Newsroom Midwest Region

News Release
July 12, 2012

Georgia Parham 812-334-4261 x 1203
612-247-5456 (cell)

Drought, Heat Take Toll on Tippecanoe River’s Endangered Wildlife

The low water level in the Tippecanoe River in Indiana has killed mussels, including this endangered fanshell. Photo is by Brant Fisher, Indiana Dept. of Natural Resources. 

The U.S. Fish and Wildlife Service is taking steps to ensure the survival of several federally endangered species of freshwater mussels in the Tippecanoe River that have been affected by the summer’s high temperatures and low rainfall. 

On July 5, 2012, the Service asked Northern Indiana Public Service Company to maintain a minimum flow from Oakdale Dam on Lake Freeman into the Tippecanoe River to alleviate low water conditions in the river that exposed mussel beds and caused the stranding and death of large numbers of mussels, including federally endangered species.

“The reality is, there is less water available for people and for wildlife.  This drought is causing water levels to drop throughout the state, and it is now being felt in places like the Tippecanoe River, which supports some of the most diverse mussel populations in the country,” said Scott Pruitt, supervisor of the Service’s Bloomington, Indiana, field office.  “The Service’s goal is to maintain the survival of mussels, some of which are in danger of extinction, as well as preserve as much as possible the recreational and other uses of the lakes and the Tippecanoe River itself.”

The Endangered Species Act prohibits take – killing or harming – federally threatened or endangered species unless a permit is granted and steps are taken to avoid and minimize take.  There are five federally endangered species in the portion of the Tippecanoe River below Oakdale Dam.  They include the clubshell, fanshell, rayed been, sheepnose and snuffbox.  The rabbitsfoot, a candidate for federal listing is also found here, along with several state-listed mussel species.

Pruitt said the Service is working with NIPSCO and the Indiana Department of Natural Resources to respond to the low water events that have twice exposed large numbers of mussels in the Tippecanoe River in the past two weeks, killing some endangered mussels.  Based on the best available information, a minimum release of 200 cubic feet per second of water from Oakdale Dam into the Tippecanoe River is needed to prevent additional mortality of endangered mussels.  NIPSCO is maintaining that minimal release while exploring other options, including pursuing a permit for incidental take of endangered mussels.

“NIPSCO is the expert on manipulating the water levels in the two impoundments on the Tippecanoe River,” said Pruitt. “The Service’s role here is not to direct how water management is done, but to ensure that the minimum flow enters the Tippecanoe River below Oakdale Dam.  We’re fortunate that at this point, water levels at the lakes have not fallen below normal operating stages.”

Pruitt said mussels are sometimes stranded during normal summertime conditions, but this year’s exposures of mussel beds in the Tippecanoe River are unprecedented.  Mussel populations are slow to recover from such events, which are especially detrimental to endangered species, whose numbers are already critically low. 

Water levels in the lower Tippecanoe River are at historic lows.  The flow is almost 200 cfs below the previously measured low, which occurred during the drought of 1988, and is more than 1,000 cfs below average for this time of year. 

Around the state, the drought is having significant impacts on agricultural crops, waterways and impoundments.  According to data from the National Weather Service (, water levels at Morse Reservoir near Indianapolis dropped almost 2 feet between July 1 and July 12.  In southern Indiana, Patoka Reservoir is more than 3 feet below normal summer pool level.

Freshwater mussels are among the country’s most imperiled species and play a key role in maintaining healthy ecosystems.  The presence of diverse and reproducing populations of mussels indicates a healthy aquatic system which means good fishing, good water quality for waterfowl and other wildlife species, as well as insurance that our water is safe. When mussel populations are at risk, it indicates problems for other fish and wildlife species, and people too.

Mussels perform important ecological functions.  They are natural filters, and by feeding on algae, plankton, and silts, they help purify the aquatic system. Mussels are also an important food source for many species of wildlife including otters, raccoon, muskrat, herons, egrets, and some fish.
For more information on endangered species and freshwater mussels, visit