Marine biologists look at hatcheries for 2 fish
Marine biologists release tiny fish to see if they can bolster 2 popular Gulf species
NEW ORLEANS (AP) — Marine biologists are trying to learn whether they can increase populations of two of the Gulf of Mexico's most popular sport and food fish — and perhaps further relax quotas on one of them — by raising and releasing small fry.
Hundreds of thousands of spotted seatrout, known locally as speckled trout or specks, and thousands of red snapper fingerlings have been released in recent years, all identifiable by tiny wire tags. The problem is finding them again.
Of nearly 600,000 or so specks released since 2006, only about 50 have been recovered, said Reginald Blaylock, director of the aquaculture center at the University of Southern Mississippi's Gulf Coast Research Lab in Ocean Springs, Miss.
On Thursday, scientists from USM and the Mississippi Department of Marine Resources released just fewer than 2,000 red snapper to an artificial reef south of Horn Island, Miss. A flexible hose was attached to their tank, a diver carried the other end to the reef, and a valve let the fish into the hose.
They're too small for electronic tags, so microwire tags invented in the 1960s are being used to try to tell whether all those little fish are having any effect on overall species numbers.
Although the first U.S. fish hatchery opened in the 1880s, the science is relatively young, said Ken Leber, associate vice president for fisheries and aquaculture research at Mote Marine Laboratory in Sarasota, Fla., and head of the Science Consortium for Ocean Replenishment — a group of five institutions including USM.
He dates the start of hatchery science to 1989. "There are precious few success stories, but we shouldn't throw out the baby with the bathwater. We need this technology in this century," he said. "We're seeing more and more habitat degradation" such as damage to seagrass meadows from river-borne sediment and damage from dredging and trawling, he said. "If the habitat disappears, it's hard to have a sustainable fishery."
Alec D. MacCall, who wrote the paper "Against Marine Fish Hatcheries" in 1989 as one side of a printed debate, said people have changed land ecosystems so much that many species can't use them any longer. That isn't the case yet in the ocean, but especially with climate change, "we're moving toward" such a situation, he said.
MacCall, a senior scientist in the National Marine Fisheries Service fisheries ecology division in Santa Cruz, Calif., said Thursday that he hasn't seen any conclusive research since his paper came out to persuade him that hatcheries have contributed significantly to repopulation of species that spend their entire lives in the ocean.
And, he said, "The real fundamental problem is fishery reform. ... If a hatchery effectively stops management reform for the natural stock, I'd be hesitant to call anything successful."
Leber said his research has shown that common snook, which spawn at the mouths of rivers and other waterways and live in the freshwater upstream as hatchlings and juveniles, can be successfully introduced in those waterways. He identified hatchery fish through genetic analysis, distributing kits through bait and gear shops to let anglers easily send in genetic samples.
A similar campaign and testing in Mississippi might be able to get more information about specks, he said.
Overnight fishing tournaments in Florida found that 3 percent of the adult fish caught in some areas were hatchery stock, Leber said.
"We're only releasing 6,000 a year. You wouldn't expect that to even show up. But if we can do that with 6,000 fish, think what I could do with 100,000 fish a year. We just cannot rear that many snook yet."
Blaylock said he uses fish taken in routine state and USM catches to assess fish populations because he knows exactly where each is caught. The scientists use magnetic wands to check for the tags. They've occasionally thought they'd found a hatchery fish only to discover it was a wild fish that had swallowed a hook.
Blaylock said USM's hatchery costs about $2 million a year to operate. It comes from a combination of federal grants, mostly from one agency or another within the National Oceanic and Atmospheric Administration, and state grants through programs including Tidelands and the Coastal Impact Assessment Program.
Texas gets millions of dollars a year for hatchery research from that state's branch of the Coastal Conservation Association, a sports fishing group, but "Mississippi isn't quite as rich as Texas, so we don't get as much direct financial support," Blaylock said.
He said he's working with red snapper and speckled trout because they're among the most popular fish in the Gulf.
Overfishing brought annual fishing quotas on red snapper, though those have risen from 4 million pounds in 1991 to just more than 8 million pounds last year, when NOAA said overfishing had ended and the population is rebounding. A new stock assessment is under way. The quotas are divided between commercial boats and recreational anglers.
Hatcheries will never eliminate fishing restrictions, Leber cautioned. "We need stronger laws than ever," he said.
Specks are not considered threatened but are "under enormous fishing pressure" because of their popularity, Blaylock said.
Since 2004, when the seatrout project started, "we've learned a lot about the culture of the fish, the tagging technology. We've developed the ability to identify all of our hatchery fish genetically. But we have not yet figured out how to efficiently catch the fish after we release them," he said. Finding ways to do that is part of the project and a graduate student's thesis topic, he said.
The student is studying whether gill nets, seines, traps or trawls are best at catching the fish while they're still small. "He's looked at some sonar tracking to try to track them as they leave to know where they go to try to sample them," Blaylock said.
But at least specks will spawn in tanks and eat easily raised plankton, though the hundreds of thousands released by USM are just a drop in the ocean.
Red snapper are a far tougher problem. Researchers must collect eggs from wild-caught females because they are still trying to figure out how to get the fish to spawn in captivity, Blaylock said.
Once hatched, they have a problem in common with snook: Their mouths are so tiny they can't eat brine shrimp or easily grown plankton called rotifers. They need the newly hatched larvae of even tinier and harder to raise creatures called copepods.
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