An electrifying way to study fish
Fish Busters' Bulletin
Monday, July 01, 2013
Media contact: Bob Wattendorf, 850-488-0520
Not everyone can step up to the bow of a boat, lean against the railing, step on a pedal and start netting fish as they float up to the surface. Although it is illegal and dangerous for anglers to fish with electricity, biologists use electrofishing boats to temporarily stun and collect fish for scientific analyses and to help manage the fishery. Florida Fish and Wildlife Conservation Commission (FWC) fishery biologists have special training to operate this equipment safely.
Electrofishing boats use a generator to create an electric current. The current flows out in an electrical field between booms that hang off the front of the boat and its metal hull. The electric field does not kill fish and can actually attract them toward the booms, before stunning those that swim within 6 to 8 feet. Biologists scoop up the fish in nets and place them in an aerated livewell to recover.
Several factors contribute to how long the fish remains stunned, including the fish’s size, the species, water temperature and conductivity, how close the fish is to the booms and how long the current is applied. In most cases, stunning occurs within seconds of the fish entering the electric field and lasts less than a couple of minutes once the fish is removed from the field.
Biologists typically identify fish by species and count and measure them, including their length and weight. Depending on the study, blood samples may be taken, stomach contents examined and tissue samples collected to determine mercury and pesticide levels or the fish’s genetic makeup. Occasionally, biologists transport some specimens to the lab or hatchery for further examination or for breeding purposes. Scientists may also harvest a few to examine their otoliths (earbones), which, once cut and ground into thin slices, show growth rings that reveal their age.
In the field, biologists also collect data to use in conjunction with fish data to evaluate the fishery and determine how best to manage the resource. For instance, they record water clarity, conductivity, dissolved oxygen and temperature, along with other information about the type of plants, specific location and substrate (for example, mud, gravel or sand). This is useful to determine why certain fish may be present or absent and to compare samples from year to year or with different water bodies.
Electrofishing tends to be less damaging than methods that entangle or trap fish, such as seines, gillnets, wire traps or trawls. It is an urban myth that electrofishing harms the eggs of female fish. In fact, biologists use electrofishing to collect brood fish to use at hatcheries as parent fish.
Electrofishing allows biologists to determine how healthy a fish population is in a particular pond, lake, river or canal. For instance, it can determine if habitat-restoration efforts, stocking programs or conservation measures were successful or if measures are needed to enhance angler enjoyment.
Information from electrofishing and other sampling methods, including angler creel surveys – where we talk to anglers to determine what they caught – provide much of the information used in quarterly fishing forecasts. To see those forecasts, go to MyFWC.com/Fishing and select “Freshwater Fishing” then “Sites & Forecasts.”
Fisheries biology is a fun possibility for a career, for those who like science, nature and the outdoors. As part of the FWC effort toward Creating the Next Generation That Cares™, the FWC set up the Florida Youth Conservation Centers Network (FYCCN.org).
The FYCCN effort includes hosting summer fish camps. The goal is to create life-long anglers and stewards of aquatic and fisheries resources. Licensed anglers and hunters who donate to youth fishing and hunting education programs help fund these camps. Over the past four years, these camps have expanded from two to 15 locations statewide and can reach 900 children annually. Besides being fun and informative, camps teach angling and boating skills and introduce campers to the possibilities of a future career.
Camp participants can see how scientists use electrofishing and learn about common freshwater fishes and angler-recognition programs on an FWC YouTube video titled “A shocking way to see fish,” available at YouTube.com/MyFWCvideos.