Pimentel, MartaVasconcelos, Raquel de Ornelas e, 1980-Freitas, Paulo Sérgio Pereira2025-01-202025-01-2020242024http://hdl.handle.net/10400.5/97337Tese de mestrado, Ecologia Marinha , 2024, Universidade de Lisboa, Faculdade de CiênciasSeahorses are known to produce sounds in different behavioural contexts, but information on the sound production in these organisms and how it may be affected by climate changes is still scarce. These animals are currently experiencing an unprecedented level of anthropogenic pressures, thus being crucial to understand how they will endure such pressures such as climate change. This study characterizes the feeding behaviour and acoustic communication of the short-snouted seahorse Hippocampus hippocampus and explores the effects of type II marine heatwaves (21.5 °C) and hypoxic ~ 27% dissolved oxygen (2.1 ± 0.1 mg O2 L -1 ) conditions. Feeding clicks were characterized by brief high frequency broadband sounds with a mean duration of 25.3 ± 1.9 ms, and a mean peak frequency of 1838.0 ± 77.1 Hz. The duration of these clicks revealed changes under marine heatwaves and hypoxic conditions compared to the control. During marine heatwave treatment, the duration decreased 15.8% (down to 21.3 ± 2.2 ms), whereas under hypoxia, it increased 30.04% (up to 32.9 ± 7.1 ms). However, there were no significant changes in the peak frequency across these treatments. Feeding clicks were also consistently associated with food intake, revealing a significant positive correlation between the number of clicks and food intake, working as an accurate measure of feeding activity. Under marine heatwaves conditions, seahorses displayed increased production of 69.16% (83.4 ± 7.89) in feeding clicks and 50.01% (51.5 ± 2.93) in food intake compared to control conditions (49.3 ± 5.01 and 34.3 ± 2.39, respectively). Additionally, sound production, exhibited a threshold effect. Specifically, below a certain threshold of approximately 19.3°C, higher temperatures were associated with increased sound production. However, beyond this threshold, further increases in temperature do not seem to have a significant impact on sound production or food intake. In contrast, findings showed a significant reduction of 75.45% (12.1 ± 1.71) in sound production and 77.19% (7.8 ± 1.14) in food intake within just one day of hypoxic exposure. Our findings suggest that climate change may impact seahorses in different ways, while higher temperatures (ranging from 19.3°C to 21.5°C) may increase acoustic signaling and feeding, hypoxia may result in decreased vocal activity and food consumption with potential impact on their growth and survival. Moreover, the present study proposes the use of sound-based techniques to monitor seahorse feeding behaviour and welfare. By detecting and analysing the soundscape, researchers can potentially measure changes in normal behaviour due to adverse environmental conditions.engHippocampus hippocampusonda de calor marinhahipoxiaclicksalimentaçãoTeses de mestrado - 2024master thesisTese de mestrado em Ecologia Marinha203877357