Lake Nipissing: Ecology & Fisheries
Richard Rowe, Senior Biologist
Lake Nipissing: The Last 100 Years

Pre-World War I:
Blue phase, shadflies & sturgeon decline

World War I:
The Beef & Bacon Initiative

1940s & 1950s
Tourism, Yellow ‘seeding’, 1st Blue-Green report

1960s & 1970s
Tourism explosion, Fisheries assessment,
ice fishing, blue ‘phased’ out
Lake Nipissing: The Last 100 Years

1980s to mid 1990s
Recreational fishing concern, NFN commercial fishery emerging

Mid 1990s to early 2000s
NFN commercial fishery concern, loss of fisheries assessment

Mid 2000s to 2010
Significant Management Efforts, Walleye fishery
slowly improving?

2010-present
Walleye fishery decline, ecosystem shifts
Habitat Changes


The creeping crisis
Loss of diversity; loss of insurance
Species Introductions & Re-colonization

Always a risk of upsetting the
ecosystem balance
Most Recent Changes in Ecosystem
Arguably the biggest changes:
Yellow Perch Catch per Net (FWIN)
60
50
40
30
20
10




10
20
09
20
08
20
07
20
06
20
05
20
04
20
03
20
02
20
01
20
00
20
99
19
19
98
0
Other Notable Changes:
Energy Flow changes in food web from zooplankton to
walleye
Herring
Smelt
Walleye observed feeding on smelt; growth changes,
movements?
Present Day Lake Nipissing Ecosystem:
The Walleye

Lake-wide, the top predator and
greatest top-down influence on
ecosystem (this could be changing)
“The most significant population
stress on Lake Nipissing walleye
continues to be human exploitation”
Monitoring the Walleye & the
Impacts We Have On It
Fall Walleye Index Netting (FWIN)
 Daily Commercial Harvest Reporting
 Angler Creel Surveys
(Other data sets, other species)

Walleye “Management” - Considerations
Q: How do you manage walleye?
A: You Don’t
Fish manage themselves – we try to
manage our impacts when needed.
Best way to manage impacts on walleye:

Protect spawning population
= protect the future
The Reasons are in the biology:


A 4-lb female lays 100,000 eggs
So?
If there are enough adult walleye left and
they spawn, they can increase the population
quickly (IF conditions are right and IF there are enough)
Lake Nipissing is ideal habitat for walleye
So?
If weather conditions are suitable and there is a enough
spawning fish, Lake Nipissing walleye will produce strong
year classes
The Key to Management –
Keep Enough Spawning Fish in the
Lake
Approach: Adaptive Management
Critical
Upper Stock
Reference Point

Limit Reference Point

A combination of science and ‘trial
and error’
The Science: Maximum
Stock Status
Sustainable Yield
The Trial/Error:
Maintain a harvest
significantly lower
than this, protect
spawning fish and
see what happens…
Harvest Level

Cautious
Maximum Harvest
Level
Healthy
Angler Harvest Control directed at
Spawning Fish


Recreational angling fishery
protected slot size
Angling season opens after spawn
NFN Management efforts to protect
spawning walleye




Mesh size (minimizes kill of larger
spawners)
Moratorium (guarantee fish left to
spawn)
Quota (guarantee fish left to spawn)
Reporting harvest (keeping track)
Signs of Modern Management
Working?
Since 2004 (when slot
started/NFN started):
Spawning stock
every year for 5
years in a row (numbers and biomass)
Signs of Management Working?
Biomass comparison
3.0000
2.5000
kg/net
2.0000
1.5000
NFN formal
mgmt
1.0000
0.5000
Slot Size
0.0000
1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008
Year
> 40 cm > 40 cm
Index Nets – wt.Biomass
walleye
Despite all other stresses on ecosystem
to this point, management efforts
seemed to be working…
Harvest seems to be at level that
allows slow increase of spawning
stock
140000
Harvest (kg)
120000
100000
80000
60000
Estimated Safe Harvest Level (Maximum sustainable)
Total of all walleye
harvested (sport +
commercial)
40000
20000
NFN formal
mgmt
Slot Size
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
0
Something happened in 2009




