Spreading the invasive spiny water flea upsets lake ecosystems

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Donn Branstrator, an invasive zooplankton specialist, holds a spiny water flea on his finger. This species has invaded all of the Great Lakes. Photo: Chris Hagen

By Megan Hopps

Researchers believe that anchors and fishing lines can help spread the invasive spiny water flea, and Great Lakes fishermen may need to follow stricter equipment cleaning regulations.

While spiny water fleas are not harmful to humans, they shift the biodiversity of the Great Lakes ecosystem, said Donn Branstrator, an ecology professor at the University of Minnesota Duluth.

The spiny water flea arrived in Lake Ontario in 1982 and spread to all of the Great Lakes by the late 1980s.

“They came from the Black Sea area and were transported via ballast water from ships,” said John Lindgren, coordinator of the Great Lakes Lake Sturgeon Collaboration, part of the Minnesota Department of Natural Resources’ Fisheries Office.

Branstrator, a specialist in invasive zooplankton, explains what makes the spiny water flea so influential on the aquatic food web.

“It’s a carnivore, which means that it’s feeding on other zooplankton,” Branstrator said. “That’s its big effect in food webs. It reduces the abundance in the diversity of native plankton in lakes, which is used by a variety of fishes that are feeding on the plankton.”

“Oftentimes there are no natural predators, parasites or competitors to keep their population in check,” he said.

The population grows so quickly that it has an environmental impact on the ecosystem, and smaller fish avoid feeding on it due to a long barb-like tail spine that runs down its body, Branstrator said.

“That long tail spine is a protective device so that small fish can’t feed on it,” he said. “They attempt it and spit it out. Big fish can feed on it, but small fish can’t, so it provides a measure of protection during spring and early summer.

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A diagram of the spiny water flea. Photo: Rachel Kraft.

“The bigger fish that do consume them have a big difficulty in passing that spine, so that spine gets hung up in the stomach like a ball and needles,” Branstrator added. “In some of the fish, the spines were penetrating the stomach wall, and the stomachs looked like a pincushion with a bunch of spines sticking out of it. So that’s likely to have some mal-effects of the life of the fish.”

The regulations of cleaning recreational equipment and boats will undergo some serious changes because of the spiny water flea’s effect on the local fish population.

“We think the way they’re getting around from lake to lake is by ensnarement on fishing lines,” Branstrator said. “The females get ensnared on all sorts of recreational equipment. It might be anchor lines as well, or the mud impacted on an anchor.”

A cold winter won’t effect the fleas – in fact, the colder temperatures help initiate their reproductive cycle.

“In the fall, the females can sense a drop in temperature and a decline in food. They produce males, and then mate with their male offspring,” Branstrator said. “So there’s this period of sexual reproduction in September and October, and the end result of that sexual reproduction is an over-wintering cyst or resting egg.”

Spiny water flea eggs can withstand many other environmental stresses.

“You can put them in chlorination for a few days, and they can survive that,” Branstrator said. “You can expose them to salt water or warm temperatures, and they survive that. They’re really durable. They’re believed to be the life stage that helps facilitate dispersal from one location to the next.

“But the eggs of this species are not very resistant to drying at all,” he said.

Branstator’s research of the spiny water flea has helped the DNR Fisheries Office create standards for how recreational boaters and fisherman should clean their equipment to prevent the spread of invasive species to other Minnesota lakes. Fisherman are advised to be careful not to spread these invaders to other lakes to protect the biodiversity of the aquatic ecosystem.

  • martavia

    How did it get introduce ther y did it cone important to talk about now

  • Tom M.

