Katie DeGoosh

Emily Schilling, Cynthia Loftin, Katherine Webster

There’s something fishy about fly larvae: Chaoborus assemblages as an indicator of fishless lakes

1. Question

2. Background on Fishless Lakes

3. Chaoborus: Ecology and Biology

4. Field and lab methods

5. Results

Species assemblages

Logistic regression model

Evaluating the model

6. Conclusions

Do Chaoborus assemblages

in surface sediment

indicate fishless lakes?

Question

Naturally fishless lakes?

Landscape barriers

Naturally fishless lakes?

Landscape barriers

Hydrologically Isolated

Naturally fishless lakes?

Landscape barriers

Steep outletsHydrologically Isolated

Why study fishless lakes?

Unique communities

Sparse distribution

Unique Communities

Zooplankton

Unique Communities

Insects

Unique Communities

Unique Communities

Chaoborus

5 common species

1. Chaoborus Sayomia

(punctipennis/albatus)2. Chaoborus flavicans3. Chaoborus trivitattus4. Chaoborus americanus

(Uutala, 1990)

MOST CHAOBORUS

Vertically migrate

(von Ende, 1979)

C. americanus

NO vertical migration

(von Ende, 1979)

C. americanus

NO vertical migration

(von Ende, 1979)

Chaoborus Life Cycle

adult

eggs

1st instar

2nd instar

3rd instar4th instar

Head of Chaoborus

Chaoborus mandibles

90 microns

Mandibles can

be found in

lake sediment

Do Chaoborus assemblages

in surface sediment

indicate fishless lakes?

Question

N

Fish-full

Fishless

Selection of Study Lakes

21 Lakes*

10 Fishless 11 Fish-full

Low High Low High Elevation Elevation

7 55 5

*Paired for landscape attributes; verified fishlessness

Core Samples

3 cores at each lake

Sample Analysis

Finding Mandibles

Identification

Slide Mount

Results

1. Species assemblage

2. Determining important variables 3. Logistic regression model

4. Model Accuracy Table

5. Evaluating the model

Species Assemblage

0%

20%

40%

60%

80%

100%

Apple

Cloud

Duck

Kerose

neLoo

n

Mid

day

Mud

North

Unnam

ed 83

85

Unnam

ed 96

33

Fishless Lakes

C. Sayomia C. americanus C. trivitattus

74307 33 82 45 9 97 1 61

Fishless

Lakes

Species Assemblage

Fish

Lakes0%

20%

40%

60%

80%

100%

Lakes with Fish

C. Sayomia C. americanus C. trivittatus

6 6 13 0 0 0 12 73 107 66 1

Stepwise Logistic Regression

Which variables best contribute to a model that indicates a fish lake ?

Chaoborus abundance

% C. americanus

% C. Sayomia

% C. trivitatus

Area (m2)

Elevation (m)

Max. Depth (ft)

pH

Modeling fishless lakesusing stepwise logistic regression

Variables in model Value P-value

Constant -2.297 0.028

Percent C. americanus 0.04 0.021

Modeling fishless lakesusing stepwise logistic regression

Variables in model Value P-value

Constant -2.297 0.028

Percent C. americanus 0.04 0.021

Logistic prob. = B0 + B1x

Modeling fishless lakesusing stepwise logistic regression

Variables in model Value P-value

Constant -2.297 0.028

Percent C. americanus 0.04 0.021

Log(p/(1-p)) = -2.297 + .04 (% am)

Logistic prob. = B0 + B1x

Modeling fishless lakesusing stepwise logistic regression

Log(p/(1-p)) = -2.297 + .04 (% am)

Modeling fishless lakesusing stepwise logistic regression

Log(p/(1-p)) = -2.297 + .04 (% am)

Rearranged:

prob = EXP(-2.297 + .04 (% am))

1+ EXP(-2.297 + .04 (% am))(fishless)

Graphing the model

0 10 20 30 40 50 60 70 80 90 100Percent C. americanus

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Pro

babi

lity

(fis

hles

s)

Fishless LakesFish Lakes

Lake Status

Lake Status

Fish Lakes

Fishless Lakes

3

4

Observed:

Predicted: FISH FISHLESS

Fish 5 3

Fishless 3 7

Total 8 10

Correct 62% 70%

Model Accuracy Table

Observed:

