Lake Michigan 2011Status and Trends of Prey Fish Populations

Chuck Madenjian, Bo Bunnell, Tim Desorcie, Margi Chriscinske,Melissa Kostich, and Jean Adams

USGS Great Lakes Science CenterAnn Arbor, MI

Lake

Mic

higa

nSp

ring

TP (u

g/L)

0

2

4

6

Lake

Mic

higa

nSa

lmon

ine

biom

ass

(kt)

05

101520253035 Historical backdrop

1960s 1970s 1980s 1990s 2000s

sea lamprey control;salmonine stocking

Great Lakes WaterQuality Agreement

Madenjian et al. 2002; Bunnell et al. 2006; US-EPA

dreissenidinvasion

Round gobyinvasionBythotrephes

invasion

1 9 7 3 1 9 8 1 1 9 8 9 1 9 9 7 2 0 0 50

1 0 0

2 0 0

3 0 0

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7 0 0

Nu

me

ric

de

ns

ity

(n

um

be

r/h

a)

1 9 7 3 1 9 8 1 1 9 8 9 1 9 9 7 2 0 0 5

Ye a r

0

1 0

2 0

3 0

Bio

ma

ss

de

ns

ity

(k

g/h

a)

Ad u l t a l ewi fe

1975 1980 1985 1990 1995 2000 2005 20100

10000

20000

30000

40000

Year

Bio

mas

s (g

/ha)

Lake Huron

Concern that salmonine consumption is exceeding alewife production

Alewife energy density has declined (need to eat 22% more alewife to maintain constant growth)- Madenjian et al. 2006.

Chinook salmon have increased their reliance on alewife as a prey (maybe not the case for lake trout?).

Year1994-1996 2009-2010

Proportion

0.0

0.2

0.4

0.6

0.8

1.0AlewifeBloaterSmeltRound gobyDiporeia

Lake Michigan Chinook salmon diet… further alewife domination

<500 mm

Jacobs et al. in review

Lake Michigan Chinook salmon diet

Year1994-1996 2009-2010

Proportion

0.0

0.2

0.4

0.6

0.8

1.0AlewifeBloaterSmeltStickleback

… further alewife domination

>500 mm

Jacobs et al. in review

Concern that salmonine consumption is exceeding alewife production

Alewife energy density has declined (need to eat x% more alewife to maintain constant growth)- Madenjian et al. 200x.

Chinook salmon have increased their reliance on alewife as a prey (maybe not the case for lake trout?).

Alewife age-class distribution is more truncated (similar to Lake Huron pre-2003). 2011: up to 80% age-1.

1 5 3 5 5 5 7 5 9 5 11 5 1 3 5 1 5 5 1 7 5 1 9 5 2 1 5

Total length (mm)

0

5

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1 5

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Perc

ent

Age 3

Age 0

Age 5Age 6

Age 8

Age 2Age 1

Age 4

Age 7

2006

1 5 3 5 5 5 7 5 9 5 11 5 1 3 5 1 5 5 1 7 5 1 9 5 2 1 5

Total length (mm)

0

5

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1 5

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Perc

ent

Ag e 3

Age 0

Ag e 5Ag e 6

Ag e 2Ag e 1

Ag e 4

Ale wi fe le n g th -ag e d is trib u tio n , 2 0 0 9

15 35 55 75 95 115 135 155 175 195 215

Total length (mm)

0

5

10

15

20

25

30

35

40

Perc

ent

Ag e-0Ag e-1Ag e-2Ag e-3Ag e-4Ag e-5Ag e-6

Age 0Age 1Age 2Age 3Age 4Age 5Age 6

Ale wife le ngth-age dis tribution, 2 0 1 0

15 35 55 75 95 115 135 155 175 195 215

Total length (mm)

0

5

10

15

20

25

30

35

40

Perc

ent

Ag e-0Ag e-1Ag e-2Ag e-3Ag e-4Ag e-5Ag e-6

Age 0Age 1Age 2Age 3Age 4Age 5Age 6

Ale wife le ngth-age dis tribution, 2 0 1 1

1 9 7 3 1 9 8 1 1 9 8 9 1 9 9 7 2 0 0 50

5 0 0

1 0 0 0

1 5 0 0

2 0 0 0

2 5 0 0

Nu

me

ric

de

ns

ity

(n

um

be

r/h

a)

1 9 7 3 1 9 8 1 1 9 8 9 1 9 9 7 2 0 0 5

Ye a r

0

3 0

6 0

9 0

Bio

ma

ss

de

ns

ity

(k

g/h

a)

Ad u l t b loa te r

1 9 7 3 1 9 8 1 1 9 8 9 1 9 9 7 2 0 0 50

1 0 0

2 0 0

3 0 0

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5 0 0

6 0 0

Nu

me

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um

be

r/h

a)

1 9 7 3 1 9 8 1 1 9 8 9 1 9 9 7 2 0 0 5

Ye a r

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7

Bio

ma

ss

de

ns

ity

(k

g/h

a)

Ad u l t ra in b o w s me l t

Deepwater s culpin1.86 kt

Slimy s culpin1.93 kt

Bloater3.70 k t

Rainbow s melt0.47 kt

Ninespine s tick leback0.04 k t

Alewife7.64 k t

Round goby1.83 k t

Lake Michigan, 2011

1 9 7 3 1 9 8 0 1 9 8 7 1 9 9 4 2 0 0 1 2 0 0 8

Year

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Lake

-wid

e bi

omas

s (k

t) Bloater

Sl imy sculpin

Deepwater sculpinRainbow smel t

Ro u n d g o b y

Ni nespine sti ckleback

Alewi fe

Conclusions and prognosis• Total prey fish biomass, as estimated by the bottom

trawl, in 2011 was 17.47 kt, the lowest value in the time series

• Total prey fish biomass has remained below 30 kt since 2007

• Two factors contributing to low prey fish biomass:

prolonged period of low bloater recruitment and intensified predation by Chinook salmon on alewives

• Adult alewife biomass density has remained low for an eight-year period and age distribution has been truncated during the past three years; characteristics similar to Lake Huron alewife population prior to collapse during 2003-2004

Conclusions and prognosis (continued)

• Whether or not alewife population collapses in Lake Michigan depends on several factors: Chinook salmon abundance, alewife year-class strength in 2012, environmental effects on alewife survival

• To quantify bottom-up effects, additional years of surveillance and additional analyses needed

• Prey fish biomass in 2011 was far below FCO

• Whether prey fish biomass will ever exceed 100 kt in the near future will depend on the ability of the bloater population to recover