AB 8:169-177 (2010)  -  doi:10.3354/ab00221

Inferring vertical and horizontal movements of juvenile marine turtles from time-depth recorders

Matthew J. Witt1, Andrew McGowan1, Janice M. Blumenthal1,2, Annette C. Broderick1, Shannon Gore3, Damon Wheatley4, James White4, Brendan J. Godley1,*

1University of Exeter, Centre for Ecology and Conservation, School of Biosciences, Tremough Campus, Penryn, Cornwall TR10 9EZ, UK
2Department of Environment, PO Box 486, Grand Cayman KY1–1106, Cayman Islands
3BVI Conservation and Fisheries Department, Road Town, Tortola, British Virgin Islands
4The Settlement, Anegada, British Virgin Islands
*Corresponding author. Email:

ABSTRACT: Acquiring knowledge of the spatial ecology of many aquatic species, particularly their juvenile life stages, is challenging when they are small in size; this limits the attachment of tracking devices that routinely provide spatially explicit information on larger juveniles and adults. Using depth utilisation data gathered by time-depth recorders, we inferred patterns of habitat utilisation of juvenile hawksbill turtles Eretmochelys imbricata occupying a shallow reef system in the Caribbean. Hawksbill turtles (n = 9, curved carapace length = 42.3 ± 9.7 cm, range = 27.7 to 60.0 cm) demonstrated diel patterns of behaviour, with greater activity and shorter dives during the day (mean duration = 7.5 ± 5.0 min, range = 2.6 to 34.4 min) and longer, less active dives during the night (mean duration = 16.6 ± 12.0 min, range = 2.5 to 61.5 min). A level of fidelity to sites facilitated recaptures (mean minimum straight-line distance from release of TDR-equipped turtles to their subsequent recapture locations = 0.9 ± 0.9 km, range = 0.01 to 2.3 km), but recapture success after 130 h, over a 43 d period, was relatively low: of 19  individuals instrumented, 9 were recaptured. From depth records, i.e. maximum depths achieved, it was clear that some recaptured individuals moved considerably during the monitoring period; 3 individuals moved to deeper waters, with minimum possible straight-line movement distances from their capture sites of 3.7 to 9.2 km. These findings emphasize the likely influence of habitat structure on site fidelity and further highlight that data from traditional capture–mark–recapture studies could lead to an underestimation of home-range size.

KEY WORDS: Habitat utilisation · Spatial ecology · Coral reef · Hawksbill turtle · Eretmochelys imbricata · Telemetry · British Virgin Islands

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Cite this article as: Witt MJ, McGowan A, Blumenthal JM, Broderick AC and others (2010) Inferring vertical and horizontal movements of juvenile marine turtles from time-depth recorders. Aquat Biol 8:169-177

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