NOAA Technical Memorandum GLERL-144

ABUNDANCES OF THE AMPHIPOD DIPOREIA SPP. AND THE 

MUSSELS DREISSENA POLYMORPHA AND DREISSENA ROSTRIFORMIS 

BUGENSIS IN LAKE MICHIGAN IN 1994-1995, 2000, AND 2005

Thomas F. Nalepa1

, David L. Fanslow1, Gregory A. Lang1, 

Derek B. Lamarand2, Laurie G. Cummins2, and Glenn S. Carter2

1

NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI 48105

2

Cooperative Institute for Limnology and Ecosystems Research, Ann Arbor, MI 48109

September 2008

UNITED STATES

DEPARTMENT OF COMMERCE

Carlos M. Gutierrez

Secretary

NATIONAL OCEANIC AND

ATMOSPHERIC ADMINISTRATION

Conrad C. Lautenbacher, Jr.

Administrator
2

NOTICE

Mention of a commercial company or product does not constitute an endorsement 

by the NOAA. Use of information from this publication concerning proprietary 

products or the tests of such products for publicity or advertising purposes is not 

authorized. This is GLERL Contribution No. 1481.

This publication is available as a PDF file and can be downloaded from GLERL’s 

web site: www.glerl.noaa.gov. Hard copies can be requested from GLERL, 

Information Services, 2205 Commonwealth Blvd., Ann Arbor, MI 48105.

pubs.glerl@noaa.gov.
3

TABLE OF CONTENTS

1. INTRODUCTION....................................................................................................................5

2. MATERIALS AND METHODS ..............................................................................................5

Sampling Sites..........................................................................................................................5

Sample Collection and Processing ...........................................................................................6

3. RESULTS AND DISCUSSION................................................................................................6

4. REFERENCES .........................................................................................................................7

APPENDIX 1. Link to data file (Excel format). 

ftp://ftp.glerl.noaa.gov/publications/tech_reports/glerl-144/TM-144_Appendix1_

LMichigan-1994-95-2000-05.xls

LIST OF TABLES

Table 1. Location and depth of sites sampled in 1994-1995, 2000, and 2005. Station 

designations and locations were associated with the following sampling programs: 

EMAP = Environmental Monitoring and Assessment Program; LMMB = Lake Michigan 

Mass Balance; GLERL = Great Lakes Environmental Research Lab, southern basin 

monitoring; GLERL* = Great Lakes Environmental Research Lab, 5-year lake-wide survey..................9

LIST OF FIGURES

Figure 1. All sites sampled in Lake Michigan in 1994-1995, 2000, and 2005. The sites 

were divided into various regions as follows: a = southern region, b = central region, 

c = northern region, d = Green Bay, and e = Grand Traverse Bay........................................................... 14

Figure 2. Designation of sites sampled in 1994-1995, 2000, and 2005 that were located 

in the southern region of Lake Michigan. Site coordinates are given in Table 1..................................... 15

Figure 3. Designation of sites sampled in 1994-1995, 2000, and 2005 that were located 

in the central region of Lake Michigan. Site coordinates are given in Table 1 ....................................... 16

Figure 4. Designation of sites sampled in 1994-1995, 2000, and 2005 that were located 

in the northern region of Lake Michigan. Site coordinates are given in Table 1..................................... 17

Figure 5. Designation of sites sampled in 1994-1995, 2000, and 2005 that were located 

in Green Bay, Lake Michigan. Site coordinates are given in Table 1...................................................... 18

Figure 6. Designation of sites sampled in 1994-1995, 2000, and 2005 that were located 

in Grand Traverse Bay, Lake Michigan. Site coordinates are given in Table 1....................................... 19

Figure 7. Mean (± SE) density (no. per m2

) of Diporeia at each of four depth intervals 
4

(< 30 m, 31-50 m, 51-90 m, > 90 m) in 1994-1995, 2000, and 2005...................................................... 20

Figure 8. Distribution of Diporeia in Lake Michigan in 1994-1995, 2000, and 2005. 

