August 22, 2002
By Wayne Gustaveson   Home Page:
Lake Elevation: 3629  Water Temperature: 79-82 F

Fishing is always great at Lake Powell but catching may get better after the Labor Day weekend when water surface temperature begins to cool and the recreational boating crowd lessens. The striper boils at Hite and Bullfrog have diminished as the night sky gets brighter. Smallmouth fishing is still steady. The ever present bronzebacks will provide some action on even the toughest fishing day. Catfish are still the best bet for catching a few fish on Lake Powell.

With fishing a bit off there is still some important fishing news to be reported. While sampling fish in the upper San Juan 6 young gizzard shad were collected. A single adult gizzard shad was captured in the same location during June 2000. No more were found until the young shad were seined last week near Nokai Canyon. We suspect that gizzard shad are now reproducing in Lake Powell.

Gizzard shad are known to compete with other young fish for food. They grow much quicker than threadfin and attain a much larger size. Their presence could negatively impact survival of young fish in Lake Powell and other Colorado River reservoirs and tributaries where they will eventually spread. But gizzard shad are more prolific than threadfin which means there will be more free swimming larval fish available for all larger fish to eat in early summer.

Considering only Lake Powell, the potential colonization of the lake by gizzard shad probably has more pros than cons. Striped bass and smallmouth are currently more abundant than their food supply. If bass and striper survival is lessened by competition for food that may have a positive effect. The fish that do survive may have more shad to eat and grow bigger and stronger.

Adult gizzard shad will grow too large for bass to eat each Fall. Some may even out grow the predatory range of all but the largest striped bass. But the hungry, overabundant striped bass population will prevent gizzard shad from stockpiling unused energy in excessive old adult shad.

The long term outlook is that threadfin shad will remain the major forage fish but their population will be supplemented by large adult gizzard shad which will produce a continual supply of shad. The net result will be more stable sport fisheries in size and physical condition. Now the only question that remains is how long it will take gizzard shad to completely colonize Lake Powell. It may be as soon as 2 years or it may take longer than 20.

We don't know for sure but it is quite certain that gizzard shad came downstream from Morgan Lake which is a power plant cooling reservoir on the San Juan River near Ship Rock NM.. Gizzard shad were accidentally stocked there in 1998 with a load of largemouth bass from the federal fish hatchery at Inks Dam TX where gizzard shad are commonly found in the river water used to service the hatchery. After the discovery of gizzard shad in Morgan Lake another hatchery truck was found to contain 5 species of unwanted fish, including gizzard shad, with the bass intended for Morgan lake.