Fish Stocking Harming Wild Fish Populations?

Kyle Sanson

Bow River in Banff National Park

Bow River in Banff National Park

For as long as I can remember, fish hatcheries have been used to maintain a sustainable amount of fish in the lakes and rivers of Ontario. Hatcheries are usually focused on trout and salmon, but stocking walleye has been utilized frequently as well. When you think about it, putting more fish into these waters would result in higher populations of fish and thus, more catchable fish.

I never questioned that idea until last month when I listened to April Vokey’s podcast titled, “Anchored”. Her July 13th podcast featured Dylan Tomine, author and passionate angler based in the Pacific Northwest. His argument is that hatcheries and stocking fish actually ruins fisheries, especially for the wild fish. He mostly talks about the steelhead rivers on the west coast, but he cites cases of rivers in the central U.S. where the same issue has occurred. Tomine stated that “…where hatcheries are introduced, overall harvest and harvestable number of fish goes down”.

I heard him say that and thought, “That makes no sense. How does increasing the amount of fish actually result in less fish?” But Tomine goes on to say that the Skagit, a river located in the northwest corner of Washington, had a harvest of around 15,000 steelhead and that lasted for decades. When the hatchery was introduced, the number harvested fish dropped almost equally to the amount of fish that were stocked. One of the biggest reasons for this is the fact that hatchery fish have negative effects on the wild fish. They have to compete for food, habitat, etc.

Not only do the wild fish have to compete with the hatchery fish, spawning also becomes an issue. Tomine said that when a stocked fish spawns with a wild fish, the survival rate of the offspring is reduced by 50% in the first generation. If one hatchery male spawns with 20 wild females, a large amount of the eggs laid will not make it.

When asked why hatcheries are used, Tomine said that the main idea behind it is to make up for loss of habitat. But he quickly shoots down this arugment by pointing out that in the Skagit, there is a thriving pink salmon, bull trout, and cutthroat trout population. These fish use many of the same spawning grounds and habitat that the steelhead use. Both trout species have either remained level or climbed in terms of their population while the pink salmon population has risen exponentially. So the argument that the hatchery is needed because of loss of habitat is poor. The only difference between the steelhead and the other species is that there are stocked steelhead in the river.

Whitemans Creek near Paris, Ontario

Whitemans Creek near Paris, Ontario

Another example given during this podcast was the Eel river, which is located in Northwest California. A hatchery program was started there in 1964 when the fish population was around 82,000 wild steelhead. In 1994, there was 1500 fish, which was both wild and hatchery. In 1994 steelhead were classified endangered, so they closed the hatchery. Prior to listening to this podcast, I would say that closing the hatchery would surely deplete the remaining fish population, but in 2014 the fish population increased to around 60,000. The fish population fell dramatically when the hatchery was introduced, and then did the opposite once it was removed. Tomine says that over the next 10 years, the Eel may be fully recovered to the 82,000 fish.

During the 60s and 70s in Montana, there were decreasing numbers of trout in their rivers and creeks. A biologist was hired to determine the issue and what he found was reductions in health and numbers of trout in all locations where hatcheries were present. The Montana government took his report and closed all of their hatcheries in 1974. In 1978, the brown trout population doubled and the rainbow trout population increase by 800%. Both species also increased in size. Montana is now regarded as the best trout fishing destination in all of North America.

It took me a while to wrap my head around the idea that putting more fish into the rivers actually harms the population. April and Dylan talk about how this is still a very heated argument in the fishing community and how they have lost friends over this topic. Regardless of which side someone is on, everyone cares about the population of the fish and wants to have sustainable numbers so they can keep catching them. Like most things in life, people all want the same thing, they just can’t agree on the method.

After listening to this podcast and doing some research, I think a handful of hatcheries in Ontario should be closed and the population numbers should be studied. If it turns out the same way as the Eel and Skagit, remaining hatcheries should be closed as well. The recovery time can take a while, but if it means we have sustainable populations for generations to come, it would be well worth it.

To listen to the Anchored podcast, click the link below.