Lake Winnipeg walleye (Sander vitreus) support Manitoba’s largest recreational and commercial fisheries. Over harvesting by the commercial fishery is placing both fisheries at risk and in 2015 the commercial fishery was described as the worst-managed in the world[1]. The current system of managing the fishery, based on a fixed multispecies quota, is built to fail. Most importantly it promotes an unsustainable overharvest of walleye. Until management of the fishery is placed on a scientific, sustainable basis, commercial, recreational and Indigenous fishers will find themselves in conflict over a shrinking resource. But with proper management, there can be fish for all.
The walleye population on Lake Winnipeg
The size of the walleye population depends on recruitment (i.e., spawning success & survival) and that varies from year-to-year. In some years, fry survival is much better than others due to favourable environmental conditions, generating strong year classes. These strong year classes occur intermittently. This century, we have seen strong year classes in 2005, 2011 and especially 2001. The 2001-year class was the strongest ever recorded and sustained large walleye harvests in the commercial fishery from 2005 – 2012.
Why is the current fishery unsustainable?
Walleye recruitment is enhanced if the spawning population contains multiple age-classes. Especially important are the older, larger female spawners that produce more and better eggs than smaller fish, enhancing fry survival[2]. The commercial fishery has reduced the population of large spawners in recent years, and only a small, declining population of jumbo3 walleye remain in the lake, primarily from the record 2001-year class. Once these old fish are gone, there will be few large walleye in the lake for many years. Currently in Lake Winnipeg, half of the female walleye do not reach spawning maturity until age 8. Walleye, however, are now harvested in the commercial fishery beginning at age 4, four years before they reach maturity.
Why the current management model ensures overfishing
The commercial fishery is governed by an individual transferable quota system where each fisher (there are ~770 on the lake)[3] holds a fixed quota that can be filled with any of three species: walleye, sauger or lake whitefish. A kilogram of each counts the same against the quota. The current total lake quota is about 7.2 million kg. Fishers naturally target the fish that is most valuable, and since the current quota system was introduced in 1986, that has almost always been walleye.
A multispecies quota system cannot work if the total quota is greater than the sustainable yield of the most valuable species[4]:
That is the case on Lake Winnipeg. The sustainable yield of walleye on Lake Winnipeg is subject to considerably uncertainty, and is likely to vary from year to year depending on the strength of recent year classes recruiting into the population. But while the sustainable yield is not known exactly, it is clear that the total lake quota of 7.2 million kilograms is somewhere between two to five times the sustainable yield of walleye. Overfishing of walleye is nearly certain. A 2011 review of the quota system recommended dividing the multispecies quota into separate quotas for walleye (3.65 million kg), whitefish (1.63 million kg) and sauger (1.24 million kg) based on recent catches4. The task force recommending these quotas worked with the best available data but it is now clear these quotas, especially for sauger, were too high[5]. The walleye quota was based largely on the large catches stemming from a freakishly large year-class from 2001. Other estimates of the sustainable walleye harvest based on lake productivity are much lower, ~1.6 million kg per annually4.
Since 2012, with the 2001-year class aging out of the population, the sustainable yield of walleye fell quickly. Overfishing has resulted in a rapid walleye population decline. The catch of medium, large and jumbo walleye3 fell 70% from 2012 to 2018. Fishers responded to declining populations of medium walleye (the most valuable size class) by changing tactics In 2015-16, commercial fishers targeted jumbo walleye with large-mesh nets (≥6”). The Province imposed maximum mesh size regulations in 2016 to curtail this harvest of these valuable, mainly (>90%) female spawners. In 2016, with fewer medium and almost no large walleye in the lake, and mesh-size restrictions to prevent targeting jumbo walleye, commercial fishers turned to small-mesh gillnets (3”) normally used to catch perch and sauger. This fishery targeted small walleye, mainly fish born in 2011. Normally small walleye make up ≤10% of the commercial catch. By 2018 that had soared to nearly 50%[6]. All of these small walleye, and 2/3 of the medium walleye are immature. Overharvest of these immature fish means there will be fewer large-reaching spawning age walleye in coming years.
