Texas focuses research on alligator gar
A fleshy tail the size and shape of the business end of a house broom rose from the smooth, green surface of the Brazos River, waving slowly in the September morning light like some broad, olive/yellow/black-spotted flag.
The tail’s owner obviously had swam afoul of the gill net that Dominik Chilleri had fed into the river not 20 minutes earlier, the top of the 200-foot-long sheet of webbing marked by a series of orange buoys.
Any idea that the seemingly half-hearted flap signaled surrender of the creature to which it was attached ended when Dan Daugherty idled the 16-foot aluminum boat close enough that Chilleri could take hold of the net and the pair, in practiced coordination, slowly worked the trapped fish to the surface with an eye on hauling it into the boat.
When the fish realized what was going on, the Brazos exploded in a fury of white water as the two Texas Parks and Wildlife Department fisheries scientists carefully heaved their catch aboard. The fish — all 5 feet and maybe 60 pounds of alligator gar — plunked on the boat’s floor, writhing and arching and squirming for perhaps five seconds before calmly yielding and allowing the pair to quickly untangle it from the webbing.
“Nice one. But not a really big one,” Daugherty said. “We’ll get more.”
And they did. Soon, five alligator gar rested quietly on the boat’s floor, the latest assemblage of their kind to be incorporated into a multifaceted research program aimed at learning more about this largest of Texas’ freshwater fish and the best ways to ensure that those fish and the increasing number of anglers who fish for them thrive.
And there has been a lot to learn. Alligator gar long have been one of the least understood and most misunderstood of the state’s diverse inland fishery.
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Link to the past
These ancient native fish with their cylindrical bodies sheathed in armor-like ganoid scales, long and wide bony snout and a mouth rimmed with a double row of spike-like teeth have been swimming in Texas waters for more than 150 million years, almost unchanged from their ancestors, who shared space with dinosaurs. But until recently — really, just in the last decade — they have been almost as wholly ignored by fisheries scientists and managers as they have been almost universally demonized by most anglers and the general public.
Just a few years ago, Daugherty, a research fisheries scientist at TPWD’s Heart of the Hills Fisheries Research Center, dove into a database of scientific journals that held mountains of published research on the nation’s freshwater fisheries. A search of the database yielded more than 20,000 “hits,” indicating scientific papers related to biology and management of largemouth bass.
Research focused on alligator gar?
“I found five papers,” Daugherty said. Those five addressed basic research such as food habits and basic natural history. None addressed managing gar fisheries.
But that was understandable, given the longtime attitude of fisheries managers, anglers and the public toward the fierce-looking fish. Gar had been subject to decades of unregulated recreational and commercial harvest and intense persecution — even government-sponsored attempts at extermination. They were seen, with no supporting evidence, as brutish, insatiable predators of “good” fish, and even dangerous to humans.
That attitude and knowledge about the fish has changed over the past decade, with Texas fisheries scientists among the leaders in efforts to learn more about gar — alligator gar in particular.
Some of that comes from fisheries managers’ shift from focusing on individual fish species — invariably those fish seen as having the most recreational or commercial value — to a more holistic approach of seeing and managing aquatic ecosystems as the complex, interconnected and interdependent world they are, where every species plays a crucial role.
Some of it comes from realizing that alligator gar were disappearing from the nation’s waters, Texas held the absolute best remaining populations, and those fish were a valuable resource not just for their important place in a healthy ecosystem but as a recreational and economic resource. Alligator gar, a fish that can grow to as much as 300 pounds and are powerful, challenging and singularly impressive looking quarry for anglers, were increasingly drawing the attention of anglers. And not just Texas anglers. The state’s “trophy” alligator gar fishery attracts a steady and growing stream of international anglers … and their money.
Once found throughout the Southeast and as far north as the Ohio River, alligator gar have disappeared or almost so from most of their native range. Only Texas and Louisiana have anything like healthy populations. And Texas has the healthiest, at least when it comes to fisheries holding truly huge individuals — fish measuring 7 feet or more and weighing 150 to 200 pounds or more.
Texas’ large river systems — the Red, Trinity, Brazos, Guadalupe, Nueces and Rio Grande, especially — provide the specialized habitat alligator gar require. And that is where, beginning about a decade ago but increasing in the past few years, Texas fisheries scientists have focused their research efforts.
