DNR fisheries technicians' critical work continues in winter

DNR fisheries technician Jody Johnston uses a grinder to repair a fish tank during the off season.

Jan. 30, 2014

Fisheries technicians are among the most visible Department of Natural Resources employees - spring, summer and fall - when they are out on the waterways, conducting surveys or working on habitat projects. But did you ever wonder what they do during the winter?

"We get that question all the time," said Jacob McWethy, a fisheries technician who works in the northern Lake Michigan and western Lake Superior districts out of Crystal Falls.

The answer: They do plenty, finishing up the work they conducted during open-water season and making sure the gear is good to go for the next year.

For instance, fisheries technicians take fin samples from the fish they collect at lake and stream surveys, but they don't work them up until the off-season.

To age the fish they've collected, the technicians take spines from the fins, cut a thin slice, and examine them under a microscope. The techs look for growth rings - similar to the rings on a tree - to determine a specimen's age.

DNR fisheries technician Jacob McWethy puts a waterproof primer on the decking of a work boat.Last year, McWethy and his partner Jody Johnston collected specimens from 11 bodies of water.

"It takes about a week of aging to finish a survey for one lake," McWethy said. "A stream survey only takes two days - we get considerably fewer fish. I'd say we'll easily spend eight weeks on it this winter."

That's not the only data they collect.

McWethy said they'll spend another week updating fish-stocking records and more time entering temperature data they collected on bodies of water.

In early summer, the techs put temperature probes (thermistors, if you want to get technical) into all the bodies of water the crew plans to survey that season. The 6-inch-long, 1-inch-diameter devices take hourly temperature readings for the entire season, until they are collected in October.

"They're wired to stumps or logs or, if there's nothing there, we'll even put a post in the water to hold them," McWethy said. "We put them in water that's deep enough that they'll be covered all year, at least 3 feet. It tells you the monthly mean temperature and - if, for instance, it's a trout stream - if the water is getting too warm to support brook trout or - in a lake - if it's getting too warm for pike or walleye.

"We monitor the trend over time to see if it's going up."

DNR fisheries technician Jacob McWethy works on an outboard motor as part of off-season maintenance.Besides working with data, the crews put in a lot of time maintaining, repairing and improving their gear.

"We winterize all the boats, trailers, outboards and water pumps," McWethy said. "It takes about two weeks to go through all our boats and gear. We refurbish them - do what needs to be done. We change the oil, change the plugs, check the trailer wiring and replace the bearings and paint or replace the floor of the boats. If there's a crack in the boat, we'll have it welded."

Last winter Johnston spent a lot of time refurbishing the district's fish-stocking unit. The two-tank fiberglass unit is separated into compartments so the unit, which is used primarily to transfer walleye fingerlings from the ponds to stocking sites, can be loaded with fish for two locations at once. Johnston removed redundant hardware, repaired the fiberglass and painted the unit. He changed the oxygen delivery system, too

"Previously, we used the same sort of diffuser that you use in a typical aquarium," he explained. "We changed those to micro-pore stones so we can use a lot less oxygen to support the same number of fish. We spend less on bottled oxygen and it's actually a lot more stable for the fish."

In addition to boats, motors and holding tanks, the crew maintains the survey gear.

DNR fisheries technician Jacob McWethy mends a trap net, part of the technicians' off-season work. "We work on the nets that have been used in the past summer and the ones that we anticipate using the next summer - fyke nets, seines, gill nets and hand nets," McWethy said. "We repair broken frames, welding and soldering, as well as mending or replacing the mesh. I'd say we spend two to three weeks at least.

Gill nets and fyke nets are marked with buoys, which must be maintained, too, but McWethy said since all of them were done last winter there aren't a lot of buoys to work on this year. "It's actually a blessing this year that we had so much ice," he said, "as it lets us get caught up on other things."

But it's not like they never get out of the maintenance barn. They'll work on habitat, too.

This winter, the crew plans a major project on Chicagon Lake, explained fisheries technician supervisor Mark Mylchreest. "We're going to put some wood structures in to increase spawning success of broadcast-spawning species, like muskies," he said. "And yellow perch string their eggs out on some of the wood masses we put in, too."

The crew starts with 20-foot logs, builds a lattice, and staples chicken wire to the logs. They pile rocks on the chicken wire to sink the structure. They plan to build about 35 of those structures, and they'll be sunk, in groups of five, in 6 to 8 feet of water.

Another habitat project is scheduled for Fortune Pond, an abandoned strip mine. The crew will build spawning structures for minnows to provide forage for the trout that are stocked there.

The structures - about 75 feet long and 25 feet wide - are built using black spruce. "We just pile them on top of each other, tying them together, and putting them shoreline extending out to about 8 feet of water and sinking them with sand bags," McWethy said.

As spring approaches and the crews prepare to begin survey work, most of the DNR's fisheries technicians are champing at the bit to get back out in the field.

Conducting surveys is "my favorite part of the job," said McWethy, a 10-year veteran of the DNR Fisheries Division. "I get too see all kinds of fish. And when we get a complaint about fishing in a certain lake, we can find out what's really going on there."

Learn more about the state's fisheries - including fish stocking, the new Aquatic Habitat Grant program, and the upcoming Winter Free Fishing Weekend (Feb. 15-16) - at www.michigan.gov/fishing.