DNR Hooking Mortality Study  2010 -2015

"Cooler By The Lake"

 

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Background on tagging. About 7 (varied each year) of us local fishermen are participating in a Michigan DNR Lake Trout Hooking-Mortality 6-year study starting in 2010. It is being conducted in Marquette (Lake Superior) and Alpena (Lake Huron). The only other study of  this type was done in 1980 and showed 15% of the Lakers died when released. However, that study had very limited deep water data, which this study covers. Its purpose is to determine the survival rate of Lake Trout caught and released to help DNR biologists evaluate whether establishing certain size catch limits are having the desired management outcome. This information will be useful where slot limits are applied as it's counterproductive to release Lakers if their survival rate is too low. The study's plan is to for anglers to collectively tag and release 600 Lake Trout each year for 3 years (which turned in to 4 years for various reasons) and 2 additional years to collect data on recaptured Lake Trout. Concurrently, DNR will tag and release roughly 600 Lakers each year from trap nets to serve as a control group. Anyone who turns in a tag will receive a $10 reward from the DNR and receive a letter telling where and when the fish was tagged. Recaptured Lake Trout tags can come from anglers, trap nets, or gill nets.

How we do it. Once I decide to tag a Laker (its my choice whether to keep or tag fish but that must be done before I see the fish), I start a timer when the fish is first hooked to record play time. Once netted, the first timer is stopped and a second timer is started. I then tag the Laker with a green spaghetti tag under the dorsal fin and take a digital picture of the fish to show the tag number and fish length. Once released, the second timer is stopped and the condition of the fish on release is noted. I then log data for each Laker which includes  playing time, and handling time, depth of fish when hooked, whether its a lean or fat, observed lamprey marks, whether the fish is bloated, how it was caught (e.g., downrigger, steel line, etc), where hooked (usually lip), location on Lake, and whether blood was present, and seagulls were in the area. For this I get paid $5 per tagged fish.

Equipment we use. The cradle shown here is an early version. It's used for placing the Lake Trout while being tagged and taking a picture. I found it difficult to use and made several modifications shown in the next picture. The timer, and digital camera, and needle for tagging are provided to us, as well as a 3-ring notebook containing log sheets and tags. Click on the pictures to enlarge, and use your back arrow to return here.

Tagging equipment

The picture below is the fish we thought wouldn't survive but then obviously did and found its way approximately 210 miles to the Apostle Islands some 44 days later. You can see the lamprey scars on its side. Note my modifications to the cradle, including the Plexiglas top, hinged end for easy release, and rubber snubbers to keep the Laker from jumping out. I still wasn't completely satisfied with it and went to a completely different system, which works much better but I don't show here.

Tagged Laker that made it to the Apostle Islands, WI

2010 Season Overall Results

2010 "Cooler By The Lake" Season Results

2011 Season Overall Results per DNR

2011 "Cooler By The Lake" Season Results

2012 Season and Overall Results per DNR

2012 "Cooler By The Lake" Season and Overall Results

 

Cooler By The Lake Tagged Lake Trout Recaptured by area map

DNR Season and Overall Study-to-Date Results (final year of tagging but two remaining for recapture data)

"Cooler By The Lake" 2013 (final year tagging)  and Study-to-Date Results

Below is a graphic illustration of where Lake Trout were recaptured through January 2014. Click on image to enlarge.

Angler recaps 2010-2013

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