Residence and movement patterns of cownose rays Rhinoptera bonasus within a south-west Florida estuary

Abstract

Between July 2003 and November 2004, 21 cownose rays Rhinoptera bonasus were tagged and tracked within Pine Island Sound estuary, Florida, using passive acoustic telemetry. Residence time of individuals ranged between 1 and 102 days. No relationship was detected between ray activity and tidal stage or time of day. Minimum convex polygons (MCP) and kernel utilization distributions (KUD) were calculated over several time frames to demonstrate the extent of an animal's home range and core areas of use. Total MCPs ranged between 0.81 and 71.78 km2 (mean = 22.01 km2), with daily MCPs as large as 25.8 km2. Total 95% KUDs ranged between 0.18 and 62.44 km2 (mean = 22.63 km2), while total 50% KUDs were smaller, ranging from 0.09 to 9.68 km2 (mean = 3.33 km2). Both MCP and KUD areas exhibited a positive relationship with residence time and R. bonasus size. As mobile, pelagic swimmers capable of traversing large distances, these data show that cownose rays travel extensively throughout this estuary, yet may remain within very small areas for extended periods. © 2007 The Authors.