Comparing sampling effort and errors in abundance estimates between short and protracted nesting seasons for sea turtles

Authored by Andrea U Whiting, Milani Chaloupka, Colin J Limpus

Date Published: 2013

DOI: 10.1016/j.jembe.2013.09.016

Sponsors: Charles Darwin University

Platforms: R

Model Documentation: Other Narrative

Model Code URLs: Model code not found

Abstract

Sea turtles have iteroparous reproduction, migrating periodically from foraging habitat to nesting grounds where they generally lay several clutches at regular intervals throughout a nesting season. The total length of the nesting season depends ultimately on environmental conditions that are conducive to the production of viable hatchlings, and varies from 3 to 4 months to year-round nesting. As with many migratory marine species, the ease of monitoring marine turtles on their nesting beaches opposed to on their foraging grounds, has resulted in a focus of research on breeding females for population studies and provides a useful albeit limited population index. To explore the precision of monitoring regimes to sample nesting turtle populations, we developed theoretical models for 3 1/2-month and 9-month nesting populations. We used individual-based models for tagged animals and parametric and non-parametric models to estimate annual nest abundance for track count data. These simulation models show that seasonality substantially influenced both the length and temporal position of optimal sampling regimes, showing a five to sevenfold greater effort in monitoring required for longer nesting seasons in order to encounter between 83 and 90\% of the annual population. The implications for trend detection and inter-annual and inter-species variations are discussed. (c) 2013 Elsevier B.V. All rights reserved.

Tags

Temperature Caretta-caretta Western-australia Marine turtles Loggerhead turtles Chelonia-mydas Internesting intervals Reproductive output Flatback turtles Green turtles