The spiny water flea’s small size makes it a large problem for Wisconsin lakes. Learn more about how we can protect our waters from this invasive species in this guest blog by Beckie Gaskill, NRF board member.
Close up of a spiny water flea. Photo by Linden Gledhill Via Flickr
What are spiny water flea?
Spiny water flea is an aquatic invasive species that is found in several lakes in the state. Although they are only in a few now, their spread could cause widespread harm to ecosystems.
They are a small, translucent water flea, measuring ¼-½ inch long. That’s about the length of a grain of rice! Their size makes them difficult to spot. However, anglers will notice them clumped onto fishing line, anchor lines and any other piece of equipment that is in water where spiny water flea hang out. These invaders were likely introduced to the Great Lakes through the ballast water* of ships. Now, they’re moving into smaller lakes in states bordering the Great Lakes. Spiny water flea has been found in 24 lakes in Wisconsin alone.
Person fishing on a boat at sunset. Photo by Mike Kuhr
What’s the big deal?
These water fleas are small, but they can wreak havoc on a lake ecosystem. The first problem caused by spiny water fleas is their disruption of the food web. They dine on small zooplankton such as daphnia, which are a large portion of the bottom of the food web in many lakes in Wisconsin. The water flea eat all sorts of small zooplankton, like cladocerans, copepods and rotifers. This puts the spiny water flea in direct competition with larval fish, which also eat zooplankton. Larval fish are the future of these ecosystems, so their survival is crucial for maintaining healthy fish populations.
Spiny water flea not only eat the prey of larval fish, but they themselves are also unsuitable prey for larval fish. This is because of the large spine on their tail. As their name suggests, spiny water flea have a spine which extends down from their abdomen. Their spine makes spiny water flea difficult for larval fish to eat. There is even some evidence that these spines will get stuck in the digestive tracts of fish, effectively starving those fish.
Close up of zooplankton (Daphnia spp.). Photo courtesy of NOAA Great Lakes Environmental Research Laboratory Via Flickr
Protecting our waters from spiny water flea
As an avid angler myself, spiny water flea is a big concern to me. Anything that has the potential to disrupt a food web is a concern to those who target any fish on a regular basis. With fish already facing so many stressors, including habitat loss and climate change, adding this invasive species to the mix is especially concerning. Unlike other invasive species, these are easily missed, other than when they clump up on fishing line or something else that has been in the water for a while.
If I fish in a lake where these are known to be present, I ensure that my gear, equipment and boat are cleaned and dried. I go so far as to cast out the line on each fishing rod that I have used and lay it in my yard to allow it to dry completely. This also means I can inspect the line for spiny water flea. So far, I have been lucky.
Beckie holding up a fish she caught while standing on a boat. Photo courtesy of Beckie Gaskill
What can we do?
As with most invasive species, prevention is the best way to protect our waters from spiny water flea. Once introduced to a system, there is no known way to rid the system of these invaders. Any changes they make to an ecosystem may become permanent.
The Clean Boats Clean Waters Program includes interns and volunteers across the state who staff boat landings. They also talk with anglers and boaters about ways to keep invasive species from moving from one place to another. One of the things that make spiny water flea especially dangerous is that female spiny water flea can reproduce asexually. This means that just one of these little invaders can get into a new lake and create an entirely new population. That is the biggest reason that prevention is key.
Young people fishing on a boat at dusk. Photo courtesy Of Dane County Land & Water Resources Department
One way that spiny water flea may potentially be moved around the state is the same way it got to the Great Lakes – through ballast water. Ballasts, live wells* and any other place where water can collect could potentially move these invasives around. They can also stay viable for several days once removed from the water. The best practice, then, is to completely clean, drain and dry all boats, trailers, gear and equipment after leaving a lake and going to a new lake. A five-day drying period is recommended to help prevent the spread.
Keeping spiny water flea and other invasives out of the 15,000+ lakes in Wisconsin is an important measure to keep lakes healthy for future generations.
Guest Blogger
Beckie Gaskill (she/her)
Outdoor and Environmental Reporter, Content Creator, and NRF Board Member
Beckie writes the Outdoors Section for The Lakeland Times as a freelance journalist. She is an associate director for the Wisconsin Wildlife Federation and is the editor of their Wisconservation newspaper. She is the Vilas County rep for Lumberjack RC&D and is a Master Naturalist. Beckie is involved in a variety of citizen science projects, is a Water Action Volunteers stream monitor, and is a NOAA storm spotter. Beckie has her own podcast and YouTube channel, and is active on social media for a variety of businesses and non-profits. She has also recently launched a Substack entitled “Midwest Conservation.”
NRF’s support for spiny water flea efforts
NRF recognizes the threat that this tiny creature poses to Wisconsin’s lakes, particularly in the northern part of the state. Through the CD Besadny Conservation Fund, NRF has funded the “Stop Spiny” campaign to prevent the spread of this damaging species. The campaign, led by the Douglas County Land and Water Conservation Department, included a series of educational presentations. The presentations describe the biology, origin, and spread of the spiny water flea and promoted actions that can prevent their spread to new waterbodies. Additionally, they organized a multi-media advertising campaign, printed and distributed thousands of promotional cleaning cloths, and provided training for watercraft inspectors.
Person collecting water samples to test for spiny water flea abundance. Photo by by Zach Stewart
Protect Wisconsin when purchasing your fishing license
If you’re an angler like Beckie, keep in mind that the new fishing license year begins on April 1st. When you purchase your fishing license, you can donate to the Cherish Wisconsin Outdoors Fund to help protect Wisconsin’s natural wonders.
The Cherish Fund is a public-private partnership between the Natural Resources Foundation of Wisconsin and the Wisconsin Department of Natural Resources. Founded in 2012, this fund helps create permanent support for the care and management of lands and waters loved by hikers, birders, hunters, and anglers alike.
*Ballast water is water held in the ballast tanks and cargo holds of ships to provide stability
*Live wells are water tanks on fishing boats for bait and caught fish
‘NRF’s support for spiny water flea efforts’ section written by Shelly Torkelson, Director of Communications