Watercraft related mortality is the major "known" cause of manatee mortality in Florida (25% of all mortality between 1977-2006). Unlike other causes of mortality (e.g. natural, perinatal, and cold stress), watercraft related mortality is amenable to human intervention. This proposal seeks funding to develop technology designed to alert vessel operators to the presence of manatees in sufficient time for them to either reduce speed or take evasive action, thus reducing vessel related manatee mortality. I have partnered with Interphase Technologies (Soquel, CA) to evaluate and modify their commercially available sonar technology to develop such a system. Preliminary field testing of two types of sonar units (Probe® and Sea Scout®) indicates that these sonar units can detect manatees in murky water. The President of the company, Mr. Charles Hicks, suggests that they can be successfully modified to reduce beam spread and increase resolution in order to enhance their manatee detection capabilities. Major advantages of these systems include their availability at moderate cost (<$2000.00) and their similarity to already familiar fish finders. Due to difficulties in obtaining the requisite permits to conduct such testing on free-living manatees in the United States, I propose to conduct the field testing in Mexico, where permits are significantly easier to obtain. Most of the work described in this proposal will be conducted by a graduate student at the NSU Oceanographic Center, and the results of these investigations will comprise this student's master's thesis. Undergraduate students from the Farquhar College of Arts and Sciences will participate in the field testing of the sonar units at the Oceanographic Center using simulated manatee targets fabricated from wood and plastic. The Marine Industries Assocation of South Florida (MIASF) has provided $1600.00 in matching funds to support the field testing of the sonar units in Mexico (Letter of support attached).