To Stock or Not to Stock

The truth is, whether you’re talking about a local farm pond, a blue-ribbon trout stream, or a massive river system, stocking fisheries can be a complicated business. Some fish can’t survive in certain habitats, and putting fish in the wrong place can interrupt the natural cycles of wild fish that are already living in the waterway. Many anglers think of fish stocking as an unassuming practice similar to planting trees in an over-logged forest or seeding different vegetables in an otherwise barren garden. However, the truth is that fish stocking is a sensitive practice that can and should only be done under the right conditions.

Restorative Stocking

As the name implies, restorative stocking is done to help restore a native species of fish to a body of water where its population has been greatly decreased either by changing water conditions or by a competitive invasive species. “Restoration stocking is used when we want to reestablish a self-sustaining population after it has been lost for some reason and cannot be recolonized on its own,” Vermont Fisheries Biologist Lee Simard said.

While this may seem like an easy practice as the fish have previously lived in the waterway, there have often been changes to the environment in their absence that must be addressed before the fish can be reintroduced. There’s a natural balance to aquatic habitats, and the loss of a specific fish species often means that another species has moved in to fill the gap. Suddenly returning fish to these environments can be like throwing a wrench into the whole system. Restoring a fish population requires intention, reason, and balance—and should only be done in certain waterways, under very specific conditions.

Simard, who currently manages the wild trout restoration and management on Vermont’s famous Battenkill River, is well acquainted with the ups and downs of restorative stocking. “The benefit is that stocking won’t have to continue long-term as the population will eventually reproduce on its own. However, suitable habitat for all life stages is required for restoration stockings to be successful.”

Suitable habitat is key to being able to restore native fish populations. Often predator populations must be culled or water quality has to be improved before native fish can be restored. A great example of this is currently underway in Yellowstone National Park, where invasive lake trout illegally stocked in the 1980s are being removed from Yellowstone Lake to make way for the native Yellowstone Cutthroat. As aggressive super predators, the lake trout were devouring the cutthroat by the thousands. So biologists have used methods such as gillnetting, poisoning, and other means to ensure that the newly introduced cutthroat could survive and repopulate the waterway.

Put-and-Take Stocking

The second type of fish stocking, put-and-take, is primarily done to create fishing opportunities in bodies of water that don’t have any catchable numbers of wild fish. This can include air-dropping fish into high mountain lakes, stocking fish in sections of river that can’t otherwise support wild fish, or dumping a few bluegills or bass into a farm pond (where legal) to give you something to do on the weekends.

“Put-and-take stockings provide fishing opportunities by stocking catchable-size fish into a waterbody where wild populations usually don’t exist,” Simard told MeatEater. “The intention is not to create a reproducing population as the habitat in these areas usually doesn’t allow the fish to survive long-term. As a result, stocking occurs each year to maintain these fishing opportunities, but they are usually very popular and can justify this continued stocking.”

Put-and-take fisheries are important for many states because they instantly create a fishery for anglers to use that otherwise wouldn’t exist. Fish in put-and-take fisheries are stocked at a catchable size, meaning anglers don’t have to wait for fish to get large enough to take lures and flies. Put-and-take fisheries are fantastic for tourism, increasing fishing license and equipment sales around the stocked waterways and giving anglers opportunities to catch and eat fish they may not have a chance to sample in other places.

However, these fisheries can be controversial. In many states, stocked fish often compete with wild fish that already live in the environment. Accordingly, most put-and-take fisheries are only created in waterways that otherwise can’t support wild fish, though on occasion, there is some crossover between stocked fish and native wild species with often disastrous results. One of the best examples of this can be found in put-and-take steelhead and salmon fisheries on the West Coast.

In Washington, Oregon, and California, over 200 million salmon and steelhead are stocked every year with the fish specifically introduced for both commercial and recreational fishing. While on the surface, this seems like a fantastic opportunity for anglers, the truth is that the hatchery-raised salmon and steelhead are almost in constant competition with the wild fish already present in the river for both food and spawning sites. This has created a continuously struggling fishery where both wild fish and stocked fish numbers are constantly in flux, making for inconsistent fishing.

Wild Fish vs. Stocked Fish

When wild fish populations and stocked fish populations share the same water, it’s usually the wild fish that lose out, even when the two populations are the same species.

“The biggest problem with fish stocking is its potential to impact existing wild fish populations,” Simard said. “Stocked fish compete with wild fish for limited food resources, they may displace wild fish from the best habitat or from a section of stream entirely, or they may even prey on the wild fish.”

Biologists are aware that these impacts exist and do their best to stock accordingly to minimize the repercussions of introducing new fish to waterways.

