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Nov. 13, 2006

Improved Red Tide Response Tracks Decline of Texas Bloom

AUSTIN, Texas — A red tide event that lingered along the coastal bend for nearly a month appears to have largely subsided, according to Texas Parks and Wildlife officials.

Water samples taken in the Corpus Christi and Port Aransas areas have shown decreasing concentrations of the red tide alga since mid-October, and there have been no reports of fish kills or respiratory irritation for over three weeks. All the Gulf beaches appear to be free of red tide.

This year’s red tide, which is a high concentration (or bloom) of an alga called Karenia brevis, first showed up near San Jose Island, causing fish kills along the island, as well as along the Corpus Christi Ship Channel and at Cedar Bayou. It first began spreading north along both sides of Matagorda Island but then was pushed south to Mustang and Padre Islands, all the while lingering in portions of Corpus Christi, Aransas and Redfish bays. At one point the bloom was visible at the north Port Mansfield jetty, but it never did spread further south.

Dead fish as a result of the red tide numbered into the millions, but game fish made up less than 5 percent of the total. The majority of the fish killed were forage fish, including Gulf menhaden, Gulf whiting, Atlantic bumper, and mullet. Biologists do not expect the bloom to have a lasting impact on fish populations.

This red tide was fairly typical of previous Texas blooms, which tend to begin in late summer or early fall and can last for weeks to months. Though it is not clear what factors cause red tides, it is known that they are a natural occurrence in the Gulf of Mexico.

The state's response to the red tide was enhanced by a twice-weekly bulletin from the National Oceanic and Atmospheric Administration which provided satellite images showing the location of red tide and forecasting where it might impact the coast.

University and state agency scientists, as well as volunteers, played an important role in finding out where red tide was occurring, where it was absent and whether it was increasing or declining.

The volunteer Red Tide Rangers in South Padre Island regularly collected water samples south of Port Mansfield as an early warning system; fortunately the red tide never impacted that area. Texas A&M University-Galveston and Texas State Department of Health Services scientists sampled portions of the upper coast showing red tide was absent from Matagorda Bay up to Galveston. University of Texas Marine Science Institute researchers tracked red tide in the Port Aransas area on a daily basis and communicated their results as the red tide was blooming and later disappearing.

Filter-feeding shellfish, such as oysters, clams, whelks and mussels, accumulate the red tide toxin in their tissues, where it can remain for weeks after a red tide has ended. The toxin, which is not destroyed by the cooking process, causes a type of food poisoning called neurotoxic shellfish poisoning.

For this reason, shellfish harvesting season is delayed in parts of San Antonio Bay and all of Mesquite, St. Charles, Aransas, Copano and Corpus Christi bays. Information about shellfish closures can be obtained by contacting the Seafood and Aquatic Life group of the Texas Department of State Health Services at (800) 685-0361.

AR 2006-11-13

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