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Tippecanoe River Endangered Mussels

Questions and Answers


1. Why is the FWS working with NIPSCO to manage the water flow downstream from Oakdale Dam?
We are working with NIPSCO to manage water flow to avoid harming or killing federally endangered and threatened mussels in the Tippecanoe River downstream from Oakdale Dam. 


2. Which species of federally protected mussels are affected?
The Service has records of the sheepnose, clubshell, fanshell, rabbitsfoot, snuffbox and rayed bean, all listed as endangered or threatened under the federal Endangered Species Act, in the Tippecanoe River (snuff box and rayed bean may no longer be present in the lower portion of the river). Other state-listed mussels also occur here. 


3. Why is it important to protect these mussels?
The Tippecanoe River supports one of the most significant and diverse freshwater mussel populations in the United States.  Under the Endangered Species Act, it is the responsibility of the U.S. Fish and Wildlife Service to make sure endangered mussels – even individual ones – are not harmed or killed.  Protecting these mussels protects other aquatic life – fish, for example - and makes the Tippecanoe River a very special place for those who live along it or use it for recreation.  There are many dense mussel assemblages with high diversity (many different species) downstream from Oakdale Dam, including several areas that support state- and federally endangered species.


4. What makes the Tippecanoe River such a good place for mussels? Why does it need to be managed?
The Tippecanoe River has all of the natural features that make it one of the country’s best waterways for freshwater mussels.  The river’s size, the make-up of the stream bed and the gradient are all perfect for mussels.  The river’s flow keeps mud and other sediment from smothering mussels.  The groundwater feeding into the river promotes ideal conditions, such as water temperature. The Tippecanoe has provided excellent habitat for mussels and other aquatic life for millennia. 


5. Why should people care about mussels?
Mussels are monitors of aquatic health: 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.

Mussels depend on the same waterways that people value, whether as a water source, favorite fishing spot, recreation area, or for their scenic qualities.  Maintaining a healthy environment for mussels helps ensure these areas are available to people as well.


6. How does the Endangered Species Act protect endangered mussels?
The Endangered Species Act prohibits take (killing or harming) of endangered or threatened species, unless a permit is issued and steps taken to avoid and minimize take to the maximum extent practical.  The Act also requires other federal agencies to conserve listed species when they authorize, fund or undertake activities that might have impacts to listed species.  In this case, the Federal Energy Regulatory Commission (FERC) has issued a license to NIPSCO to operate a hydroelectric dam on the Tippecanoe River.  FERC is required to consult with the Service to ensure that their action (licensing of the dam) does not cause take of endangered mussels. That means that actions taken under the FERC license (such as regulating the flow from Oakdale Dam) cannot result in killing endangered mussels downstream. 


7. Don’t droughts and mussel exposures happen naturally anyway?
Droughts, and exposure of mussel beds, do happen naturally, but the addition of dams on the Tippecanoe River has changed how droughts manifest themselves downstream.  The frequency and severity of drought impacts on mussels has likely intensified.   Flow through Oakdale Dam if not properly managed can expose mussel assemblages that never or rarely get exposed under natural conditions. Exposed mussels can survive temporarily by burrowing to find water, but in droughts with hot or very cold weather, they can die quickly.


8. What does the FERC license require for water releases?  What is meant by “run of the river?”
FERC’s license requires NIPSCO to maintain “run of river” (i.e., they must release water equivalent to an approximate cumulative inputs) at Lakes Freeman and Shaffer.  However, there currently is not a biologically valid way to measure the volume of water entering the two lakes from numerous creeks, groundwater, etc.  The current requirement is to maintain water level in the lakes within an identified range with the assumption that if lake level is constant, then input must approximately equal output.  The problem with this metric is that it is a regulatory definition under FERC and not meaningful in biological terms.  It does not account for evaporation, leakage, etc., which is significant, especially during times of drought and high temperatures.  NIPSCO and the Service have now determined a biologically-valid measure of run-of-the-river, which is included as part of NIPSCO and the Service’s Abnormal Low Flow (ALF) Plan to protect federally listed mussels in the Tippecanoe River.


9. How can NIPSCO avoid violating the Endangered Species Act?
As an interim measure, while an ALF Plan was under development by the Service, maintaining a minimum 500 cubic feet per second flow, measured at the Delphi gauge, was determined to be a conservative approach to avoid killing endangered mussels and thus avoid violation of the Endangered Species Act.  The Delphi gauge was selected because it is operated by a third party scientific agency (the U.S. Geological Survey), and it is located approximately in the middle of the section of river where most federally listed mussel species have been found.  The Service and NIPSCO have now completed an ALF Plan and are ready, based on review at FERC to implement a science-based plan to protect mussels downstream of Oakdale.  NIPSCO has immediately implemented one component of that plan (measuring compliance at the USGS Oakdale Gauge rather than the USGS Delphi Gauge) which may result in more stability to Lake Freeman water levels.  FERC would evaluate any changes in NIPSCO’s license required to implement the ALF procedures. The Service could then issue a letter assuring that take (harm or killing) of endangered and threatened mussels is avoided under the agreed upon process.  NIPSCO and the Service expect to begin implementation of the ALF Plan by the end of the summer of 2014. 


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