Testing Regulation Changes for Lake Temagami Lake Trout: Computer Modeling

1
Testing Regulation Changesfor Lake Temagami Lake
TroutComputer Modeling
An Introduction to Fisheries Management Support
System (FMSS)
2
What is FMSS

• A computer tool that helps us decide what
  regulations may or may not work on a fish
  population
• This computer model allows you to look into the
  future to see what COULD happen to your fishery
  with different regulations (relative
  effectiveness of regulations)

3
How it Works

• 1.Make a computer model of Lake Temagami lake
  trout population that reflects what we know.
• 2. Tell computer to predict the future of lake
  trout under different conditions (environmental
  factors are at work in the model hence why we do
  100 runs of each scenario).
• 3. Try different regulations and see what happens

4
What are we trying to find?

• A set of fishing regulations that should lead to
  a stable or increasing lake trout population, no
  matter what random environmental conditions
  occur.

5
What Do We Need to Do?

• Set up the model lake and lake trout population
  in FMSS to be as similar to Lake Temagami as
  possible
• Know the biology
• Know the history
• Know how the lake is fished

6
Considerations for the Model A combination of
biology, science, assessment experience

• Life history of a Lake Temagami lake trout
  (biology, lake assessments)
• Used a slightly smaller size lake than Lake
  Temagami but with calibration it mimics the
  productivity of the lake.

7
Modelling-just one tool in the box

• Understanding of lake productivity, fish
  community, level of sustainable effort, maximum
  sustainable yield, growth rates, age of maturity
  etc.- Status Report results
• Plugging in our knowledge of the lake results in
  this dumb box acting like the Lake Temagami lake
  trout population..within reason

8
What we plugged in for Lake Temagami

• Average summer effort last 3 summer creels (2.28
  rd hrs/ha/yr)
• Average winter effort last 3 winter creels (1.1
  rd hrs/ha/yr)
• Calibrated model (established starting condition)
  based on iterations that result in maximum yield
  value(0.61 kg/ha/yr) when maximum sustainable
  effort is 3.5 rd hrs/ha/yr. This included many of
  the measures we have been collecting on Lake
  Temagami (size at 50 maturity, L-infinity,
  growth rate etc).
• The calibration of the model made it work like we
  understand Lake Temagami (large lake with a
  complex fish community that includes lake trout
  as a keystone predator).
• The model is designed to mimic lake trout lakes
  and we just fine tune it to the Lake Temagami
  condition.
• The properties of lake trout lakes that drive the
  model come from the Boreal Shield Watersheds and
  previously published relationships

9
What would be considered a successful set of
regulations?
1. of lake trout more or less
Unacceptable
Risky
Best Bets
2. Does the population crash?
Not acceptable to experience a crash- population
fails
10
Test Regulations- we heard these

• No fishing (demonstration run)
• Status quo-same season, limit 3 (where we are
  headed with no change)
• Status quo season, reduce limit to 2 (conforms to
  recommended provincial limit)
• The following are in response to requests from
  some Lake Temagami tourist operators
• Status quo season, limit 2, 1gt24
• Extend winter season by one month, 3 fish limit
• Extend winter season by one month, 2 fish limit
• Extend winter season by one month, 2 fish limit,
  1gt24
• Extend winter season by one month, 2 fish, 1 over
  24, close July season

11
Some Results...
12
Some More Results...
13
Even Some More Results...
14
The Problem with Limits

• Good apportioning tool for fair share
• Not effective at limiting harvest unless catch
  rates are super-high

15
A Summary so far
Unacceptable
Risky
Best Bets
Require enhancements
16
Improving the Odds for Risky Choices Add-on
Enhancements to Consider

• lines from 2 to 1 (no clear science based answer
  on effect Boreal Shield text-it would likely
  increase the safety margin in risky choices)
• Baitfish restrictions reduce effectiveness of
  lake trout anglers (again no definitive answer)
• Education (release rate, survival, compliance)

17
What else may improve numbers?from the draft LT
toolkit
18
What else might work?
Unacceptable
Risky
Best Bets
19
Conclusion

• Barring any extreme events
• -environmental (ie. low water levels)
• -biological events(ie.new exotic species intros)
• -no significant increases in angler effort
• The model suggests that in the short term
  the status quo is a risk to the fishery(38
  likely to rain). The 2 fish limit will
  marginally reduce that risk (36 likely to
  rain)-how much risk is too much with lake trout.
  Other strategies ( ie.1 line in winter during
  trout season) or other viable suggestions(promotio
  n of catch and release, careful handling)
  although presently not quantifiable may reduce
  the risk further.
• Further
• The 100 smaller lake trout lakes will
  recover from their present status (in 10 yrs) may
  help in dispersing pressure from Lake Temagami in
  future. This limited effect may be more immediate
  if the surrounding smaller waters of Zone 11
  adopt the one month winter season identical to
  Lake Temagami.