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Golden Alga in Texas

Archived News Release

April 1, 2002

Possum Kingdom Fishery Recovering from Algae Hit

AUSTIN, Texas — Although this 17,700-acre reservoir northwest of Fort Worth has been around since the start of World War II, state fisheries biologists are treating Possum Kingdom like it's a brand new lake.

An extensive fish kill on Possum Kingdom caused by a prolonged golden algae bloom last year had a significant impact on several game fish species, including largemouth bass and striped bass, according to Texas Parks and Wildlife biologist Mark Howell. To help the fishery recover from these losses, the agency is considering management strategies similar to those used to build fish stocks in new impoundments.

In addition to increasing stocking rates to help replenish bass populations, TPWD is considering a couple of regulation changes that, if adopted by the TPW Commission at its April 4 meeting, will reduce angler harvest temporarily.

It appears that nature has already begun the recovery process, Howell said. Recent gill net surveys, combined with last fall's electrofishing surveys, have given TPWD a good picture of the extent of the damage to fish populations. Howell is encouraged by what he sees.

"We actually caught more largemouth bass during our electrofishing surveys last fall than in 2000, but what was noticeably different was that most of these were juvenile fish and based on subsequent genetic analysis a lot of the fish appeared to be there from our stocking efforts last May," Howell noted. "But there also was evidence of natural production, so we know that we had some brood fish left in Possum Kingdom. We did find very few larger bass and that's why we proposed increasing the length limit to 16 inches."

Biologists also report a dramatic growth rate for these young bass, which indicates a healthy population of forage fish at Possum Kingdom. "These fish looked really fat and in great shape," Howell said. "If they continue to grow like they are now, they should reach 16 inches in a couple of years. We're seeing a lot of similarities to a new fishery. These fish are growing well and I expect that to continue, barring any golden algae outbreaks."

TPWD conducted a gill net sampling in January targeting striped bass. Although the catch rate was only about a third what it was before the fish kill, the size distribution confirmed what biologists theorized - that the larger stripers were able to avoid the golden algae toxins and survived.

"Most of the fish we sampled were above legal size and up to 25 inches long, were in excellent body condition and have been growing well," Howell said. "That's an indication that the larger fish found refuge in the river during the algae bloom. Adult striped bass will typically initiate a spawning run type activity even though they do not reproduce naturally in Possum Kingdom. We actually sampled more large fish this year than last year."

Because no small stripers were reported in the gill net survey, Howell considers last summer's emergency stocking of striped bass fry proved unsuccessful. Fisheries managers typically stock fingerling-sized fish to ensure higher survival, but last year's striper production at the Dundee State Fish Hatchery was wiped out by the golden algae, leaving TPWD without stocks to replenish Possum Kingdom and other reservoirs. The fry from the 28 million striped bass eggs and 37 million hybrid bass eggs were lost as a result of being exposed to the toxin.

This year, TPWD plans to distribute striped bass hatchery production across several of its facilities to minimize the chance for a repeat catastrophe. Biologists also plan to increase the stocking rate at Possum Kingdom and have proposed a change in harvest regulations for this lake from a five fish daily bag to two.

On an optimistic note, Howell reported much higher catch rates for white bass than previous surveys and that most of the fish sampled were of legal size and should

provide ample harvest opportunity at Possum Kingdom while largemouth and striped bass populations are allowed to recover. He also reported good populations of blue catfish in the reservoir.

"I think we can be cautiously optimistic right now," Howell said. "That was devastating to have golden algae go through the reservoir twice."

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Additional Information:

In October 2003 Texas Parks and Wildlife hosted the Golden Alga Workshop in Fort Worth, Texas, bringing together researchers from all over the United States and abroad to determine what methods might be used to manage the Golden Alga blooms occurring across Texas. Background information and speaker presentations may be found in the Golden Alga Workshop section.

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