THUNDER BAY — A Lakehead University researcher hopes to learn more about the spiny waterflea's potential impact on the health of the walleye population in the lakes of Quetico Provincial Park.
It's a key part of the work that Michael Rennie, an associate professor in biology, will conduct over the next three years with the help of a $75,000 grant from the Quetico Foundation.
The project will probe how the spiny waterflea and climate change are affecting the early growth rates and mercury loads of fish.
According to Ontario's Invading Species Awareness Program, the spiny waterflea poses the greatest threat to the biodiversity and structure of native zooplankton communities on the Canadian Shield since acid rain.
Its main diet is zooplankton, the food supply for small fish and the young of several species of sport fish including walleye, bass and yellow perch.
Native to Eurasia, the spiny waterflea was introduced to the Great Lakes in ballast water from ocean-going ships.
It has spread to more than 100 inland lakes in Ontario including watersheds bordering Minnesota.
"We've sort of speculated that they might have an impact on fish because they tend to bring down zooplankton concentration," Rennie told Tbnewswatch.
He said evidence came in a recent University of Minnesota study that found they were affecting the growth of fish in the first year of their lives.
Working closely with the Ministry of Natural Resources and the Quetico Park biologist, Rennie's team will study archived "aging structures" from fish that were sampled in previous studies.
"When you go to age a fish, you take a scale or a fin, and it kind of looks like a tree ring, where you get regions of really dense growth when they're not growing very fast, but they spread out when they're growing very quickly," he explained.
Researchers will use the aging structures to try to back-calculate the sizes of young fish, to see if there are changes in lakes where the spiny waterflea has arrived.
The Invading Species Awareness Program's website indicates this can cause an average 30 to 40 per cent decline in native populations of zooplankton.
The spiny waterflea can spread easily between waterbodies, travelling on angling equipment, in bait buckets and in live wells.
Rennie said "Every year they go to look for them, they find a few more. They move around. Whether it's entirely due to human vectors is maybe up for discussion. They bunch up on fishing gear, downriggers and stuff like that, so it's pretty easy to see how they move from one lake to another."
His research project, however, will focus on Quetico lakes where the waterflea has been established for awhile, as opposed to lakes which have not had time to respond to their arrival.
"The reason they're a big worry," Rennie said, is that if fish can't get big enough in their first year for lack of food, "then they're going to experience over-winter mortality, and that's going to be reflected in core population sizes."
A second part of the study will look at the impact of the spiny waterflea on lake herring, which eat zooplankton over their entire lifetime.
Rennie said one of the reasons they are a focus is that when walleye mature, they feed on other fish instead of zooplankton.
"Particularly in lakes where you find the biggest walleye, they tend to be in lakes that have lake herring," he said. "They've got this great big fatty food source swimming around that they wouldn't have otherwise."
The results of the study will be used in the development of adaptive management plans for Quetico.