Charting effects of catch and release
ALPENA – Those who don’t win big during the Michigan Brown Trout Festival might still get a reward for their catch, and help the Department of Natural Resources with a lake trout study.
Biologists with the DNR have been getting help from commercial fisher and charter boat captains to determine how well lake trout survive being hooked and, if too small, thrown back, DNR Fisheries biologist Jim Johnson said. The findings so far are affecting how the department is managing the species. Anglers could be finding tagged lake trout, and claiming the $10 reward for turning it in, for years to come.
The DNR started the study after hearing reports from anglers that lake trout were being found dead and floating on the surface after being thrown back, Johnson said. Biologists shared this concern, and wanted to see if it had any merit. If not, length limits on the species could be doing more harm than good.
To see how well lake trout handled the stress of being brought up through 80 to 100 feet of water, the DNR devised an experiment, Johnson said. Charter captains would tag and photograph lake trout after catching them, then let them go. Meanwhile, Gauthier & Spaulding Fisheries used its trap nets to catch and tag another group of lake trout.
“Those fish were in great shape, we didn’t expect them to have any problem,” he said. “Those were our control group.”
Each group tagged 300 to 600 lake trout per year, with 1,643 fish in the control group and 710 tagged by recreational anglers, Johnson said. The actual number for the second group is probably closer to 900, with more tag numbers going into the database every day. With about 30 people helping the DNR, the project is getting a boost during the tagging phase.
“It’s a big team effort, it’s been a lot of fun, actually,” he said.
Anglers who catch a tagged lake trout can turn the tags in for $10, Johnson said. Tagged fish have a green wire loop fastened near the base of the fish’s dorsal fin. Anglers can call Johnson at 356-3232, ext. 2571, and report the tag number, date and catch location, and the lucky angler’s phone number.
“They’ll get a letter back explaining where and when that fish was tagged, who tagged it, and sometimes whether or not the trout was wild … and they’ll get a $10 check,” he said.
So far, things are looking bad for caught and released lake trout, Johnson said. The study is showing that at least half the lake trout caught and released are not surviving. This has the DNR reconsidering its length limits.
When the department started the study in 2010, the length limit for lake trout caught between a point near Presque Isle and Black River was 22 inches, Johnson said. It’s since been changed to 15 inches, in part because of the study’s findings.
“Fortunately, the lake trout population has been coming up,” he said. “The population is looking so healthy lately, it’s looking like we’re not needing length limits as much as we used to.”
When lake trout are caught on a downrigger, the system whips lake trout up to the surface so quickly they can’t adapt to the pressure change, Johnson said. The species is good at adapting to quick changes in water pressure, but when they’re brought to the surface too quickly, their capillaries burst as a result of the pressure change. Ultimately, the fish die of barotrauma.
While fish gas bladders also can expand from being brought up from the depths, lake trout are usually able to recover, Johnson said.
The DNR is conducting the same study on Lake Superior, where lake trout are being brought up from 150 feet of water. Surprisingly, the fish are faring well. The difference could be fishing techniques; instead of downriggers, Lake Superior anglers are using wire lines or jigs, then reeling the fish up to the surface.
“Jigging for them is much more likely to not hurt the fish,” he said, adding Lake Huron anglers practicing catch and release should experiment with the method.
This is the last year the DNR and its partners will tag lake trout for the study, Johnson said. He expects to compile the results in three years, but the long-lived fish could be swimming through Lake Huron for a few decades. It’s not uncommon for them to live to 20 years.