Predicted: FISH FISHLESS

Fish 5 3

Fishless 3 7

Total 8 10

Correct 62% 70%

Model Accuracy Table

Observed:

Predicted: FISH FISHLESS

Fish 5 3

Fishless 3 7

Total 8 10

Correct 62% 70%

Model Accuracy Table

Observed:

Predicted: FISH FISHLESS

Fish 5 3

Fishless 3 7

Total 8 10

Correct 62% 70%

Model Accuracy Table

Observed:

Predicted: FISH FISHLESS

Fish 5 3

Fishless 3 7

Total 8 10

Correct 62% 70%

Model Accuracy Table

Observed:

Predicted: FISH FISHLESS

Fish 5 3

Fishless 3 7

Total 8 10

Correct 62% 70%

Model Accuracy Table

Using the model

Using the model

Using the model

History in Sediment Core

Recentsediment

Old sediment

History in Sediment Core

Recentsediment

Old sediment

Current Conditions

History in Sediment Core

Recentsediment

Old sediment

Current Conditions

Historical

History in Sediment Core

Evaluating the model

3 Historically fishless lakes

Evaluating the model

3 Historically fishless lakes

Speck

Stocked in 1962

Evaluating the model

3 Historically fishless lakes

Tumbledown

Stocked in 1966

Speck

Stocked in 1962

Evaluating the model

3 Historically fishless lakes

Tumbledown

Stocked in 1966

Speck

Stocked in 1962

Ledge

Stocked in 1968

Evaluating the model

3 Historically fishless lakes

TumbledownSpeck Ledge

Evaluating the model

3 Historically fishless lakes

TumbledownSpeck Ledge

Pb-Dated Sediment CoresSteve Norton, Ron Davis (Davis, 1994)

Evaluating the model

3 Historically fishless lakes

TumbledownSpeck Ledge

19571956

1952

r = 3 r = 1 r = 2

Species Assemblage

0%

20%

40%

60%

80%

100%

Tumbledown(1956)

Speck (1957) Ledge (1953)

Historically Fishless Samples

C. americanus C. Sayomia C.flavicans

41 2327

Species Assemblage

0%

20%

40%

60%

80%

100%

Tumbledown(1956)

Speck (1957) Ledge (1953)

Historically Fishless Samples

C. americanus C. Sayomia C.flavicans

41 2327

90%

57%70%

Applying the model

0 10 20 30 40 50 60 70 80 90 100Percent C. americanus

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Pro

babi

lity

(fis

hles

s)

Fishless LakesFish Lakes

Lake Status

Lake Status

Fish Lakes

Fishless Lakes

0 10 20 30 40 50 60 70 80 90 100Percent C. americanus

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Pro

babi

lity

(fis

hles

s)

Fishless LakesFish Lakes

Lake Status

Speck Pond

70%

C.americanus

62% probability (fishless)

Applying the model

0 10 20 30 40 50 60 70 80 90 100Percent C. americanus

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Pro

babi

lity

(fis

hles

s)

Fishless LakesFish Lakes

Lake Status

Ledge Pond

90%

C. americanus

78% probability (fishless)

Applying the model

0 10 20 30 40 50 60 70 80 90 100Percent C. americanus

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Pro

babi

lity

(fis

hles

s)

Fishless LakesFish Lakes

Lake Status

Tumbledown

57%

C. americanus

49% probability (fishless)

Applying the model

Conclusions• Chaoborus mandible assemblages in surface sediments

DO indicate fishless lakes

• The dominant species in fishless lakes is Chaoborus americanus

• Logistic regression can be used to find the probability that a given sample reflects fishless conditions

Log(prob) = 2.297 + 0.04 (% C. americanus)

• The model accurately classifies fishless lakes 70% of the time

• Historically fishless ponds can be identified by applying the model to sediment core samples

Committee Members: Dennis Anderson

Cynthia Loftin Michael Kinnison

Katherine Webster Ann Dieffenbacher-Krall

Diadem Strout

Kim Gibbs

Jason Houle

Paul Kusnierz

Christine Guerette

Field and Lab Assistants

Dawn Bavaro

Anne Fleischman

Matthew Day

Rebecca Clark

Additional Funding

Penobscot County Conservation AssociationUM Association of Graduate Students

Keith McCullough

Benjamin Reining

Erin Wilkinson

Jennifer Wilcox

Catherine Gannoe