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Totally Shocked Electricity helps biologists track game fish on Lake Michigan.
The old man in the straw hat looked as stunned as the fish when the big yellow carp floated up next to his bobber. For more than an hour, he had been sitting in his webbed aluminum lawn chair on the harbor's shore, hoping such a fish would be tempted by his nightcrawler. But the carp wasn't particularly interested in eating, having just been stunned by a 5,000-watt jolt of electricity sent through the water by a slow-moving, 18-foot jon boat. On board the boat were Steve Robillard and Dan Makauskas, biologists from the Department of Natural Resources' Lake Michigan fisheries program, conducting one of the four fish assessments they do each summer at Jackson Park Harbor in Chicago. As a portable gasoline-powered electric generator roared, two probes on the front and six "ticklers" on the sides directed the current 8 feet down and 5 feet out from the boat. "The electric shock knocks the fish out for a few seconds to a few minutes," Makauskas said, "but it doesn't kill or hurt them. Their muscles are moved by electricity just like a human's, and the current causes them to get rigid so they can't move. The negative charge in their body is attracted to our positive charge, which causes them to rise." Fish are brought aboard with a long-handled net and placed into a small holding tank. While most eventually will be returned to the water, the unfortunate carp will not. Because carp are bottom feeders, they are kept for contaminant sampling, Robillard said. The fish are filleted and sent to the Illinois Environmental Protection Agency
The electric field temporarily stuns fish for easy capture. for testing. The tests reveal the amount of contaminants in their flesh—information that is then used by the Department of Public Health in setting fish consumption advisories. Although the health department currently discourages eating carp from Lake Michigan, Robillard said contaminant levels have continually declined since the assessments began in 1995. However, he said, levels have begun to plateau in recent samplings because the lake is so much cleaner. The summer sampling is conducted twice in May, once in June and once in July at North Point Marina in Winthrop Harbor, Waukegan Harbor, the inner harbor at Jackson Park and Calumet Harbor. The survey's goals are to determine what species of fish are in Lake Michigan and how healthy those fish are. "Before we started this sampling, we obtained our data from the Illinois Natural History Survey's creel survey," Robillard said. "The obvious limitation on that (survey) was that we'd only see the fish anglers were keeping. We wanted to see what other fish were available and indices of their health—weight, length, ages and numbers. We can't sample everywhere, but this gives us a year-to-year idea." Game species targeted by the surveyors include brown and black bullhead, black and white crappie, bluegill, sunfish, pumpkinseed, northern pike, yellow perch and smallmouth, largemouth and rock bass. Non-targeted species include carp, alewife, freshwater drum, gizzard shad, golden shiner, goldfish, white perch and white sucker.
Though some species were common to all the harbors (largemouth, alewife and carp), brown bullhead were found only at Jackson, green sunfish and white crappie only at North Point, and northern pike and goldfish only at Waukegan. In 2000, North Point contained 10 of the 12 targeted species and seven of the eight non-target species;
With the exception of carp and largemouth and smallmouth bass over 10 inches, all the other fish have their lengths and weights recorded before going back into the water. Although they too are weighed and measured, the black bass are subjected to another painless procedure before they're released. For the past two summers, biologists have been using a syringe to inject a tiny passive integrated transponder (PIT) tag under the Electro fishing provides valuable information on the health and quality of the fishery.
skin of the larger bass. The tag is inactive until the fish is recaptured, at which time a hand-held tag reader passed over the fish can read the 10-digit code it contains. The tags allow surveyors to see how much a fish has grown from year to year and whether it moves from harbor to harbor. Bass that receive PIT tags have the third spine on their dorsal fin clipped so they're instantly recognizable the next time they're caught. "It's just like cutting a toenail," Robillard said as he performed the operation with a toenail clipper. "It doesn't hurt them, and it doesn't affect their swimming ability." Makauskas said the PIT tags cost about $4 each, while the tag reader costs $500-$600. Manufactured by Biomark Inc., Boise, Idaho, PIT tags and readers also are used downstate on pure muskies at Kinkaid, Otter and North Spring lakes and on sturgeon in the Wabash and Mississippi rivers. Only four of the 250 fish tagged on Lake Michigan in 2000 were recaptured in 2001, with small-mouth growing two inches and largemouth growing one inch. Robillard attributed the low recovery rate to several factors: a large number of fish; fish movement between harbors where sampling is not conducted; relocation of fish by tournament anglers; and the relatively small areas that are sampled. "North Point is a huge harbor, and we sample only about 5 percent of it," he said. "The same with Waukegan. We can only do the inner harbor at Jackson Park because the outer harbor's too deep. We only sample a small portion along the western breakwall of Calumet Harbor because the rest is open lake." Eleven fish that were tagged during the spring of 2001 were recaptured in later assessments, and Robillard said the numbers should grow in next year's sampling since 375 fish were tagged this year. While the PIT program is a work in progress, the biologists said they have been able to draw some conclusions about the fishery based on the summer assessment. "They seem well-fed," Robillard said. "There's a good variety of ages (juveniles to 10 years) for bass. Bluegill, sunfish, rock bass and pumpkinseed are 1-4 years old and healthy. "The harbors have what these fish need," he continued. "Jackson Park has shallow areas, deep areas, good vegetation and an abundant food supply. The same for Waukegan and North Point. Largemouth like vegetation, while smallmouth like the rocks. We're routinely getting 3- to 4-pound bass. We had a 6-pound largemouth at North Point. We're seeing rock bass up to 10 inches, with 7 to 8 inches being the average size. The other species are all showing consistent numbers from survey to survey."
