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Summer 2010 collapse of the Lake Nipissing zooplankton community subsequent to the introduction of
the invasive zooplankter Bythotrephes longimanus
Jean-Marc Filion
A Lake Nipissing Partners in Conservation case study
Correspondence address:135 West Peninsula Rd, North Bay, ON P1B [email protected] April 4, 2012
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2010 – Sampling Stations – Lake Nipissing
S3
S6
S5
S8
S4S2
S1
N GooseIs
ManitouIs
French River
South Bay
Sturgeon Falls
NorthBay
CallanderBay
5 km
Surface area 873 km2 Average depth 4.5m 5% of all Ontario angling
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Horizontal strata sampling method
Direction of travel
Float
Weight
Net
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Net being hauled horizontally150 m at a depth of 1 m
in this instance.
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Depth data loggerinserted in net tomonitor depth of haul
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Taking the animals out of the net, and washingthem into a large, white, plastic tub
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Samples, once concentratedwith 80 micron filter
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The Players
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Young
Adult
Juvenile Tim
e
With each molt, an additional barb is added
Bythotrephes longimanus
barb
barbbarb
barbbarb
barb
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Large transparentpredator – is out-competed byBythotrephes longimanus
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Geotrichia Conochilus unicornis
Blue green algae Colonial rotifer
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Lake herring (Cisco) (Coregonus artedi) - to 18 inches approximately
Yellow perch (Perca flavescens ) – to 12 inches approximately
Rainbow smelt (Osmerus mordax) – to 8 inches approximately
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Yellow walleyeStizostedion vitreum
This fish waslive-released
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S8 - Summer 2010 abundances of Bythotrephes longimanus
and its impact on zooplankton abundance
Results
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2010 – Sampling Stations – Lake Nipissing
S3
S6
S5
S8
S4S2
S1
N GooseIs
ManitouIs
French River
South Bay
Sturgeon Falls
NorthBay
CallanderBay
5 km
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30 May 7 Jun 13 Jun 20 Jun 27 Jun 6 Jul 11 Jul 19 Jul 31 Jul 10 Aug 20 Aug 20 Sep0
20
40
60
80
100
120
9
103
39
83
113
42
103
14
3
11 14
S8 - Bythotrephes longimanus average abundances
Populati
on expan
sion
Population crash
2010
an./m3
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0
50
100
150
200
250
300
23
3 17
291
11
75
13
30
53
140
55
230
73
36
110
5 114
22
52 6 217 19
63 4 315 11 7
14 11 16
Bythotrephes longimanus abundances per stratum per date
30 May 7 Jun 13 Jun 20 Jun 27 Jun 6 July 11 July 19 July 31 July 10 Aug 20 Aug 20 Sept
Station 8 - Lake Nipissing, 2010
1m 5m 10m
an./m3
Popu
latio
n ex
pans
ion
Population crash
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Bythotrephes eats zooplankton
So what is the zooplankton population doing during this time?
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30 May 7 Jun 13 Jun 20 Jun 27 Jun 6 Jul 11 Jul 19 Jul 31 Jul 10 Aug 20 Aug 20 Sep0
1
2
3
4
5
6
1m 5m 10m
Zooplankton mostly at d > 5m(mainly Daphnia galeata mendotae)
Zooplankton recoverymostly at d > 5m
(mainly Copepods)
S8 - Zooplankton abundance per date per stratum
2010
Relativescale
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30 May 7 Jun 13 Jun 20 Jun 27 Jun 6 Jul 11 Jul 19 Jul 31 Jul 10 Aug 20 Aug 20 Sep0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
Relativescale
S8 - Zooplankton abundance (averaged over the strata )
Population crash due to Bythotrephes predation
2010
Partial recovery later in the summer
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Large Daphnia galeata mendotae populationS8, May 30th, 2010 in the 5m stratum
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Mostly daphnia
Mostly daphnia
100 Bythotrephes 3900 Bythotrephes 150 Bythotrephes
300 Bythotrephes 40 Bythotrephes 10 Bythotrephes
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1900 Bythotrephes720 Bythotrephes 750 Bythotrephes
1000 Bythotrephes170 Bythotrephes
400 Bythotrephes
Fewer daphnia
Zooplankton depleted in all strata
June 13
June 20
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3100 Bythotrephes 990 Bythotrephes 480 Bythotrephes
By the end of June, the spiny water flea had pretty well eliminated most of the zooplankton in the water column
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1500 60 150 Bythos
60 300 70 Bythos
By July 11, 2010, Bythotrephes itself had crashed to much lower abundances.Only small remnant zooplankton populations remain over much of the lake.