Is overfishing by anglers a concern on Lake Winnipeg?
Anglers are not the problem in the Lake Winnipeg walleye fishery. Creel surveys on the lake indicate that anglers take less than 5% of the walleye, while the commercial fishery takes over 90%. The Indigenous food fishery takes the remainder. While anglers are not the cause of the walleye population decline, they are directly affected by overharvest in the commercial fishery. The recent survey by the Manitoba Wildlife Federation of Lake Winnipeg anglers shows clearly that most feel the fishery is in decline. A large number fault the commercial fishery and many anglers suggest that it needs to be closed.
Do we need to close the commercial fishery?
No! Lake Winnipeg is remarkably productive and if it is managed sustainably, there can be plenty of fish for all. But the current multispecies quota system cannot work. It ensures unsustainable overfishing of the most valuable species: walleye. Even worse, under the current system, sauger have been overfished to the point of extirpation on Lake Winnipeg and may not recover. Ever.
It is clear that the current quota system is unsustainable. It is in the interest of all fishers to move the fishery to a sustainable basis. That would be the best outcome. But there is an alternative. In Alberta, where a similar conflict between commercial and recreational fishers existed, a review of the fishery presented three options: 1) the status quo, which meant collapsed fisheries; 2) move the fishery to a sustainable basis, with commercial and recreational fishers sharing the resource under scientific sustainable management; or 3) close the commercial fishery. Commercial fishers would not agree to the necessary changes needed to manage the fishery sustainably. The Alberta government opted for Option 3, closing the commercial fishery in favour of the more valuable recreational fishery[7].
The same three options exist in Manitoba. The status quo means a collapsed Lake Winnipeg walleye fishery and the extirpation of sauger on the lake. A sustainably managed fishery is possible, but requires better scientific data, better enforcement of regulations, and changes to the quota system.
What does sustainable fishing look like?
A sustainable fishery has the flexibility to adjust the harvest with the current stock size using harvest control rules. Quite simply, when the population is healthy, the catch can increase. When the population is declining, the catch is reduced. This cannot currently be done in the Lake Winnipeg fishery with fixed quotas. A system of sustainable management requires good data on current stock size, and the flexibility to adjust harvest rate. We have neither in the current Lake Winnipeg fishery. This system must change if we are to move the fishery to a sustainable basis.
Sources and notes
[1] https://www.theglobeandmail.com/news/national/seafood-watch-calls-manitoba-fisheries-worst-in-world-urges-boycott/article27173668/
[2] Johnston TA, Wiegand MD, Leggett WC et al. 2007. Hatching success of walleye embryos in relation to maternal and ova characteristics. Ecology of Freshwater Fish 16: 295-306.
[3] A Profile of Manitoba’s commercial fishery. Manitoba Sustainable Development: http://www.gov.mb.ca/waterstewardship/fisheries/commercial/pdf/mb_com_fish_profile.pdf
[4] Squires D, Campbell H., Cunningham S et al. 1998. Individual transferable quotas in multispecies fisheries. Marine Policy 22: 135-159.
[5]http://www.gov.mb.ca/waterstewardship/fisheries/commercial/pdf/lwtf2011.pdf
The Task Force noted concern about declining sauger when they recommended the 1.24 million kg quota. In 2017, the harvest was 1.75 million kg with a harvest rate of 56% (Source: Manitoba Sustainable Development). This means the entire harvestable population is less than 400,000 kg. The recommended quota is roughly three times the size of the population. That is clearly unsustainable.
[6] Data from Manitoba Sustainable Development.
[7]http://www.edmontonjournal.com/alberta+government+kills+commercial+fishing+industry+stocks+decline/10264848/story.html
