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Integrating video and acoustic non-invasive techniques to monitor the professor luiz saldanha marine park (PLSMP)
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With global biodiversity in decline, cost-effective and affordable technologies are urgently needed to monitor the impacts over marine environments. Long-term monitoring is essential for preserving ecosystem functions by assessing biodiversity, spatial and
temporal dynamics, and the effects of human activities on behaviour. Marine organisms depend on sound for communication, navigation, and foraging, making Passive Acoustic Monitoring (PAM) a non-invasive and effective method for studying biodiversity and
anthropogenic impacts. Since its development in the mid-20th century, acoustic monitoring has become a valuable tool in ecology and conservation, particularly when used alongside visual or genetic methods.
This thesis explores the integration of video and acoustic monitoring in the Professor Luiz Saldanha Marine Park (PLSMP) to study fish acoustic communities and the impact of anthropogenic sounds on their behaviours. The main aims are to compile underwater
fish sounds using PAM, identify sound sources through Baited Remote Underwater Visual Systems (BRUVS), examine temporal variations across protection levels/habitats, compare monitoring techniques, and validate acoustic indices against traditional
biodiversity indices. These visual and acoustic approaches help assess behaviour patterns and the impact of anthropogenic activity on key marine species.
Acoustic recorders were deployed at three locations with varying habitat types for 15 months. A literature review of species in the area identified 28 soniferous and 71 potentially soniferous fish, representing 18.6% and 52.6% of the reported species, respectively. Acoustic analyses revealed 33 putative fish sound types, categorised as either continuous or pulsed. Combining hydrophone data with BRUVS showed some limitations in identifying sound sources. By comparing recorded sounds with those in the literature, six sound types were tentatively linked to specific fish families. Sounds #4, #8,
and #33 resembled those of the Serranidae family; #10 matched Triglidae; #15 was similar to Sciaenidae; #42 to Pomacentridae; and #43 to Scorpaenidae.
Fish sound occurrence was analysed across seasons, times of day, and protection areas. While seasonal variation was limited, increased sound production and diversity occurred at sunset and night. Spatial differences suggested that rock substrate and distance to the estuary influenced the presence and variety of fish sounds. The biodiversity and abundance indices from three methods (UVC, BRUVS, and PAM) were also compared to assess their relative effectiveness, highlighting their complementarity in assessing fish biodiversity.
Additionally, a pelagic drift BRUVS study focused on blue shark resence and foraging behaviour. Juveniles were mostly observed in spring, closer to shore, especially in the epipelagic and mesopelagic zones, indicating the area may serve as a nursery.
Adults were more commonly sighted offshore, particularly near submarine canyons.
Environmental factors such as temperature, visibility, and proximity to the coast influenced shark behaviour. Notably, acoustic analysis showed that boat noise reduced both the duration and frequency of shark interactions with the BRUVS.
This study shows that the combination of visual and acoustic methods are effective tools for monitoring fish acoustic communities and elusive species like the blue shark.
The combination holds great promise for assessing fish biodiversity and the impacts of environmental change, supporting improved marine management and conservation.
Descrição
Tese apresentada no ISPA-Instituto Universitário para cumprimento dos requisitos necessários à obtenção do grau de Doutor em Biologia do Comportamento
Palavras-chave
Passive acoustic monitoring Marine protected areas Soundscapes Fish communities Monitorização acústica passiva Áreas marinhas protegidas Paisagens sonoros Comunidades de peixes