Values given as mean density (no. per m2

). Small crosses denote sampling sites................................... 21

Figure 9. Mean (± SE) density of Dreissena r. bugensis at each of four depth intervals 

(< 30 m, 31-50 m, 51-90 m, > 90 m) in 1994-1995, 2000, and 2005...................................................... 22

Figure 10. Distribution of Dreissena r. bugensis in Lake Michigan in 1994-1995, 2000, 

and 2005. Values given as mean density (no. per m2

). Small crosses denote sampling sites. 

For 2005, contours were manipulated slightly in the northern, mid-lake region to reflect 

more realistic patterns. Although not thoroughly sampled, this region would have few 

individuals because of extreme depths .................................................................................................... 23

Figure 11. Mean (± SE) density (no. per m2

) of Dreissena polymorpha at each of four 

depth intervals (< 30 m, 31-50 m, 51-90 m, > 90 m) in 1994-1995, 2000, and 2005 ............................. 24

Figure 12. Distribution of Dreissena polymorpha in Lake Michigan in 1994-1995, 

2000, and 2005. Values given as mean density (no. per m2

). Small crosses denote 

sampling sites. For 2000 and 2005, contours were manipulated slightly in the northern,

mid-lake region to reflect more realistic patterns. Although not thoroughly sampled, 

this region would have few to no individuals because of extreme depths............................................... 25
5

Abundances of the amphipod Diporeia spp. and mussels 

Dreissena polymorpha and Dreissena rostriformis bugensis in 

Lake Michigan in 1994-1995, 2000, and 2005

Thomas F. Nalepa, David L. Fanslow, Gregory A. Lang, 

Derek B. Lamarand, Laurie G. Cummins, and Glenn S. Carter

1. INTRODUCTION

This technical report provides basic results of benthic surveys conducted in Lake Michigan in 1994-1995, 

2000, and 2005. The focus of these surveys was to assess lakewide trends in abundances of the amphipod 

Diporeia spp., the zebra mussel (Dreissena polymorpha), and the quagga mussel (Dreissena rostriformis 

bugensis). These lakewide surveys were an expansion of a monitoring program in the southern basin 

that has examined trends in the abundance and composition of the macroinvertebrate community since 

1980 (Nalepa 1987, Nalepa et al. 1998). The original purpose of the monitoring program was to assess 

the response of the benthic community to phosphorus abatement efforts in the mid-1970s (Nalepa 

1987). However, after D. polymorpha became established in the southwestern portion of the lake in 

1989 (Marsden et al. 1993), the monitoring program detected several dramatic changes in the benthic 

community in the early 1990s. For one, the Diporeia population began to systematically disappear 

(Nalepa et al. 1998). Also, D. polymorpha rapidly expanded and soon became dominant in the nearshore 

region. To determine if the same dramatic changes in the southern basin were occurring over a broader 

lake area, the monitoring program was expanded in 1994-1995 to include the entire lake. Sampling in 

these two years was conducted jointly with several other Lake Michigan programs -- Environmental 

Monitoring and Assessment (EMAP) and Lake Michigan Mass Balance (LMMB). After 1994-1995, 

lakewide monitoring of Diporeia and Dreissena populations continued at 5-year intervals (i.e., in 2000 

and 2005) as part of a regular monitoring program. 

The purpose of this report is to provide all abundance data collected in 1994-1995, 2000, and 2005, and 

to provide basic details of the lakewide sampling program, including station locations, sampling methods, 

and laboratory procedures. Data are presented with little attempt at interpretation; detailed analysis and 

discussions of relevance will be provided in other publications (see Nalepa et al. in press). 

2. MATERIALS AND METHODS 

Sampling Sites

The location and depth of sites sampled in 1994-1995, 2000, and 2005 are given in Table 1. For 

organizational purposes, the sites were placed into five regions of the lake: southern, central, northern, 

Green Bay, and Grand Traverse Bay. In 1994-1995, samples were collected at 88 sites during two cruises 

in 1994 (late July and early September), and one cruise in 1995 (late August/early September). Sampling 

sites were part of either EMAP, LMMB, or the GLERL monitoring program in the southern basin. 

