Transcript Guest Lecture 3 – Londer 2012 (pptx)

Justin G. Mychek-Londer and David (Bo) Bunnell
Acknowledgements
• Great Lakes Fisheries Commission (GLFC)
• Great Lakes Restoration Initiative (GLRI)
• USGS Great Lakes Science Center
• My Advisors: Bo Bunnell, James Diana
• Vincent Belill, John French III, Melissa Kostich, Kevin Keeler, Mark Rogers,
Lynn Ogilvie, Betsy Puchala, Linda Begnoche, Steven Pothoven, Chuck
Madenjian, Bruce Davis, Dave Bennion, Greg Jacobs, Timothy DeSorcie,
Barbara Diana, Scott Nelson, Jean Adams, Jeff Holuszko, Solomon David,
and others I’ve forgotten.
• The Crew of the RV Grayling Ed Perry and Jim Paige
• Susie Q Commercial Fishery in Two Rivers, WI
• School of Natural Resources at The University of Michigan, Ann Arbor
•
•
•
•
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Laurentian Great Lakes
Ecology in Lake Michigan
My research
Hypothesis testing
Results
Discussion
Implications
Outline
Laurentian Great Lakes
• Glacial
• Colonization
• Human influence
– Pollution
– Exploitation
– Extinctions
– Habitats
– Climate change
– Invasive species
Credit: COSEE
Credit: COSEE
Non-natives
• Engineering: Canal systems
• Sea lamprey
• Alewife
• Introductions
•
•
•
•
Brown trout
Rainbow trout
Smelt
Alewife control
– Chinook salmon
– Coho salmon
Lake Michigan
•
•
•
•
•
•
Within US territory
Inshore and offshore
Extinctions, extirpations
Recent environmental change
Offshore Ponto-caspian invaders
Offshore native aquatic species
Lake Michigan coregonid complex
• Prior to 1936 six named
deepwater ciscoes
• Commercial Fishery
• Restoration
WHITE = extinct, extirpated
BLACK = present day
RED = extirpated, restoration consideration
Coregonids
hoyi
(bloater)
Superior Michigan Huron
X
reighardi
(shortjaw)
X
johannae
nigripinnis
(blackfin)
X
X
X
X
X
(deepwater)
kiyi
X
Ontario
X
(shortnose)
zenithicus
X
Erie
X
X
X
X
X
X
X
Ballasts: Ponto-caspian invertebrates
1995
• Bythotrephes spp.
• Zebra mussels
• Quagga mussels
2000
2005
Quagga
mussels
•Quagga effects
-Inshore and offshore
-Span LMichigan basin
-Estimates in trillions
-Establish in sediments
-Dreissenid biomass > prey fish
Ballasts: Round goby
• First found in St. Clair River (D. Jude, 1990)
• Now in all Great Lakes
• Benthic, wide diet
– larger (>60 mm) molluscivores
•
•
•
•
May outcompete natives for food and space
May bioaccumulate toxins
Concerns about impacts
Migrate offshore in winter
Native invertebrate preyfish food
• Diporeia
• Mysis
• Copepods
Lake-wide biomass
of prey fish in 2008
Lake-wide biomass of
prey fish time series
500
Ni n e s p i n e s ti c k l e b a c k
De e p wa te r s c u l p i n
Ra i n b o w s m e l t
Slim y s c u lp in
450
400
Ro u n d g o b y
Bl o a te r
L a k e -wid e b io ma s(k t)
350
Round goby
4.65 k t
2008: 94%
decline from
the peak in
1989
Prey fish
biomass
has
never
been
lower
Al e wi fe
300
250
200
150
100
Alewi fe
8.27 k t
Bloater
3.33 k t
Rain bowsm
elt
0.8 9 k t
Slim
ysc ulp in
2.75k t
Nines pine s tic k lebac k
0.50 k t
Deepwate rsc ulp in
5.2 3 k t
GLFC objective:
500-800 kt of
planktivore
biomass
At 25 kt = 5% of
objective at best
50
0
1973
1980
1987
1994
Ye a r
2001
2008
Slimy sculpin
(Cottus cognatus)
2000
1500
Since 1990, general
Increasing trend
•Benthic
1000
•No swim bladders
500
