchical Bayesian modeling, separating occurrence (presence/absence) and conditional abundance processes, indicated that species dynamics were primarily structured by the occurrence component. The probability of lemon shark presence was higher on sandy beaches in the sector locally known as the “inner sea” (mar de dentro), the more sheltered side of the archipelago facing the South American mainland, and increased significantly in the presence of scaled sardines. Swell intensity showed a negative effect on occurrence, whereas no consistent effects of environmental variables were detected on conditional abundance. These findings reveal spatial–temporal overlap between sardine aggregations and lemon shark presence, suggesting that prey availability acts as a structuring factor in shallow coastal habitat use. In the second chapter, 63 ethnoecological interviews were conducted with artisanal fishers, surfers, and tour guides, addressing three main dimensions: (1) patterns of sardine aggregation and associated environmental drivers; (2) characterization of the coastal predation phenomenon locally known as “arrufo”; and (3) the influence of shark presence on human activities. Responses were analyzed through content analysis, comparative statistics, and mixed models, and were subsequently contrasted with aerial drone records. Interviewees reported recurrent predation strategies, including herding of sardine schools, use of wave energy, and facilitation among different predator species, including fish, seabirds, rays, and sharks. There was strong consensus in interpreting “arrufo” as a joint predation event or feeding frenzy, often identified by the aggregation of seabirds at the surface. Perceptions of sharks varied among groups: fishers associated their presence with economic losses, surfers reported concern about accidents, while tour guides emphasized their educational and tourism value. Taken together, the results demonstrate that the archipelago’s shallow waters function simultaneously as feeding grounds, aggregation sites, and zones of intense trophic interaction, where ecological and social processes overlap. The study highlights the potential of citizen science and local ecological knowledge as complementary tools for understanding rapid and difficult-to-monitor ecological events, contributing to participatory management and conservation strategies in marine protected areas.

 

COMMITTEE MEMBERS:
Externo à Instituição - JOSE GARCIA JUNIOR - IFRN
Presidente - 1378974 - LIANA DE FIGUEIREDO MENDES
Interna - 1718747 - PRISCILA FABIANA MACEDO LOPES