Alaska Fish & Wildlife News
Why Non-Native Fish Introductions
Can be a Pain in the Bass
It was a beautiful fall evening in September when a resident of Sand Lake was top-water fishing for rainbows with his favorite surface popper lure. Hit after hit, he was into the rainbows, but one hit suddenly felt a bit different. He reeled up and right away recognized he had something other than a rainbow on his line. Perhaps it was a grayling? That would have been interesting. Sand Lake hadn’t been stocked with grayling in years. It was dark outside, and he couldn’t quite see what he had. He decided to keep the fish and head home where he could give his catch a closer look. When he got there what he discovered was quite a shock. He hadn’t caught a grayling… he caught a bass… the first bass ever caught in Alaska.
News of this unusual catch spread quickly across the internet. There are no native bass species in Alaska. The nearest bass populations are over 1,000 miles away. So, how on earth did it get in Sand Lake? Could bass survive in Alaska? Would it be a problem if they did? And for that matter, why aren’t many of the warm-water species that are so fun to fish for in the lower 48 also stocked here? In social media and in the news, these questions and many others were asked repeatedly, and they are very good questions that warrant more thorough discussion. In this article, I’m going to answer some of these questions and explain why unauthorized non-native fish introductions are a bad idea and against the law in Alaska.
To dig into this topic, let’s continue with our story about the bass. In the immediate aftermath of its discovery, we at the Department of Fish and Game had our own questions; several being the same as everyone else’s. Where did it come from? Are there more? Is there a reproducing population? And what species was it? As odd as that last question may sound, we legitimately weren’t sure. Initially, we thought it was a largemouth bass, but when we pulled out a key to verify that, not all the anatomical details of the fish lined up with the species description. They didn’t for smallmouth either, or spotted bass. To be fair, the bass that was caught was only about 7.5 inches, and smaller bass like these are often trickier to identify. We cut a piece of the tail fin and sent the tissue sample to the University of Alaska Fairbanks for a genetic test to give us a definitive answer. A couple of weeks later, we had confirmation that the fish caught out of Sand Lake was in fact a largemouth bass.
In the week following the discovery of the largemouth bass, several Department staff surveyed Sand Lake to see if there were more bass present. We set various kinds of nets and traps and fished with hook and line. We surveyed at different times of the day and night, and the only fish we caught were rainbows, char, and sticklebacks – species the Department either stocks into Sand Lake or knows to be there naturally. We also caught one Arctic grayling – evidence that our nets were picking up species that aren’t very abundant in the lake. However, we didn’t catch another bass. That doesn’t mean there aren’t others. It just means that, at this point, we haven’t found evidence of a large reproducing population of them. Still the question remained, could that even happen?
Could bass live in Alaska?
“Could that even happen?” was one of the most frequent questions we received, and one that we have asked ourselves. We cannot say for certain that bass would survive here, but this is what we know; largemouth bass occur naturally in the eastern United States and Canada including northerly states and provinces like Minnesota, Wisconsin, Michigan and Ontario, all areas that have cold winters and sometimes temperatures that fall below those in Southcentral Alaska. Smallmouth bass are found in a similar range, except they don’t extend down into southern states like their largemouth counterparts do. Both largemouth and smallmouth bass have broad temperature tolerances, typically thriving in water 60° to 75° F. In northern areas, largemouth bass will seek out deeper water during the winter where they are able to survive beneath the ice, if oxygen levels don’t decline too low. We will be monitoring Sand Lake this winter to see how water temperatures and oxygen levels align with the published tolerance ranges for largemouth bass. Due to the prolonged winters we have here, bass in Alaska would most likely be stunted compared to fish found down south and have a shorter window to reproduce in the spring. However, if largemouth bass could/did become established, this would be detrimental to our native fish.
Both largemouth and smallmouth bass are voracious predators and will eat a variety of prey. As adult fish, they are often the top predators in the lakes they inhabit. Because of this, they have the capacity to change the entire food web in places where they are introduced. In British Columbia and many other parts of the world, introduced largemouth bass are designated as ‘invasive species’ which are non-native species that cause harm to the environment, the economy, or people. According to the Invasive Species Council of British Columbia, largemouth bass have led to the local extinction of several prey fish populations in the province. Largemouth bass have been listed among the top 10 invasive fish species in the world because of negative impacts from disease transmission or predation on native fish populations. Smallmouth bass have been similarly introduced throughout the western U.S. and around the world and are also considered invasive in many places. Smallmouth bass can affect native fish and invertebrates through direct predation as well as through competition for prey. Would any bass species illegally introduced to Alaska have a similar effect? I’d argue we can’t afford the risk of finding out.