•Highly developed
sensory
2009
2005
2001
1997
1993
1989
1985
1981
1977
1973
0
•Polygnous nest
guarding males
•Live 7-9 years TL
~125mm
•Other studies have
addressed egg
predation
3000
Coregonus hoyi
2500
2000
1500
1000
500
0
19
70
19
75
19
80
19
85
19
90
19
95
20
00
20
05
Numeric density (#/ha)
Age-0 bloater (< 120 mm)
Year
800
600
400
200
0
19
70
19
75
19
80
19
85
19
90
19
95
20
00
20
05
Numeric density (#/ha)
Adult
bloater
(>
120
mm)
1000
Year
•Better lake trout food
•Sex ratio, survivial bottleneck
•30 year cycle hypothesis
•Planktivore
•Max length ~ 275 mm, 12 YO
Round goby
3000
2000
1000
25000
20000
15000
10000
5000
0
1973
1979
1985
1991
1997
2003
2009
Deepwater sculpin
(Myoxocephalus thompsonii)
0
USGS long
term trawl
data by species
1973
1978
1983
1988
1993
1998
2003
2008
X-axis = year
Y-axis =
Mean g/ha
Diet, Distribution
•Diporeia, Mysis – Most important for SS and DWS
• SS: copepods, eggs, cladocerans, diverse,
adaptable
• DWS: fish eggs, copepods, less diverse
• RG: bivalve oriented, diverse in Great Lakes
•Distribution in deepwater benthic zones:
•RG new to system: Expected in Lake Michigan in
winter based on Lake Erie
•SS and DWS depth segregation, SS 60-83, DWS
past 90m (Madenjian and Bunnell, 2008)
(g/ha)
Hypotheses about benthivore diets
1) Within species prey specific diet proportions
will vary significantly across time and sampling
locations
2) Between sculpins diet overlap should be high,
while between goby and sculpins overlap
should be moderate
3) All 3 benthic predators eat bloater eggs
- SS eat the most, most frequently
Methods
• Diet proportions
SS=1016, DWS=699
RG=552
• Sampled at
FF, STB, TR, MSK
depths 69-128m
• When
Jan-May 2009–2010
• Diet Proportions
– Used dry weight
proportions
time/space effects
analyses and diet
overlap analyses
SLIMY SCULPIN DIETS
TR
FF
STB
MSK
MONTH 2009 2010 2009 2010 2009 2010 2009 2010
JANUARY
X
X
FEBRUARY
X
X
MARCH
X
X
APRIL
X
X
X
X
X
X
MAY
X
X
X
DEEPWATER SCULPIN DIETS
TR
FF
STB
MSK
MONTH 2009 2010 2009 2010 2009 2010 2009 2010
JANUARY
X
X
FEBRUARY
X
X
MARCH
X
X
X
APRIL
X
X
X
X
X
X
MAY
X
X
X
X
JUNE
X
ROUND GOBY DIETS
TR
FF
STB
MSK
MONTH 2009 2010 2009 2010 2009 2010 2009 2010
JANUARY
X
X
FEBRUARY
X
X
MARCH
X
X
APRIL
X
X
X
X
X
X
MAY
X
X
Analysis
Hypothesis 1: time and space effects
General linear models (GLM)
• Individual models built for single predator and single prey:
• Prey categories selected: accounted for > 88% of each
predators overall diet proportions
• Sampling unit:
Nets weighted by the number
of fish within a net
• Time
– Day of year (DOY): TR January only
• Space
– Location (port): all samples
Schoener’s and Morista’s
Analysis: Hypothesis two, Overlap
Tested overlap between species within each port
• Schoener’s = 1 – 0.5(Σ│pxi - pyi│)
• pxi proportion of food category i used by species x
• pyi is the proportion of food category i used by species y
•C = Morista’s: overlap between species j and k
•pij = proportion resource i of total resources used by species j
•pik = proportion resource i of total resources used by species k
•nij = # of individuals of species j using resource category i
•nik = # of individuals of species k that use resource category i
•Nj and Nk = the total number of individuals of each species in
the sample (Morista, 1959).
