| dc.description.abstract | Freshwater cetaceans are seven highly threatened species with restricted ranges that inhabit rivers in close proximity to human populations. Over the past two decades, it has become increasingly clear that the limited resources to monitor population trends and existing knowledge gaps have hampered the design of effective conservation actions, with one species of river cetacean, the baiji (Lipotes vexillifer), being declared extinct. In this dissertation, I review the current state of knowledge on river cetaceans and provide new insights into the ecology and distribution of two South American freshwater dolphins, the boto or Amazon River dolphin (Inia geoffrensis) and the tucuxi (Sotalia fluviatilis). In Chapter 1 I summarise what is currently known regarding their taxonomy, distribution, and ecology. Chapter 2 reviews the current global conservation status of river cetaceans through a combination of expert elicitation and a synthesis of literature on threats and management. I also identify knowledge gaps and use this data to inform subsequent chapters. To improve the management of these species, I recommend future conservation efforts that build local capacity in each range country, strive for regional cooperation, and increase knowledge and public awareness. In Chapter 3, I interview fishers from the Peruvian Amazon to better understand their perceptions and interactions with the Amazon River dolphin and the tucuxi. I report perception of competition and negative perceptions, the use of Amazon River dolphins as bait for the piracatinga catfish fishery, and bycatch of both species in purse seines and gillnets. The results allow prioritisation of which ports should be monitored in order to reduce bycatch and direct take. In Chapter 4, I use satellite transmitters to identify overlap between monitored Amazon River dolphins and key threats in their range. All dolphin home ranges overlap with areas of small-scale fishery catch. Existing dams are relatively far away from dolphin populations, but proposed dams are less than 200 kilometres upstream. Monitored animals are close to a proposed hydroway, which will result in an increase in vessel traffic and recurrent dredging. In Chapter 5, I estimate the density of both species in a previously unexplored area of the western Amazon of Peru while also testing the application of environmental-DNA (eDNA) for validating species presence. Sampling for eDNA is successful at detecting both species at 68% of the sampled locations. I discuss potential applications of this method for addressing knowledge gaps. In Chapter 6, I summarise the significance of the findings of my dissertation and suggest what should be done in the future to better conserve river dolphins. Using a variety of methods, including questionnaires, satellite transmitters, distance sampling, and eDNA, this dissertation provides baseline data for river dolphins in Peru. I propose that for the sustainability of their populations in Peru, research should concentrate on tracking population trends and estimating human-caused mortality. Participation of local communities in key conservation actions, such as the design and implementation of protected areas, research, and law enforcement, would increase the likelihood of conservation interventions being successful. | en_GB |
