MEPS 609:197-207 (2019)  -  DOI: https://doi.org/10.3354/meps12821

ABSTRACT: While there is an established and expanding body of literature on population trends of sea turtle nesting females, studies focusing on male sea turtles are only recent (although they have increased over the past 10 yr). Filling this gap is important for understanding sea turtle population dynamics. We provide the first estimates of demographic parameters of adult males from the mixed ground of Rocas Atoll, an important breeding and feeding ground for green turtles in the South Atlantic. Abundance estimates were obtained from a 5 yr mark-recapture effort between 2003 and 2007 using open-population models. Annual abundance estimates varied from 86 to 146, and the total estimated number of males that used the area within the study period was 294 individuals (superpopulation). Differences among estimates indicate a transient pattern (i.e. marked individuals that were never recaptured) and highlight open population dynamics, where there is a mix of transient and resident animals using the area for breeding and/or feeding. Most recaptures occurred in consecutive years or in 2 yr intervals, indicating some level of site fidelity. A similar pattern also influenced apparent survival estimates, with annual survival varying between 0.47 and 0.51 when considering transients and residents, and between 0.78 and 0.80 when considering only residents. It was not possible to evaluate population trends based on the 5 yr mark-recapture data, as robust projections would require 18 yr of monitoring with comparable effort. Therefore, understanding the open dynamic of this population requires a long-term monitoring effort, and is critical for understanding the role of Rocas Atoll in the conservation and management of green turtles in the South Atlantic.

KEY WORDS: Mark-recapture · Population modeling · Breeding ground · South Atlantic