The importance of passive integrated transponder (PIT) tags for measuring life-history traits of sea turtles. (December 2019)

• Record Type: Journal Article
• Authors: Omeyer, Lucy C.M.; Casale, Paolo; Fuller, Wayne J.; Godley, Brendan J.; Holmes, Kelle E.; Snape, Robin T.E.; Broderick, Annette C.
• Is Part Of: Biological conservation. Volume 240(2019)
• Publication Date: 2019-12
• Subjects: Caretta caretta -- Chelonia mydas -- Flipper tag -- Green turtle -- Loggerhead turtle -- Tag loss; Conservation of natural resources -- Periodicals; Nature conservation -- Periodicals; Ecology -- Periodicals; Environment -- Periodicals; Environmental Pollution -- Periodicals; Electronic journals; 333.9516
• DOI: 10.1016/j.biocon.2019.108248
• Languages: English
• ISSNs: 0006-3207

Abstract

Highlights: Importance of PIT tags for gaining accurate estimates of life-history traits and population parameters for sea turtles. Excluding PIT tags led to underestimation of reproductive periodicity, reproductive longevity and annual survival. Female abundance and recruitment to the nesting population were overestimated in the absence of PIT tags. Flipper tag loss underestimated by a factor of two without the use of PIT tags at Alagadi Beach. Abstract: Capture-mark-recapture studies rely on the identification of individuals through time, using markers or tags, which are assumed to be retained. This assumption, however, may be violated, having implications for population models. In sea turtles, individual identification is typically based on external flipper tags, which can be combined with internal passive integrated transponder (PIT) tags. Despite the extensive use of flipper tags, few studies have modelled tag loss using continuous functions. Using a 26-year dataset for sympatrically nesting green ( Chelonia mydas ) and loggerhead ( Caretta caretta ) turtles, this study aims to assess how PIT tag use increases the accuracy of estimates of life-history traits. The addition of PIT tags improved female identification: between 2000 and 2017, 53% of green turtles and 29% of loggerhead turtles were identified from PIT tags alone. We found flipper and PIT tag losses were best described by decreasing logistic curves with lower asymptotes. Excluding PIT tags from our dataset led to underestimation of flipper tag loss, reproductive periodicity, reproductive longevity and annual survival, and overestimation of female abundance and recruitment for both species. This shows the importance of PIT tags in improving the accuracy of estimates of life-history traits. Thus, estimates where tag loss has not been corrected for should be interpreted with caution and could bias IUCN Red List assessments. As such, long-term population monitoring programmes should aim to estimate tag loss and assess the impact of loss on life-history estimates, to provide robust estimates without which population models and stock assessments cannot be derived accurately.