Number of spawning walleye in index netting
Management stayed the same – reported
harvest at desired level
Suspicion that ecosystem was
changing…again
One bad year of data or was this a real
change?
THE Alarming Trend: Spawning Stock
3.0000
2.5000
1.5000
1.0000
0.5000
0.0000
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
20
11
kg/nett
2.0000
Year
THE Alarming Trend: Spawning Stock
3.0000
2.5000
1.5000
1.0000
0.5000
0.0000
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
20
11
kg/nett
2.0000
Year
What Happened?



Many contributing factors likely
played a role: harvest, ecosystem,
nature cycles
No one specific cause for the
latest decline
Harvest STILL Drives the Fishery?
3
120000
2.5
100000
2
80000
1.5
60000
1
40000
0.5
20000
Year
10
20
09
20
08
20
07
20
06
20
05
20
04
20
03
20
02
0
20
01
0
Spawning Stock (kg/net)
140000
20
Harvest (kg)
Measured Harvest (NFN + angler yr previous)
Spawning Stock Biomass (kg/net)
Harvest STILL Drives the Fishery?
3
120000
2.5
100000
2
80000
1.5
60000
1
40000
0.5
20000
Year
10
20
09
20
08
20
07
20
06
20
05
20
04
20
03
20
02
0
20
01
0
Spawning Stock (kg/net)
140000
20
Harvest (kg)
Measured Harvest (NFN + angler yr previous)
Spawning Stock Biomass (kg/net)
Harvest STILL Drives the Fishery?
3
120000
2.5
100000
2
80000
1.5
60000
1
40000
0.5
20000
Year
10
20
09
20
08
20
07
20
06
20
05
20
04
20
03
20
02
0
20
01
0
Spawning Stock (kg/net)
140000
20
Harvest (kg)
Measured Harvest (NFN + angler yr previous)
Spawning Stock Biomass (kg/net)
Harvest STILL Drives the Fishery?
3
120000
2.5
100000
2
80000
1.5
60000
1
40000
0.5
20000
Year
10
20
09
20
08
20
07
20
06
20
05
20
04
20
03
20
02
0
20
01
0
Spawning Stock (kg/net)
140000
20
Harvest (kg)
Measured Harvest (NFN + angler yr previous)
Spawning Stock Biomass (kg/net)
Harvest STILL Drives the Fishery?
3
120000
2.5
100000
2
80000
1.5
60000
1
40000
0.5
20000
Year
10
20
09
20
08
20
07
20
06
20
05
20
04
20
03
20
02
0
20
01
0
Spawning Stock (kg/net)
140000
20
Harvest (kg)
Measured Harvest (NFN + angler yr previous)
Spawning Stock Biomass (kg/net)
Harvest STILL Drives the Fishery?
3
120000
2.5
100000
2
80000
1.5
60000
1
40000
0.5
20000
Year
10
20
09
20
08
20
07
20
06
20
05
20
04
20
03
20
02
0
20
01
0
Spawning Stock (kg/net)
140000
20
Harvest (kg)
Measured Harvest (NFN + angler yr previous)
Spawning Stock Biomass (kg/net)
Harvest STILL Drives the Fishery?
3
120000
2.5
100000
2
80000
1.5
60000
1
40000
0.5
20000
Year
10
20
09
20
08
20
07
20
06
20
05
20
04
20
03
20
02
0
20
01
0
Spawning Stock (kg/net)
140000
20
Harvest (kg)
Measured Harvest (NFN + angler yr previous)
Spawning Stock Biomass (kg/net)
IF Harvest Still Drives Fishery:
Extra harvest had to occur in 2009 and 2010
Measured Harvest (NFN + angler yr previous)
Spawning Stock Biomass (kg/net)
3
X
120000
100000
X
2.5
2
80000
1.5
60000
1
40000
0.5
20000
Year
10
20
09
20
08
20
07
20
06
20
05
20
04
20
03
20
02
0
20
20
01
0
Spawning Stock (kg/net)
140000
Harvest (kg)

