Population density estimation of southern stingrays Dasyatis americana on a Caribbean atoll using distance sampling

ABSTRACT

1. The southern stingray Dasyatis americana is a benthic mesopredator found in varying densities throughout Caribbean shallow reef systems, yet despite its increasing inclusion in fisheries, many aspects of its population ecology are still unknown.
2. Belt transects and distance sampling techniques were used to estimate seasonal abundance of an unexploited, isolated population of southern stingrays in lagoon and forereef habitats at Glovers Reef Atoll, Belize.
3. Southern stingrays were the most abundant elasmobranch in both shallow lagoon margin (< 5 m) and shallow forereef (< 15 m) habitats in all sampling seasons. Lagoon density showed no seasonal variation and was estimated at 245 (95% CI 226–265) individuals per km².
4. Forereef sampling indicated lower densities compared with the lagoon habitat, as well as seasonality with a significantly lower stingray density in November of 25 (16–37) compared with either of the April surveys of 100 (71–141) and 78 (53–116). Total population size for all lagoon habitat was estimated as ~8400 stingrays (7700–9100, 4%CV).
5. This is the first study known to utilize distance sampling techniques on benthic elasmobranchs. Absolute estimates of population density are crucial in wildlife management and will be an important tool in tracking community and trophic dynamics in affected systems of declining top predators, particularly in species devoid of natural identifying marks.

Copyright © 2012 John Wiley & Sons, Ltd.