Why Is The Missouri Conservation Department Shocking Fish?

Recently while kayaking in Ha Ha Tonka cove, LakeExpo team member Robby Bruewer saw a group of people behaving strangely.

The men were leaning over the side of a boat, with some sort of probe in the water. Then they were casting nets and drawing them out of the water... with fish inside.

This is not a legal way to catch fish recreationally, but these guys were conservation agents, and they were using electrical current to stun nearby fish in order to measure and count them, for the purpose of assessing population health.

The fish awaken from their stunned state after a short while, and resume activity. The electrofishing is a catch-and-release operation.

From the MDC's website about electrofishing:

Electrofishing works well for counting some, but not all, species of fish. We also use trap nets and hoop nets for surveying populations. What’s important is that we collect each species at the same time of the year and using the same method so that we can compare our data with other years.

For example, we survey largemouth bass with electrofishing gear in April and May once the surface water temperature reaches 65 degrees. We collect crappie in trap nets in October. We survey channel catfish in the summer by using hoop nets baited with aged, foul-smelling cheese. We set gill nets below wing dikes in the Missouri River during late winter for sturgeon.

Our knowledge of when and how to survey fish populations was not accumulated overnight. Present-day biologists have learned from past efforts how and where to obtain “representative” samples of fish populations.

When possible, a biologist may collect 500 or more fish of a given species to get a representative sample. To be accurate, a sample should contain all sizes of the fish in the population from fingerlings to large adults.

As is the case with any survey, obtaining a good sample provides solid information about the whole population. In the case of fish sampling, the data we collect helps us gain an understanding of the population structure of a species.