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S8 Results
Aug. 7, 2010 Kevin O'Grady captures a 35 cm walleye with only Bythotrephes in its stomach.
Aug. 13, 2010 Stéfane Filion captures a 30 cm walleye with only Bythotrephes in its stomach.
Come August some harvestablewalleye started consuming Bythotrephes
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Food web implications
walleye
snails
minnows
insectlarvae
perch
copepods cladocera
herringsmelt
Energy flowBefore introduction of Bythotrephes
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Food web implicationswalleye
snails
minnows
insectlarvae
perch
copepods Cladocera
herringsmelt
Energy flowAfter introduction of Bythotrephes
Bythotrephes
Lostto
sediments
Nutrientsmay recyclein early fall - wind /shallowdepths
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Food web implications(before Bytho)
walleye 1 kgperch 10 kgzooplankton 100 kgphytoplankton 1000 kg
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Food web implications(after Bytho – no collapse)
walleye 0.1 kgperch 1 kgBytho 10 kgzooplankton 100 kgphytoplankton 1000 kg
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Food web implications(after Bytho – after collapse)Energy flow constricted
walleye 0.001 kg = 1 gperch 0.01 kgBytho 10 kg * 1/100 0.1 kgzooplankton 100 kgphytoplankton 1000 kg
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Fisheries management implications(present system)
Healthy walleye pop + Healthy ecosystem Max. sustainable yield = 100,000 kg
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Fisheries management implications(present system)
Healthy walleye pop + Healthy ecosystem Max. sustainable yield = 100,000 kgStressed walleye pop
(harvest set at 2/3 of m.s.y.) = 66,000 kg
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Fisheries management implications(present system)
Healthy walleye pop + Healthy ecosystem Max. sustainable yield = 100,000 kgStressed walleye pop
(harvest set at 2/3 of m.s.y.) = 66,000 kg
NFN gets 2 fish for every 1 fish sport fisheryNFN harvest quota set at 44,000 kgSport fishery quota set at 22,000 kg
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Fisheries management implications(Energy flow restricted)
Healthy walleye pop + Unhealthy ecosystem Max. sustainable yield = 50,000 kg (too high?)
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Fisheries management implications(Energy flow restricted)
Healthy walleye pop + Unhealthy ecosystem Max. sustainable yield = 50,000 kgStressed walleye population
(harvest set at 2/3 of m.s.y.) = 33,000 kg
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Fisheries management implications(Energy flow restricted)
Healthy walleye pop + Unhealthy ecosystem Max. sustainable yield = 50,000 kgStressed walleye population
(harvest set at 2/3 of m.s.y.) = 33,000 kg
NFN gets 2 fish for every 1 fish sport fisheryNFN harvest quota set at 22,000 kgSport fishery quota set at 11,000 kg
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Fisheries management implications(Energy flow restricted)
NFN gets 2 fish for every 1 fish sport fisheryNFN harvest quota 22,000 kgSport fishery quota 11,000 kg
2011 harvest resultsNFN quota set at 40,000 kg or so
Caught 21,000 kg
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Fisheries management implications(Energy flow restricted)
Healthy walleye pop + Unhealthy ecosystem Max. sustainable yield = 50,000 kgVery stressed walleye population (large walleye?)
(harvest set at 1/3 of m.s.y.) = 17,000 kg ???
NFN gets 2 fish for every 1 fish sport fisheryNFN harvest quota set at 11,000 kgSport fishery quota set at 6,000 kg
(Just one of many management options)
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Fisheries management going forward
• We are at a critical point• Doing nothing is the worst option• We are out of time• Nobody wants the take the medicine• Need a plan and a way to sell it /implement it
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Food web implicationsA number of problems may arise from the introduction of Bythotrephes.
“We demonstrated that increases in trophic position of the magnitude reported here can lead to substantial increases in fish contaminant concentrations.”
Bythotrephes invasion elevates trophic position of zooplankton and fish: implications for contaminant biomagnificationMichael D. Rennie • Angela L. Strecker • Michelle E. Palmer
Biol Invasions (2011) 13:2621–2634DOI 10.1007/s10530-011-0081-0
Nineteen lakes studied, focused primarily on lake herring (Coregonus artedi)
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Food web implications of the addition of smelt to the ecosystem
“Rainbow smelt invasion may affect the accumulation of persistent lipophilic contaminants and heavy metals such as mercury in top predators.”
