Zebra mussels in Kosciusko County lakes

Monday, August 17

Zebra mussels (freshwater bivalves that have a distinctly triangular shape) are common in Kosciusko County lakes… but not all of them! In May-August 2019, the Lilly Center research team installed PVC multi-tiered samplers (you can see what they looked like in the pictures below) onto piers across 14 major lakes in Kosciusko County, 12 of which have been infested with zebra mussels for multiple years and two of which have yet to be invaded.

Key takeaways from the zebra mussel study:

  • Zebra mussel spawning is triggered by warm water, a fact evidenced by high colonization numbers in July.
  • The story of zebra mussels in our lakes is complex. The amount of summer spawning and colonization varies between our lakes and across them from area to area. Right now, zebra mussels seem to be a lot more prevalent in some lakes than others.
  • Careful recreation is still super important! Two of our major lakes – and maybe more of our smaller ones – are still uninfested!

Like many other bivalves, zebra mussels are filter feeders. They eat by sucking in water, filtering out all the particles, and spitting out what they do not want (along with the water)… but they are picky! They avoid blue-green algae cells.

Also, zebra mussels will attach to anything: Steel, wood, plastic and rocks are all places they are found frequently in Kosciusko County. These mussels do not just collect a few a time; they prefer to colonize, and will quickly clog pipes and amass on the propellers and hulls of boats. That is one reason why it is important to carefully clean equipment used in a lake: it helps prevent zebra mussels from spreading to new lakes!

For more reading, visit the USGS and this helpful page from the state of Massachusetts.