Manatee Awareness & Protection Resource

Effects of Boating

Water-Based Recreation

People are attracted to Florida’s coasts due, in part, to an abundance of water-based recreational opportunities (Antonini et al., 2002). Florida is the number one destination for marine recreation in the United States, including boating, with an estimated 22 million participants annually (Leeworthy & Wiley, 2001). With over one million, Florida ranks first in the nation in numbers of registered boats (National Marine Manufacturers Association, 2005). Since 1980, the number of watercraft registered in Florida has increased 120 percent (Bureau of Economic and Business Research, 1981; Florida Fish and Wildlife Conservation Commission, 2006).

Between 1974 and 2001, 1058 manatees were killed in Florida by watercraft. As of 2003, an additional 1184 surviving manatees were scarred from collisions with boats. As the number of registered vessels increases in the state of Florida, so does the number of manatees killed by watercraft. Of particular note is the rate of increase in manatee mortality, which for overall deaths was 5.8% between 1974 and 2000, but for watercraft collisions was 7.2% (U.S. Fish and Wildlife Service, 2003). Questions remain as to what degree the increase in manatee mortality is due to increased boating in Florida, increased manatee populations, or a combination of both.

Whale Key in the Florida Keys, Monroe County

Figure.  Whale Key in the Florida Keys, Monroe County.

Boating Patterns and Activities

Patterns and intensity of boating activities are considered when determining whether manatee protection zones are necessary within an area (68C-22.001 F.A.C.). To characterize boat use, local governments typically rely on counts of registered vessels — readily available from county tax departments—and on information characterizing the size and distribution of area boat facilities, such as marinas, boat ramps, and residential docks. Unfortunately, detailed spatial and temporal descriptions of recreational boat use are frequently unavailable. When such information is available, it likely has been collected using two primary methods: (1) map-based mail surveys and (2) aerial reconnaissance. The spatial boating data mapped on this website were compiled using these two methods.

Mail Surveys of Boaters

In 2001, the Florida Fish and Wildlife Conservation Commission partnered with Florida Sea Grant to develop scientific methods to map boating activities on the water and characterize boaters (Sidman & Flamm, 2001). A map-based mail survey was determined to be an appropriate method to capture both behavioral and spatial aspects of recreational boating. Since then, map-based mail surveys have been conducted for Tampa and Sarasota Bays (Sidman et al., 2005), Greater Charlotte Harbor (Sidman et al., 2005), and Sarasota County (Sidman et al., 2006).

Recipients of the mail survey draw on a map the departure site, travel routes, favorite destinations, and congested areas associated with their last two pleasure boating trips. In addition, they characterize their trips according to vessel type, departure date and time, and duration on the water. They also identify activities they engage in while at particular destinations, and identify and rank reasons for selecting departure sites, travel routes, and favorite destinations. The mapped information on returned surveys is digitized into a geographic information system (GIS)—a computer application used to store, view, and analyze geographical information, especially maps. Descriptive data about boaters including demographic and trip information is linked to the spatial data within the GIS.


Example of a Map-Based Survey Distributed to Boaters.

Figure. Example of a map-based survey distributed to boaters.

Aerial Surveys of Boating Patterns

Aerial surveys to document boating patterns have been implemented for the coastal waters of Brevard, Broward, Charlotte, Lee, and Sarasota counties. Surveys were conducted using fixed wing aircraft flying a standard flight path at altitudes ranging from 500 to 1000 feet (Gorzelany, 1998; Gorzelany, 2000; Gorzelany, 1999b; Gorzelany, 1999a; Gorzelany, 2002b; Gorzelany, 2002a). Multiple flights were conducted in each county and their starting and ending locations were varied. A single observer/videographer used an image-stabilizing, digital, hi-resolution camcorder with date and time imprint to record all vessels in use. The observer provided voice-over audio recording of vessel location and characteristics through a remote microphone attached to the aircraft headset. The start time for individual surveys was alternated between mornings and afternoons to capture daily variations in boating patterns.

Video footage was transferred to a Digital Video Disc (DVD) and, then, each vessel in use was digitized into a GIS. Digital Orthophoto Quarter Quadrangle (DOQQ) images were used to more accurately map vessels within the GIS. Quality control consisted of comparing mapped vessels with the original video footage. GIS spatial data were linked to attribute data, which included vessel type  and length, direction of travel (if under way), and a unique alphanumeric code for each observed vessel. Environmental conditions including weather, wind speed and direction, and Beaufort scale were also recorded.

Snapshot of video footage taken from aerial reconnaissance and resulting GIS data file Snapshot of video footage taken from aerial reconnaissance and resulting GIS data file

Figures. Snapshot of video footage taken from aerial reconnaissance and resulting GIS data file.

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