Ecosystem effects of Rainbow Smelt (Osmerus mordax) invasions in inland lakes: A literature reviewRebekah C. Rooney and Michael Paterson
Canadian Technical Report of Fisheriesand Aquatic Sciences 2845 (2009)
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Children (to age 15) and women of child bearing age
Walleye in this range must be released
March 2011, MOE Guide to eating sport fish in Ontario. Consumption advice in the tables is based on an average meal size of 227 grams for an average size adult of 70 kilograms (154 pounds).
Meals per month
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S3
S6
S5
S8
S4S2
S1
N GooseIs
ManitouIs
French River
South Bay
Sturgeon Falls
NorthBay
CallanderBay
5 km
Lake Nipissing Outlet – French River HeadwatersS4 - Zooplankton community structure
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S4 – A biodiversity refugeS4 is located in an area of crucial importance to Lake Nipissing as it serves as both a fish and zooplankton refuge, thus helping to preserve biodiversity. It is near the outlet of Lake Nipissing, which drains in a southwesterly direction via the French River. The bathymetry of this area is unusual in that a cold water refuge is available due to the deeper waters available in this location. The maximum depth that we were able to find using our Hummingbird depth sounder was 54m.
In the summer this areabecomes a cold waterrefuge for the lakeherring (cisco) and thesmelt. Warmer waterson top and oxygen depletion at depth keepthe fish sandwichedin a definite band, as indicated by this picturetaken of our Hummingbirdsonar unit.
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S4
0.5 kmDepths in metres
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7,0
6,0
5,0
4,0
3,0
2,03,04,0
1,0
8,8
9,0
8,0 6,07,0
5
10
15
20
25
30
35
40
45
0
Depth (m)
S4 - French River - D.O.(mg/L) - 2001
July August
5
10
15
20
25
30
35
40
45
0
20
22
18
16
10
14
12
8
6
6
8
10
12
14
16
18
20
S4 - French River - Temp. (C) - 2001
Depth(m) July August
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4 mm
New Players
Mysis relicta
Chaoborus
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1 5 10 15 18 23 28 31 34 380
5
10
15
20
25
30
0
1
2
3
4
5
6
21.3
28.7
7.0
4.1 2.3
2.7 1.81.6
0.4 0.2
S4 –Bythotrephes and zooplankton abundances vs depth
Bythotrephes
Zooplankton
Zooplanktonabundance(Relative scale -max is 6)
Bythotrephesabundance(an/m3)
Depth (m)
July 10, 2010
Fish zone
Something interestingmay be going on atthese depths
Bythotrephes abundances correlate negatively with depth
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1 5 10 15 18 23 28 31 34 380.0
5.0
10.0
15.0
20.0
25.0
30.0
Diaptomus Cyclops Epischura lacustris Senecella calanoides
S4 - Relative abundances of Copepod taxa vs depth
Depth (m)
Relative abundance
Copepod abundances correlate positively with depth
Something interestingmay be occurringat these depths
Fish zone
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1 5 10 15 18 23 28 31 34 380.0
5.0
10.0
15.0
20.0
25.0
Daphnia Bosmina Eurycercus Latona setifera
S4 - Relative abundances of selected Cladocera taxa vs depth
Something interestingmay be occurring atthese depths
2000/2001 sampling indicatesthat a 9-spine sticklebackpopulation exists at depthat S4 – exactly at what depthis not known at this time.
Relative scale (max is 30)Mostly D. pulicaria
Fish zone
Diaphanasoma birgeionly collected in traceamounts and only in the 1m stratum
Depth (m)
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1 5 10 15 18 23 28 31 34 380.0
2.0
4.0
6.0
8.0
10.0
12.0
Conochilus Geotrichia Ostracoda
June 10, 2010
S4 - Relative abundances of Conochilus,Geotrichia and Ostracoda taxa vs depth
Relative scale(max is 30)
Depth (m)
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Callander Bay
S3
S6
S5
S8
S4S2
S1
N GooseIs
ManitouIs
French River
South Bay
Sturgeon Falls
NorthBay
CallanderBay
5 km
S1 - Zooplankton community structure
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0.5 kmS1
Callander Bay
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July 7 Aug 10.00
5.00
10.00
1.0
3.8
5.55.0
9.1
0.4
Bythotrephes abundance by date & by stratum
1m 5m 8m
S1 - Callander Bay
an./m3
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Jul 7 Aug 10
5
10
15
20
25
30
0.4 0.40.60000000000000
1
S1 - Leptodora abundance1m5m8m
Relative scale
In 2000/2001 Leptodora was quite abundant reaching abundances ofover 100 an./m3 in mid-August. In2010, Leptodora is only present intrace amounts in early July, and is not collected Aug. 1st.
