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A tropical trough: Warm water and lots of food leads to winter growth in rare freshwater mussels
Midwest Region, February 21, 2018
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The arrow indicates the size at which the mussel was moved the warm system. All of the shell past this mark is new growth. Left to right are Black Sandshell, Washboard and Salamander Mussels.
The arrow indicates the size at which the mussel was moved the warm system. All of the shell past this mark is new growth. Left to right are Black Sandshell, Washboard and Salamander Mussels. - Photo Credit: Megan Bradley USFWS

Each autumn native juvenile mussels are transported to Genoa from our trailer and cage sites and are held in stasis in the mussel building on station until spring arrives and the river water begins to warm. This year a new idea emerged; warm up their system water. Using a heater, a pump to circulate water and algae feeders a recirculating system was built to maintain the mussel pan system at nearly 70°F and keep the growing (hopefully) juveniles fed.

Of course, all of the mussels didn’t go into this warm system. Instead, they were split between the cold and warmed systems to make sure that if the system failed then all of our mussels weren’t in one basket. There were five species produced this year that we divided; Black Sandshell, Washboard, Salamander Mussel, Federally Endangered Higgins’ Eye, and Fragile Papershell. In order to find out whether the new system is effective for creating a good environment for growth we are measuring groups of each species of mussel that remained in the cold system as well as in the warm system each month. 

After one month the mussels in the cold system remained the same size while those in the warm system grew. Our visual observations told us the same thing (See pictures below) because the new growth is great enough that we see it on most of our animals as they crawl around in their pans but it’s still valuable to be able to evaluate growth statistically. We hope that this means that many more mussels will be large enough to release each year, making it possible for Genoa National Fish Hatchery to release many more mussels over time, working towards our goals of conserving these rare species.


Contact Info: Megan Bradley, (608) 689-2605, megan_bradley@fws.gov
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