EDITORS NOTE: You can hear the podcast I did with Eric on the subject by clicking on the link here.
THE EARLY DAYS OF STOCKING
The Manitoba government has a long history of fish stocking, dating back more than a century. Since 1917, the province has stocked desirable species in Manitoba lakes. Early stocking efforts were often driven by the social palate for new or popular species, and many were experimental, requiring little planning. As angler behaviour and motivations in our multi-use fisheries became more complex, so did our interest in evaluating the rationale and results of publicly funded stocking programs.
Today, fisheries management agencies continue to stock fish as novel recreational fisheries for the public to enjoy (e.g., tiger trout in a small pothole lake) or as a supplement to high-pressure fisheries (e.g., walleye stocking in popular cottage lakes). These days, decisions on whether a given lake should be stocked with trout are made after an in-depth assessment of the history of the lake, fisheries surveys, angler use, habitat, and overwintering potential, among other deciding factors.
Illegal stocking
Even with regular provincial stocking of seven salmonid species and walleye across Manitoba, some individuals are illegally introducing new species into public waters. Sometimes referred to as ‘bucket biologists’, these individuals perpetrate illegal introductions of live organisms, posing a significant risk to our valuable fisheries.
Unfortunately, this has become increasingly common across North America, where some individuals feel motivated to modify a fishery to suit their own interests. Understanding the motivations of illegal stocking is not always easy, but the consequences can be damaging to the resource we all love and share.
Illegal introductions in Manitoba
Illegal introductions of fish species from the Centrarchid family (i.e., smallmouth, largemouth, crappie, and bluegill) are on the rise in Manitoba. Research tells us that centrarchids are already pushing northwards due to climate change, creating suitable conditions in previously unsuitable latitudes, and illegal stockings accelerate this phenomenon. Centrarchids are very hardy and versatile, able to adapt to a wide range of ecological and environmental conditions.
It is difficult to predict what effects these introductions have on individual lakes and rivers, but any time we add a new predator to an ecosystem, it poses some risk to its inhabitants. Notably, when they have a competitive advantage in their interactions with other predators or prey.
Eastern Region
In the eastern region of Manitoba, six possible illegal stockings have been confirmed since 2021. For example, Hunt Lake has been a stocked trout lake since 1955, and as of 2023, has produced 247 master angler trout (brook, brown, and rainbows 20+ inches long), and the lake is a popular attraction for the area. In 2023, reports were confirmed that largemouth bass were illegally stocked into Hunt Lake. As a result, future trout stocking plans for this lake are on hold until the situation is properly assessed, and a management action plan is made.
This issue is not limited to Hunt Lake, we have also confirmed reports of crappie being introduced into lakes within Nopiming Provincial Park, as well as new smallmouth populations in backcountry lakes not connected to known smallmouth bass waters.
Western Region
The Goose Lakes in Roblin are some of the most productive rainbow and brown trout waters in Manitoba. In fact, in 2010, the town of Roblin hosted the National Fly-Fishing Championship, where competitors fished trout in both Goose Lakes. These lakes are unique in that they grow trophy trout consistently, all within the limits of a small town with lodging and restaurants, providing a local attraction and economic benefits. Despite their small size, the Goose Lakes boast an incredible 1,273 master angler records, with confirmed catches of rainbows up to 28.5”, and browns up to 25.5”. However, in recent years, the number of master angler submissions in these lakes appears to be declining.
Around 2018, fisheries staff received reports of illegal stockings into the Goose Lakes. A 2022 fisheries survey confirmed this report, finding smallmouth bass and walleye were well established, with both adults and juveniles being encountered. In 2023, trout stocking was discontinued until management plans are determined. Though any trout recovery plan, even in small waters such as these, would be expensive and may take years to see results. So, for the time being, Manitoba has lost two of its most productive stocked trout waters.
Northern Region
One of the most concerning regions in which we are seeing illegal stocking efforts is in Manitoba’s north. The pristine lakes and rivers of Manitoba’s northern region support incredible trophy fishing destinations for walleye, pike, lake trout and more, in addition to important Indigenous subsistence and commercial fisheries.
