The History and Mystery of Hybrid Fishes

As a fisheries scientist myself, I always find these new discoveries interesting and exciting. But as an angler, I don’t expect to tussle with any new-found fish on a fly rod anytime soon. These days, most of the recently described fish species are found in obscure habitats in remote locales. Case in point—dragon snakeheads, an entirely new family of fishes that inhabit underground aquifers in India.

As Miles noted regarding the discovery of new fish species, “they’re not being created, they’re not making two new ones a week, we’re just finding them.”

Very cool and very true.

Well, mostly true.

An Unexpected “Discovery”
Enter the sturddlefish, a “new” species that was recently created in a lab via unintentional hybridization of Russian sturgeon eggs and American paddlefish sperm. Sturgeon eggs will sometimes begin development solely by sitting in close proximity to sperm without actually being fertilized, a process called gynogenesis.

Scientists wanted to induce the development of critically endangered Russian sturgeon to help conserve the species. They did not expect fertilization to occur—or a viable sturgeon x paddlefish hybrid offspring to develop.

The top fish is a Russian sturgeon and the bottom is an American paddlefish. In between, two varieties of hybrid 'sturddlefish' created by accident (Kaldy et al., Genes 2020).

That said, hybrid fishes are really nothing new—if you’ve fished enough places, you’ve likely caught one or many. Most hybrid fish are sterile so they aren’t distinct or new species, merely a combination of the two parental species, usually created by humans. In relatively rare cases, fish hybridization occurs naturally, but this isn’t necessarily a good thing.

Across the Western United States, populations of native cutthroat trout are losing native genetic composition by hybridizing with non-native rainbow trout. However, state fish and game agencies do intentionally produce various sterile hybrids in fish hatcheries for the benefit of fisheries and anglers alike. You may be familiar with tiger trout, tiger muskie, splake, wiper, saugeye, chumpy, cuttbow, and other fun “frankenfish” portmanteaus.

Why Hybrids?
One word, and I promise it’s the last nerd word: heterosis. Also known as hybrid vigor, heterosis refers to a phenomenon when hybrid offspring have increased or improved biological qualities compared to the parent species. Essentially, when done purposefully, 1 + 1 = 3. That is, resulting hybrids might grow faster, bigger, and/or be more aggressive. Many of these fish are sterile and thus don’t waste energy growing gonads and trying to spawn. They put their calories toward getting more calories, and that makes them grow bigger, faster.

Additionally, for managers, hybrids can be used to improve fisheries as a whole. Hybrids are especially useful in reservoirs, which are “unnatural” fisheries from their manmade beginnings. In fact, since hybrids rarely reproduce, managers can closely control hybrid populations through stocking practices and harvest regulations. Thus, in the right management situations, hybrids can be stocked in fisheries even if one or both parental species aren’t native to the waterbody.

Once stocked, the often voracious hybrids feast on undesired or overpopulated fish populations. Ultimately, this creates less competition for other desired gamefish, and thereby, healthier ecosystem balance and better fishing. Being sterile and unable to reproduce, most hybrids will eventually all get caught or die over time, unless fish & game stocks them again.

Many anglers might be familiar with various hybrid sunfishes, which are popular additions to stocked lakes and ponds. They’re great family fun, and I can’t hate on 2-pound ‘gills bred with green sunfish, but it’s the predatory hybrids that reign supreme in America.

The Mount Rushmore of Hybrid Fishes

Wiper (striped bass x white bass)
Wipers, or hybrid striped bass, result from the crossing of striped bass and white bass. Originally produced in the 1960s with striper eggs and white bass sperm, they can also be produced through the reverse. However, due to the wealth of eggs female stripers produce, the original “Palmetto” cross remains most common.

With good reason, wipers are among the most stocked hybrid gamefish in the United States. They won’t rival actual stripers for overall size, but wiper find a happy medium between the revered striper and the much smaller, pesky white bass. Record hybrid striped bass exceed 20 pounds and pull like a freight train. Similar to true stripers, hybrid stripers feed in open water, so they are useful management tools to control over-abundant prey fish populations, such as various shad species in Southeastern U.S. reservoirs.

