Cold weather hurts hyacinth, giant salvinia and hydrilla

[Ray]

While a hard freeze such as the one that hit Texas this past weekend can severely damage coastal fisheries, it can be a blessing for inland waters.
“To be honest, I'm hoping for another one — the colder the better,” Howard Elder, of Texas Parks and Wildlife Department's inland fisheries division, said of the recent frigid spell. “It helps us a lot.”
As an aquatic vegetation biologist, Elder's main focus is, by default, fighting invasive aquatic plants such as water hyacinth, giant salvinia and hydrilla that threaten to smother inland waters. The effects damage fisheries, destroy wetlands' ability to support wildlife and restrict or even prevent human access to waterways.
The worst invasive plants are natives of warm climates — South America, mostly — and have limited tolerance to cold temperatures. Freezing temperatures kill them — particularly the floating plants such as hyacinth and salvinia.
Appreciate the help

“A good hard freeze can kill a lot more (invasive aquatic plants) than our crews ever could with herbicides,” Elder said.
And East Texas, where water hyacinth and giant salvinia have established colonies that cover thousands of acres of water, got a good hard freeze this past week.
“It was down to 16 degrees, here. And it lasted for three days. There was ice everywhere. That's going to help us a whole lot,” said Elder, based in Jasper.
Any invasive plants that were on the bank were almost certainly killed, Elder said. Small ponds were frozen over, and that ice works wonders.
”I'm sure almost all the mature hyacinth that was exposed to the freezing temperature were hammered,” Elder said.
While the freezing temperatures certainly killed some of the rampant invasive aquatics plants, it didn't come close to killing them all, or even most of them.
Less of a bad thing

“What it does, though, is give us a little breathing room,” Elder said. “There's still going to be a lot of it that survives. But it gives us a chance to hit it hard. Anything that reduces it is good.”
The same thing can be said for the freeze's impact on invasive fish species that have thrived, to the detriment of native fish, in some local waterways.
Bayous, streams and other waterways in and around Houston are infested with large and growing populations of invasive fish such as tilapia and armored catfish — species that compete with native fish and, in the case of armored catfish, burrow into banks and accelerate erosion.
Like the invasive plants, the invasive fish are natives of tropical or semi-tropical areas and can't handle truly cold temperatures.
This past weekend's freezing weather was too much for some of the invasive fish.
“I checked some areas on White Oak Bayou and saw quite a few dead invasives — tilapia and armored catfish,” TPWD fisheries biologists Winston Denton said. “I know there were mortalities in the other bayous, too. That's a positive thing.”
Even a frigidly cold wind blows some good, it seems.