Along the same lines of discussion, the Department often gets asked about stocking other nonindigenous species like crappies, perch, bluegill, walleye, muskies and catfish. Alaska has always taken a very conservative stance on stocking fish, and this is entirely to protect our highly-valued salmon, trout, and other resident fisheries. Non-native warm water species would compete with Alaskan species for prey, or prey on them directly. Alaska’s shortened warm seasons compared to where most sunfish, perch, and catfish are naturally found would result in slower-growing, stunted smaller fish, generating less angler interest. The extra competition for space and prey would also lower survival of juvenile salmon and trout. Therefore, to avoid these outcomes, non-Alaskan fish species are simply not stocked anywhere in the state.
Why stock native fish?
Alaska is fortunate to have world-class fisheries that the Alaska Department of Fish and Game is constitutionally mandated to protect. Because of this, we have very strict stocking policies. Per our policy, we only stock species present in and native to the state, and only use local broodstock. This means we collect local eggs to raise in our hatcheries and then stock these native fish when they are big enough to survive on their own. We stock fish for two main reasons: to provide angling opportunities and to reduce fishing pressure on wild fish populations. We have careful and scientifically-based policies for where and when we stock these fish. We have extensive protocols to prevent disease transmissions. We generally don’t stock hatchery fish into lakes that have wild populations, and most of the fish we stock are not capable of reproducing.
One fair question we are often asked is ‘why do we stock rainbow trout and Arctic grayling in lakes that technically fall outside their native ranges in Alaska?’ This is a valid point, but one factor considered when determining where fish will be stocked is our ability to provide quality fisheries to anglers in Alaska. This is also a big part of the Division of Sport Fish’s mission, so in some places where we stock fish outside their native range in the state, we do so to provide angler opportunities. However, we do so in a manner that is highly controlled, monitored, and scientifically-designed to keep native fish populations in those areas safe and healthy. Many lakes that we stock, especially in the Anchorage and Fairbanks areas, were rock quarries or borrow/ gravel pits, and not natural lakes, thus never having natural populations of fish to begin with. However, even in these totally closed stocked lakes, our stringent stocking policies help ensure that if these fish would ever escape in a flood or some other way, they would have a low risk of spreading diseases or begin reproducing on their own. These precautions are not met when someone decides to take matters into their own hands and illegally stock fish, and herein lies one of the greatest threats we have to the health of our native fish populations in Alaska.
Over the years, there have been many instances of illegal fish introductions with several of them resulting in reproducing populations. Most notably, this has occurred with northern pike and Alaska blackfish, but we have examples of this happening with yellow perch, muskies, goldfish/koi, and now potentially with largemouth bass. In some of these cases like with the perch, muskies and several pike populations, the Department has already removed them from the lakes they were introduced to. However, removal of these illegally-introduced species comes at a great cost. It’s expensive, and it’s difficult to do without at least some level of collateral damage on other species. However, when people illegally stock fish or other animals, they may not understand the risks of what they are doing. Likely, the average ‘bucket biologist’ isn’t stocking fish to be malicious. Sometimes it’s a group of kids who don’t know better. Sometimes it’s just someone who wants different fish in their local lake. Regardless of the reason, doing this is extremely reckless…and, again, illegal. Per Alaska Statute (AS 16.35.210), it is against the law to import any nonnative fish into the state for the purpose of release into Alaska waters, and it is illegal to release ANY live organism without a permit into waters of the state from which it didn’t originate. Doing so is a class A misdemeanor that could result in up to a $10,000 fine, jail time, and restitution for damages caused by the species introduction. The penalties are seriously hefty, for good reason. Fisheries in Alaska contribute greatly to our state’s economy and they are a vital component of healthy ecosystems. Without even realizing it, someone moving fish, frogs, water bugs or anything else on their own could introduce diseases or parasites to the waters they stock. This is a huge risk that could kill entire populations of native fish. Further, people unknowingly could introduce an animal or plant that thrives, takes over, and becomes an invasive species here. Once in a waterbody with an outlet, the introduced species can spread to other areas. Even if the introduction happens in a closed lake, there is no guarantee that a population couldn’t become a source for other illegal introductions in the future. Certainly, with northern pike, we’ve seen that scenario play out many times.
The pike problem
The case with northern pike is probably the most well-known, prolific and consequential situation we have in Alaska with illegal fish introductions. Beginning decades ago, pike were illegally-introduced from their native range in Alaska to the Mat-Su Valley, Anchorage, and Kenai Peninsula areas, where they are not native. Through many illegal introductions over the years as well as dispersal via connected waters, pike are now in over 100 different lakes and rivers in these areas. Pike, too, are top predators in the waters they inhabit. Their impacts have ranged from completely wiping out trout populations in shallow lakes on the Kenai Peninsula, to resulting in the loss of king salmon fisheries in places like Alexander Creek, to reducing sockeye returns in places like Shell Lake, to having a negligible effect in waters that don’t offer great habitat for them. Adequately explaining the dynamics with invasive pike here is a lengthy story in and of itself, but the point is that it’s complicated and often very difficult to predict the exact impacts they’ll have, but where it’s bad with pike, it’s really bad. We’ve spent millions of dollars in grant funding trying to chip away at fixing the pike problem in Southcentral Alaska. It’s best not to risk this happening again with a new species, never mind one that isn’t even native to the state like largemouth bass.
