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Biologists go techno fishin’ across Indiana lakes

What looks like nothing more than an easy boat ride across Lake Everett’s surface for Steve Donabauer, an assistant biologist with the Indiana Department of Natural Resources (DNR), is really a day of “hard work” gathering data on the fish populations.

What’s deceptive is that his effort involves setting neither nets nor traps to catch fish in the 43-acre Allen County lake, nor even use of a hook, line or sinker. In fact, Donabauer never touches a fish.
Instead, he “fishes” with sonar – sophisticated sonar, to be sure – but the equipment works much like a typical electronic fish locator used by countless anglers to find and catch fish. Mounted along the left side of his 18-foot boat is a split-beam transducer which emits sound waves to the bottom echoing back to a laptop computer in the boat.

The computer is linked to a real-time global positioning system (GPS) unit storing and processing large amounts of data. By integrating the electronic signals with complex computer software, biologists can estimate the abundance and biomass of fish.
 “We want to know the total volume of fish in Lake Everett,” Donabauer said. “The equipment and sampling techniques we are using should give us a precise estimate of the overall number of fish in the lake.”

According to Donabauer, Lake Everett is overrun with gizzard shad, a silver forage fish which hurts fishing by competing with bluegills and other sport fish. To reduce the shad population, biologists plan to apply the fish toxicant rotenone to the lake in September. Meanwhile, Donabauer’s data will help monitor the decline in shad and success of the project.

He also uses the electronic gear to study fish populations in Crooked and Round lakes in Whitley County. At Crooked Lake he hopes to get an idea of the number and locations of ciscoes, deepwater fish difficult to sample using traditional equipment.
At Round Lake, Donabauer is assessing the number of bluegills, bass and other fish present.

“What we’re doing is called hydro-acoustic sampling and should open up a whole new way to look at lakes and their fish populations,” he said.

Plans are to use the equipment to also construct detailed contour maps of each lake, plot their aquatic plant beds, quantify plant abundance and even provide data on zooplankton, which are microscopic animals and part of the aquatic food chain.
In mid-April, Donabauer found zooplankton throughout the water column of Lake Everett at night. The next day, they were concentrated in water deeper than 24 feet.

“We learn more about our lakes every time we use the equipment,” he said.

Plant eradication needs permit

Before you remove aquatic plants from a public lake, check with the DNR. You may need a permit before proceeding.

State law requires that residents of a public lake who want to chemically control or physically remove aquatic plants along more than 25 feet of their shoreline, a total surface area of more than 625 square feet or at water depths greater than 6 feet, must first obtain a written permit from the DNR.

Residents who treat less than the specified amount do not need a permit. This allows property owners to control small areas of aquatic plants around piers and swimming areas interfering with lake use.
“Aquatic plants play an important role in lake ecology,” according to Rod Edgell, DNR assistant fisheries biologist. “However, removing plants is sometimes necessary to allow residents and anglers access to the lake.”

When using any pesticide, it’s important to follow the product’s label directions, and only use herbicides registered for aquatic habitats. Improper use of any aquatic herbicide is not only illegal, but can be hazardous to humans and aquatic life.

In most cases, permits to chemically control aquatic plants are granted only to licensed pesticide applicators who have knowledge and training in the proper use of pesticides.

“We recommend lake residents combine their resources and hire a licensed applicator for large-scale treatments,” Edgell said. “Applicators are trained to properly identify target plants and use the most appropriate herbicide.”
In most cases, permits are issued only for control of non-native plants such as Eurasian watermilfoil and curly-leaf pondweed. Native plants seldom interfere with lake use and are rarely treated on a large scale.

Permit applications are available at the Northeast Regional Office, 1353 S. Governors Dr., Columbia City, IN 46725 or by calling 260-244-6805. The application fee is $5. Processing may take up to six weeks, so plan accordingly.

Questions regarding pesticides and their use should be directed to your local Purdue University county extension office. You can find your office at http://extension.purdue.edu/extsite/counties.shtml or by calling 888-398-4636.

Wildlife Orphans

Indiana Conservation officers are asking the public to please leave wildlife young where they find them.

Spring and summer is the time of year when wildlife mothers often place their young in areas shared with people. When well-intended individuals come across young wildlife, the first inclination is to assume the mother has abandoned them and the young will need help.

“Generally, this is not the case,” said Col. Mike Crider, director of the Division of Law Enforcement. “Wildlife mothers often leave their young for long periods of time. Deer, for example, will leave a fawn for up to two or three days. The wildlife mother will return to feed and care for their young.”

Here are some facts to consider when finding young wildlife:
•Some wildlife mothers leave the nests for long periods of time and only return to feed the young. They are even less likely to return if there is a constant human presence seen as a possible predator.
•Human scent added to the nest site can increase the possibility of a predator finding the nest.

•By removing the young from the nest, the odds of survival are decreased.

•Rehabbing young wildlife requires significant knowledge and effort. Wildlife can only be rehabilitated by individuals licensed by the DNR; their primary purpose is to address injured wildlife and they do so out of their own pockets.

Inundating these people with wildlife young not necessary to remove from the nest to begin with adds a significant burden to these volunteer wildlife rehabilitators.

•Wildlife young have a mortality factor, which is a part of nature.
“Of course, there are times when the presence of young wildlife may need to be addressed,” said Crider. “Before disturbing young wildlife, make contact with the appropriate Department of Natural Resources authorities who can best guide you in your situation.”

The views and opinions expressed in this column are those of the author and not necessarily those of Farm World. Readers with questions or comments may contact Jack Spaulding by e-mail at jackspaulding@hughes.net or by writing to him in care of this publication.

5/7/2008