S1- Leptodora kindtii
S1 - 2010
140
14
1.4
0.14
an./m3
- mouth areaof 0.5 m2 – 300micron Nitex mesh.
S1 - 2001
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Jul 7 Aug 10
5
10
15
20
25
30
0.1
12.5
0.3
7.5
0.600000000000001
6
S1 - Diaptomus abundance
1m 5m 8m
Relative scale
By the end of the 1st week of July Bythotrephes had driven Diaptomids at S1 to trace amounts. Historicaly abundances at this time were in the 15000 an./m3 range. By the 1st of August the Diaptomids are recovering somewhat.
S1- Diaptomids
S1 - 2010
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Relative scale
By the end of the 1st week of July Bythotrephes had driven Cyclops at S1 to trace amounts. Historically abundances at this time were in the 20000 to 40000 an./m3 range. By the 1st of August the Cyclops are recovering somewhat.
S1- Cyclops
S1 - 2010
Jul 7 Aug 10
5
10
15
20
25
30
0.4
24
12.5
7.5
S1 - Cyclops abundance
1m 5m 8m
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Relative scale
By the end of the 1st week of July Bythotrephes had driven Daphnia at S1 to trace amounts. Historically abundances at this time were variable but typically in the 5000 an./m3 range. In 2010, by the 1st of August Daphnia were very abundant at depth. In 2001 only D. retrocurva was collected at S1. In 2010 only one D. retrocurva individual was collected, the rest being Daphnia galeata mendotae.
S1- Daphnia
S1 - 2010
Jul 7 Aug 10
5
10
15
20
25
30
0.3
5
0.3
4.5
0.4
30
S1 - Daphnia abundance
1m5m8m
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Jul 7 Aug 10
5
10
15
20
25
30
0.1
S1 - Bosmina abundance
1m 5m 8m
Relative scale
By the end of the first week of July 2010, Bythotrephes had pretty well eliminated the Bosmina sp. from Callander Bay. They remain absent from the collections on Aug. 1st. In 2000/2001 their average abundances come July were in the 5000 to 20000 an./m3 range. The ‘U’ shaped curve from 2001 may imply that Bosmina may serve as a food source for juvenile and larval fish who move on to other prey as they reach a larger size.
S1- Bosmina sp.
S1 - 2010
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Historically Diaphanasoma at S1 was a highly variable species, sometimes attaining abundances as high as 40000 an./m3, only to almost disappear from the collections the week after. Collections in 2000/01 were made using vertical hauls. This may imply horizontal patchiness. Populations were usually small at the beginning of July, but then increased to an average of 10000 an./m3 come the first of August. In 2010, Diaphanasoma was not collected on July 7th, 2010 and showed little sign of becoming abundant on the 1st of August. It was absent from the collections at the 8m stratum. Bythotrephes may be keeping this species at low abundance levels at S1.
Jul 7 Aug 105
1015202530
2.5 1.5
S1 - Diaphanasoma abundance1m5m8m
Relative scale
S1- Diaphanasoma birgei
S1 - 2010
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S1 was sampled July 7th and August 1st, 2010. Holopedium gibberum was onlycollected in trace amounts from the 5m stratum on July 7th. Historically,Holopedium had average abundances of around 100 an./m3 in early July and early August. It would seem that Holopedium disappears quicker and attains lowermaximum abundances since the introduction of Bythotrephes.
S1 – Holopedium gibberum
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Jul 7 Aug 10
5
10
15
20
25
30
0.1
10
0.2
7.5
S1 - Conochilus unicornis abundance
1m5m8m
Jul 7 Aug 10
5
10
15
20
25
30
0.1
10
0.2
4.5
S1 - Geotrichia abundance
1m5m8m
Relative scale
Relative scale
Conochilus unicornis and Geotrichia, not collected in any important amount in 2000/01is now becoming common to moderately abundant as summer progresses at S1.
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In the winter perch turn to eating snails and mayfly naiads. They could do the same in the summer.