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 (it’s 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 it’s 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.
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.
2010 Season Overall Results
- Marquette anglers tagged 524 lake trout between 12 April and 10 November 2010. That is close to our goal of 600 fish.
- DNR staff here tagged 600 lake trout from trap nets between 18 May and 07 July 2010.
- A total of 114 recaptures were reported during 2010 (thus far), which is about 10% recovery rate.
- Most of the recaptures came from gill nets (50), followed by recreational anglers (42), and then by trap nets (21).
- The longest number of days at liberty (how many days between tagging and recapture) was 155 days.
- The shortest number of days at liberty was 0 days.
- Tagged lake trout have been caught at the Apostle Islands, Wisconsin to the west and near Whitefish Point to the east.
2010 "Cooler By The Lake" Season Results
- We tagged and released 222 Lake Trout.
- We caught one Lake Trout on 19 July that was tagged by a fellow angler on 13 July.
- Of our 222 Lake Trout tagged, 9 have been recaptured this year. We didn't catch any of our own tagged fish.
- One Lake Trout we tagged on 25 July and recorded as "belly up" when released as it didn't look like it would make it (see the picture above). However, on 7 September (44 days later) it was caught at the Apostle Islands, Wisconsin, travelling approximately 210 miles from our release point. Another of our tagged fish was caught past Munising.
- Our best day of tagging was on 12 October, when we tagged and released 15 Lake Trout. Oh, we also kept 6 Lakers.
- The fish we tagged were caught at an average depth of 167'.
- The average length of the Lake Trout we tagged was 20.8", the longest being 27.5".
2011 Season Overall Results per DNR
- Marquette anglers tagged 595 lake trout between 15 April and 4 November 2011. That is close to our goal of 600 fish.
- DNR staff only tagged 38 lake trout from trap nets because of staff shortages early in the spring, missing the window for Lakers in trap nets.
- A total of 222 recaptures were reported during 2011.
- Recreational anglers recaptured 44% (97), commercial and DNR gill nets recaptured 38% (84) and trap nets recaptured 18% (41).
- The longest number of days at liberty (how many days between tagging and recapture) was 551 days.
- The shortest number of days at liberty was 0 days.
- Tagged lake trout have again this year been caught at the Apostle Islands, Wisconsin to the west and near Whitefish Point to the east.
2011 "Cooler By The Lake" Season Results
- We tagged and released 345 Lake Trout in 2011.
- Of our 345 Lake Trout tagged, 22 have been recaptured so far.
- Of the 31 Lakers recaptured, 3 were caught near Keweenaw Bay and 2 in the Munising area.
- Of the 222 Lake Trout we tagged last year (2010), 37 were recaptured so far.
- We caught 4 tagged Lake Trout, only one of which had our own tag. Three of the 4 Lakers were tagged in 2010.
- Our best day of tagging was on 11 August 2011, when we tagged and released 18 Lake Trout.
- The fish we tagged were caught at an average depth of 176'.
- The average length of the Lake Trout we tagged was 20.4", the longest two being 35.4".
2012 Season and Overall Results per DNR
- The furthest location a fish was recaptured was near the Knife R., NE of Duluth, MN (a 26.3 inch fish swimming at least 375 miles in 116 days, averaging 3.23 miles/day).
- DNR tagged 567 Lake Trout in 2012 from trap nets as part of the control group.
- Marquette anglers as a part of this study tagged and released 590 Lake Trout during 2012.
- The greatest number of days at liberty was 887 (2.4 years), and one fish was caught the same day it was tagged.
- The biggest fish tagged was over 37”.
- We’ve had more than 14 reports of multiple green reward tags being caught in one day by an angler/group, with two anglers reporting catching 3 tags in one day.
- The majority of tagged fish were recaptured in the study region (between Granite Island and Laughing Fish Point).
- To date study anglers have tagged 1,717 Lake Trout and the DNR staff tagging 1,206 Lake Trout from trap nets as a part of the control group.
- 27 people have recaptured a total of 2 or more of green reward tags, with one angler recovering 10 and one recovering 9 tags (this excludes research anglers).
- 3 fish were reported being caught by the tag (1 of which only the tag was landed). More fish may be caught by anglers this way than reported.
- A total of 631 Lake Trout have been recaptured since the study began, a rate of around 21%. Note that recaps are still coming in.
- Recaptures by source for Angler-tagged fish was: 36% commercial gill nets, 56% recreational fishing, 4% MIDNR gill nets, and 4% trap nets.
- Recaptures by source for trap net tagged fish was: 32% commercial gill nets, 28% recreational fishing, 2% MIDNR gill nets, and 38% trap nets.
- In the Lake Huron part of our study, Alpena Fisheries Research Station personnel tagged 1,354 lake trout out of trap nets and research anglers have tagged 688 fish since 2010. To date, 187 trap-net tagged and 16 angler-tagged lake trout have been recaptured.
2012 "Cooler By The Lake" Season and Overall Results
- Tagged and released 314 Lake Trout in 2012.
- Tagged and released 881 Lake Trout 2010-2012. Of those, 129 (14.6%) have been recaptured to date.
- Number of days from tagging to recapture (days at liberty) ranged from 8 days to 852 days.
- Average length of tagged Lakers was 20.5", smallest 15.7", largest 31.4".
- Click to expand on the map below which shows where our Lakers were recaptured. Use your back button to return here.
- The average depth of tagged Lakers was 196 feet.
- Our biggest tagging date was 12 August when we tagged and released 20 Lake Trout (and kept 7).
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
We tagged and released 1,212 Lake Trout
Through January 2014, 249 of our fish were recaptured, a recovery rate of 20.5% (I'll update this midsummer)
Below is a graphi
c illustration of where Lake Trout were recaptured through January 2014. Click on image to enlarge.
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