The alligator gar gets its name from the shape of its snout and the rows of sharp teeth. Photos by Chris Young.
Biologists helping ancient fish make comeback in Illinois
September 29, 2013 at 05:16 PM
When fisheries biologist Rob Hilsabeck holds up a 14-inch alligator gar to show its teeth, it looks like he’s holding a creature straight out of a book about prehistoric animals.
The State Journal-Register
And, well, he is.
The alligator gar, the largest native gar, is an ancient fish with a lineage almost 120 million years long. It has inhabited the Lower Mississippi River drainage from Louisiana and Texas north to Illinois for more than three million years.
Despite their fearsome appearance, alligator gar don’t bother people. But it’s a different story for other aquatic life. The alligator gar is a top predator, growing to almost 200 pounds in size. And the fish live for decades.
But just because the alligator gar has survived on Earth this long doesn’t mean it’s had an easy time. Within the last century, it was found in the Illinois River at least as far north as Beardstown.
The last alligator gar confirmed in Illinois was caught in 1966. Photo courtesy of the Illinois Department of Natural Resources.
However, the last confirmed alligator gar was caught in Illinois in 1966 near Cairo. They fell prey to habitat loss and people who found the big fish easy pickings in shallow backwaters.
By 1994, officials determined the species was no longer present in Illinois and removed it from the state list of endangered species.
In recent years, the U.S. Fish and Wildlife Service has been working with states in the gar’s historic range to begin a reintroduction program.
Illinois has released the fish in promising habitats, such as the Sanganois State Fish and Wildlife Area in Cass County.
The Sanganois lies near the confluence of the Sangamon and Illinois rivers. Before the Sangamon was straightened and made to empty into the Illinois River at Beardstown, it broke into braided channels in the Sanganois.
What remains is a complex of backwater wetlands, sloughs and lakes that the gar might find useful.
Eat or be eaten
The alligator gar is a river fish that moves back and forth from the main river channel to backwater areas to spawn. They also can survive in some large lakes.
So Hilsabeck, a fisheries biologist with the Illinois Department of Natural Resources, released just over 650 fish, averaging about 13 inches, into the Little Sangamon River and Crane Lake early in September.
Other alligator gar have been released into sites including Powerton Lake near Manito, Hennepin & Hopper Lakes north of Peoria, and Spunky Bottoms, a restored backwater wetland in Brown County.
First, biologists must rear the fish to a size large enough they won’t simply be food for other fish, including other native species of gar.
“They are long and slender, so they go down easy,” Hilsabeck said with a laugh. “So, you either eat the alligator gar now or he is going to eat you later. It’s fish-eat-fish world.”
Nathan Grider, a biologist in DNR’s office of mines and minerals, studied alligator gar for his graduate thesis at the University of Illinois Springfield.
For his study, Grider monitored the growth rates and diets of 100 alligator gar into The Nature Conservancy’s Merwin Preserve at Spunky Bottoms in September 2011. Stocked fish were 24 inches long, big enough that predators would leave them alone.
From May to October 2012, fish were recaptured using a technique that did not harm the fish, and their diets were analyzed. The largest individual grew to 14 pounds and 38 inches long in just 17 months.
Mostly the gar ate gizzard shad — not sportfish such as bass, crappie or bluegill, Grider said. Researchers hope the gar will eat Asian carp, but Grider said it is too early to draw any conclusions.
.Nathan Grider (left) holds a 14-pound alligator gar from The Nature Conservancy's Merwin Preserve at Spunky Bottoms in Brown County. Also working with Grider are Doug Carney, Illinois Department of Natural Resources (second from left), Nerrisa McClelland of the Illinois Department of Natural Resources and Rob Hilsabeck of DNR. Photo courtesy of Nathan Grider.
Mobile, but vulnerable
Grider went back to Spunky Bottoms this month to see what effect last spring’s flooding had on the gar, since the levee separating the preserve from the river was breached.
He said no alligator gar were recaptured.
“Some of them are probably still there,” Grider said. “It was already a needle in a haystack, because we put 100 fish in there and it is a pretty big place. We would have to do an intensive survey.”
Hilsabeck said alligator gar are very “mobile” fish.
“It depends on how many alligator gar stuck around and how many decided they wanted to take a look out in the river,” he said.
With many floodplains cut off from rivers by levee systems, fish like alligator gar had fewer places to spawn.
“They like to spawn way up into these floodplains and that made them very vulnerable to humans,” he said. “Especially when they are 200 pounds and their backs are sticking out of the water way up in these floodplains.”
He said radio telemetry work shows fish moving from main channels inland.
“Whenever there is a flood pulse in the spring, they charge right in there,” he said. “That is one of their challenges. A lot of these big river fish like paddlefish and sturgeon, suffer from the lack of connectivity.”
Hilsabeck said there appears to be a large enough food base to support alligator gar today. Still, the fish take a long time to mature and reproduce.
“It is many years before they become sexually mature,” Hilsabeck said. “It is like the alligator snapping turtle, too. There is that weakness there. If you put too much pressure on the larger fish, you are going to eliminate them.”
Rob Hilsabeck releases 13-inch alligator gar in the Sanganois State Fish and Wildlife Are.
Hilsabeck said the project has been a cooperative effort with support from other agencies, state fish hatcheries and private hatcheries like the Exelon hatchery located on Pool 14 the Mississippi River near the Exelon Nuclear Quad-Cities Generating Station.
Jeremiah Haas, a biologist with Exelon, brought a hatchery truck with the fish to be stocked in the Sanganois.
The hatchery raises mostly walleye, hybrid striped bass and rare mussels and takes on a few side projects such as alligator gar.
“We thought about keeping one for the fish tank in the office,” he said.
Then the thought of a toothy fish growing from 14 inches to 200 pounds flashed through his mind.
“But we figured it would outgrow the tank in no time.”
Uniquely adapted to survive
The alligator gar does well in southern states, so it tolerates warm water well, thanks to an adaptation that lets them gulp air at the surface.
“At 80 degrees (water temperature), these fish would die in a few minutes if they couldn’t gulp air,” said Illinois Department of Natural Resources fisheries biologist Rob Hilsabeck.
Metabolism ramps up and oxygen levels drop when water warms up during the summer months.
The gar have a “swim bladder” connected to a membrane behind the nose and mouth that allows them to take in air when needed.
Alligator gar released into the Sanganois State Fish and Wildlife Area gulped air from the surface as they swam away.
How big do they get?
Longnose gar: State record: 17 pounds, 5.28 ounces
North America: 50 pounds, 5 ounces
Shortnose gar: State Record: 5 pounds, .96 ounces
North America: 6 pounds, 6 ounces
Spotted gar: State record: 7 pounds, 13.44 ounces.
North America: 28 pounds, 8 ounces
Alligator gar: records range from 279 pounds to 327 pounds, depending on method used to catch fish.