Aquatic grasses causes pros, cons for Texas wildlife

Aquatic grasses, many of them invasive species, can grow so thick that they render boating, swimming, skiing, fishing, and hunting near impossible. In some lakes, landowners cannot even get their boats out of their boat docks.

Texas Park and Wildlife Department (TPWD) biologists reported in a press release that in 2017, Caddo Lake, in East Texas, was covered by more than 6,000 acres of invasive giant salvinia. Giant salvinia can double in size in less than a week, forming mats up to three feet thick. It can choke out native plants that are habitats for local fish and birds.

But Caddo Lake got a break from Mother Nature.  Now the giant salvinia plants have been reduced to just over 1,500 acres.

How did that happen?

John Findeisen, Brookland Aquatic Habitat Enhancement Team Leader, reported in the TPWD press release that “We can thank Mother Nature for the cold snap and subsequent flooding that caused a massive decrease in giant salvinia on Caddo and other infested East Texas lakes.

“A hard freeze in January 2018 made a huge dent in the giant salvinia, freezing much of the plant material and loosening the dense mats. This was followed by high water inflows a month later, pushing the remaining giant salvinia into the open lake where it was destroyed by wind and waves and washed up on shore.”

But most of the time we don’t get that much help from Mother Nature. Man has to supplement. Herbicide applications can help keep invasive plants, not just giant salvinia, under control.

Findeisen said, “Since September 2017, TPWD and its contractors have treated 18,340 acres of giant salvinia statewide.”

Hydrilla is a major invasive species in many of our lakes. Bass fisherman love hydrilla.  It is the perfect bass cover.  Bass feed on minnows, shad, and other bait fish in and along the edges of hydrilla beds.

But hydrilla can get out of hand. Years ago, when Bastrop Lake was very heavily invested with hydrilla, much of the lake was unfishable. It was so thick that some bass anglers tried tossing very heavy jigs into the air and letting the jig crash through the hydrilla mat. Often, hungry bass under the mat would eat up the jig.

In these infestation days, huge mowing machines would mow large strips in the hydrilla just like a lawn mower in your backyard.

Today Bastrop has some hydrilla but not too much. Perfect for fishing. Actually, hydrilla is no longer the predominant aquatic grass in Lake Bastrop. Eel grass is much more abundant. Eel grass, like its name, is long slender strips of dark green grass. Bass love it. 

Tom Ray and I fished Bastrop last week and caught 12 largemouths on the eel grass patches. Because of lower water temperatures in winter, the eel grass is not yet on the surface. But we could see dark patches several feet under the surface in our polarized glasses.

Several years ago the hydrilla problem on Lake Austin became so acute that landowners persuaded TPWD to do something. Grass carp were released into the lake. But they didn’t know where to stop eating.  They ate all the aquatic vegetation. Lake Austin quickly declined from one of the great trophy bass lakes in Texas to a poor one. Many years before the same thing happened on Lake Conroe. Will Lake Austin make a comeback as a trophy lake?  Who knows? Probably not.

Because noxious weeds can be spread easily from one lake into another, TPWD is making a concerted effort to encourage boaters to clean their trailers, livewell, and motor props to stop the spread. Most boat ramps now have signs warning of the problem and encouraging boaters to be diligent in cleaning their boats and gear of any aquatic grasses.

Actually, boaters can be fined for up to $500 for transporting invasive species. It’s easy to pull out of a boat ramp and forget to clean the boat and trailer.  Hopefully, game wardens would show a little mercy to those of us who are getting more forgetful.