Managers at the U.
S. Fish and Wildlife Service Crystal River National Wildlife Refuge (CRNWR) desire to update their management intention regarding the operation of select springs including Three Sisters Springs. They wish to refine existing parameters used to predict the presence of federally threatened Trichechus manatus latirostris (Florida manatee) in the springs and thereby improve their manatee management options. The U.
S. Geological Survey Sirenia Project has been tracking manatees in the CRNWR area since 2006 with floating Global Positioning System (GPS) satellite-monitored telemetry tags. Analyzing movements of these tagged manatees will provide valuable insight into their habitat use patterns.
A total of 136 GPS telemetry bouts were available for this project,representing 730009 locations generated from 40 manatees tagged in the Gulf of Mexico north of Tampa, Florida. Dates from October through March were included to correspond to the times that cold ambient temperatures were expected, and thus requiring a need for manatee thermoregulation and a physiologic need for warm water. Water level (tide) and water temperatures were obtained for the study from Salt River,Crystal River mouth, Bagley Cove, or Kings Bay mouth,and Magnolia Spring. Polygons were drawn to subdivide the manatee locations into areas around the most-used springs (Three Sisters/Idiots Delight, House/Hunter/Jurassic, or Magnolia and King),Kings Bay, Crystal/Salt Rivers and the Gulf of Mexico.
Manatees were found in the Crystal or Salt Rivers or in the Gulf of Mexico when ambient temperatures were warmer (>20 °C), and while they were found in or near the springs (particularly Three Sisters Springs) at colder ambient water temperatures. There was a trend of manatees entering springs early in the morning and leaving in the afternoon. There was a strong association of manatee movements in and out of the Three Sisters/Idiots Delight polygon with tide cycles: manatees were more likely to enter the Three Sisters/Idiots Delight polygon on an incoming tide,and leave the polygon on an outgoing tide. Both movement directions were associated with midtide. Future analysis will incorporate human activity and a finer spatial scale, including movements between Three Sisters Springs and Idiots Delight and nearby canals.
Source: usgs.gov