Spiny waterfleas discovered in Burntside Lake

The Minnesota Department of Natural Resources (DNR) confirmed that spiny waterfleas were discovered in Burntside Lake near Ely last week. They were discovered by an angler when he observed them collecting on fishing lines in the water.

“Spiny waterfleas can spread when boats, fishing or bait harvesting gear become contaminated with egg-laden females or when water from the infested lakes and rivers is transported,” said Rich Rezanka, DNR invasive species specialist. “Although the waterfleas can die between fishing trips, they might be carrying resting eggs that can begin a new infestation.”

Spiny waterfleas are currently found in Lake Superior, Mille Lacs Lake, Fish Lake, and the U.S.-Canadian border waters such as Lake of the Woods, Rainy Lake and Namakan Lake as well as lakes on the Gunflint Trail north of Grand Marias.

Spiny waterfleas can collect in masses, entangling on fishing lines, downrigger cables, and anchor lines. The masses can resemble gelatin or cotton batting with tiny black spots, which are the creatures’ eyes or eggs. Individual animals are difficult to distinguish without magnification because they are only one-fourth to five-eighths inch long.

Spiny waterfleas are zooplankton - microscopic animals like the Daphnia in lakes. They have a long tail spine with up to three pairs of barbs. As a predator, they eat other zooplankton, often becoming abundant in late summer and fall.

Anglers are often the first to discover spiny waterfleas because they become attached to fishing gear. The waterfleas can be a nuisance to anglers, collecting in gobs on fishing lines and downrigging cables.

Spiny waterfleas can change the species and numbers of zooplankton, which may harm those lake ecosystems. Native zooplankton are an important food source for small fish.

However, spiny waterfleas are not good forage and may actually compete with fish for desirable native zooplankton.

In response to this new infestation, the DNR will:

• Designate Burntside as infested with spiny waterflea prohibiting the transport of water and requiring draining of livewells, bait containers, and bilges.
• Update the signs at water accesses on Burntside to indicate the presence of the waterfleas.
• Increase watercraft inspections and enforcement efforts at the water accesses
• Provide area businesses with information on spiny waterfleas.

Before leaving the water access, boaters and anglers should:

• Remove aquatic plants and animals, including gelatinous or cotton-batting-like material from fishing lines, downrigger cables, anchor ropes or waterfowl decoy cords.
• Drain water from livewells, bait containers, and bilges by removing the drain plugs. (Those who want to keep live bait must replace lake or river water with tap or spring water.)

Boaters and anglers should also:

• Dispose of unwanted live bait, fish parts, and worms in the trash.
• Wash/spray the watercraft and gear with hot high pressure or hot tap water for several minutes before transporting to another water.
• Dry the watercraft and gear thoroughly for at least 24 hours and preferably five days before transporting to other waters.

Experts believe spiny waterfleas originally arrived in the U.S. from Eurasia in the ballast water of cargo ships. They were first found in Lake Superior in 1987.