The aforementioned INHS creel surveys match the results from the summer assessment, Robillard said. In 1999, anglers caught 38,000 rock bass, keeping 11,000. In 2000, they caught 46,000 rock bass, keeping 9,000. There were 3,700 smallmouth and 1,100 largemouth taken and released in 1999, compared to 4,900 and 1,100, respectively, in 2000. Largemouth and smallmouth are strictly catch and release on the lake, but that could change if their populations continue to grow. "The last stocking of small-mouth on the lake was in the mid-to late-1960s" Robillard said. The length and weight of a fish provide information about its growth and health.
A PIT tag is injected into the fish. This will allow for easy identification when the fish is recaptured. "They were hatchery leftovers. We've been seeing a gradual increase in their numbers. These fish have come back on their own." In addition to the summer harbor assessment, Robillard and Makauskas also use their shocking boat to survey salmon and trout when they return to spawn in the fall. Harbors covered in the fall are North Point, Waukegan, Diversey and Jackson, but not Calumet. DNR has been conducting the fall salmon and trout survey since the late 1970s. "We hit the sites where we stock the fish," Makauskas said. "North Point technically isn't a stocking site, but the fish come back there." Now in the second year of a five-year cycle, the Department stocks 100,000 brown trout, 100,000 rainbow trout, 305,000 chinook salmon and 300,000 coho salmon into the lake each year. Coho and chinook salmon are stocked at Waukegan, Diversey and Jackson harbors, while rainbows go to seven sites and brown trout to 10 sites. Before they leave DNR's Jake Wolf Fish Hatchery, the rainbow trout and 100,000 chinook salmon are fin-clipped by volunteers from Salmon Unlimited. The fin-clipped salmon are all stocked at Waukegan. Robillard said coho salmon return to spawn after their second summer in the lake, while chinook return after one to five years, browns after one to four years and rainbows after two to six years. The salmon die after spawning, while the trout are capable of spawning multiple years. "In 1999, there was a lake-wide reduction in the number of chinook that was stocked," Robillard said. "That year, there was an increase in the number of returning juveniles, so the reduction actually helped the overall population. The fall shocking last year showed another increase in the number of juvenile chinook returns. The majority of them were 1-year-olds from Waukegan. We're seeing faster growth rates and earlier maturities. For every one that comes back, there are more out there continuing to grow.
Like the carp in the summer assessment, salmon and trout captured during the fall are not returned to the water. After being weighed and measured, they're checked for clipped fins that reveal where and when they were stocked. Their otolith bones (similar to a human ear bone) are removed to determine their age, Continued growth of sport fish populations is one of the main goals of fisheries managers, but to achieve it, they must know the relative size and health of the fishery. Over the years, biologists have used creel surveys, seines, gill nets and electro-shocking to monitor fish, and lately have developed such new methods as implanted radio transmitters and underwater TV cameras. On the horizon, but currently too expensive, Robillard said, is equipment that uses implanted biotransmitters and global positioning satellites to pinpoint locations of individual fish and the depths and temperatures of waters where they're swimming. Sometime soon, someone will probably develop a way to tell what the fish want to eat too. If the old man in the straw hat had that information, he'd spend less time in that lawn chair and more time playing with his grandchildren. The PIT tag reader confirms that the tag is working properly.
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Waukegan had seven target species and six non-targets; Jackson had eight targets and six non-targets; and Calumet had three targets and three non-targets.
and fillets of their flesh are taken for contaminant sampling.