Calibration of winter manatee counts at power plants. Final report.

Abstract

Currently used aerial-survey methods in the study of manatee populations and distributions at the Tampa Bay Power Plants, do not yield accurate populations estimates. Problems in the survey methods arise principally from bias that can skew the count-based estimates. Only by developing some understanding of such biases, and subsequently applying correction factors, can scientist and managers develop accurate perspectives regarding manatee abundance and trends. In response to this, a project was undertaken at the same location as previous studies (the Tampa Electric Company (TECO) Big Bend power plant discharge canal at Apollo Beach) for three years in an attempt to refine techniques and develop appropriately rigorous calibration indices. The ultimate goal, once the survey and analytical techniques are completely established, is to apply this approach to developing correction factors (Indices) for all major winter manatee aggregation areas where visibility (and hence counting) is impaired. In this study a variety of methods are employed to develop a correction factor that will help obtain a more accurate count of manatees. These methods include uniquely marking individual manatees, flying tandem aerial surveys and conducting flights in the morning and afternoon of the same day. A total of 15 animals were counted and studied during this project. Results of the activities are described.