Scientists with the National Oceanic and Atmospheric Administration issue an annual prediction of brown shrimp catches based on monitoring juvenile population numbers, growth estimates and the environment.
Federal scientists are predicting a harvest of 55 million pounds of brown shrimp for this month through June 2014. That’s slightly below the historical 52-year average of 56.5 million pounds. They predict the Louisiana portion of that catch to be about 29 million pounds and the Texas portion about 26 million pounds.
“Brown shrimp are important to the economy of Gulf Coast communities,” said Roger Zimmerman, director for the National Oceanic and Atmospheric Administration Southeast Fisheries Science Center’s Galveston Laboratory. “They are popular among seafood consumers and as bait used by recreational anglers. We always like to see plenty of shrimp available in seafood markets and bait shops. But this year recruitment of shrimp larvae to the bays was late, which may impact their abundance.”
About 60 percent of the shrimp harvested in the U.S. comes from the Gulf of Mexico. The total domestic shrimp harvest brought in $518 million in 2011.
The juvenile brown shrimp population and growth estimates are obtained by monitoring the inshore commercial shrimp fisheries in Texas and Louisiana. Data is obtained from multiple state and federal offices and the commercial shrimp industry.
According to NOAA, young brown shrimp begin entering the estuaries in Texas and Louisiana in mid-February and continue through July, depending on environmental conditions.
This year, two environmental indicators favored shrimp production: Saline waters in the marshes and winds sustaining the tidal height. But the cool spring temperatures were unfavorable for shrimp growth. Shrimp don’t grow as fast in cooler waters because the temperature affects their metabolism, Zimmerman said. Also, the number of post-larval shrimp peaked later than usual, and the near shore brown shrimp catch in Louisiana in May was smaller than average, about 29 million pounds versus an average of 30.8 million pounds, Zimmerman said.
Clint Guidry, president of the Louisiana Shrimp Association, said shrimp season predictions by NOAA can be hit or miss.
Guidry said he also tends to consider the dead zone forecast issued at the beginning of the summer each year by Louisiana State University and the Louisiana Universities Marine Consortium in Cocodrie when looking to the next year’s shrimp season.
The dead zone is an area of low to no oxygen that forms off the coast of Louisiana and Texas east summer.
It is formed when excess nutrient pollution from the Mississippi River flow into the Gulf of Mexico. Those nutrients, coupled with the warm summer sun, spark an overgrowth of algae that blooms, dies and them decomposes, eating up the oxygen in Gulf waters as it decays.
That large area of dead water can stress shrimp populations, which migrate between Louisiana’s inland estuaries and the open Gulf during their life cycle.
Zimmerman said shrimp move offshore during the summer. More are crowding into the Texas waters, perhaps because the dead zone is impeding their ability to move into the open Gulf.
With the dead zone predicted to be between 7,286 and 8,561 square miles this year, it could be one of the largest on record, which wouldn’t be good for shrimp, Zimmerman said.
The biggest dead zone recorded to date, in 2002, reached 8,481 square miles.
But just like any forecast, Zimmerman said the shrimp season forecast is based on current conditions, which can always change. A tropical system could churn up the Gulf and disperse the dead zone, making it more favorable for shrimp and other marine life.
“The mathematical prediction based on environmental factors and the catch in Louisiana and the Texas bays suggest it will be a little bit below average year,” Zimmerman said. “But it’s kind of like a weather forecast. You don’t really know until you get halfway through the season.”