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Synoptic Survey Conditions for Winter 2008

Due to warmer than average weather, the Florida Fish and Wildlife Conservation Commission will not conduct the annual statewide manatee synoptic survey this winter.

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The Florida Fish and Wildlife Conservation Commission (FWC) will not conduct the annual statewide manatee synoptic survey this winter, due to much warmer than average weather.   The FWC conducts synoptic surveys to meet the state’s requirement for an annual count of manatees in Florida waters, weather permitting. The goal of the survey is to achieve the highest minimum count by surveying areas where researchers expect to see the most manatees. Researchers need specific weather conditions to successfully conduct these surveys.  The state developed these requirements because surveys conducted in less than favorable conditions produce low counts as many animals may be missed. Unfortunately, conditions this winter never met the state’s minimum requirements.

The FWC attempts to conduct annual manatee synoptic surveys to provide researchers with a snapshot of manatee distribution around the state of Florida at the time of the survey. This survey is a minimum count and cannot be used to estimate population size or assess long-term population trends.

Researchers conduct this interagency manatee survey during the coldest months of the year, usually between January and early March. When temperatures are low, manatees move to warm-water sites, such as natural springs, thermal discharges from power and industrial plants, and deep canals.  During synoptic surveys, teams of observers fly over warm-water sites to count the animals gathering at these sites.

Ideally, synoptic surveys take place during cool weather, following a prolonged period of cold weather with low winds and bright sunshine. The FWC will only conduct the survey if conditions meet all of the following requirements simultaneously:

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 temperatures below 68° F near most major manatee aggregation sites.
   
3. No winds forecast above 15 knots in the entire survey area on survey days.
   
4. No sky conditions forecast as “mostly cloudy” or “rainy” in the entire survey area on survey days.
   

The FWC is currently working towards improving methods to produce synoptic surveys that are more statistically accurate and less dependant on very cold weather conditions.

Weather conditions this winter
This year the weather was too warm to meet the above criteria.  According to the National Weather Service, La Nina conditions in Florida lead to winter temperatures well above average.  Weather in early January came close to meeting the criteria. When temperatures did not drop as low as predicted, the agency decided to wait for stronger cold fronts in February.  However, February temperatures averaged higher than normal with few cold nights, and many warm days with highs in the 80s.  

These warmer air temperatures produced warmer than average water temperatures statewide for this time of year. For example, in January and February Tampa Bay water temperatures averaged 63° F, Fort Myers averaged 68° F, Naples averaged 78° F, and Brevard County near Cape Canaveral averaged 73° F.  Water temperatures in the southeastern part of the state were even warmer.   Tampa Bay’s average water temperatures were about 12 or more degrees higher than the temperatures during the record manatee count in 2001 and about five degrees warmer than temperatures during last year’s synoptic survey.  In years with marginal weather conditions, counts are usually much lower than in years with prolonged cold fronts. When water temperatures are higher, manatees are less likely to seek refuge at warm-water sites, making them more difficult to find and count.

Other manatee aerial surveys
Recent information from manatee aerial surveys conducted in several parts of the state to assess manatee distribution show that manatees did not aggregate at warm-water sites as much as in previous years.  For example, bi-monthly counts in Broward County show steep declines in the numbers of manatees present at warm-water sites from January to February. The decline in numbers indicates manatees were dispersing.  On the west coast, Mote Marine Laboratory counted less than 10 animals at the Florida Power and Light (FPL) Fort Myers power plant and in the Orange River during their February flight of Lee County. The average five-year synoptic count for this same area is 237. Following a February cold front, the FWC counted 175 manatees at the Tampa Electric Big Bend power plant in Tampa Bay. The average five-year synoptic count for this location is 268.  Aerial surveys from other warm-water sites also resulted in much lower than average counts for these months. Low counts at these sites indicate that the statewide manatee count would be significantly lower than those conducted in years with favorable conditions. For example, surveys conducted late in the season under less than ideal conditions in 1999 and 2002, resulted in low counts.

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