The next time you catch a walleye in the Mississippi River near the Quad-Cities, or eat one that came from there, you may want to thank MidAmerican Energy and Commonwealth Edison companies.
More specifically, you may want to thank Larry LaJeone and David Bergerhouse. They, along with one other biologist, two technicians and half a dozen summer workers, are responsible for producing 20 percent or more of the walleye population of Pools 13, 14 and 15 of the Mississippi River.
``Natural walleye reproduction in the Mississippi River is, due to many factors, not stable,'' said Mr. LaJeone, a ComEd senior biologist who is the coordinator of the fish hatchery and rearing facility at the Quad Cities Nuclear Power Station, Cordova. ``Some years the walleye spawn is ample to sustain the walleye population -- other years it is not. The work we do at Cordova flattens or smooths out the up/down cycles. We help and sustain nature by filling in the voids.''
When the nuclear power station at Cordova was built, a 3 1/2-mile-long and 185-foot-wide canal was created to cool the water that had been used to cool the reactor. The water had to be cooled before it re-entered the Mississippi River so that the river's ecology would be disturbed as little as possible. When alternate methods of cooling were implemented, the canal was no longer needed.
In 1983, the electric utilities that owned and operated the generating station joined forces with Southern Illinois University to turn the canal into an 80-acre fish-rearing pond. Shortly thereafter, Mr. LaJeone and Mr. Bergerhouse, an assistant research professor at SIU, started helping nature.
Initially, striped bass were picked to be hatched and raised at Cordova and released into the Mississippi, but the emphasis has since been switched to the native walleye. Stripers are still raised, but to a much lesser extent, some 2,000 to 5,000 per year.
``We have a target to produce 175,000 walleye fingerlings per year,'' Mr. LaJeone said. ``We release 125,000 into Pool 14 and 50,000 into Pool 13. Some years we raise many more than our target -- those fish go to either the Illinois or Iowa DNR (Department of Natural Resources) for stocking in other waters. Last year we produced 432,000, which is a great year, but certainly not our record, which is 750,000. Since 1984, our facility has produced a total of 2.9 million fish.''
Many local anglers can remember when walleye fishing in Pool 14 was fair at best. Now spring and fall will find up to 100 boats below the Clinton Dam angling for a far more abundant walleye population.
``Even though Pools 13 and 14 receive our fingerlings (the juvenile walleyes), we have tracked our fish as far south as Pool 18 -- and they probably migrate farther than that,'' Mr. LaJeone said with pride. ``Our studies have shown that at least 20 percent of the walleyes in Pool 15 at Moline were produced at Cordova.''
Mr. LaJeone can make that statement with confidence and accuracy because about one-third of the Cordova-produced fish are easily identified by a brand. The fingerlings about to be released are literally branded with a dark vertical mark about mid-body on the fish's left side. The brand is applied to the fish by touching them one at a time to a piece of metal that has been cooled to minus 300 degrees by liquid nitrogen. Branding does no short- or long-term harm to the fish and makes it permanently identifiable by even the untrained eye.
The Cordova walleye project starts each April, when Mr. LaJeone and Mr. Bergerhouse collect fat native female walleyes from the Mississippi River. The eggs are milked from the females in an on-site fish laboratory and placed in glass tubes for incubation. After hatching, the hundreds of thousands of 3-day-old walleyes are released into the canal.
The tiny fish are left completely on their own to feed on natural plankton, then larvae of several insects and finally on small natural minnows. Yes, some cannibalism does occur with more aggressive fingerlings -- but that is nature at work.
After spending just two months in the canal, the fingerlings, by then 2 to 8 inches long, are ready for stocking. The young fish are herded a few at a time into a catch basin where they are collected in nets for branding, the final step before release and stocking.
``Biologically, conditions are very good for walleye in the Mississippi River,'' Mr. LaJeone said. ``The food supply is abundant. Whether naturally spawned or stocked, a 1-year-old fish is normally about 8 inches long; at 2 years, 13 inches; and at 3 years, 17 inches. The minimum legal length to harvest walleye is 15 inches. We have found our walleye to reach over 11 pounds in seven years.''