SANDFIELD—Ministry of Natural Resources (MNR) representatives outlined its Lake Manitou walleye stocking plans to hopefully increase populations of the fish at the annual general meeting of the Lake Manitou and Area Association (LMAA), last week.
“We are very fortunate tonight to have Denis Gendron (MNR management biologist, Sudbury District) and Kim Tremblay (regional fisheries specialist) here tonight, to present the walleye stocking plan that our fishery committee has been meeting and working with them on for the last 10 months,” said Mike Costigan, LMAA president.
The MNR representatives provided an outline of Lake Manitou, noting for instance clear lakes do not provide ideal walleye habitat and that Manitou is the largest lake within a lake Island in the world.
“Lake Manitou is one of the bigger lakes in the Sudbury District,” said Mr. Gendron. It has a mean depth of 14.6 metres and a maximum depth of 49 metres.
Ms. Tremblay explained Lake Manitou is a highly valued natural lake trout lake. Lake trout and walleye co-exist, generally inhabiting different habitats (one above thermocline/one below). “Walleye are also a valued sportfish species in Manitou and in the zone wide plan for (fisheries management zone 10),” she said. “Our current understanding is that anglers have rarely, if ever, caught walleye in Manitou before 1990. Their origins are unknown, but they may have been introduced or re-introduced in the 1990s. Regardless, walleye have been established for at least 35 years.”
“Lake Manitou is an important source for walleye eggs for the MNR’s fish culture and stocking program,” said Mr. Gendron. The MNR has been collecting walleye eggs for stocking programs since 2005, and the ministry collects between 2-7 million walleye eggs each year from the lake. “These eggs support MNR walleye stocking across the Northeast region, education programs and community hatcheries. Each mature female walleye can produce over 300,000 eggs. In Manitou, this equates to an average of approximately 15-16 females used for fish culture operations.”
In a history of Lake Manitou fisheries assessments, they have included fall walleye index netting (FWIN) and broad scale monitoring (BsM) surveys of the lake in 2011, 2016 and 2022, explained Ms. Tremblay.
“Mike (Costigan) and group met with us several times to look at increasing the number of walleye being stocked in Lake Manitou, due to declining populations,” said Mr. Gendron.
“The fish culture program has capacity to grow up to 4,000 walleye yearlings (80-120 grams, kept in the hatchery for one full year), and stocked in the spring,” said Mr. Gendron. “This larger size fish can be fin clipped and are expected to have higher survival rates. Measurable results could take close to 10 years.”
Success can be monitored through broadscale monitoring scheduled in 2028 and potentially again in 2033. “Hopefully, we will see good results and after five years have an idea of the results and can adjust the plan if needed,” said Mr. Gendron.
The meeting was told the stocking plan for Lake Manitou includes, over 10 years, annual spring yearling stocking with a target of 2,500 walleye (each year) can be redirected from within the Sudbury District plans in 2025. MNR will work towards the stocking of up to 4,000 yearling walleye for the next five years. Stocking spring yearlings annually will be the target. The spring yearlings are the largest size available and provides the best chance of survival, considering the complex fish community. Fin clipped fish provide opportunities to better understand stocking survival.
A five-year checkpoint in 2030 will be conducted to evaluate the plan and provide adaptive management based on: angler information on fin clipped fish and annual egg collection trends, a 2028 broadscale monitoring fisheries assessment results and provincial fish culture and stocking program capacity and demands. A revised plan for 2030-2035 will be established, but the goal will be to continue stocking walleye during that time frame.
Ms. Tremblay said, “Normally, we look at ways to increase fish populations without stocking, but this is a special interest project (with the Blue Jay Creek Fish Culture Station in Sandfield) we are trying this experimental stocking here.”
“We will try stocking to solve the issue (of declining walleye populations),” said Mr. Gendron, noting there can be many factors involved.
One of the predators of walleye is bass because they compete for the same food sources, the meeting was told. Ms. Tremblay said when bass and walleye are competing for food, bass will be the winner.
Ms. Tremblay outlined the Lake Manitou stocking plan objectives. “Lake Manitou is a unique and complex fishery. The proposed experimental stocking efforts have the following objectives: replace potential and perceived losses from egg collection to ensure future egg collection can continue; combined with 2024 changes to FMZ 10 recreational fishing regulations (walleye >18 inches to be released), there is potential to reestablish the population or to maintain a viable walleye fishery; and determine success of stocking larger size classes of walleye.”
The MNR will continue evaluating alternative egg collection options, reevaluate walleye egg requirements with the potential to reduce egg targets for the next few years. Monitoring will include 2028 broadscale monitoring, angler survey if clipped fish caught and a review of lake trout stocking objectives.
In looking at the history of Lake Manitou fisheries assessment, Ms. Tremblay explained fall walleye index netting (FWIN) took place in 2000, while broad-scale monitoring surveys were conducted in 2011, 2016 and 2022.
For Lake Manitou, the catch per unit effort (kilogram per net), the walleye biomass (kilogram/hectare) has declined over time while the catch per unit effort for Lake Manitou walleye has also declined below the average for the zone, with one fish having been caught in the nets during BsM in 2016 and next to no walleye caught in 2022,” said Mr. Gendron.
“It looks like in 2022 there were no walleye left (through BsM),” said one LMAA member.
“There were lower numbers but this is the case in a lot of other lakes in the province,” said Ms. Tremblay. “Manitou is not alone in this story.”
Ms. Tremblay explained the age structure for walleye in Lake Manitou used to have multiple year classes (ranging from 4-16 years old). In 2011, in the category of four to 16 years old, the numbers provided a pretty good range in the broadscale monitoring, but five years later there were no young fish. In 2016, one 16-year-old walleye was captured. No walleye were sampled in 2022, even though the number of nets set in walleye habitat were increased. “Declining catches of walleye have also been observed during MNR’s egg collection,” she said.
“Walleye do not have a good spawning class every year,” said Mr. Gendron.
The meeting was told there were changes in the fish community from 2011-2022, with an increasing number of smallmouth bass, which compete with both walleye and lake trout.
The MNR representatives outlined several factors to the decline of the walleye fishery on Lake Manitou, including invasive species (proximity to the Great Lakes is a risk factor e.g. spiny waterflea, zebra mussels); shifts in fish community with limited amount of energy in a system and competition for resources; smallmouth bass numbers are increasing; harvest (this is unknown, but considering walleye are a desirable species, it has potential to be a factor); and climate change.
“I commend all of you, (MNR) and the (LMAA) fishery committee, for this plan,” said one u member. “I’m hoping in the next few years we will have a good walleye class.”
