A Day on the Clifford J – Assessing Illinois’ Lake Michigan Fisheries

Photos courtesy of IDNR Division of Fisheries.

The late April sun is just revealing itself as the strangely shaped boat crawls past the Waukegan Harbor lighthouse. Captain David Atkinson rocks the throttle, and the big diesel engine responds with an increased roar and the building whine of a turbocharger making all those on board thankful they are wearing hearing protection.

Despite a the ruckus, the 49-foot boat pushes through the water at less than 10 mph. The Clifford J, named for the captain’s uncle, was built in the late 1930s specifically for netting fish on the Great Lakes. Fully enclosed, with only sliding metal doors for access, it can fish across all seasons, with only heavy ice keeping it in port. The boat was first purchased by Captain Atkinson’s father, Burt, and has been in the family for nearly 50 years. The Illinois Department of Natural Resources has hired the boat and crew (captain and first mate) to do surveys for almost as long.

Inside the belly of the vessel, Lake Michigan Program biologists search in vain for a comfortable spot for the journey, instead settling on familiar resting places. It will be a 45-minute run to the first of two bottom set gill nets. At 1,700 feet in length, nets for the Spring Index Assessment are the longest used all year. Each net is made up of eight separate panels. Each panel has a different mesh size. The smallest, 1-inch stretched measure, is like a shoreline smelt net and catches small-bodied fish, while the largest 5.5-inch stretched measure, can capture larger predators.

This represents the busiest survey the biologists will undertake for the year. A total of 16 different stations off both Chicago and Waukegan are sampled, covering depths ranging from 18 to 270 feet.

Hauling up the Nets

The boat slows as the captain spots the 6-foot-tall buoy, topped with an orange flag, that marks each end of the assessment net 120 feet below. The first mate, retired schoolteacher Steve Ceskowski, leans out the open door near the starboard bow holding a 3-foot metal hook. Ceskowski used to make his living working on commercial fishing boats before teaching high school history. Now, he spends his retirement reliving a bit of his youth.

As Atkinson maneuvers the boat close to the buoy, Ceskowski corrals it with the hook and brings it inside the boat. The line trailing off the buoy is lifted over a roller hanging off the side of the boat and into the jaws of a hydraulic winch. As the winch rotates, it dumps the line onto the worktable where it is quickly run into a plastic bin. A chain anchor rattles across the table, marking the halfway point to the net. When the winch starts to deposit the net on the table, the buoy line is untied from the net and the bin is slid out of the way.

Removing Fish from the Nets

As the net moves down the table the fish are untangled and removed by the biologists and tossed into a separate plastic bin. The biologists also try to remove any knots in the mesh, called snaps, so the net is in good condition for the next set. Any missed tangles are cleared by Ceskowski before he neatly lays the net in a large plastic box.

The first mesh in the boat is the 5.5-inch and only a few yards in is the first lake trout. Lake trout are the most common predator collected in the survey. Vulnerability to bottom set gill nets and increasing abundance results in lake trout being collected at most stations. Several more lake trout follow the first and then Atkinson announces, “mesh change,” signifying that the 5.5-inch mesh is ending, and the 4.5-inch is beginning.

The biologists stack an empty bin on top of the first to keep each panel’s catch separate. The 4.5-inch collects several more lake trout and a burbot. The mottled brown burbot is the only freshwater member of the cod family. It tends to stay near the bottom, liking rocky substrate and cold water.

As the different mesh panels come on board, the biologists continue to clear the net. At this station lake trout are most common, but a lake whitefish is also collected. Lake whitefish are excellent table fare and the target of commercial fishing in several of the Great Lakes, including northern Lake Michigan. They are present in Illinois waters, but not in large numbers.

The variety of fish species collected in this assessment depends, in part, on what station is being sampled. Species such as spottail shiners and yellow perch are more common at shallower depths while bloater (chubs) and deepwater sculpin are usually found in the nets farthest offshore. Alewife, lake trout and the round goby can appear at any station.

As the smallest meshes cross the table, alewife start to appear, first showing up in the 2-inch mesh. Most are 8- to 9-inches in length. Alewife of this size have started to reappear the last few years after a long absence. While there are not many, their presence is encouraging.

Next is the 1.5-inch mesh, usually the best alewife catcher. These 6- to 8-inch alewife are more common, and hundreds can be caught in the single 50-foot panel giving it the nickname of “silver curtain.” Today’s catch is lighter, and the panel is cleared in a few minutes.

The final mesh is the 1-inch and not much is caught. A few fragile 4- to 5-inch alewife are gently removed from the net. A couple handfuls of round goby are tangled at the very bottom of the net. A single rainbow smelt rounds out the catch.

Collecting Fish from the Second Net

As Atkinson aims the boat toward the second net, the stack of eight plastic bins (one for each panel) is slid out the way, and the process is repeated as the second net is hauled up. The two assessment nets are then reset at different stations to be retrieved the next day.

Processing the Catch

As the tug heads back to the harbor, the biologists begin to process the catch. All the fish are measured, weighed, sexed, checked for parasitic sea lamprey wounds or scars, and stocked species are checked for fin clips. Up to 25 individuals of each mesh’s catch of alewives are saved for removal of otoliths (ear bones used to age the fish) in the lab. Alewives are of particular interest since they are the primary prey of salmon and trout that support a popular sport fishery. Aging structures are saved from many of the species caught in the survey. This allows biologists to get an idea of the age structure and growth rates of the various populations, both of which are important considerations when managing fisheries.

Data Used to Make Informed Management Decisions

This annual assessment of both predators and prey helps biologists monitor trends in vital population metrics (e.g., relative abundance, age and growth, sex ratios and relative survival) of important species in the ecosystem. The data collected from the day’s sampling, combined with data collected by other state, federal and tribal agency biologists around the lake, will inform management decisions on stocking levels and harvest regulations to ensure predator-prey balance is maintained in the food web, and shared fisheries are sustained for public benefit.

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Dan Makauskas has been a Lake Michigan fishery biologist for the Illinois Department of Natural Resources for more than 30 years, and when not working on the Clifford J, he can be found at the Lake Michigan Program office in Des Plaines.