“Luckily, most of these problems can be mitigated by carefully selecting where and how many fish to stock. In Vermont, put-and-take trout stockings are limited to areas that do not have robust wild trout populations, reducing the chance that any of this competition occurs. Extensive disease testing is conducted to make sure stocked fish are healthy, and “triploid” or sterile fish are sometimes used to reduce the risk of genetic introgression.”

Well-managed stocking efforts can produce excellent fisheries so long as the natural balance of the waterway is maintained. However, before fisheries scientists realized it might not be the best idea to drop new species willy-nilly into new waterways, many alien species were introduced to places that they didn’t belong, changing the face of many fisheries forever.

“If done wrong, stocking can have long-term effects on native fish populations,” Simard told MeatEater. “Out West, non-native rainbow trout stocked into many streams have hybridized with native cutthroat trout, altering the genetic integrity of these populations. Brook trout are another example, as they have become established in many areas and are also outcompeting native cutthroat in the West. In the Eastern US, where brook trout are native, the opposite is often occurring as stocked brown trout are outcompeting brook trout in many areas.”

Simard and other fisheries biologists are still dealing with the lasting effects of past ill-informed stockings.

“Most of these lasting impacts resulted from stockings that occurred decades ago,” Simard said. “Stocking is still a very important tool in our toolbox to create fisheries and help manage populations, but we need to be very aware of the risks and learn from the mistakes we made in the past.”

Stocking More and Stocking Less

One of the biggest factors of successful stocking programs is knowing exactly how many fish need to be stocked in each waterway and often more importantly, when stocking needs to stop. This can vary between fisheries and each waterway’s specific needs. Therefore, it’s important for fish and wildlife agencies and fisheries biologists to keep a close eye on fish populations in stocked waterways to ensure that they aren’t stocking too many or too few fish to meet both the demands of anglers and to maintain the health of a fishery.

“For restoration stockings, we are trying to restore a naturally functioning system,” Simard said. “To create this, the number of fish stocked is often increased or decreased based on the ecological conditions within the waterbody. We need to stock enough fish for the restoration effort to be successful, but we don’t want to stock so many that the ecological balance is disrupted.”

Conversely, put-and-take stocking focuses more on creating fishing opportunities, so stocking numbers are determined more by angler demand than environmental cohesion.

“The purpose of put-and-take stockings is to create fishing opportunities so the number of fish we stock is directly related to the amount of fishing pressure on that waterbody,” Simard said. “If our surveys show more people are fishing a stocked area, we will increase stocking to maintain the quality of that fishery. On the flip side, if our surveys show no one is fishing there, we reduce or even end stocking so that we aren’t wasting our resources and don’t negatively impact wild populations.”

Stocking Forage Fish

Whether you’re stocking fish for anglers or restoring a native fish population, ensuring those fish's survival is priority number one. This means you must make sure they have a clean and healthy habitat with plenty of cover and food, which means you also have to stock some type of forage fish for them to subsist on.

While in smaller ponds and private creeks this might mean dumping a bucket of minnows into the water a couple days a week, in larger lakes and rivers, this often means stocking and managing a species like smelt, tilapia, herring, whitefish, or panfish, so the fish you originally intended to stock have enough food to survive. This extra effort is often worth the cost as many stocked fish populations can thrive so long as they are provided with the proper forage. However, it can be a delicate subject, as you’re once again adding a new species to a new environment. It needs to be done correctly.

“In a few rare instances, forage fish may be stocked into a waterbody to improve the success of a stocking, but the situation has to be just right.” Simard told MeatEater. “In Vermont, we don’t raise forage fish within our fish culture program, but we have transported smelt from one waterbody to another in a few cases to bolster a forage base that was out of balance. More frequently though, we try to fix the cause of that imbalance rather than just stock more forage. We could do this by reducing the number of predatory fish we stock, or we could try to improve habitat conditions.”

Stocking For the Future

One of the sad realities of our nation’s fisheries is that they have been overfished, polluted, and otherwise poked, prodded, and mucked around with to the point where many are on the brink of vanishing altogether. While fish stocking has been a beneficial tool used to combat the collapse of many fisheries, the truth is that it’s not a magical solution to all our fishing issues. There have been many stocking success stories, such as the introduction of Pacific Salmon to the Great Lakes, and the complete resurrection of the Lahontan Cutthroat in Nevada’s Pyramid Lake, but there have been just as many failures.

Stocking fish has been the reason for many a fishery’s downfall, such as the introduction of bighead carp decimating the food web of the Mississippi River, stocked rainbow trout crossbreeding with native cutthroat, and introduced predatory fish like snakehead and pike completely wiping out native fish species across the country. So, no matter how often you feel that a certain waterway doesn’t have enough fish, it’s important to remember that all fish stocking has a ripple effect that goes far beyond just having a slow fishing day. While it can go wrong so quickly and so easily, when it’s done right, fish stocking may just be the thing that will keep us on the water and catching fish for years to come.