Many anglers have heard of Athapapuskow Lake south of Flin Flon, which boasts a destination drive-to fishery for giant lake trout, pike, walleye and burbot. In recent years, anglers have reported catching smallmouth bass in Athapapuskow in increasing numbers. Despite a misguided decision by the province to stock 81 adult smallmouth into the lake in 1940/41, bass were not captured in that lake until recent history, possibly indicating a second effort to establish bass through unauthorized introduction.
The extensive movement of smallmouth bass in Manitoba, both by historical government efforts and contemporary illegal stockings, has led to Manitoba having the northernmost distribution of smallmouth bass in North America (Mid Lake, 30 kilometres south of Thompson). The next closest populations outside of Manitoba are just north of Williams Lake, British Columbia, where they are officially considered an invasive species. The addition of smallmouth in the north will present a risk to existing fisheries. We also do not know how well they will even perform in these climatic extremes – is catching many slow growing medium-sized smallmouth worth putting our trophy lake trout, pike and walleye at risk?
Biology of invasion
To put the risk of illegal stocking in perspective, it is important to understand what happens when we introduce a new predator to a lake. In every lake, there is a finite amount of nutrients and energy available that support that lake’s biomass (the total weight of aquatic life in the lake). Within that biomass, we must account for every level of the food web (i.e., algae, aquatic plants, zooplankton, aquatic insects, baitfish, predators). So, if that biomass is a pie and every species has its slice, then any new predator must carve out its own slice, and because the total amount of food available to predators remains the same, the increase in abundance of the newcomer comes at a cost to somebody else.
The first few generations of newly introduced predators in a lake will typically grow fast and often attract the attention of anglers who observe the sudden appearance of a novel trophy fishery. There are biological reasons for this – the ecosystem is not yet adapted to the newcomer and so there is lots of food available to relatively few fish and they grow fast. As time goes by, density and competition increase, sometimes leading to a stunted population, and anglers lose interest.
This issue is compounded if anglers do not develop a taste for eating these fish, as is often the case with largemouth and smallmouth bass, due to the legacy of protective management and their elevated status within the fishing community. Smallmouth bass can taste delicious, and it is highly suggested that anglers consider harvesting them as eating bass will relieve pressure off our other sportfish and will likely promote healthier growth and more balanced size structure for bass populations.
Management options
Once a species has been illegally introduced, fisheries managers must re-evaluate how that fishery is managed. Culling sounds like a possible option, however, it is often ineffective. Unless you can remove most individuals from the waterbody, it will only delay the problem. For example, one study conducted by the New York Department of Natural Resources attempted an intensive seven-year removal program of adult, juvenile, and young-of-year smallmouth bass from a 271-hectare lake where bass were not native. In all, 53,947 smallmouth bass of all sizes were culled over seven years using electroshocking. Despite successfully reducing the overall biomass of smallmouth, the result of this massive effort was an overall increase in the abundance of juveniles.
One might ask, why not drain the lake, or use a chemical like rotenone to wipe out problem species where they pop up? While draining or chemical treatment are often the only way to completely eradicate an unwanted fish species, this typically only works in small waterbodies and does not specifically target the unwanted species. It will kill much of the aquatic life in that system and will take years for that community to recover. Clearly, with the scale of illegal stocking that is being observed in Manitoba, this is not a practical all-around option.
Illegal stocking puts Manitoba’s trout stocking efforts in a vulnerable position, as fisheries managers may have to discontinue stocking if trout cannot effectively co-exist with introduced species and are being outcompeted. There is a long list of features biologists look for in prospective stocked trout waters, measured against the habitat and thermal preferences of various trout species. Losing these lakes to illegal stocking ultimately decreases everyone’s opportunities and access to those fish because we are not always able to simply find a new lake.
Collective responsibility to protect Manitoba’s fisheries
Many anglers are aware of aquatic invasive species and the risks they pose to our fisheries. Anglers should also consider the potential impacts of moving sportfish species into new lakes. The reality is that when people take stocking into their own hands, they are posing a major risk to the balance of that waterbody’s food web.
Illegal stocking is a complicated issue. It only takes one individual to make a decision that will ultimately impact thousands of anglers, without regard to the risks they may pose, and the new species is there to stay. As anglers, we all have the responsibility to conserve our fisheries, and sharing information within the fishing community on the potential risks of illegal stocking might be enough to change someone’s mind.
If you become aware of someone illegally introducing live fish into Manitoba waters, please call the Manitoba Turn in Poachers T.I.P. line at 1-800-782-0076.