Those efforts are illuminating previously unknown insights into the fish, their natural history, value in aquatic ecosystems and value to anglers.
The insights reveal a fascinating fish and fishery and point the way toward managing the fishery for the benefit of gar, gar anglers and the fisheries on which both depend.
Much of the information comes from research such as that Daugherty and Chilleri engaged this past week. The pair launched their boat on the Brazos downstream from Waco and made their way to an isolated deep pool, where they set three 200-foot gill nets in the river. Those deep pools, experience has proven, are where gar spend most of their time.
By constantly monitoring the nets, the researchers can quickly collect fish that swim into the webbing, avoiding mortality of captives.
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Females are bigger
Once in the boat, the fishes’ total length and girth are measured and recorded.
Measurements also are taken of the length of the fish’s snout from tip to eyes, the length of the base of the anal fin and length of the fish from nose to base of the tail. Those three measurements, TPWD researchers have learned, can be plugged into a formula to determine the sex of the fish, crucial information in understanding population structure.
Large alligator gar — those measuring 6 feet and longer — are almost invariably females, TPWD research has shown. Out of the thousands of adult alligator gar TPWD researchers have handled, only a handful of males measures 6 feet or longer. And none was 7 feet or longer. All truly huge alligator gar are females, Daugherty said.
And it takes decades for fish to grow to that size. While alligator gar grow quickly when young — some can each 30 inches in a year — that growth slows considerably after the first 10 years or so. It can take a fish 20 years to grow to 6 feet. Truly huge alligator gar — those 7 feet and longer — can easily be 50 or 60 years old or older, Daugherty said.
After measuring, a small fin clip is taken from the fish for genetic testing, and each fish is fit with a pair of tags. An external tag noting that the tag was placed by TPWD and including an identifying number is affixed near the dorsal fin. A PIT (passive integrated transponder) tag — a tiny electronic device with a unique number readable by hand-held scanner — is injected beneath the fish’s scales.
After tagging, the fish is released.
The thousands of gar that TPWD and cooperating partners have tagged have yielded invaluable information on gar movement, annual survival, population size and other behavioral insights. Recaptures of tagged gar are common. One huge gar — a 7-footer — captured and tagged in a deep pool in a Texas river in 2011 has been recaptured three times, twice by anglers who released the fish and again by a TPWD crew.
All four of those captures occurred in the same deep pool, Daugherty said. And that underscores another insight collected through the agency’s research. In Texas river systems, alligator gar populations in upper and lower reaches of the rivers have distinct abundance and size structures. Upper reaches of the rivers have “pocket” populations of alligator gar, where fish tend to hold in distinct areas — usually deep pools, where they spend almost all of the lives, never traveling any great distances upstream or down.
These populations tend to have more larger fish and fewer smaller fish than population in lower reaches of rivers. In the lower reaches of rivers, gar move longer distances are more numerous but also hold more smaller fish, a wider range of fish sizes but few very true giants.
Why? One reason, Daugherty said TPWD research has shown, is that the overbank-flooding necessary for alligator gar to successfully spawn is more common in the lower reaches of rivers than the upper reaches.
The difference in populations and population dynamics of those populations suggests that those fisheries can be managed differently.
“It suggests we could manage the fishery at regional levels,” Daugherty said. Currently, Texas has a statewide alligator gar bag limit of one fish per day, with a single exception for Falcon Reservoir.
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There’s much to learn
TPWD’s multifaceted gar research over the last several years — which includes cutting edge use of side-scan sonar to locate and survey gar populations, acoustic transponders to monitor movement, stable isotope data to learn more about gar’s use of saltwater habitats, and improved aging techniques — are paying dividends.
“We’re finally getting to the point where we have a critical mass of information we can use to guide us in making better informed management decisions,” Daugherty said. And that includes learning what Texas anglers want from their alligator gar fishery, he said.
Earlier this year, TPWD initiated an in-depth online survey of the state’s gar anglers. The survey, which ran during June and July, drew more than 9,000 participants. Results of that survey are being compiled and will be used by fisheries managers in looking at future management considerations.
“That information — input from anglers — is an important piece of the puzzle,” Daugherty said.
It’s a puzzle that could decide the fate of a fishery unique to Texas.