Request from anglers:

Increase the daily possession (bag) limitfor brook trout in Upper Peninsula streamsfrom 5 fish to 10 fish

Biological review next slides

Sociological review: online surveypublic meetings

Brook Trout History• Population declines in late 1800s and early 1900s

- habitat degradation & overfishing• Habitat improvement, stocking, & regulations• Daily possession limits

late 1800s – 50 fish1968 – 10 fish2000 – 5 fish

Brook Trout Regulations• Daily possession limits are based on a variety of

biological and sociological factors• Biological

Goal = sustainable harvestAvoid long-term declines in trout abundance

• SociologicalEquitably divide harvestReflect sentiment of sufficient harvest for one tripEstablish targetSimplify regulations

Biological Considerations

• Considerations:– How often do anglers catch 6, 7, 8, 9, or 10

trout?– How often do anglers that catch more than 5

fish harvest the additional catch (pre-2000)?– How important is fishing mortality versus

natural mortality?

• Electrofishing surveys on numerous streamsabundancesize and age structuregrowthmortality

• Creel surveys (harvest data)most applicable = Wagner et al. (1994)four popular brook trout streams in west UP1988-1992 (10 fish limit)

• Computer simulations

Data Sources

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Number of legal brook trout per trip

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s E. Br. Escanaba River

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Number of legal brook trout per trip

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s W. Br. Escanaba River

UP Creel Data (1988-92)

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Number of legal brook trout per trip

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M. Br. Ontonagon River

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Number of legal brook trout per trip

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s Iron River

Creel Limit = 10 fish, MSL = 7”, 2,585 total trips (average 2.4% > 5 fish)

0.4% 1.1%

4.1% 3.9%

U.P. Harvest Estimates• 5 fish limit harvest decreased by 10%• Fishing mortality averaged 10% (age 1 and older)

Save 1% of population• Total annual mortality = 71-81%

Computer Simulation• Model inputs

– Hooking mortality– Catchability– Fishing effort– Annual recruitment– Voluntary release– Minimum size limit– Annual survival*– Mean length-at-age– Initial population size

• Only Michigan data used

Scenarios• Increase voluntary release by increments of 30%

• 3 arbitrary starting levels- 10% (low)- 40% (medium)- 70% (high)

• Vary survival, population density, and hooking mortality

• Exploited and unexploited populations

40%70%100%

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Population increase Catch increase Harvest reduction

Perc

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10%→40% 40%→70% 70%→100%

Results: Total population

Error bars represent range of results across all density and

hooking mortality levels

Results: Population >7”

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Population increase Catch increase Harvest reduction

Perc

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10%→40% 40%→70% 70%→100%

Simulation Summary

• Increasing brook trout release– 2% increase in total population– 5% increase in population >7”– 10% increase in catch >7”– Maximum 30% increase in catch >7”– Harvest reduced 25%-100%

• Why?– Fast growth and early maturation of juveniles– High natural mortality of older individuals– On average: For every age 2 brook trout, there are an

additional five age 1 fish (no shortage of spawners)

Biological Review

ConclusionThe proposed daily possession limit change would have minimal effects on brook trout populations.

Social Considerations

PurposeAllow successful anglersto keep more fish

Side EffectAdds complexity to troutstream regulations

Trout Stream Regulations

Upper Peninsula: 5 fish,plus an additional 5 brooktrout, but no more than 3 trout15” or greater

Lower Peninsula: 5 fish, butno more than 3 trout 15” orgreater

Social Considerations

Question: What is more important to you?- increased opportunity for harvest- simpler fishing regulations

Other sociological factorsEquitable distribution of harvest?How many brook trout is enough?Reasonable target?

Please take the online survey

Thank You

www.michigan.gov/dnr

Great Lakes, Great Times, Great Outdoors