Stock enhancement is the process of raising fish in a hatchery and releasing them to a body of water to add to existing fish populations or create a population where one previously did not exist. For decades, the marking of fish has been used to determine the successfulness of stocking programs in recreational waters. Researchers have commonly used a chemical that produces fluorescent marks on the internal bony structures of fish. Because workers can never be sure if they are netting a marked fish in the field, they must spend many hours in the lab, dissecting sampled fish and examining their bones to determine if they were part of the stocking program.
Researchers at the University of Arkansas Pine Bluff (UAPB) tested the application of calcein, a fluorescent dye that produces visible external marks on fish, as a potential substitute for traditional chemicals. After being marked with calcein, crappie were stocked in eight Arkansas reservoirs, which were later sampled to determine the survival rate of stocked fish.
UAPB researchers found that the use of calcein allowed for near real-time estimates of stocking success since the marks are visible on the surface of the fish for at least a year. To sample a population of the dye-marked fish took only a day or two, as opposed to the hundreds of hours required to analyze fish marked with traditional chemicals in the lab. Additionally, instead of being sacrificed, the sampled fish can continue to contribute to the fishery.
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