ONSERVATION OFFICIALS TRYING TO SAVE ENDANGERED, PALID STURGEON SPECIES

ST. LOUIS - Biologists are releasing 8,000 pallid sturgeons into the Mississippi and Missouri rivers in an effort to find out why the fish is sliding toward extinction.

The pallid sturgeon was listed as endangered in 1990, triggering a national effort by conservation officials in 13 states to rescue a species that has outlived the dinosaur. The sturgeons were released at three sites on the Missouri below Hermann, and six on the Mississippi downstream from St. Louis.

In April 1992, Missouri got a head start by spawning thousands of sturgeons at the Conservation Department's Blind Pony Fish Hatchery at Sweet Springs. Eggs and semen had been collected from five pallids turned in by commercial fishermen.

The Missouri testing took longer than expected. The fish continued to grow, and eat and tie up hatchery space.

The 8,000 sturgeons now measure 16 to 18 inches long.

"When these fish were small they were difficult to tell from shovelnose sturgeon," said Heman. "But, as they grew, they began to develop pallid sturgeon characteristics. Dr. William Pflieger, MDC ichthyologist, and Dr. Frank Cross, professor emeritus of the University of Kansas -- both sturgeon experts -- examined the small sturgeon. They both reported that physical characteristics indicated that these fish were pallid sturgeon."

Heman said there is a general agreement among U.S. sturgeon experts that physical measurements are the only reliable method for separating hard-to-tell sturgeon species.

Heman also said Kim Graham, the fisheries research biologist who helped select the brood stock, and Jerry Hamilton, the hatchery manager at Blind Pony, are two of the most respected authorities in their fields. They are convinced that releasing these fish does not pose a threat to the survival of purebred pallid sturgeons. "I feel it is time to move ahead with this program," said Graham.

Each sturgeon will receive an external tag and a tiny "binary coded" tag implanted in the head. The external tags will be yellow plastic strips resembling 1.5-inch strips of spaghetti. They will be attached near the pectoral fin, which is the fin nearest the fish's head.

Each will bear a message asking commercial fishermen or others who encounter the tagged fish to report the sighting. Each implanted tag carries a magnetic code that MDC biologists can read with special sensors, even if the external tag is lost.

"We have learned a great deal about pallid sturgeons from this project already," said Heman. "The captive spawning techniques developed by Jerry Hamilton and his staff at Blind Pony Hatchery will be an immense asset as restoration work continues, and we now know how to keep young pallids alive in a hatchery for extended periods. By stocking the fish in the Missouri and Mississippi rivers, we will begin a new phase in which we learn about pallid sturgeons' movements, habitat preferences and survival in the wild. We stand to gain an enormous amount of information about a species whose life history is mostly a question mark at present."

The pallid sturgeon is one of the largest fish in Missouri, sometimes reaching 80 pounds. It exists in low numbers from the upper Missouri and lower Yellowstone rivers to the lower Mississippi River in Louisiana. Nearly all of its habitat has been destroyed or modified by river channelization, construction of impoundments and related changes in water flow.