Striped Bass Invade Lake Pleasant

Arizona Game and Fish is trying to solve a fishy problem at Lake Pleasant

October 20, 2004

PHOENIX - Arizona Game and Fish Department biologists are conducting a study at Lake Pleasant using the newest leading edge technology to find out the effects striped bass are having on the very popular sportfish community.

Striped bass invaded Lake Pleasant via the Central Arizona Project or CAP canal system. The concern now is that the striped bass may compete with other sportfish in the lake, such as largemouth and white bass, for their main food source, which is threadfin shad.

"Lake Pleasant has historically been regarded as one of the premier largemouth bass fisheries in Arizona. We share the concern with many Lake Pleasant anglers that the invasion of striped bass following completion of the New Waddell Dam in 1992 may be negatively impacting the existing fish community," says Game and Fish Department biologist Marianne Meding.

Meding and other department biologists have embarked on an intensive three-year evaluation of Lake Pleasant to determine if the growing striped bass population is indeed a cause for concern, and to identify ways to properly manage the reservoir so the striped bass population can co-exist with other predators in the lake.

Beginning in November, biologists will conduct gill netting and electrofishing surveys to get information on the lake's fish populations, such as their diets, ages, and size. In order to identify if striped bass are reproducing in Lake Pleasant, biologists will sample for larval fish and fish eggs using light traps and net tows.

Early next year Meding will begin the process of estimating predator and prey fish population sizes using hydroacoustics. This procedure uses sound energy that is sent through the water. When the sound hits an object with a different density from that of the water, such as the air bladder of a fish, the sound is reflected back. This is a very high tech way for biologists to estimate the numbers and sizes of fish.

Game and Fish biologists will also begin early next year implanting radio tags in the abdomen of striped bass to determine seasonal migration and spawning movements.

"The tag emits a radio frequency that can be tracked using a special receiver. Some tags are even capable of sensing temperature and oxygen concentrations in the water. Our plan is to survey the lake every two weeks to determine where the fish are and the kinds of habitat they use," says Meding.

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