What do we know about the population trend of the Bolivian River Dolphin: A Population Analysis with long-term data

Abstract

Abstract South American river dolphins face significant threats from intense human activities, resulting in habitat loss, fragmentation of their natural connectivity, overfishing, pollution, and incidental and intentional catches (e.g., for use as bait for fisheries). From 1998 to 2022, twelve surveys were conducted in a river system in the Mamore River (Ibare-Tijamuchi-Mamore) basin, one of the primary distribution areas of the Bolivian river dolphin (BRD - Inia geoffrensis boliviensis). Generalized linear models (GLMs) were used to assess population trends. The most supported model does not definitively indicate a decline in population. The estimated mean annual rate of population change for BRDs over the 24-year monitoring period was − 0.0115 per year. The mean count of BRDs in the Ibare River is approximately 21.2% of the mean count in Tijamuchi, while in the Mamore River, it is 41.1%. However, there is still no evident decline in the populations in the sub-basin of the Mamore River. This study highlights the importance of still monitoring river dolphin populations. Similar population dynamics are observed in other river dolphin species in the Amazon region, necessitating immediate actions to mitigate or reduce mortality and reverse the concerning trend exhibited by these populations.