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Three Sisters Springs Manatee Information

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Three Sisters Springs documents and important information.

Guidelines for
Opening and Closing the Three Sisters Springs Unit
of the Crystal River National Wildlife Refuge
to Visitor In-water Access,
Manatee Season November 15, 2016 to March 31, 2017

Environmental and biological factors are evaluated daily and considered when determining whether to open or close Three Sisters Springs to in-water access for visitors. 

There are three main environmental predictors of manatee presence inside Three Sisters Springs (the Springs): tide, air temperature, and water temperature in the Gulf of Mexico. Generally at lower tides, manatees are absent or in low numbers in the Springs and on an out-going tide leave the Springs through the narrow spring run, often into the sanctuaries at Idiots Delight I and/or II. Conversely, manatees tend to return to the Springs on an in-coming tide and rest or nurse until the tide begins to turn again. While many manatees follow these patterns, some manatees deviate from the norm. 

Ambient air temperature, Gulf water temperature, and tides are key factors in predicting manatee presence in the Springs. Generally, when morning temperatures are below 45ºF (7ºC) and the Gulf water temperature is below 68ºF (20ºC), manatees seek thermal refuge in freshwater springs, including Three Sisters Springs, on an incoming or high tide. When the Gulf water temperature measured at a USGS gauge near Shell Island (mouth of Crystal River) is below 60ºF (15ºC), large numbers of manatees are likely to aggregate in the Springs. Conversely, a measured water temperature above 60ºF in combination with falling tides and rising air temperature conditions, generally cause manatees to leave the Springs to forage. When these environmental factors are considered in combination, the U. S. Fish and Wildlife Service can begin to predict the presence or absence of manatees in the Springs. 

A flow-chart was designed to use data from the previous evening and forecasted conditions at sunrise to to assist in the determination of whether to open or close the Springs the following morning. The measured variables are used to inform management on the likelihood that manatees will be present in Three Sisters Springs and the need to close the Springs to prevent disturbance. The predictors were based on data obtained during the winter of 2014-15. The flow chart was tested for 104 days from December 19, 2015, to March 31, 2016. The flowchart accurately predicted the Springs’ open/closed status 83 times (79.8%) and incorrectly predicted the status only 10 times (9.6%). There were 5 times (4.8%) when the prediction was off by 1 to 2 hours after sunrise and 6 times (5.8%) when the accuracy of the prediction was undetermined due to lack of data. Natural factors that made the prediction inaccurate included wind speed, wind direction, magnitude of tide, and actual high and low tide times (e.g., a strong west wind would keep the tides high, causing manatees to stay in the springs longer). 

Biological factors considered when determining open or closed status include observed manatee distribution and specific behaviors. Under a specific suite of environmental conditions that includes a strong or prolonged cold front, manatee numbers in the Springs can be in the hundreds. The Springs may be closed to visitor access especially if the observed distribution of manatees includes the narrow spring run and areas outside of the closed lobes. If temperatures begin to warm before an outgoing tide, this same large aggregation of manatees may begin to leave the Springs through the spring run. Under such conditions, these biological factors may prevent the opening of the Springs. Manatee behavior must also be considered when evaluating spring opening/closing. Observations of mating herds, high numbers of nursing mother/calf pairs, or injured/stressed animals may also warrant the closure of or prevent the opening of Three Sisters Springs to in-water visitors. 
As a final consideration, reduced water clarity in the Springs may limit staff ability to fully evaluate the numbers of manatees resting in the Springs, particularly at sunrise when the angle of the light is low. When the water clarity is rated a 3 or 4, low to no visibility (see attached Biological Guidelines flowchart), the Springs may remain closed for manatee and human safety. Visitors may disturb or injure resting manatees by accidentally colliding with them if they can’t see them. Refuge staff may need to keep the Springs closed until they can conduct an accurate assessment of the Springs’ manatee abundance and distribution. Common causes of reduced water clarity include low light, glare, wind, and turbidity associated with manatee activity in the Springs. 
All of these environmental and biological factors are considered in determining the open or closed status of Three Sisters Springs to visitor in-water access (see attached flowcharts). 


 Biological Guidelines Used to Determine the Open or Closed Status of the Three Sisters Springs Unit (Springs) of CRNWR to Visitor In-water Access, November 15, 2016 to March 31, 2017 


Environmental Guidelines Used to Predict the Open or Closed Status of the Three Sisters Springs Unit (Springs) of CRNWR to Visitor In-water Access, Manatee Season
November 15, 2016 to March 31, 2017


News Release - Three Sisters Springs Winter Management 2016-2017


 FAQs Winter Protocol for Closing-Opening Three Sisters Springs



U.S. Fish and Wildlife Service Offers Refined Alternative for Access to Three Sisters Springs

Seeks 14-day Public Review as 2015-16 Manatee Season Nears

November 10, 2015

A refined proposal to provide access to Three Sisters Springs at Crystal River National Wildlife Refuge is being released today and it includes three noteworthy changes from an August draft proposal released by the U.S. Fish and Wildlife Service.

After reviewing more than 2,600 comments from citizens, local leaders and the business community, the Service released a revised draft Environmental Assessment for public comment that it believes better matches up its need to protect manatees with local tourism and business interests and its partnership with the City of Crystal River.

The refined alternative, referred to as Modified Guided In-Water Manatee Viewing or Alternative D, would reduce the maximum number of visitors allowed in the water at any one time from 29 to 13, including required guides. It proposes changes to how people will access the water and limits access points. And finally, it proposes to shift responsibility for issuing permits to tour operators and dive shops from the Service to the City of Crystal River. This is possible since the City is a co-owner/manager of the property. A Memorandum of Understanding would be put in place that would clearly outline the process and how access would be managed. The Service will continue to provide training to permit holders and manage permitted access for commercial film and photography professionals.

If Alternative D is selected, the Refuge would immediately implement all components except for the lottery selection processes for both snorkeling, and photography and commercial filming in the Springs. Those processes will be utilized for the season beginning November 2016. If this alternative is implemented during the current manatee season (November 2015 – April 2016), snorkelers and photographers will be provided access on a first-come, first-served basis. When the lottery selection processes are in place, the Refuge and the City of Crystal River will widely announce the availability.

The Service seeks public review of this draft Environmental Assessment, which can be found at, and at Comments must be submitted by November 23, 2015. The Service anticipates making a final decision in December, 2015.
Comments may be e-mailed to


Please note that comments, including personal information, will become available to the public. You may request at the top of your comments that we withhold this information from public review; however, we cannot guarantee that we will be able to do so.

Click Here for the Full Press Release

 Draft Environmental Assessment, Manatee Wildlife Viewing on Crystal River NWR Three Sisters Springs, Citrus County, Florida 



•  Three Sisters Springs second Environmental Assessment News Conference audio file. 



Learn more about Human/Manatee interactions in these two monitoring studies conducted at Three Sisters Springs between December 2014 and April 2015.

The first study was conducted in December 2014 to January 2015
Manatees, People, and Three Sisters Springs, final 28 page report.
Appendices I and II and III.
Appendix IV Charts.
Appendix V Low tide.
Appendices VI and VII and VIII.

View the three-part second study through this slide presentation.
Results of the 2015 Manatee and Human Interactions Observational Studies, Three Sisters Springs, Conducted by USFWS Biology Interns and Volunteers.


Last Updated: Sep 20, 2016
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