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Manatee Synoptic Surveys

The synoptic surveys are winter aerial surveys that cover all of the manatees' wintering habitats in Florida.

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 The word “synoptic” means presenting a general view of the whole. The current manatee synoptic survey is a simultaneous count of manatees over a broad area. The Florida Fish and Wildlife Conservation Commission (FWC) uses these surveys to obtain a general count of manatees statewide. The FWC coordinates an interagency team that conducts the synoptic surveys from one to three times each year (weather permitting). The synoptic surveys are conducted in winter and cover all of the known wintering habitats of manatees in Florida. The survey is conducted to meet Florida state statute 370.12 (4), which requires an annual, impartial, scientific benchmark census of the manatee population. From 1991 through 2007, the counts have been conducted 24 times.

These statewide, interagency surveys are currently conducted during the coldest weather of the year (January through March) when manatees move to warm-water sites, such as natural springs, thermal discharges from power and industrial plants, and deep canals. The ideal conditions for the current synoptic survey are cool weather, following a prolonged period of cold weather (usually following multiple cold fronts), low winds, and bright sunshine. Weather conditions and manatee behavior during the survey have a large effect on the synoptic counts. For that reason, the counts are used as indicators of relative abundance within a year and are not suitable for assessing long-term population trends. Counts can vary depending on whether it is warm or cold, sunny or cloudy, calm or windy. Manatees are more easily counted a few days after a cold front when it is slightly warmer, clear, and windless. A warming trend with sunny, windless conditions following cold weather increases the likelihood that manatees will be resting at the water's surface, where observers can easily spot them.

Although there is no single formula for predicting the best days to conduct the current  synoptic survey, FWC scientists use a list of minimum criteria to help predict the most appropriate day to conduct a survey.

Minimum Criteria for Conducting the Current Synoptic Survey

1. Air temperatures forecast to be less than or equal to 49° F near most major manatee aggregation sites* on at least 3 of 5 days prior to the survey
2. Water temperature below 68° F near most major manatee aggregation sites
3. On the survey days, no winds forecasted above 15 knots in the entire survey area
4. On survey days, no sky conditions forecasted as “mostly cloudy” or “rainy” in the entire survey area

Surveys will only be scheduled if all of these minimum requirements are met simultaneously.

There are unfavorable weather conditions that cause poor short-term water clarity:

1. Absence of sunny and clear skies
2. Heavy rain in previous 48 hours
3. High winds in previous 48 hours (above 20 knots)

Forecasts that include such conditions may be sufficient to postpone a survey.

Sometimes weather conditions meet the criteria in some parts of the survey area but not in others — especially while a cold front is slowly passing through — or a cold front may fail to reach the southern part of the state — causing warm weather in some survey areas. Although conditions may be excellent for surveying in some areas, they may not be appropriate statewide, and the survey may be delayed until the weather is more appropriate in all parts of the state (from the Panhandle to the Florida Keys).

Constraints:

• Weather forecasts are now widely available on TV, radio, newspapers, and the Internet, but those forecasts are usually highly variable and inconsistent for events 4–5 days in advance. Surveys are not scheduled based on the single lowest temperature forecast available or the single best forecasted weather conditions. Instead, researchers use a representative forecast that is typical of the range of forecasts available.
• Many weather forecasts are available 4–5 days in advance, but most do not give the projected wind speeds more than 2–3 days in advance. No water temperature forecasts are available. The common forecasts do not address many of the factors needed to make the proper decision (for example, wind speed and water temperature).
• Often cold fronts fail to drop to the south (over Florida) or will be less severe than forecasted.

Timing a synoptic survey is not an easy task, given the unpredictable nature of Florida weather and the logistics involved in organizing a survey of this magnitude on short notice. Synoptic surveys are scheduled about 5 to 7 days in advance, which gives staff members time to notify the proper authorities such as power plants, the Federal Aviation Administration (FAA), local sheriff and police departments, and airport towers. Because the surveys are organized many days in advance, sometimes weather conditions are not perfect on the day of the survey. However, with each season, staff members become better at predicting the best time to count manatees, and the higher counts in recent years are, in part, reflective of improved knowledge.

On Florida's east coast, counts using current synoptic methods are made at sites from Jacksonville to the Florida Keys. On the west coast, counts are made at sites from the Wakulla River to the Everglades. During the statewide manatee synoptic survey made in February 2007, 18 observers searched for manatees in 20 areas on both coasts. Observers were staff members from 14 state, federal, and county agencies, as well as research laboratories, non-governmental organizations, and universities. Seventeen observers in aircraft located and recorded manatee sightings in the state's waters. Two ground teams counted manatees at power plants and waterways not visible from aircraft.

Improvements to the Synoptic Survey

The current synoptic survey method provides a minimum count of manatees, but it does not provide a population estimate.  In addition, not all Florida waters are included in the current survey. Survey flights concentrate on areas where manatees are known to gather in large groups during cold weather, but do not cover other areas like the Florida Panhandle or deeper, colder waters like the center of Tampa Bay. Therefore, an unknown number of manatees in these areas are not counted. Biologists at the FWC’s Fish and Wildlife Research Institute are improving the synoptic survey by developing new survey methods which may: 1.) potentially include all possible manatee habitats in Florida; and,  2.) allow biologists to estimate the number of animals that are not seen, hence, not counted during aerial surveys.  Other improvements may include: 1.) having two observers per plane searching the survey area to help determine how well observers detect manatees; 2.) repeatedly flying multiple passes over the survey areas to increase the chance of spotting manatees; and, 3.) flying the surveys during times when manatees are not concentrated at winter aggregation sites, which will eases the problem of trying to accurately count large numbers of manatees in a single area (e.g. power plant discharge canal).

*The manatee warm-water aggregation sites are listed in the United States Fish and Wildlife Service Florida Manatee Recovery Plan: U.S. Fish and Wildlife Service 2001 Florida Manatee Recovery Plan, (Trichechus manatus latirostris), Third Revision. U.S. Fish and Wildlife Service. Atlanta, Georgia. 144 pp. + appendices.

Synoptic aerial surveys of manatees, east and west coasts of Florida, 1991 to 2007

Year	Date	East	West	Total
1991	January 23–24	687	580	1,267
1991	February 17–18	828	650	1,478
1992	January 17–18	904	940	1,844
1995	January 21–22	669	787	1,456
1995	February 06–07	917	906	1,823
1996	January 09–10	1,223	1,054	2,277
1996	February 18–19	1,452	1,178	2,630
1997	January 19–20	906	1,335	2,241
1997	February 13	797	918	1,715
1998	January 29–30	1,110	908	2,018
1999	January 06	842	1,023	1,865
1999	February 23	900	1,123	2,023
1999	March 06	960	1,400	2,360
2000	January 16–17	634	1,012	1,646
2000	January 26–27	1,138	1,085	2,223
2001	January 05–06	1,559	1,741	3,300
2002	March 01	864	894	1,758
2003	January 09	1703	1140	2,843
2003	January 21–22	1813	1314	3,127
2003	January 26–28	1,705	1,311	3,016
2004	February 20	1,198	1,307	2,505
2005	January 26	1,594	1,549	3,143
2006	February 13-17	1,639	1,474	3,113
2007	January 30–February 1	1,412	1,405	2,817