"We did not know they were in the river until we started checking and found them five years ago," Gustaveson said. "The gizzards had been established in Morgan for nearly four years before anyone started to look for them elsewhere. No one looked for them before that time. Navajo reservation biologists are in charge of the reservoir. It was so far from us we had no idea what was going on."

Last fall, technicians pulled in 10 different species of fish, including three- and six-pound stripers, two-pound smallmouth bass, largemouth bass, young crappie, sunfish, walleye, catfish, shad, carp, and a rare find, flannel mouth suckers, native to the Colorado River drainage.

"We look at the adult population and see how it changes from year to year. If we go to the same spot at the same time each year we can tell if we get a big catch one year and small catch the next year that our population is changing somewhat," Gustaveson explained. "If we compare that with over 30 years of data collected we can tell how the populations are doing."

The nets were set along rocky points in both shallow and deep water for two consecutive nights. Each net is 100 feet long and 6 feet deep. Four panels of monofilament mesh with openings ranging from three-quarters of an inch to 2 inches collect a balanced sample of both small and large fish.

The nets were anchored on shore and then stretched out to their full length. A weight was attached on the end with a floating marker. Once settled, the net conforms to the contour of the shore and lake bottom. Depending on water depth the net may fall 20 to 60 feet.

Technicians collected more fish than they anticipated in the two-day survey. The nets were left in place overnight. During the day fish see the nets and avoid them. At night, as they cruise the shallow shoreline and rocky structure, they are more likely to get caught in the nets.

"Most of the fish at Lake Powell are structure-oriented, and they will be within 6 feet of the bottom during the evening so we are more likely to catch the fish we are after with this technique," Gustaveson said.

After each net was pulled and the fish plucked from the twisted monofilament snare the nets were reset into the water for a second sampling the following morning. Then each fish was separated by species for processing. Stripers overflowed one bucket while crappie, catfish, green sunfish and walleye filled another. Smallmouth and largemouth bass filled yet another bucket. The fish were counted, body scales were taken for aging studies and digestive systems opened and examined for content.

It was a tedious process that took several hours. In the end, the results were very encouraging. Not only does Lake Powell now have another forage base for its prized game fish, but also the fish themselves will no longer have to deal with the feast-and-famine pattern they have had to contend with when threadfin shad populations are low.