Tuesday April 29, 2003
by Sheryl Loucks, staff reporter
A new initiative to rid Haliburton Forest's lakes of rock bass was presented to the Haliburton Highlands Outdoors Association during its annual spring meeting.
David Brown, a biologist with the Ontario Federation of Anglers and Hunters, made a detailed presentation about the destruction that rock bass are wreaking on the lake trout's feeder prey, which hurts the trout population. Brown's data comes from research over the past two decades both locally and within provincial universities. Brown says in the 1980s there were 11 species of prey fish in Clear Lake but by l996 the number had dropped to five after the arrival of rock bass.
Brown says OFAH is starting to do its own analysis in order to assist the Ministry of Natural Resources find solutions to fish and game problems. In this case, OFAH asked anglers to collect the heads of trout from MacDonald and Clear Lakes and submit them.
OFAH's team has analyzed pieces of calcium carbonate from the fish heads. These chunks show the researchers rings like those in a tree which help them to determine the age of the fish and the amount of growth the fish experience each year.
Brown says they found a 25 per cent decline in the growth rates of the adult population of trout since the introduction of rock bass in Clear Lake, and a 23 percent decrease in MacDonald has translated into a 42 percent reduction in the length and weight from the 1980s to 1996.
Brown says there is a lot of noise being made about over-harvesting of trout but he argues rock bass are having a bigger impact. He said their research shows that in these lakes there have not been temperature changes to affect growth rates.
He says anglers are not as aware of the problem rock bass pose to trout because as the trout have less prey fish to feed on they become more vulnerable to anglers - in other words there have been great years for fisherman but lousy ones for trout.
Brown said the rock bass are gorging on small prey fish after the ice melt cleaning them out of feeder streams, and in general getting to them before they can properly breed or the trout can get at them.
Since rock bass are a shallow water fish, Brown said, many anglers thought they wouldn't have an impact on the deep water trout. He says the research shows that the biomass, or number of fish in a given lake, is not changing but the type of fish found there is.
OFAH puts a higher value on trout and considers the rock bass to be a cancer. Brown says they now have approval from the MNR to launch an invasive species program and a campaign to try and eradicate rock bass from Haliburton Forest.
The two themes are to teach anglers to check boats and equipment carefully so they are not transferring-invasive species from lake to lake and to not dump bait buckets-in lakes. They also want to stress to anglers that the transfer of fish from one lake to another is illegal.
Brown says that for the removal campaign they have secured funding from the Ontario Living Legacy Trust. They are going to use a high tech electrofishing boat to selectively capture rock bass in MacDonald and Clear Lakes. The removal program is starting this spring with a marker study that will tell OFAH how many rock bass there are.
Early this summer, Brown says they are planning to hold a rock bass fishing tournament as well. In the fall, the plan is to harvest the two- to three-year-olds near t he shore and continue with assessment work.
"Iím not sure how well this is going to work. But if we can get 10 more years of production out of the trout and then have to go back every ten years to clean out the Rock Bass then it's worth it," says Brown.
Brown says initiatives such as a walleye study in Kawartha Lakes and a habitat mapping project may also provide, other useful information. Several ideas, grinding them up for feed for trout. Brown said he would look into those ideas but expected there would be significant red tape from various ministries.