Integrating Multiple Techniques to Estimate Population Size of an Impacted Dusky Dolphin’s Population in Patagonia, Argentina

DEGRATI, MARIANA; LOIZAGA DE CASTRO, ROCÍO; COSCARELLA, MARIANO A.; SUEYRO, NICOLÁS; CRESPO, ENRIQUE A.; DANS, SILVANA L.

Small Cetacean Conservation: Current Challenges and Opportunities

Frontiers Media SA

Año: 2022; p. 22 - 30

Successful conservation strategies require an accurate estimation of population size,and this parameter is one of the most important factors that determine the rate ofvarious evolutionary processes. In this study, we integrated information from genetic,photo-identification, and aerial surveys of dusky dolphins to determine the effectivepopulation size and the number of dolphins that inhabit the gulfs of Península Valdés[Golfo Nuevo (GN) and Golfo San José (GSJ)] and are exposed to tourism vessel traffic.Photo-identification sessions and biopsies samples were collected from a researchvessel between 2004 and 2013 to estimate the number of dolphins in the area bycapture–recapture methods and the effective population size using mtDNA data. Inaddition, four aerial surveys were carried out using line transects to estimate densityvia distance sampling. The long-term effective size estimated was 992.87–1,103.19individuals. During the photo-identification period and by applying a mark rate of0.416, the total estimated individuals in GN was 374 (95% CI: 237–511). For GSJ,the estimated individuals in the area were 55 (95% CI: 2–108, mark rate 0.692). Fromaerial surveys, the overall density estimate was D= 0.13 dolphins/km2(95% CI: 0.052– 0.35; CV: 49.60). The estimation for GN was 325 (95% CI: 130–875), whereas for GSJ, it was 104 (95% CI: 42–280) individuals. These are the first estimations of the numberand the effective population size for dusky dolphins in a small-scale area along northPatagonia. Dusky dolphins groups are impacted by anthropogenic activities; therefore,the information reported here contributes population information to help to the speciesmanagement and conservation.