Trinity River flooding a boon to alligator gar spawn

The Trinity River's alligator gar fishery, world famous for producing trophy-size fish, got a much-needed boost this year when flooding created perfect conditions for the primitive fish to pull off a rare, hugely successful spawn. Photo: Picasa

Updated 1:30 pm, Tuesday, December 29, 2015

Anglers fishing for trophy-size alligator gar in the Trinity River in 2040 and beyond may well look back on 2015 with particular appreciation for what this year gave them.

Chances are good many of the 150- to 200-pound or heavier alligator gar those anglers catch from the Trinity 25 to 40 years or more from now will have been hatched in 2015, a year that saw what may be the most productive spawning season the slow-growing, armor-plated fish have enjoyed in decades.

“The flooding we’ve seen in Texas this year has been a tragedy for so many people, and you can’t understate or diminish that human impact; it was horrible,” said Craig Bonds, director of inland fisheries for Texas Parks and Wildlife Department. “But if you’re looking for something positive from all that water, it did provide benefits to fisheries. Some of those benefits will be around for years to come.”

Alligator gar in the Trinity River are one of those positives, Bonds said.

Record-setting rains and weeks-long flooding in much of Texas this year caused considerable human misery and economic losses. But that flooding, coming after almost a decade of pernicious, persistent drought, proved a super-charger for inland fisheries by filling reservoirs, pumping nutrients into fisheries, flooding shoreline vegetation that provided cover for just-hatched fish and resulted in outstanding survival of the year’s annual crop of largemouth bass, crappie and other game fish.

While the high water proved a benefit to almost all freshwater fish, it was particularly advantageous for alligator gar. For alligator gar in the Trinity and other Texas rivers, the floods produced the rare combination of conditions necessary for them to successfully reproduce at all.

Decades to mature

Alligator gar spawn only in areas holding flooded terrestrial vegetation. Female gar, which take a decade or more to grow to 60 inches or so and reach sexual maturity, move into grassy, weedy flooded shallows where they are followed by packs of smaller males. The female releases her eggs and the attending males fertilize them.

The sticky eggs attach to stalks and leaves of the submerged terrestrial vegetation where they hatch after several days. The larval gar hang in the flooded areas, growing amazingly quickly.

“You can almost watch them grow,” Bonds said. “They’ll get to 4-5 inches really fast.”

As the flooding recedes, the young gar end up in oxbows or sloughs or the main river channel where they can live for decades, feeding almost exclusively on shad, buffalo, carp, freshwater drum and other “rough” fish. And they can get huge. Alligator gar can grow to more than 300 pounds and live almost a century. A 327-pounder caught in Mississippi was 95 years old, its age calculated by counting the annual “growth rings” in its otolith, or ear bone.

Texas, and particularly the Trinity River, holds the nation’s premier “trophy” alligator gar fishery, regularly producing fish weighing more than 150 pounds and often more than 200 pounds. The state rod-and-reel record is 279 pounds, with a 302-pounder caught on a trotline and a 290-pounder taken with a bow.

Perfect conditions

The Trinity’s alligator gar fishery has become world famous, drawing anglers, many from other counties, who want the experience of hooking and landing one of these huge, fierce-fighting, strikingly atavistic fish.

But the Trinity’s gar fishery is a relatively fragile thing. Their specialized spawning requirements mean they successfully reproduce only in years when rivers or reservoirs flood and the high-water holds long enough for the fish to spawn, the eggs to hatch and the young fish to grow big enough to survive. And in Texas, such conditions have become increasingly rare.

Drought combined with human manipulation of river hydrology has made these conditions increasingly rare. TPWD research indicates alligator gar along the middle reaches of the Trinity River failed to produce any young in 17 of the past 47 years, with only limited young gar produced in some of those “successful” years.

This year was different.

Texas this year saw the wettest May statewide in the 120 years such records have been kept. The Trinity River was out of its banks from late spring through much of the summer, overlapping alligator gar spawning season.

“You couldn’t have dreamed up better spawning conditions than what the Trinity saw this year,” Bonds said. “The river was so high for so long. It hit just perfect, and the fish took advantage of it.”

TPWD staff documented alligator gar spawning throughout the summer. Staff of TPWD’s Richland Creek Wildlife Management Area found swarms of huge alligator gar spawning in flooded areas of the WMA and shot some of the most amazing video of the event, including underwater shots of alligator gar eggs and larval gar. (The video can be found on YouTube.)

The Trinity’s alligator gar have not had a successful spawn since 2007, Bonds said. And for the past several years agency researchers have had a devil of a time finding young alligator gar for ongoing studies. That was not a problem this summer.

“They were everywhere,” Bonds said of young gar.

This off-the-charts spawn bodes well for the future of the river’s alligator gar fishery. The fish born this year will be important components of the Trinity’s fishery for decades to come.

“Thirty, 40 and even 50 years from now, anglers will still be catching alligator gar from the 2015 year class of fish,” Bonds said.