Understanding the Population Dynamics of Dusky Dolphins (Lagenorhynchus obscurus) in Golfo Nuevo, Patagonia, Through Long-Term Monitoring

Abstract

Estimates of apparent survival and abundance are crucial for understanding the population dynamics of sentinel species. To achieve this, it is necessary to establish a baseline of these parameters for effective management planning in areas strongly impacted. This is the case of the dusky dolphin (Lagenorhynchus obscurus), a species inhabiting the Argentine coasts. In Golfo Nuevo, information on the demographic parameters of this species, which coexists with tourism activities, remains insufficient. In this study, the abundance of dusky dolphins in Golfo Nuevo, Patagonia, Argentina, was estimated through long-term monitoring using the mark-recapture model for open populations (POPAN model). Moreover, the apparent survival rate of this species was estimated for the first time through live recaptures using the Cormack–Jolly–Seber (CJS) model. Photo-identification surveys were conducted from 2004 to 2022, and models were built using the MARK program, selecting the best models based on the lowest AIC. Our results suggest that in Golfo Nuevo, the apparent survival rate is high, around 0.95 ± 0.01, whereas the local abundance reached 2862.81 individuals throughout the entire sampling period. The number of individuals showed an increase with an average annual change rate of 4.65%. These findings represent a baseline estimate of abundance, apparent survival and population trend for dusky dolphins. However, future studies should prioritize estimates of site fidelity and emigration to achieve accurate estimations of true survival rates for the species. Our results contribute to the understanding of dusky dolphin population dynamics and can be considered in management and conservation projects at the local level.