One question that arose with the largemouth bass discovery in Sand Lake, and is also a common question with pike, is how exactly fish like these get moved around. Probably the most common idea people have is that eggs or live fish are transported to different water bodies by waterfowl. While it is true that pike have adhesive eggs that theoretically can stick to bird feathers, eggs will quickly dry out when they are out of water. If birds were a natural mechanism of dispersal for pike, pike would be in all shallow lakes and slow-moving weedy rivers and marshes in Southcentral Alaska, but they’re not. Despite the significant problems we have with them, pike are in a relatively small fraction of the available habitat for them in Southcentral, and everywhere they are found is either road or float-plane accessible, or directly connected to waters that are. If pike were naturally moved around by birds, pike would be a native species to this region. With largemouth bass, birds are even less likely to be the cause of the introduction. While bass also have adhesive eggs, males intensely guard them in nests dug into the sediment of lakes, making it unlikely that waterfowl even encounter their eggs. Even if they did, the nearest largemouth bass populations to Alaska are the invasive populations in British Columbia, and birds can’t transport bass eggs or live fish long distances without desiccation (i.e. drying out). Therefore, it isn’t plausible that a bass ended up in Sand Lake without someone putting it there, but how exactly that happened is currently unknown.
One publication about the Sand Lake bass discovery highlighted an option for ordering largemouth bass from the retail giant, Amazon. Thankfully, that option turned out not to be true, at least for Alaskans. The Amazon distributor is aware of Alaska’s laws regarding importation of game fishes and does not ship them here. However, while we’ve turned over a lot of stones to rule out certain online distributors, we can’t rule out the internet altogether, or simply someone motivated to make the trip to Alaska with live fish. Regardless of how or why this happens, it is never, under any circumstances, a good or legal idea to release fish into the wild…which brings up another good question…
Don't set pets free
What should you do if you are an aquarium owner and have fish or other critters that you no longer want or can care for? Your first thought might be to let it go, believing this is the kindest option. Aside from the legal and devastating ecological ramifications we’ve already discussed, this is often the harshest option for your pet. The Department occasionally gets reports of red-ear slider turtles that turn up in local lakes, or even snakes that get let go. For these kinds of critters and most tropical fish, they often can’t survive winters here and end up starving or slowly succumbing to the cold. In some cases, though, aquarium species do survive and flourish just like the common aquarium plant, Elodea, that is now a significant invasive species problem statewide, or the signal crayfish that has made itself at home in Buskin Lake in Kodiak. Rather than risking more of those kinds of scenarios, if you have aquarium pets that you no longer want, try to re-home them. If you cannot find new caretakers, contact local pet stores where you live. Many will gladly accept your animal and re-sell it versus seeing it inhumanely released into inappropriate conditions. If those options don’t work, call a vet or your local animal care and control facility to properly euthanize amphibians and reptiles. For fish, especially a larger one, it can be dispatched just as you would a salmon you catch, with a cranial contusion (i.e. quick bonk to the head). For smaller fish, place them in a zip lock bag with a small amount of water and put them in the freezer. Harsh as that might sound, it is more humane than having that process take months over the course of a winter.
When it comes to invasive species in Alaska, preventing problems before they start will always be our best strategy. We can all do our part by being aware of our fish transportation laws, recognizing the important reasons behind them, and being responsible pet owners. We can’t always predict the kinds of consequences that may arise from non-native species introductions, but it is best not to gamble with our precious fishery resources to find out. If you ever have questions about whether you can possess a certain species, contact the Alaska Department of Fish and Game. We’ll find the answer for you or help you determine if you need a permit. If you ever observe or learn of anyone releasing live fish or other organisms into waters of the state, report it right away! If you ever catch another bass or anything else that’s not a native Alaska fish species, we’ll want that fish brought into our office. Finally, if you are out anywhere in the state and see an animal or plant that doesn’t look like it should be there, collect it or take a photo, get a location (GPS coordinates are great) and report it by calling 1-877-INVASIV or visiting the ADF&G invasive reporting webpage.
Kristine Dunker is a research fishery biologist specializing in aquatic invasive species with the Alaska Department of Fish and Game, Division of Sport Fish, in Anchorage, Alaska.
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