Biologists fail to successfully spawn two female Atlantic sturgeon
Researchers at two facilities to review work and are confident that future efforts will produce viable eggs
Plans to rear thousands of young sturgeon for release in Bay tributaries this year were dashed as biologists failed to successfully spawn either of two "ripe" female Atlantic sturgeon this summer.
Nonetheless, they say valuable lessons were learned that may help future efforts to successfully spawn sturgeon-a crucial element of any effort to restore the largest fish native to the Bay.
"I'm disappointed we weren't able to produce anything, but still think we are moving forward," said Brian Richardson, sturgeon project leader with the Maryland Department of Natural Resources. "We learned a lot this year. I mean a ton. And we probably have a good idea of where we could have done a better job."
Atlantic sturgeon, a 120-million-year-old relict of the dinosaur age, were once abundant in the Bay and along the East Coast, but were heavily overfished in the late 1800s and never recovered.
Sturgeon spend much of their lives along the coast but return to their native rivers to spawn. In the Bay, only a small population remains in the James River - and possibly the York. No evidence of reproduction has taken place in Maryland in 35 years.
As a result, biologists believe a hatchery-based stocking program is likely the only way the fish will ever be restored to more areas. But efforts are hampered because there are few to work with. Not only are adult sturgeon rare, female sturgeon typically do not reach maturity until they are 12-15, or even older. Even then, they only spawn every two to three years.
This spring, the first egg-bearing Atlantic sturgeon was caught in Maryland's waters since 1972. The 170-pound, 7.5-foot fish was taken to the Horn Point Laboratory of the University of Maryland's Center for Environmental Science.
Separately, a female sturgeon at Mirant Energy's aquaculture facility at its Chalk Point plant on the Patuxent River that had been reared in captivity for 12 years was also discovered to be "ripe" with eggs.
Biologists had hoped to spawn both fish and stock some of their young in tributaries to determine what habitats they use, survival rates and other information that would be vital to any future large-scale reintroduction program.
Both efforts were unsuccessful. Biologists monitored the progression of eggs for weeks and, when they thought the wild sturgeon kept at Horn Point was ready, injected her with hormones to induce spawning.
The eggs were surgically removed but turned out to be of poor quality. Efforts were further hampered when biologists were not able to get sperm from captive males, and had to use frozen sperm collected in earlier years. Fertilization rates were low and ultimately, no viable eggs were produced.
Meanwhile, the captive fish at the Mirant facility unexpectedly released her eggs in a tank during a weekend, dashing those hopes as well.
Jerre Mohler, a biologist at the U.S. Fish and Wildlife Service's Northeast Fishery Center in Lamar, PA, who has pioneered research on spawning captive sturgeon, said the Horn Point fish was only the 14th captive Atlantic sturgeon biologists attempted to spawn. Just seven attempts were successful, and almost all of those involved fish that were nearly ready to produce eggs when taken from the river.
"It's not like we've had hundreds of fish to practice on," he said. But, he added, "just because you had a couple of fish that didn't respond the way you wanted, that's no reason to throw in the towel."
Scientists want to review everything from the type of hormone used to induce spawning to the diet fed to the females while in captivity to see what can be done to improve results on their next try.
"We're still learning. We're generating more information each time we do it," said Andrew Lazur, who oversees the hatchery at the Horn Point Laboratory. "It's just a matter of maybe one or two more fish until we nail it right on the head. I'm totally confident this is going to be happening here in the next couple of years."
Biologists said the Horn Point fish did well after surgery and hope to hold her until she is ready to spawn again in two or three years. Also, several other sturgeon that have been held captive since a 1996 experimental release in the Nanticoke River are expected to mature in the next couple of years.
In another step forward, Mirant invested in a streamside culture facility at its plant along the Potomac River in Alexandria, VA. When hatcheries successfully produce larvae, the facility will allow them to be reared in river water until they grow large enough to be released. The goal is to make sure the fish "imprint" on the river upon their release so they will return when they mature more than a decade later.
"We want to make sure these things are imprinted and, in the future, when we have fish to release, ensure they will actually return to where we are putting them out," said Steve Minkkinen, who heads the USF&WS Maryland Fishery Resources Office.
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