Diet Research for the Shortnose Sturgeon

Article excerpt

It may fall upon the National Fish Hatchery System to prevent the extinction of the shortnose sturgeon (Acipenser brevirostrum). This fish has been listed as an endangered species since 1967. Its recovery plan, published by the National Marine Fisheries Service in 1998, calls for a captive-rearing program since wild populations may need to be augmented with hatchery-raised fish. Since the late 1980s, national fish hatcheries, the National Marine Fisheries Service, and state agencies have investigated fish culture techniques to raise this rare and unusual fish.

The Bears Bluff National Fish Hatchery in South Carolina, a satellite of the Warm Springs Regional Fisheries Center in Warm Springs, Georgia, is studying the early life history of this ancient fish. As part of this effort, it has conducted diet studies in captivity to increase the efficiency of hatchery propagation. Ultimately, that will translate into improved survival of young fish, benefiting their conservation and achieving it at a lower cost.

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The shortnose sturgeon has suffered from the typical suite of environmental impacts that have hurt other fishes, says Bears Bluff fish biologist James Henne. For example, shortnose sturgeon naturally made extensive upstream migrations to reproduce, but dams have impeded their access to historic spawning habitat. Changes in river flows from dams have also affected the fish by altering oxygen levels, river flows, and water temperatures. Over-fishing and incidental catches in commercial fisheries operations have had impacts on the shortnose sturgeon as well.

The fish is named for its snout, which sets it apart from all the other sturgeons. It's most similar to the widely distributed lake sturgeon that naturally occurred over much of the inland waters of the South and Midwest and through the Great Lakes. The shortnose sturgeon was naturally confined to the estuaries and major streams tributary to the Atlantic coast from Florida to New Brunswick. Across its range along the coast, it does appear locally abundant in southern rivers like the Santee and Altamaha, but culture programs and intensive protection are still needed to conserve the species as a whole.

Toward that end, the Bears Bluff NFH maintains a refugium population of adult shortnose sturgeon that originated from hatchery stock. Over the last 10 years, hatchery biologists have made impressive progress in learning sturgeon culture techniques.

"Early on, the experience was simply learning to keep fish alive. There's a steep learning curve when you're trying to culture a fish where the techniques aren't well known," said Henne. "We've gotten better. Though our fish aren't intended for release in the wild, in the event their conservation necessitates that, we have the technology and techniques to do it. …