An Ecological Classification of Open-Water Habitats in

Lake ErieChristine Geddes1, Jeff Tyson2, Edward Rutherford1,

Damon Krueger1, Stuart Ludsin3, and Timothy Johnson4

1 Institute for Fisheries Research, MDNR, University of Michigan, Ann Arbor, Michigan2 Lake Erie Headquarters, ODNR, Lake Erie Headquarters, Sandusky, Ohio3 Great Lakes Environmental Research Laboratory, NOAA, Ann Arbor, Michigan4 Glenora Fisheries Station, OMNR, Picton, Ontario

Why?

•Framework for understanding ecosystem structure and function

•Establishment of reference conditions

•Management applications, e.g., yellow perch & walleye management

Offshore Definition

Open Water

>15 meters

Offshore Shallow

3-15 meters

Littoral

½ mile inland – 3-meter contour

Current Schema

Current schema based on depth, temperature, productivity, and thermal stratification.

West Basin

Central Basin

East Basin

Potential Variables

•Thermal characteristics•Hydraulic characteristics•Outwelling zones•Substrate type•Light/turbidity•Biological characteristics•Proximity to lakebed features

Adapted from: Saylor and Miller, 1987

Reproduced from: Mullen, 1976

Productivity zones

Jeff Tyson, ODNR, Classification

West Basin

Central Basin

East Basin

Outwelling zones (thermal characteristics,

light, biology) (Sub-basin was feature-based)

Hydraulic characteristics (gyres, light, biology)

Hydraulic/thermal characteristics (gyres, light, temp., biology)

Strategy: hierarchical, largely conceptual

Jeff Tyson, ODNR, Classification

Twenty habitat zones were delineated based on physical characteristics (e.g., circulation, basin) or unique features (e.g., Presque Isle Bay).

Our Strategy

1) Summarize input variables by 10-minute grid cell

2) Perform a two-step cluster analysis

3) Compare classification with previous classification

4) Test classification with biological data

Input Variables—Bathymetry & Slope

Source: NOAA

Extent: lake-wide

Resolution: 60-meter

0

63

Depth (m)

Input Variables—Temp. & Temp. Difference

Source: NOAA CoastWatch/AVHRR

Extent: lake-wide

Resolution: 10-minute grid cells*

*available at 1.7-km resolution

Input Variables—Substrate Type

Source: OSU, SeaGrant

Extent: lake-wide

Input Variables—Circulation Patterns

Courtesy of Beletsky et al., 1999

Input Variables—Circulation Patterns

1 234

56

7

West Central East

Bill Schertzer proposed the “7-Box Model”

0

63

Depth (m)

Summarizing Variables

2170.6523.321.4709CircSubstr_1Temp_diffTempBathGrid

Two-Step Cluster Analysis

…is an exploratory tool designed to reveal natural groupings (or clusters) within a data set that would otherwise not be apparent.

Advantages

--Handling of categorical and continuous variables

--Automatic selection of number of clusters

--Output includes several analysis plots and statistics

Preliminary Results

ODNR

Preliminary Results

ODNR

--within cluster percentage chart

--cluster pie chart

--rank of cluster importance

--importance measure (chi square or t-test of significance

Cluster Size

5

4

3

2

1

2814114917N =

Simultaneous 95% Confidence Intervals for M

Cluster

54321

TEM

P_C

24.0

23.5

23.0

22.5

22.0

21.5

TwoStep Cluster Number = 2

Bonferroni Adjustment Applied

(N) Non-signif icant

Varia

ble

SUBS_SMSUBS_B

SLOPESUBS_SG

SUBS_MBATH_M

SUBS_GTTEMPDIFF_C (N)

TEMP_C (N)

- Log10(Probability): larger value is more significant

403020100

Tolerance

Significance

Testing the Classification

•Sport and commercial fish catch rates

•Survey data (trawl, gillnet, acoustic) on forage fish density

•Tag return data on walleye movement

•Lower trophic level (i.e., zooplankton and benthos) densities

Questions/Discussion Points

•Scale

•Variables

•Boundary Definition

•Cross-walking classifications

•Capturing dynamic processes

•3D nature of the environment

--Resolution

--Variables

--Boundary definition

--Cross-walking classifications

--Dynamic processes

--3-D nature of the environment

10-minute grid cells?

What do we want to use the classification for?

Questions/Discussion Points

--Resolution

--Variables

--Boundary definition

--Cross-walking classifications

--Dynamic processes

--3-D nature of the environment

Physical habitat classification?

OR

Ecological classification (i.e., physical AND biological)?

--Resolution may determine variable importance

--Circulation? Etc.

Questions/Discussion Points

--Resolution

--Variables

--Boundary definition

--Cross-walking classifications

--Dynamic processes

--3-D nature of the environment

15 meters?

Fuzzy boundary?

Questions/Discussion Points

--Resolution

--Variables

--Boundary definition

--Cross-walking classifications

--Dynamic processes

--3-D nature of the environment

How do we do this?

Questions/Discussion Points

--Resolution

--Variables

--Boundary definition

--Cross-walking classifications

--Dynamic processes

--3-D nature of the environment

Processes are dynamic…

do we create a classification for a particular time period (e.g., fall)?

mean summer circulation

Questions/Discussion Points

--Resolution

--Variables

--Boundary definition

--Cross-walking classifications

--Dynamic processes

--3-D nature of the environment

GIS

Questions/Discussion Points

• Zooplankton• Chlorophyll a• Temperature• Dissolved oxygen• Light levels

• Fish biomass& density

• Trawling & gillnetting (sp. composition, fish for diet analyses)• Collection of macroinvertebrates & ZP (prey production)

IFYLE Field Program (Fish Focus)IFYLE Field Program (Fish Focus)

Courtesy of Stu Ludsin

RelativeFish

biomass(dB)

ZP biomass(mg/l)

DO(mg/l)

Temperature(° C)

Transect H

15

Night

82 2 82 23 82 26 82 29 82 32 82 35 82 3820

15

10

5

0

-110

-90

-70

-50 High

Low

15

15

0

15

Depth(m)

82 22 82 25 82 28 82 31 82 34 82 3720

15

10

5

0

Day

0

0

0

IFYLE Example (courtesy of Stu Ludsin, GLERL, NOAA)