Wipers also do better than stripers in warmer, less-oxygenated water. As such, they are stocked in a variety of waterbodies from striper’s native range along Atlantic Coast all the way to the West Coast and in between. Since they grow fast and taste great, they’re also valuable in aquaculture; if you order “striped bass” at a restaurant, you’re more than likely being served a hybrid striped bass. And, given their size and fight, if you hook into a wiper with a properly equipped rod and reel, you’re more than likely in for a good time.

Tiger Trout
Tiger trout are a hybrid cross of a female brown trout and male brook trout. To be honest, you’d be forgiven if you hadn’t seen or heard of this hatchery-raised fish prior to about 2010. However, since non-native brown trout were brought to the United States in the 1800s, tiger trout have been occurring “naturally,” albeit rarely, where brookies and browns overlap. Nowadays, they are widely stocked for sport and management applications. Thanks to their vibrant, stripe-like patterns and instagramability, these colorful fish have exploded in popularity in the last decade. Hashtag, Lance V.

Accordingly, many state management agencies have increased the presence of tiger trout in stocked fisheries. But, this is not just to appease “influencers” and “ambassadors”—tiger trout have been relevant in scientific literature dating back to 1950s. Like most hybrids, tiger trout are sterile, so managers can control their abundance. Like actual tigers, tiger trout are exceptional predators. They generally grow faster than their parent species and eat other fish from an earlier age. Thus, managers often stock them as “biological controls” to help restore ecosystem balance when fisheries get overpopulated. In those type of fisheries, tigers can approach 20 pounds and exceed 30 inches—that’s grrrrreat!

Tiger Muskie
Not to be outdone, tiger muskies more than live up to their moniker in appearance and performance. Produced by crossing a northern pike and a true muskellunge, these tigers are perhaps the premiere hybrid sportfish. We’re talking size, fight, and teeth. They are also one of the most common naturally bred hybrids. However, the vast majority that anglers encounter were produced in hatcheries, where managers typically use male pike and female muskellunge. Size-wise, big tiger muskies usually fall between big pike and big true muskies, but they reach trophy size much faster.

After years of overharvest that caused true muskellunge populations to plummet, managers ramped up production of tiger muskies in the 1950s and ’60s. More recently, a shift toward catch-and-release culture has allowed true muskies to recover. Yet, tiger muskies are still stocked today, especially outside the native range of true muskies. The current “modern day” tiger muskie world record was caught in Idaho in 2013, weighing almost 45 pounds. The traditional world record tiger muskie weighed 51 pounds, famously caught on Lac Vieux Desert on the Wisconsin-Michigan border in 1919. Ironically, this would have been a naturally produced fish and, for the time being, remains the king of hybrids.

Splake
Rounding out our hybrid fish Mount Rushmore is a beautiful char cross that packs a punch for anglers. Splake are produced by crossing male brook trout and female lake trout. They are fertile but have not been documented reproducing outside a hatchery.

While the first artificial hybridization traces back to the 1870s, like with other hybrids, American interest in splake started in earnest during the 1950s. After lake trout populations crashed in the Great Lakes, splake were introduced as a faster-growing alternative with moderate success. Today, game departments stock trout in various higher elevation reservoirs west of the Mississippi and in lakes with cooler temperatures in the upper Midwest and Northeast. Like tiger trout, big splake can approach 30 inches. The world record is just over 20 pounds—nothing to scoff at.

Earning Their Stripes
Some anglers argue that since hybrids are stocked and can be bred for aggression, these fish don’t present as much challenge as natural fish populations. That’s really not the point (or necessarily true). Hybrid fish are produced to serve as management tools and to provide angling opportunities—catching a beautiful hybrid for the first time is a new and exciting experience. It also doesn’t need to be a complicated experience.

You find hybrids where you find hybrids. That is, where they are stocked. The State of Utah actively stocks all four species discussed above, and many states stock two or three. Interested anglers should keep an eye on current data and study historic stocking reports, which are readily available online. With experience, you may notice some intricacies between hybrids and their parental species—I’ve found big tiger muskies more readily take smaller lures than standard muskies—but largely, hybrids can be caught with similar approaches to their parent species.

There’s a lot to like about hybrid fishes in the right waters. They provide new and interesting fisheries, often while helping biologists manage an ecosystem. Nothing is more valuable than a native fish in its native range, but it is always interesting to see what new fish will be discovered or created next.

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