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Gizzard Shad Change Dynamics
New Chapter in Angling Opens at Lake Powell

Learn more about gizzard shad

By Wayne Gustaveson
DWR Lake Powell Project Leader
(Posted on www.wayneswords.com, Jan. 1, 2003)

At year end Lake Powell was 38 feet lower than the previous December. Inflow during 2002 was the lowest on record as drought continued to strangle the western US. The current lake level of 3620 is still above the 1993 low point, 3618, but that level will be surpassed as the lake continues to drain.

A significant fishing regulation change was instituted in January 2002 when the smallmouth bass creel limit was increased from 6 to 20 fish. The measure was taken to educate anglers that voluntary catch-and-release of smallmouth bass was not necessarily the best plan when smallmouth reproduction and survival were at high levels. Lack of angler harvest and poor forage conditions had slowed bass growth resulting in very few large bass being caught.

By year end, the results of this strategy were gratifying as the ratio of eleven inch bass in the population increased from 47% to 73%. Still the ratio of bass larger than 13 inches was low but the growth trend is progressing in the right direction. Comparison of bass size caught by anglers and by nets showed that anglers caught smaller fish on average.

Forage, particularly threadfin shad, had been at low levels for a number of years. Shad numbers increased in 2002. The increase was not remarkable as measured with trawls and tow nets. This was not a peak shad year but showed signs of a forage building year that may lead to a peak in the future. The biggest change in shad numbers occurred midlake with shad numbers at Bullfrog at the highest point in a decade.

While shad sampling numbers were not impressive, game fish certainly found forage conditions to their liking. Striped bass over the whole lake increased dramatically in plumpness. Growth in length will follow next year if forage remains high. As with smallmouth bass, there is a promise of bigger striped bass in the future.

The biggest news of 2002 was the population expansion of gizzard shad. A single adult was found in the San Juan during 2000. No additional gizzard shad were found in 2001. Similar sampling in 2002 had very different results. Six young gizzard shad were caught in seines in August. Then 78 adult shad were caught in nets in November. These shad were BIG. They averaged 11 inches long and weighed half a pound. The biggest shad was 15 inches and over a pound and a half. The population had expanded from the San Juan inflow downlake some 25 miles to Piute Canyon. These adult shad will be able to move unmolested through the reservoir and quickly expand the gizzard shad population and range after the spawn in 2003.

Other gill net results show that adult striped bass and smallmouth bass numbers are less than the previous two years. That may be a factor in the increased growth and physical condition of both species. The bad news is that largemouth bass numbers are very low. But dramatic changes in lake habitat are in store. New brush will grow while the lake is low. When the lake does begin filling again the new flooded brush habitat will favor the recovery of largemouth bass and crappie.

The future of Lake Powell fishing is bright with positive indicators glowing on every front. Forage and fish habitat is increasing, and the lake will begin rising in 2003. While 2002 may have been a rebuilding year near the bottom of the cycle, it was still a very productive year for anglers. With gizzard shad now becoming established a new chapter in Lake Powell angling is opening.