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More Fish Data to Come, Thanks to New Raft

October 15, 2008 - Everywhere you look, someone is inventing a new gadget to make some task simpler. And there is always the search for the fastest method to collect lots of fish.

Our sampling gear, or gadgets if you like, include trapnets, gillnets, minnow traps, angling, trawling, sonar and electrofishing. Electrofishing involves transmitting an electrical current into the water that temporarily stuns fish, which are then netted. The fish are released alive after biological data, such as length, weight and sex, are recorded.

Maine fisheries biologists have been effectively electrofishing for several decades. Boat units are used in lakes, ponds and river sections where concrete or hard gravel boat launches exist. For wading waters, such as small streams, shallow sections of rivers and pond shorelines, backpack units are used.

Waterbodies without launches for trailered boats and that are too deep for wading were off-limits to sampling by electrofishing equipment until June 2007. At that time a new piece of sampling equipment became available, the electrofishing raft. It includes a 14-foot inflatable raft, 15-horsepower motor, aluminum frame with netter's chair, holding tank and electrofishing system (generator and control box).

All components of the raft can carried by a two-person crew -- no need for a suitable boat launch, just strong backs. Once at the water, the components can be reassembled in 30 minutes and sampling can begin. For night work, the netter's platform on the raft's front has two large lights powered by a deep cycle battery.

Commercially manufactured electrofishing rafts are available but tend to be heavier, larger and more expensive. Inland Fisheries and Wildlife's raft was created in two months through discussions with biologists using electrofishing rafts elsewhere in the United States, working with local fabricators and with the skills of several Maine biologists. By designing and fabricating our own raft, we were able to tailor it to meet our unique sampling needs -- and keep the cost to 40 percent of commercially manufactured units.

There is always a learning curve associated with any new piece of equipment, and this was especially true regarding the raft. It goes without saying that jagged rocks, woody debris and random pieces of metal in the water become more of a concern due to the rubber exterior of the raft. The lightweight nature of the raft and the absence of a keel make handling in a current or on windy days very different from either of the department's two electrofishing boats.

Probably the most interesting feature of the raft is the netter's seat over the bow. On an electrofishing boat, netters stand on a large deck instead. Some biologists have quickly adjusted to the new seated perch, while others prefer the decks.

How useful has the raft proven since last June? More than 30 waters have been sampled throughout the state, waters which would not have been possible to electrofish without the raft.

At the moment, Maine is the only state fisheries agency in the Northeast and one of the few east of the Mississippi River that has an electrofishing raft. Without the knowledge and hard work of IFW fisheries biologists Jason Seiders (Bangor office) and Scott Davis (Sidney office) the electrofishing raft would not be such a successful fish sampling device for fishery biologists of the department.

Joseph Dembeck is a research fisheries biologist with the Bangor office of the Maine Department of Inland Fisheries & Wildlife.

By JOSEPH DEMBECK, Portland Press Herald, October 9, 2008


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