DNA analysis of fish eggs
• Hypothesis 3: Bloater eggs
• DNA analysis on viable fish eggs
• 10 analyzed per sample
• Known DNA
– Bloater, SS, DWS, RG
Bloater
DWS
SS
RG
Results: For all fish sampled
SS N=1016
DWS N=799
RG N=552
Results:
space GLMs
Ports: all samples
 N = Nets (Fish)
SS = 45 (1016)
DWS = 40 (699)
RG = 36 (552)
Alpha significance
SS ≤ 0.010
DWS ≤ 0.017
RG ≤ 0.017
 Many effects
Space
prey
mysis
diporeia
fish eggs
limnocal
senec
bival
chironomids
factor
depth
port
year
depth
port
year
depth
port
year
depth
port
year
depth
port
year
depth
port
year
depth
port
year
depth
SS
0.347
<0.001
0.331
0.039
<0.001
0.760
.
.
.
0.041
<0.001
0.017
0.188
0.015
0.418
.
.
.
0.079
0.059
0.079
.
predator
DWS
0.071
<0.001
0.870
0.024
<0.001
0.240
0.201
0.017
0.477
.
.
.
.
.
.
.
.
.
.
.
.
.
RG
0.061
<0.001
0.004
.
.
.
.
.
.
.
.
.
.
.
.
0.148
0.074
<0.001
.
.
.
0.051
predator
Time
TIME EFFECTS
Day of year (DOY)
TR only
N = nets (fish)
SS=22 (468)
DWS=19 (238)
RG=18 (156)
Alpha set to:
SS: 0.05/4 =
≤ 0.012
DWS: 0.05/3 =
≤ 0.017
RG: 0.05/2 =
≤ 0.025
prey
Mysis
diporeia
fish eggs
limnocal
bival
Few effects
chironomids
factor
depth
doy
year
depth
doy
year
depth
doy
year
depth
doy
year
depth
doy
year
depth
doy
year
SS
0.010
0.179
0.158
0.320
0.164
0.561
.
.
.
0.191
0.195
0.155
.
.
.
0.842
0.019
0.198
DWS
0.023
0.042
0.191
0.004
0.032
0.961
0.237
0.936
0.271
.
.
.
.
.
.
.
.
.
RG
0.114
0.516
0.506
.
.
.
.
.
.
.
.
.
0.621
0.131
0.038
.
.
.
• Schoener’s = overlap between SS and DWS = 0.62
• Morista’s = overlap between sculpins = 0.70
• No overlap between goby and sculpins (0.41 vs. SS; 0.36 vs. DWS
• Schoener’s: overlap between SS and DWS 0.62
• Morista’s = no overlap between sculpins
• No overlap between RG, sculpins using either index
Results: Hypothesis two, overlap
• Values:
0 = no overlap
1 = perfect overlap
≥ 0.6 = overlap
possible competition
Overlap analysis using
Schoener's
DWS
port species SS
SS
X
X
DWS 0.62
X
FF
RG
0.41 0.36
SS
X
X
DWS 0.38
X
TR
RG
0.12 0.11
SS
X
X
X
STB DWS 0.62
RG
0.19 0.15
NMS
supports
diet
overlap
RESULTS: Egg Genetics
•
•
•
•
85 bloater eggs
February- May
All four ports
Eyed eggs
19 @April 17-20
14 @ May 1, 18
Eyed bloater
egg eaten by
slimy sculpin
• 31 eggs in FF in APR
26 individual SS
Apr 17, 20th
• 66% consumed by SS
34% by DWS
• RG ate minimal eggs
0
0
0
0
0
0
0
Summary for benthivore diets
• Hypothesis 1) space vs. time, within species
– Diets did not vary through time
– Diets differed across ports for all species
• Hypothesis 2) Diet overlap
– Diet overlap did occur between sculpins
– Goby diets did not overlap with any sculpin species
• Hypothesis 3) Bloater eggs
– Most were consumed by slimy sculpin - true
– DWS – also ate bloater eggs – true
Worth noting on diets:
• Space vs. time
– Cover more space
• Without Diporeia
– SS diets became broad
– DWS turned almost completely to Mysis
• High egg cannibalism
– Species coexistence
• RG impacts offshore on sculpin diets
– minimal, perhaps minimal in offshore foodweb
Part II
• Determination of:
– Gastric evacuation - digestion
– Index of fullness – how much food in a sculpin stomach
– Daily ration
• Use these estimates, empirical data and diet data to model
– How many bloater eggs eaten in one day, by one slimy
sculpin
• Scale up from an individual sculpin to:
– to population and lakewide levels of annual bloater egg
predation by sculpin
• Input data into recruitment models to determine if sculpins
eat enough bloater eggs to limit bloater recruitment
interannually
– Can be done for other prey types hypothetically (i.e., Diporeia)
•
Approach
Diets now we
know
Gastric
evacuation
rate
(GEVAC)
Bloater
Eggs Eaten
Population
Level
Daily
Consumption
