The Hunt Creek Fisheries Research Station is equipped with several small watercraft (rowboats, johnboats, and canoes) for conducting fisheries investigations on inland lakes and navigable streams. Research personnel also rely heavily upon the station’s electrofishing barge, or stream shocker, to conduct fisheries population estimates in wadeable streams.

Although several types of electrofishing equipment may be used to sample fish from streams, the most commonly used item at the Hunt Creek Fisheries Research Station is the stream shocker. The stream shocker consists of a wooden barge, generator, electrofishing control box, and two to three probes. Generated electricity is passed through an electrofishing control box that regulates the electrical current produced by the generator. The probes, as well as a copper plate attached to the bottom of the wooden barge, are connected to the electrofishing control box. The probes are submerged into the water and the appropriate safety switches are depressed, causing the electrical current produced by the generator to flow from the electrofishing control box to the copper plate on the bottom of the barge, through the water to the probes, and back to the control box, completing a circuit. The current of electricity passing through the water temporarily stuns fish in the immediate vicinity of the probes, allowing them to be netted. The netted fish are immediately placed into a livewell to recover.

Electrofishing is a common method used to sample fish populations in streams, and does not harm the fish if done properly. Once the fish are collected, research personnel take the measurements of interest (total number of fish, lengths, weights, and often scale samples for age analysis) and release the fish alive. If a mark-recapture survey is being conducted, two electrofishing passes through the stream are made. All fish collected during the first electrofishing pass are counted, given a unique mark (often a small fin clip at the top of the tail), and released back into the stream. During the second electrofishing pass, all fish that are captured are examined for marks, counted, and released. A population estimate of the total number of fish in the sampled stream can then be generated by assuming that the proportion of marked fish in the second sample is representative of the proportion of marked fish in the total population (the population estimate is equal to the number of fish marked on the first run multiplied the number of fish captured on the second run, all divided by the number of marked fish captured on the second run). Electrofishing can also be used to gather data for generating population estimates with methods other than mark-recapture, such as capture-recapture and depletion techniques.

Population estimates are very useful to research biologists who use them to determine the status, size, and age structure of the fish in a stream that is being studied. Changes in population estimates over time can be used to evaluate the effectiveness of experimental manipulations, such as fisheries regulation changes, habitat alterations, or species introductions. Research findings are used to help formulate fisheries management recommendations.