Endangered Florida Manatees Will Benefit From Ocklawaha Restoration

 

 


  Rodman Dam and Buckman Lock are barriers to the movement of manatees into the Ocklawaha River system, including Silver Springs.

  The dam and lock are the main causes of manatee deaths in the area.

  The restored Ocklawaha will provide ideal manatee habitat, contributing to the survival of this endangered species.

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After Rodman Dam is removed, the endangered Florida Manatee will once again be allowed to follow its historical migratory pathway up the Ocklawaha River and its tributaries and springs.  The restored Ocklawaha system will provide important habitat for this endangered species.

 

Since l968, Rodman Dam and Buckman Lock have blocked passage of manatees into the upper reaches of the Ocklawaha River and Silver Springs.  The river had been a source of food and shelter for manatees as evidenced by sightings and manatee skeletal remains.  These manatees traveled from the St. Johns River, which is noted for its use by east coast and resident manatees.  The Ocklawaha River connects Silver Springs to other rivers and the ocean. 

 

To restore the Ocklawaha River, Rodman Dam (also known as Kirkpatrick Dam) will be breached and the barge canal and Buckman Lock closed.  Manatees, as well as migratory fish, will again be able to move unhindered into the upper reaches of the river where they feed on native aquatic vegetation and find shelter in the waters of the many springs that line the river.  According to the environmental impact statement, 13 species of fish have been eliminated or drastically reduced from the Ocklawaha basin by Rodman Dam. For example, large schools of shad, mullet and striped bass were commonplace up river at Silver Springs and are now only seen in limited numbers.

 

Rodman Structures Kill Manatees

According to a l997 report by the Florida Bureau of Protected Species Management, “access to the upper Ocklawaha will be granted to manatees only as a result of planned restoration efforts.”  This is because the dam and lock have been a significant source of manatee mortality.  Since l974, they have crushed or drowned at least ten manatees that tried to pass through these water control mechanisms.  Closing gates at the lock crushed three of these manatees, and the other seven were killed at the dam where rushing water pinned them against the rocky debris and spillway structures.  An additional nine manatees were found dead in the area, but the cause of death could not be conclusively determined. 

 

In 1999, Buckman Lock’s gates crushed one of the biggest manatees ever recorded in Florida. At 2,800 pounds, she was so large the state official that tracked her movements named her after the Greek goddess Hera.  Before her death at the Rodman Reservoir, Hera was tracked for almost a decade moving up and down the coast of Florida and over-wintering in Blue Spring State Park on the St. Johns River. 

 

In an effort to prevent more manatee deaths, U.S. Fish and Wildlife Service required the state of Florida close the Buckman Lock until protection devices are installed. The lock was closed February 2000 * NEED TO CHECK DATE *. Installation of an acoustic ray device at the lock and a protection grate at the dam has cost taxpayers $1.2 million. The lock is scheduled to be operational again before the end of 2002.

 

Restoration of the Ocklawaha River will eliminate use of the Buckman Lock and Rodman Dam structures, removing the leading cause of manatee deaths in the area.  Manatees are known to move between Blue Spring State Park and sections of the St. Johns River centered on the barge canal. Removing Rodman Dam and closing Buckman Lock would allow manatees to move freely into the Ocklawaha River, a significant tributary of the St. Johns, without risk of being crushed by dam or lock structures.

 

Springs Habitat Can Be Regained

The waters of Rodman Reservoir covered twenty natural artesian springs when the Ocklawaha was impounded.  After Rodman is drained and the natural flow of the river restored, these springs will again flow freely into the Ocklawaha, providing additional habitat and warm water refuge for manatees.

 

A recent study by the St. Johns River Water Management District indicates that over the last 20 years spring flows in north Florida have declined by twenty percent.  The bad news for manatees is that when decreased flow rates occur simultaneously with higher river levels and cold temperatures, the probability increases that cold river water will intrude on the warmer spring runs where manatees take shelter.  At the current rate of decline in spring flow, Blue Spring State Park may no longer be a reliable winter refuge for manatees in another 20 years.

 

Restoration of springs currently drowned by Rodman Reservoir would provide winter refuge for the cold-sensitive manatee, as well as abundant food, fresh water and shelter.

 

Predictions of future manatee use of the river can best be determined by considering surveys of manatees in the area.  In l997, 104 manatees were counted at nearby Blue Spring State Park, compared to the 18-25 found there in the 1970s.  In addition, groups of 4 to 5 manatees frequently have been sighted trying to enter Buckman Lock, with as many as 28 counted in a single month.

 

Protecting and restoring the diminishing habitat of the endangered Florida Manatee is vital to the survival of the species. The restored Ocklawaha River should provide ideal manatee habitat. According to the U.S. Fish and Wildlife Service, restoration “will have a positive effect on the conservation of the manatee.”

 

References:

Lefebvre, Ph.D., Lynn W., “Possible Significance of the Ocklawaha River to the Florida Manatee,” U.S. Fish and Wildlife Service. *ADD YEAR*

Smith, Kent. The Effects of Restoration of the Ocklawaha River in the Vicinity of the Rodman Basin on Manatees and Manatee Habitat. Bureau of Protected Species Management, Florida Department of Environmental Protection. July 1997.

U.S. Fish and Wildlife Service.  FWS Log No. 96-513C: Biological Opinion.  January 6, 1997.

 

For additional information contact:

            Florida Defenders of the Environment

            4424 NW 13th Street, Suite C-8

            Gainesville, FL 32609-1885

            phone:  (352) 378-8465

            fax:  (352) 377-0869

            email:  fde@fladefenders.org

            web:  http://www.fladefenders.org

 

Updated December 2002.