Corpus Hatchery Raising Juvenile Flounder

T his year, the number of juvenile flounders caught by the Texas Parks and Wildlife Department as part of its annual survey hit an all-time low, worrying fisheries biologists across the state.

For decades flounders have had declining numbers off the Texas coast. In a recent article, “Gulf ’s Environment Is In Hot Water,” penned by Kim McGuire for the Houston Chronicle, Leslie Hartman, TPWD’s Matagorda Bay Ecosystem Leader was quoted as saying, “It’s been warm, too warm, for southern flounders the past couple of years. 

“You don’t see the effect as much on the adults, but you do with juveniles. In a couple of years, fishermen in Texas are going to start to notice.”

Southern flounders spawn only in cold water and prefer temperatures around 62 degrees Fahrenheit. Water temperatures off the coast have been rising for years, especially the wintertime lows. This year, for the first time on record, the daily average surface water temperatures in the Gulf of Mexico never fell below 73 degrees.

Not only does it dictate whether they spawn or not, it also plays a major role in whether the fish become male or female. Cold water tends to produce females, which are bigger than males and prized for their meat.

That trend was observed at the University of Texas Marine Science Institute in Port Aransas, which led the state’s first efforts to get the fish to spawn in captivity to start a restocking program.

“We are trying to produce as many of those guys as possible,” said Natural Resource Specialist, Ruben Chavez at the fish hatchery in Corpus Christi in recent visit. “Our yearly quota is about 25-50 thousand. We are still learning that species; we haven’t been doing that too long, still a learning curve. Now that we have southern flounders we are culturing year-round.”

Joan Holt, former director of UTMSI Fisheries and Mariculture Lab explained that 64 degrees Fahrenheit is where the spawn is about 50/50 split between males and females, which is what you want in a fishery. If you raised the temperature above that threshold, you get less females and more males.

Having a fish population that is seriously skewed toward one gender would obviously be detrimental to its long-term survival.

So are temperatures creating more male southern flounder? The jury is out on that answer but there are strong indications that’s what’s happening.

During this year’s spring gill net season TPWD crews observed more adult southern flounder than they had the year before. Still, the numbers were low enough to be the fourth-worst on record, and state data shows southern flounder numbers dropping since the early 1990s.

Mark Fisher, science director for the department’s coastal fisheries division reported that the flounder are showing a pretty steep and steady decline. Any improvement in recent years likely has been due to stricter fishing regulations and restocking efforts. One of the regulation changes was banning gigging flounder during the fall, a controversial move, but one that state fisheries managers thought necessary.

It’s not just Texas that is experiencing the decline in juvenile female southern flounders. Alabama and other states in the western Gulf have reported during their spring sampling effort, not one of the 10 ecosystem teams was able to collect a juvenile flounder in the seine nets.

Whether southern flounders ultimately adapt to its changing environment remains to be seen. Studies suggest that coastal Texas may be on the edge of southern flounder’s natural range, which means it wouldn’t take much to force the population to shift elsewhere.

 

 

 

Email Tom Behrens at ContactUs@fishgame.com

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