Zebra mussel veligers (larvae) have been found in the Whitefish Chain, said Dan Swanson, aquatic invasive species (AIS) specialist for the Minnesota Department of Natural Resources (DNR).
That’s important information, Swanson said, because it indicates that there’s an adult breeding population of zebra mussels in the lake.
Zebra mussels were only recently discovered on the Whitefish Chain, in mid-July. Veligers are the mussels’ free-floating microscopic young, invisible to the naked eye.
Swanson and the DNR knew that adult mussels were in two basins of the chain, Cross and Lower Hay lakes, but couldn’t be sure they were breeding. In order for the mussels to breed, Swanson said, a male and female need to be located in relatively close proximity, probably within five feet of each other.
Swanson and other DNR staff members took plankton samples not long after the discovery of the zebra mussels. Taking the samples involves using a fine net that’s systematically dropped into the water and lifted back up.
The net gathers a relatively small sample, and it’s a testing method used on many area lakes.
Out of the five samples Swanson and his team took from Lower Hay Lake, one sample had a single veliger and another sample held two veligers.
Pelican Lake, Swanson said, has a pretty comparable population to the Whitefish Chain. In August 2012, the DNR collected five samples from Pelican and none held veligers.
But, in samples taken this year from Pelican Lake, there were eight veligers in one sample and six in another.
By comparison, the same test was administered on Gull Lake in August 2012 at four sites. In those samples, the number of veligers ranged from 832 in one sample on the low end to 2,154 in one sample.
Gull Lake was again tested in June 2013. In those four samples, the least number of veligers found was 1,300 in one sample, and the sample with the most veligers had a whopping 16,760.
Swanson said the presence of veligers in the Whitefish Chain gives the DNR an idea of what the population of zebra mussels there looks like.
“I would call this a clue,” Swanson said. “It doesn’t tell us a lot of things we’d like to know but it does give you an idea. It’s not just one isolated zebra mussel that just happened to land somewhere.”