Silva Iolanda M, Jesus Nádia, Castro Joana, Luís Ana Rita
MARE-Marine and Environmental Sciences Centre/ARNET-Aquatic Research Network/Ispa-Instituto Universitário de Ciências Psicológicas, Sociais e da Vida, 1149-041 Lisbon, Portugal.
AIMM-Associação para a Investigação do Meio Marinho, 1500-399 Lisbon, Portugal.
Animals (Basel). 2024 Oct 17;14(20):2998. doi: 10.3390/ani14202998.
The impact of vessels on dolphin populations has been extensively studied worldwide. The common dolphin, , has been observed in the Tagus estuary for the past two centuries, and during the last several years, these sightings seem to have increased. This area has high levels of maritime traffic throughout the year, both commercial and recreational. To understand the possible effects of vessel traffic on dolphins' behavior, land-based observations were carried out from March 2022 to March 2023. For a total of 67 events (48.9 h of dolphin sightings), differences in behavioral budgets were noted. Although "neutral reaction" was the most observed response when vessels were in the vicinity of dolphins, "negative reaction" was also common and five times more abundant than "positive reaction". The GEE model showed statistical differences between these reaction types (positive, neutral, and negative). Markov chains' analysis revealed distinct patterns in the behavioral transition probabilities, as dolphins were more likely to switch to a traveling state when vessels were nearby. This study is the first step towards understanding a potential impact source in the area since it is expected that tourism companies expand due to the increase in dolphin sightings in the estuary.
船只对海豚种群的影响在全球范围内得到了广泛研究。普通海豚在过去两个世纪里一直在塔霍河口被观察到，在过去几年中，这些目击事件似乎有所增加。该地区全年都有大量的海上交通，包括商业和娱乐交通。为了解船只交通对海豚行为的可能影响，于2022年3月至2023年3月进行了陆地观测。在总共67次事件（48.9小时的海豚目击）中，注意到了行为预算的差异。虽然当船只在海豚附近时，“中性反应”是最常观察到的反应，但“负面反应”也很常见，且比“正面反应”多五倍。广义估计方程模型显示了这些反应类型（正面、中性和负面）之间的统计差异。马尔可夫链分析揭示了行为转变概率的不同模式，因为当船只靠近时，海豚更有可能切换到游动状态。由于预计旅游公司会因河口海豚目击事件的增加而扩张，这项研究是了解该地区潜在影响源的第一步。
