Invasive plants, mussels a growing threat to lakes

Published on Saturday, 14 February 2015 23:42 - Written by Steve Knight,

It won’t be long and a flotilla of boats will be heading out on lakes around Texas for the spring/summer boating season.

Texas has about 600,000 registered boats, many of which are fishermen that are on the lakes year-around. Others are pleasure boaters that will return to the water in mass around Memorial Day.

For the most part East Texas boaters will find lake near full capacity. Only a handful, Tawakoni, Fork and Cooper remain dangerously low.

Even though ramps and stumps are not a problem, there are other obstacles that could make boating difficult or eventually hamper fishing. Texas Parks and Wildlife Department is already monitoring a long list of invasive animal and plant species, and the concern is that more are on the way.

“Right now, fishermen should be most concerned with zebra mussels, especially in North and Central Texas, and giant salvinia in East Texas,” said Craig Bonds, TPWD’s Inland Fisheries Division Director. “It is very important to practice the clean, drain, and dry procedure for boats and trailers in between fishing trips. There are new invasive species seemingly every month coming to Texas.”

Giant salvinia was first discovered in Texas on Toledo Bend Reservoir in 1998. It has since popped up on 47 lakes mostly in East Texas. In many cases small infestations were discovered early and removed before the plant was able to spread. That includes Lake Palestine where it was discovered around boat ramps on several occasions.

One place it has become established is Caddo Lake. TPWD biologists and others have continually been waging a war against the float mats of giant salvinia for years. Efforts have already geared up for this year.

“Probably the best way to think about how giant salvinia will impact Caddo Lake this year, is to review what happened last year,” said Tim Bister, TPWD district Fisheries biologist. “The cold winter of 2013-14 reduced the amount of salvinia that was present in many areas of the lake by March 2014.  There were still some areas that contained some large mats of salvinia, and these ended up being areas that were targeted for giant salvinia weevil releases during the year.”

Even with winter’s impact there was enough of the plant remaining, especially since it can double in size in a week. TPWD found funding enough to treat about 2,200 acres of salvinia with chemicals in 2014. In addition, the Greater Caddo Lake Association of Texas released more than 70,000 giant salvinia beetles combined in Pine Island Pond and the Willowson Woodyard as a non-chemical treatment.

“By the time we conducted our annual invasive vegetation survey in September 2014, there was approximately 2,405 acres of giant salvinia on the Texas side of Caddo,” Bister said.

Bister said this winter hasn’t been as cold, so he doesn’t expect much help from Mother Nature. The first beetle release for treatment was Saturday. Contract sprayers have already been lined up for herbicide application as soon as the salvinia begins to show signs of spring growth.

Although zebra mussels may be a bigger problem in other parts of the state, there is concern they could find their way into East Texas.

Zebra Mussels or their larvae (veligers) have been documented in seven lakes and zebra mussel DNA has been found in 16 lakes,” said Brian Van Zee, TPWD Fisheries regional supervisor from Waco.

The lakes they have been found in include Belton, Bridgeport, Lavon, Lewisville, Ray Roberts, Texoma and Waco. Lakes with zebra mussel DNA are also mostly in Central Texas, but it has also been found in Palestine, Fork, Tawakoni, Caddo and Bob Sandlin.

A European import that can attach in such numbers that they block water intact pipes, clog water intact on boat engines and attach to recreational piers making them dangerous, biologists believe Texas is waging a battle to slow zebra mussel spread instead of stopping it.

“Honestly, I think the best we can hope for is to slow down their spread. Now does that mean that every lake in the state will become infested? No, some lakes and areas of the state likely won’t support zebra mussels due to various environmental or biological reasons,” Van Zee said.

Last July TPWD adopted a regulation requiring all boaters to drain all the water from their boats before leaving or approaching any fresh water lake to slow the spread of zebra mussels.

Those are just two of biggest problems right now. TPWD’s Bonds said other major issues of concern to fishermen and boaters around the state right now are water hyacinth, salt cedar and armored catfish.

Invasive plants are such a concern TPWD has developed two websites for the public to learn about them and what they can do to keep them from spreading. Those websites are: and