Have you ever been fishing your favorite lake, reservoir, stream, or pond and caught a bream that just didn't look right? Perhaps it looked like a bluegill but had a larger mouth and yellow-margined fins, or perhaps it looked like it had some pumpkinseed in it. This fish may have been a hybrid between two species of sunfish.
But did you know that sunfish species can and will naturally hybridize? It is more common than you might think, especially in artificial systems like farm ponds or other heavily altered systems, or where a species was not naturally occurring but introduced. There is probably no group of fish in North America that hybridizes more readily than sunfish.
Sunfish belong to the genus Lepomis in
Many pondmeisters are familiar with the hybrid bream sold by sport fish suppliers for pond stocking. These fish are known by several names; hybrid sunfish, green gill, or Georgia giant are commonly used. They are a good option for small ponds because they grow quickly, especially when fed, and they are easy to catch, but should not be stocked as prey for bass or with other species of sunfish.
Most commercially produced hybrid sunfish result from crossing male bluegill with female green sunfish. The fish are brought into the hatchery, encouraged to release their reproductive goodies, and the mix is used to produce the desired hybrid.
Hybrid bream produced for stocking are 85 to 95 percent males, which makes them less likely to overpopulate. Fewer fish mean more food per fish and faster growth. And because they readily accept commercial feed, they can grow faster than bluegill or redear sunfish under similar conditions.
But did you know that sunfish species can and will naturally hybridize? It is more common than you might think, especially in artificial systems like farm ponds or other heavily altered systems, or where a species was not naturally occurring but introduced. There is probably no group of fish in North America that hybridizes more readily than sunfish.
Sunfish belong to the genus Lepomis in the family Centrarchidae (the sunfish family; includes black bass, crappie, and more). There are currently 13 accepted species of lepidomorphs, but with ongoing genetic studies, you never know when a species may be split into two separate species. And the distributions of many of these species overlap - that means they are found together. In a natural stream or lake, or in a larger artificial reservoir, it is not uncommon to catch 3 or 4 species all hanging out in the same area.
To make matters more complicated, they all spawn about the same time of year and within the same temperature range. Add to that the fact that all species spawn in similar habitats - usually shallow areas with sand or gravel.
Then consider that there are limited spawning areas within each water body. In fact, two or more sunfish species will commonly nest together in the same colony. When an individual of one species departs its nest, a male of another species will commonly swoop in and make the nest his own.
You can see where this is going. When you get a lot of horny fish of multiple species in a finite area, it's like Spring Break in Cancun.
It doesn't take much. Maybe there's a male bluegill and a male redear sunfish nesting five feet apart. The females of each species arrive, deposit their eggs, and the males release their milt (sperm) just above the eggs. With just a slight current, maybe a swipe of a caudal fin, a few of those sperm are swept off course. Five feet really isn't that far when the current is helping.
Or it could be a case of mistaken identity. Picture a male bluegill waiting patiently as it passes by. "Hello, lady, I love your red earrings," the male bluegill swoons. "Meh, you'll do," says the female redear sunfish.
The resulting offspring can be quite beautiful. With 13 distinct species, there theoretically could be 77 different first-generation crosses! And while they may or may not look very different from their parents, a test of genetics is the only way to know for sure if they are a hybrid and of which species, but a good fish biologist can usually make an accurate identification.
The good news is that, despite ample opportunity for hybridization in the wild, the species barrier isn't too easy to cross. Some combinations, such as warmouth-bluegill and warmouth-redear sunfish, have proven difficult to produce under controlled conditions. However, there has been plenty of evidence of them existing in the wild.
Further, a waterbody usually maintains distinctly separate species instead of trending towards a single mixed species. So, what keeps a water body from becoming a giant melting pot? It may be that hybrids tend to be less successful at reproducing than their parents. They are often less fertile, skew towards one sex or the other, or perhaps are just not as attractive to potential mates.
Whatever the reason, although hybrids are not incredibly rare, they are certainly not overly common under most circumstances. But there are exceptions, especially in heavily altered habitats.
And it is not just the sunfish that can hybridize within the family. The black basses, a.k.a. the genus Micropterus, which includes largemouth, smallmouth, and spotted bass, are known to hybridize. Ever heard of a meanmouth bass? That's a spotted bass crossed with a smallmouth bass, or more rarely, a largemouth-smallmouth anomaly.
Supposedly, this fish was named "meanmouth" when a school was observed attacking a person swimming in a pond. Several bass supposedly leapt from the water and struck the swimmer on her head and chest.
Later, they were observed attacking a dog in the same pond.
Now I don't know about all that, but I do know that these hybrids do exist in the wild where spotted bass and smallmouth bass co-occur. I have caught them in Mississippi in the canal section between Pickwick Reservoir and Bay Springs Lake, and they are relatively common in Table Rock Lake, Missouri, and many other locations.
In the lab, researchers have even hybridized Micropterus species with Lepomis species! In the 1960s, they 'successfully' crossed largemouth bass with warmouth, green sunfish, and bluegill. Attempts to cross crappie (Pomoxis) with rock bass (Ambloplites) did not succeed. Thank goodness.
To my knowledge, these cross-genus hybrids do not occur naturally, though I have seen anglers claim they do online. The most recent was a young angler who was convinced he had just landed a largemouth bass crossed with a bluegill. It was a warmouth, but in his defense, that is what that cross might look like!
So, the next time you catch a crazy looking fish, snap a photo and show it to a fish biologist. You might have caught something unique!
Dr. Wes Neal, Extension Professor at Mississippi State, serves as the State Extension Fisheries Specialist and is passionate about educating the public on small-lake and pond management. He is an avid researcher on topics from farm pond management to sport fish genetics. Wes is the lead editor of Small Impoundment Management in North America, the only textbook on the subject. He loves to hunt and fish, wes.neal@msstate.edu.
Reprinted with permission from Pond Boss Magazine
