When the bloom bites
Monday, November 30th, 2009Fish not the only organism affected by algae’s toxin
Flu-like symptoms are all the rage on cable news these days. The so called swine flu pandemic is sweeping the world.
But down in South Texas, something else is causing the coughing, sneezing, wheezing, runny nose and watery eyes: red tide.
The unpredictable, though not uncommon, bloom of algae releases a toxin that causes respiratory distress in humans and kills fish by the thousands.
The algae is suspended in the water. Humans contract the toxin while swimming and while breathing air near the water. The toxin becomes airborne from crashing waves or other disturbances.
Robert Holmes wore a cloth mask over his mouth and nose while fishing the north jetty at South Padre Island.
“Some people are more sensitive,” Holmes said.
Holmes, a North Texas resident who was visiting the coast, purchased the mask at a drug store and wore it while catching mangrove snapper on the beach side of the jetty.
John Martinez was susceptible to the tide too, though he wore no mask at the jetty.
“It could be worse,” Martinez said. “We could be at work.”
It was worse for some: the fish. Of the thousands of fish washed up on the beaches, most are mullet and hardhead catfish, said Alex Nuñez, a member of Texas Parks and Wildlife’s Kills and Spills Team.
The fish are filter feeders and have modified gill rakers that take in more of the red tide toxin.
“I seems like the need to feed is greater than common sense,” Nuñez said.
The red tide affects all fish and shellfish, Nuñez said. Oysters and shrimp are susceptible, too.
Shellfish harvested from waters where red tide is blooming should not be eaten because the consumer eats the whole body, and the whole body can be affected by red tide. Fish caught in red tide waters may be eaten because the whole body is not consumed, and the edible tissue, the meat, remains safe, Nuñez said.
When oysters or other shellfish are affected by red tide, state officials will close or delay the harvest season. The delay gives the animals time to flush the toxin from their bodies.
The easy catch of fish on the beach should be avoided, too.
“We always tell people don’t eat the dead fish,” Nuñez said.
With all fish being susceptible to red tide, that includes popular sport fish such as redfish and speckled trout.
“You drive enough miles of beach, you find everything,” said Jim Tolan, a TPW research scientist in Corpus Christi. “They all succumb to red tide.”
All sizes of fish are susceptible, too, Tolan said. “Everything that you can think of that you want to fish for is washing up on the beach,” he said.
Tolan said he does not know how a red tide affects fish behavior, whether they flee from it. He said research on fish behavior during red tide is scarce.
“I don’t know that anybody’s ever studied fish behavior because it’s difficult to predict when a red tide’s going to hit, and when it does, it wipes everything out,” Tolan said.
Nuñez said he thinks the red tide pushes fish away, “but that’s something I really don’t know for sure.”
So if the red tide is lethal across so many areas of the ecosystem, how does the ecosystem recover?
Tolan said it may be severe on a 50- mile stretch of beach, but beyond that, the wildlife is unharmed. When the red tide dissipates, animals from outside the affected area will move in and join animals that survived.
“You’re not going to wipe the Gulf clean,” Tolan said.
Red tides are unpredictable, Nuñez said, and they appear to be caused by several factors.
“When they reach a perfect storm, then the blooms just seem to grow in concentration,” he said.
No control measures are available for fighting red tide, either. The red tide affecting deep South Texas has persisted for several weeks, and they generally occur in late summer and early fall.
The current bloom is expected to dissipate soon, Nuñez said.
- By Thomas Phillips
Source:
LoneStar Outdoor magazine, Issue November 13, 2009, Volume 6, Issue 6
http://www.lsonews.com/images/stories/issues/nov1309.pdf