Invasive Species in Leech Lake

This is the second of four educational reports the Stewards on Leech Lake will be preparing this year.

In the Cottager Survey conducted last fall, people requested more information about invasive species. The Team from Fleming College discovered that we have, what is believed to be, a low level introduction of spiny water fleas in Leech Lake.

The Eurasian spiny water flea came to North America in the ballasts of ships from Russia about 30 years ago. First infestation was in the lower Great Lakes where they are now impacting recreational salmon fishing because they are present in numbers that can tangle fishing equipment. Dr. Norman Yan from York University first found them in Leech Lake in 1995. Fifty lakes in the Muskoka region are known to be infested. The worst case appears to be Harp Lake near Huntsville.

Transmission from lake to lake occurs on fishing line or nets but can also be transmitted in live wells, bait cans, transom wells or engine cooling water.

Research continues and it is still not known what the eventual impact of this creature will be in lakes such as ours. The worst case scenario would be that these creatures prey on smaller zoo plankton reducing their population. A spiny water flea consumes 3 times as many small creatures as native predator species, up to 20 small aquatic animals per day. These small animals are the preferred diet of juvenile fish so there could be an impact on fish populations in the lake. Juvenile fish apparently cannot ingest spiny water fleas so their presence does not provide another source of food. Most larger fish will eat spiny water fleas but cannot successfully digest the one inch long spiny tails. They have been known to kill large fish in other lakes in Muskoka.

In a healthy lake system, small aquatic creatures are capable of filtering all of the water in a lake every 10 days. Spiny water fleas do not filter water. A decline in the population of small aquatic life in the lake would inevitably result in water that is less clear, and potentially more susceptible to algae blooms. Spiny water fleas prey on herbivore zoo plankton which consume vegetation and help to keep algae levels under control. There is no known method of eradication.

So what can we do?

There are several things we can all do to protect Leech Lake from further infestation of these predators.

1. Learn to recognize spiny water fleas. Please see the photograph below.

Spiny Water Fleas (1/3” to 5/8” body)

2. Inspect fishing lines, nets etc and remove any gelatinous material. A photograph of spiny water fleas on fishing line is included below.

Spiny Water Fleas on fishing line.

3. Drain water from bilges, watercraft, engines, live wells or bait containers before leaving a body of water.

4. Never release water, bait, fish or animals into the lake from another body of water. Empty bait buckets on land before leaving another body of water.

5. Wash boats, watercraft, canoes and kayaks with hot water and allow to dry for 5 to 7 days before launching into Leech Lake. Spray with high pressure water if possible. The coin operated car wash on Taylor Rd. is an excellent spot to do all of this. Bleach does not kill spiny water fleas.

We will be posting a sign at the boat launch to inform people launching boats about the issue and steps that should be taken to prevent further infestation.