Percorrer por autor "Rodrigues, Alfredo"
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- The impact of touristic whale-watching on Delphinus Delphis and Tursiops truncatus in the Algarve Coast: combining acoustic analysis and land observationsPublication . Forli, Maria Julia; Peres dos Santos, Rui Pedro; Rodrigues, Alfredo; Castilho, RitaTouristic whale watching (WW) is an important socioeconomic activity worldwide. Recently, short and longterm impacts caused by WW have been reported for several cetacean species, including Delphinus delphis and Tursiops truncatus, the two most observed species in Portugal. Most of the operations in mainland Portugal are concentrated on the South Coast (Algarve). However, despite their importance for the region, studies focused on the impact of this activity on the animals are still scarce. We used acoustic behaviour analysis and land-based observations to determine the alterations in the vocalization patterns of these animals caused by WW vessels and the length of exposure to this stressor. We found WW presence significantly altered five out of six acoustic parameters of whistles, whistle rate, and whistle type distribution for D. delphis, whereas T. truncatus exhibited significant changes in three acoustic parameters. Conversely, T. truncatus significantly reduced echolocation click rates, while D. delphis did not show significant changes. We also found that the Central region of this coast is the most affected, with animals exposed to WW vessels for up to 38.9% of daylight hours. Furthermore, 66.7% of the observation time in this area had several vessels that exceeded the limit established by law. These results suggest that our study species are impacted by WW, while D. delphis is more affected during social behaviours, and T. truncatus is more affected during foraging activities. Both behaviours are biologically significant, and their disturbance might, in the long term, lead to adverse effects at the population level by decreasing reproductive success and fitness. A gap in knowledge, inadequate legislation and compliance issues threaten the development of a sustainable WW industry in the Algarve and might endanger local populations, therefore immediate attention is needed.
- Opportunistic data for assessing abundance and site fidelity of fin whales (Balaenoptera physalus) in the Faro area, PortugalPublication . Gennari, Ginevra; Rodrigues, Alfredo; Carvalho, Pedro; Gil, Susana; Magno, Ramiro; Castilho, Rita; Peres dos Santos, Rui PedroThe distribution and migration of fin whales (Balaenoptera physalus) remain poorly understood in parts of the North Atlantic. One of these regions is the Algarve in southern Portugal, which is shaped by seasonal upwelling and the exchange of Atlantic and Mediterranean waters. This area represents a potentially critical yet poorly understood habitat for this species. This study presents the first comprehensive assessment of fin whale abundance and site fidelity in the Faro area, located approximately between 36–37° N and 8–7° W. Data was collected from 2020 to 2024 through photoidentification and GPS vessel tracks, in collaboration with a local whale-watching company. A regional catalog of 86 individuals was established, and an open spatially explicit capture-recapture model estimated a population of 1.476 individuals. Sightings peaked in spring, likely linked to phytoplankton blooms and foraging opportunities. While re-sighting rates were low, some individuals returned across years, indicating possible seasonal site fidelity. Our results demonstrate the value of data collected from platforms of opportunity in an under-surveyed region, providing a foundation for ongoing monitoring efforts. Results also highlight the Faro area’s ecological relevance as a seasonal feeding ground for fin whales and offer insights to support future conservation in the eastern North Atlantic.