April 05, 2013
by Justin Hill
So, if you have read my previous post you now have an idea of how and why we age fish. If you haven't read it, shame on you. Go back and look for “Fish of a Certain Age”. Those of you who have read it; you are my favorites and are ready for some more science. OK, by a show of hands how many of you have seen the odd looking noisy boats out in your local lakes? You know the ones that look like the picture on the left. You can put your hands down now, I can't see you anyway. This is a FWC electrofishing boat. Biologists use these boats to collect fish for all sorts of scientific analyses such as measuring length and weight, collecting blood samples, tagging, determining age and mercury and pesticide levels.
As the name implies, an electrofishing boat applies electric current to the water using a generator. A biologist at the front of the boat has control of a pedal switch that releases the electricity. It then travels to the poles, called booms, at the front of the boat and into the water. The electric field they produce does not kill the fish but temporarily stuns those that swim within 6- to 8-feet of the booms. The fish can then be scooped up and handled with little stress or injury. The electricity's effects on the fish are typically minimal. Several factors contribute to how long the fish remains stunned, including the size of the fish, the specie, and the temperature and conductivity of the water. In most cases, stunning occurs within the first few seconds of entering the electric field and lasts from a few seconds to several minutes. This sampling technique can be much less damaging than methods that entangle or trap fish, which may injure or even kill them. Electrofishing also does not harm the eggs of female fish; in fact, the FWC uses electrofishing to collect females for breeding at the state hatcheries.
Electrofishing is a luxury only freshwater biologists have. The conductivity of saltwater is higher than the conductivity of fish. So, in saltwater, the electricity goes around the fish instead of through it, rendering this technique ineffective for our saltwater kin. It is even less effective for anglers, considering it is illegal for you to use. Keep an eye out on your next fishing trip for these boats. FWC biologists will respectfully keep their distance to avoid disturbing your fishing. However, if you have questions, you may approach the boat if the generator – which is quite loud while operating – is off. You may also approach FWC employees near boat ramps when they are launching or loading their boats. They can answer your questions and give you information about your local lakes and rivers.
Remember, for a closer look at FWC's research like our Facebook page at facebook.com/FWCResearch.