Bloater Eggs
Produced
Index of
fullness and
daily ration
Individual
sculpin prey
specific daily
consumption
GEVAC using live sculpins
GEVAC
• Digestion rate
• Two main hypotheses:
– Vary by temperature
– Vary by prey type
• Methods:
– Fed known quantity of food w/known dry-weight
– After 30 min, leftover food removed
– Digest in chamber for 24, 48, 72, 120, 168 Hours
– Euthanize, remove stomach, dry undigested prey
– Quantify %dry-weight remaining → digestion rate
GEVAC results
• Slimy sculpin
• No variation
– by temperature
(panel a)
– or prey type
(panel b)
– Very slow:
temps
GEVAC
results
• Deepwater sculpin
– No variation by temperature
Index of fullness
• Used additional fish from our diet samples
– 1) Dry fish in a drying tin
– 2) Separately dry each fishes stomach contents
• Index of fullness
– Definition: Dry weight of an individual fishes stomach contents divided by
the dry weight of everything else making up the rest of the fish
– Ratio, used in other studies
– Larger fish, expect a lower ratio
• Three hypotheses for index of fullness
– 1) Vary within species according to date sampled
– 2) Vary within species according to location in Lake Michigan sampled
– 3) Would be lower than when measured in 1976, due to ecological change
Index of fullness
Results
• A) = SS B) = DWS
• FDW important
• No location
effects!
• No temporal
effects! (Jan-Apr)
• Max values
HIGHER THAN
1976 !?
Daily Ration
• a fish consumes grams of food per day per a unit of fish size
• Regression to determine daily ration =
𝑺/𝟏𝟎𝟎 × 𝟐𝟒 𝒉 × 𝒓 (h-1) ×FDW
– Where:
• S = index of fullness regression equations (herein)
• 24 h = 24 hours in one day
• r = GEVAC rate (herein)
• FDW = fish dry weight (this is explanatory variable)
• Mean daily ration = 32 mg dry weight across all samples
• Apply diet proportions to this daily ration weight
– Gives weight of bloater eggs eaten by single sculpin in
one day
Population level daily consumption
• USGS Trawl data = numbers of SS and
bloater per hectare
• GIS: total hectares: in depth strata 5 to
115m = (SS/ha x #ha) = slimy population
• Daily ration of bloater eggs in
individual SS diets by total SS
population (> 40 mm)
• Bloater: numbers + fecundity = total
bloater egg production
Consumption modeling
Diet
Bloater
Eggs Eaten
Bloater Eggs
Produced
Gastric
Evacuation
Rate
Individual
Average
Meal Size
(Daily
Ration)
Population
Level
Daily
Consumption
Individual
Prey Specific
Daily
Consumption
Initial lakewide consumption
modeling results for year 2010, done
in 2010
• Bloater egg production consumed = 40.7%
• Sensitivity analysis = 20-130*%
A closer, more recent look however….
Likewise
does not
seem to fit
Take homes
1) Diet proportions did not vary across time, but did vary across
space
2) Overlap between sculpins, none between goby and sculpins
3) Gastric evacuation was slow, not affected by temps, prey type
4) Without Diporeia, slimy sculpin diets diversified, whereas
deepwater sculpin consumed almost entirely one prey, Mysis
Take homes
5) Despite present differential site based availability, and steep
declines in Diporeia abundance since 1976, index of fullness
was similar across locations, and mostly higher in 2009-2010
6) Bloater and deepwater sculpin eggs were found in sculpin
diets in high numbers, but this may not limit bloater
recruitment
– further research needs to address DWS recruitment
limitation
7) Restoration
Reintroduction of bloater into Lake Ontario may succeed if
sculpins truly control recruitment of bloater through egg
predation in Lake Michigan because slimy sculpin lakewide
biomass in Lake Ontario is currently at low levels, and
deepwater sculpin exists only marginally
Thanks: [email protected]