Northland jellyfish reappear, this time in Namakan Lake

[Lee Borgersen]

Northland jellyfish reappear, this time in Namakan Lake
Tiny freshwater jellyfish, seldom seen in Northland waters, were spotted in recent days in Namakan Lake along the Ontario
By: John Myers, Duluth News Tribune



  Tiny freshwater jellyfish, seldom seen in Northland waters, were spotted in recent days in Namakan Lake along the Ontario

border.

Thousands of the small jellyfish were spotted Saturday by Steve Geving, a Lake Superior area fisheries

specialist for the Minnesota Department of Natural

Resources who was kayaking on Namakan Lake in Voyageurs National Park with his wife, Glenita.

“We were sitting in our kayaks off North Mitchell Island. You could see 10 or more in some spots, then do a few strokes and see nothing. Some were dime- to nickel-size,” Geving, of Duluth, told the News Tribune. “They were whitish, opaque.”

Gary Montz, a research scientist for the DNR, said biologists have speculated that water temperature and abundance of zooplankton, jellyfish food, may play a role in the jellyfish developing to a noticeable size that floats to the surface.

In 2006, another warm summer, Chad Polecheck of Esko, a former Minnesota conservation officer, told the News Tribune that he saw “thousands and thousands” of the jellyfish while fishing on Little Sturgeon Lake north of Hibbing in late July. At first he thought it was pollen in the water, but he captured

several of them in a jar and watched them “pulse” through the water. Another 2006 report came from Dodo Lake near Duluth.

Those jellyfish were on display for a time at Fisherman’s Corner bait shop outside Duluth.

Geving said they snorkeled Saturday among the whitish, opaque jellyfish for some time.

“Pretty neat little critters,” he noted.

While they have been around for years, most people have never seen a freshwater jellyfish because they spend most of their lives as underwater polyps that live on or near lake bottoms.

Only occasionally, and scientists aren’t sure why, do the polyps develop into dime- to quarter-sized jellyfish that can be seen floating and pulsing near the surface.

Most sightings are in August and September, experts say. The “blooms” last only a few days.

”It’s really exciting for us. We’re trying to get more information on it,” said Mike Ward, Voyageurs superintendent, who said park staff would attempt to find more of the critters.

DNR biologists in past years said there is little information on freshwater jellyfish in Minnesota. They often go unreported for years and then several reports come in at about the same time.

Montz said there have been reports this summer of jellyfish in Crab and Banadad lakes in the Boundary Waters Canoe Area Wilderness, Long Lake near Cotton and Airport Lake in Winona County in southern Minnesota.

“This year seems to be a bumper crop,” Montz said, adding, however, that seeing a jellyfish is still a rarity. “If people are not out at the right time and looking at the water, you could miss a bloom on a lake.”

It’s still safe to go into the water, officials say. While freshwater jellyfish have tiny tentacles to sting and capture zooplankton, they are too small to sting people like their larger saltwater cousins can.

Freshwater jellyfish — Craspedacusta sowerbii — have been in Minnesota lakes for decades. They are naturally occurring now, but they probably are an invasive species, possibly from Europe. So far, however, there’s no sign of any ecological disruption or damage from their presence.

Some scientists have said there could be more jellyfish now as northern lakes get warmer earlier in the year and stay warmer later. Northland lakes on average now have two weeks less ice cover than they did 50 years ago. Some speculate that, as warmer water reaches the polyps attached to the bottom of lakes, more of the polyps mature into jellyfish “blooms.” The jellyfish-stage critters then reproduced asexually and tiny eggs attached to the bottom of the lake and became polyps, restarting the cycle.

Usually, when in the jellyfish form, the creatures are white or green and nearly gelatinous — 99 percent of their bodies consist of water. The jellyfish lacks a head, has no skeleton and contains no organs for respiration or excretion.

Freshwater jellyfish are found throughout the world but were first reported in 1880 in England. They were first reported in the U.S. in 1908, according to the University of Michigan’s Museum of Zoology.