Can we “find” extra or unexpected
harvest in 2009, 2010 to make sense of
existing data?
Confirmed Sources:
 Non-compliance NFN moratorium (ballpark
#’s based on occurrences)
 Commercial spearing possibilities (ballpark
numbers based on weather)
 Undetected angler non-compliance with slot
size (ballpark numbers based on Alberta
model)
 Dokis FN commercialization (ballpark #’s
based on confirmed reports)
Extra Harvest Factor:
3
120000
2.5
100000
2
80000
1.5
60000
1
40000
0.5
20000
Year
10
20
09
20
08
20
07
20
06
20
05
20
04
20
03
20
02
0
20
01
0
Spawning Stock (kg/net)
140000
20
Harvest (kg)
Measured Harvest (NFN + angler yr previous)
Spawning Stock Biomass (kg/net)
Extra Harvest Factor:
3
120000
2.5
100000
2
80000
1.5
60000
1
40000
0.5
20000
Year
10
20
09
20
08
20
07
20
06
20
05
20
04
20
03
20
02
0
20
01
0
Spawning Stock (kg/net)
140000
20
Harvest (kg)
Measured Harvest + Estimated Extra
Spawning Stock Biomass (kg/net)
What Happened - Final Thoughts




Should we have done more in 1998;
2004?
Did we let our collective guard down for
compliance during a time when it was
needed most?
Did we live off the ‘principle’ of the fishery
during times of record low interest?
Did we get unlucky from a weather and
cyclical perspective?
Varying degrees of “Yes” to all of these…
Where Does This Leave Us
Moving Forward?
The Ecosystem
 In a state of flux
 SWF abundant,
 Yellow perch dominant,
 Walleye’s place uncertain
Where Does This Leave Us
Moving Forward?
The Walleye Fishery
 Seem to be ‘skinnier; maturing a bit
later
 This + the ‘double gauntlet’ is
leading to or has led to a serious
situation called ‘recruitment
overfishing’
Age 0-1
Age 2-3
Age 3-4
Age 5-7
Age 8+
Age 0-1
Age 2-3
Age 3-4
Age 5-7
Age 8+
Recruitment Overfishing
?
Age 0-1
Age 2-3
Age 3-4
Age 5-7
Age 8+
Where Does This Leave Us
Moving Forward?
The Challenge for the Future
11
20
10
20
09
20
08
20
07
20
06
20
05
20
04
20
03
20
02
20
01
20
00
20
19
19
99
9.00
8.00
7.00
6.00
5.00
4.00
3.00
2.00
1.00
0.00
98
total mean catch (#/net)
FWIN Catch Walleye < 30 cm
Year


Record numbers of young captured in FWIN 2 yrs in a row
Can we get them through to become prime spawning
stock?
Where Does This Leave Us
Moving Forward?
The Challenge for the Future
11
20
10
20
09
20
08
20
07
20
06
20
05
20
04
20
03
20
02
20
01
20
00
20
19
19
99
9.00
8.00
7.00
6.00
5.00
4.00
3.00
2.00
1.00
0.00
98
total mean catch (#/net)
FWIN Catch Walleye < 30 cm
Year


Record numbers of young captured in FWIN 2 yrs in a row
Can we get them through to become prime spawning
stock?
Where Does This Leave Us
Moving Forward?
The Challenge for the Future



How do we assure that enough of these young make
it through?
Chances for success depends on both major fisheries
IF we make it through – how do we get better
compliance during those ‘lean years’?
The Next 5 Years:
Our Biggest Crisis or Our
Greatest Opportunity?