    Jeff and any other biologists,
    I don’t want to fight with anyone, you guys want to do studies, fine. But why do we have to wait to do anything until a peer reviewed study is done? invasive’s increasing the whole time. According studies already done native fish are not getting consistant recruitment because of invasive species effects, starvation, predation etc…. Invasives are getting good recruitment. Stocking Perch at 2 inches makes spiny fleas, alewives, zebra mussels threats a non-issue, thus a better chance to survive and eat said invasives. But the plan is to restore the alewives not native, and restrict recruitment of native fish. Low native predators all invasive’s thrive, the proofs in the lake. Once the carp start smacking around the public, they wont listen to we need more studies, they’ll want action. Do all the studies you want, help us restore the natural ecosystem, take all the credit, I don’t care who gets the credit. Waiting bad for us, good for the carp.

  • Tom M.

    Well Jeff, I suppose we could wait until they get here, then see. Or we can spend a couple million bucks feeding spiny fleas to them to create another study. They are filter feeders correct? They will suck them in, will they spit them out? This article says spiny fleas a problem, we have predators for them,I’d rather they were converted to native fish than invasive species. It’s logical to think Asian Carp will eat them. Restoring native fish increases the natural “biotic-resistance” that has been studied, we know how to get rid of too many native fish, which right now have an unlimited food supply from out of town. We are far away from too many native fish, very close to too many Asian Carp.

  • Jeff

    Tom,
    Overlap in range doesn’t necessitate consumption. A peer-reviewed article might have an example of carp consuming spiny waterflea , but I am not seeing one. But few intensive studies exist in the ponto-caspian.

    And if we are talking bighead carp which are primarily zooplanktivorous, then you might have spiny waterflea consumption. However, that may only be nearshore which is where you overlap with yellow perch for resources, and still no offshore consumption of the waterflea.

    So it might not be as clear cut.

  • Tom M.

    Dear Jeff, I asked Chapman, and they’re from the same place as Asian Carp. Since they are just another piece of protien in the water like larval fish there’s no reason for them not to. Only small fish have trouble, 50 pound carp, no problem.

  • Capt. Bill

    I have been fishing the great lake for over 60 years and I really like yellow perch and small mouth bass. But I have never met a fish that I didn’t like as long as the stretched my line.

  • JGML

    Screw salmon, and screw alewife. Why the hell are we now managing the Great Lakes for non-native species (salmon and alewife) instead of native (perch, walleye, lake trout, deepwater sculpin) species? I’ll tell you why, because WDNR and Michigan DNR, and the feds sold out to special interest salmon fisherman, and sold out to the short term economic interests instead of managing our lakes and fisheries for long term sustainability. All this with virtually no public input despite that it is the public that pays the wages of these “mismanagers” and pays now and in the long run for dumb fisheries management practices. Morons – why would you reduce salmon stocking — their main prey, the alewife is on the ropes and we have been trying to get rid of the alewife since the 1950′s. Until alewife are gone, lake trout won’t come back because alewife eat young of year lake trout and prohibit natural reproduction (recruitment), and alewife can negatively affect many other native fishes.
    Good luck you moronic managers, I’m sure managing the lakes for species (pacific salmonids) that are boom-bust anyway (for reasons we still do not understand) even in their natural habitats will work out great for bringing consistent year to year tourism to the Great Lakes.

  • Jeff

    While nearshore perch may be growing faster with Bythotrephes as a diet item, their impact on other offshore species through differential retention is actually pretty high. As they are kept in fish stomachs due to the long caudal spine, they cannot consume other food, and they grow less. This isn’t the case for all preyfish, but when you consider the impact that less preyfish could have on salmon, having less Bythotrephes would be preferred.

    There is no evidence that spiny waterflea will be a food for carp.

  • Tom M.

    The Perch in Green Bay are growing faster eating spiny fleas according to one study they were packed with them. another study said they could be controlled with abundant predators. Also I believe you’ll find spiny fleas will provide food for Asian Carp,(I asked the expert actually) as will zebra and Quagga mussel larvae (veligers) documented. Now Perch will eat all 4 of these invaders including juvenile Asian carp. I would much rather have a healthy Perch population than to surrender to a flea and do nothing.