Site locations in EMAP were based on a random, probabilistic design (Stevens 1997) within the 85 m 

contour, while site locations in LMMB were focused in offshore, depositional areas. Sites in the GLERL 

monitoring program were located at various depths throughout the southern basin (Nalepa et al. 1985). 

Of the sites sampled in 1994-1995, there were 49, 33, and 6 sites sampled within each of these programs, 
6

respectively. The number of sites sampled was expanded to 157 in 2000. Included were 21 EMAP and 10 

LMMB sites that were sampled in 1994-1995, and all 40 sites that were part of the GLERL monitoring 

program and regularly sampled since 1980. The other sites (n = 86) were added to provide broader spatial 

coverage of the lake. Added sites were mostly along transects at 20, 30, 45, 60 m, and 80 m on both the 

east and west sides of the lake. In Green Bay, 2 of the 5 sites sampled in 1994-1995 were not sampled 

in 2000 and 2005, but 5 sites were added as part of an assessment of food resources available to lake 

whitefish. One site was sampled in Grand Traverse Bay in 1994-1995; this site was sampled in 2000 and 

2005 along with 20 additional sites that were also part of the food resource assessment. All sites sampled 

in 2000 were re-sampled in 2005, plus an additional 3 sites located in the southern basin. The location 

of sites within each of the five regions is given in Figure 1, and by-region site designations are given in 

Figures 2-6. 

Sample Collection and Processing 

Sampling procedures were the same at all sites on all sampling dates. Samples were taken in triplicate at 

each site with a Ponar grab (sampling area = 0.046 m2

). Sediments were washed through an elutriation 

device fitted with a 0.5-mm mesh net, and retained residue was preserved in 5 % formalin containing rose 

bengal stain. 

In the laboratory, all Diporeia spp. and dreissenids were picked and counted under a low-power magnifier 

lamp (1.5 X). In replicates with high numbers of individuals, the sample was randomly subdivided 

and only a portion of the total sample counted. For Diporeia spp., the sample was split using a folsom 

plankton splitter. For dreissenids, the sample was randomly placed into a divided tray (4 quadrants) and a 

subsample counted. For both taxa, at least 300 individuals were counted in a given replicate. 

3. RESULTS AND DISCUSSION

Data collected in each survey period are given in Appendix 1 (excel file). Values for Diporeia, D. 

polymorpha, and D. r. bugensis are provided as the number found in each replicate grab in each of the 

three sampling periods. The three taxa are coded as DIPO, DPOL, and DBUG in the file, respectively. 

To convert to number per m2

, multiply values by 21.42. 

To briefly summarize temporal trends, sites in the main basin (i.e. not within Grand Traverse Bay or 

Green Bay) were placed into four depth intervals (< 30 m, 31-50 m, 51-90 m, > 90 m) and mean (± SE) 

densities of the three taxa were determined for each interval. Sites in Grand Traverse Bay and Green Bay 

were excluded since most were not sampled all three periods. Differences between sampling periods and 

intervals were tested with a two-way ANOVA (period x interval) after ln +1 transformation. If sampling 

periods were significantly different, a multiple range test was performed (Tukey’s LSD). 

Over the 10-year sampling period, dramatic changes occurred in populations of Diporeia and D .r. 

bugensis. For Diporeia, overall densities were significantly different between the three sampling 

periods (P < 0.001). Densities were significantly lower in 2000 compared to 1994/1995 (P < 0.001), 

and significantly lower in 2005 compared to 2000 (P < 0.001). The year x interval interaction was also 

significant (P < 0.001). Declines over the 10-year period in the < 30 m, 31-50 m, 51-90 m, and > 90 m 

depth intervals were 96.9 %, 99.6 %, 91.6 % and 72.8 %, respectively (Figure 7). Declines were most 

evident in the southeastern, eastern, and northern portions of the lake between 1994-1995 and 2000, while 

declines in the western portion of the lake were most severe between 2000 and 2005 (Figure 8). 
7

In contrast, D. r. bugensis increased dramatically over the same period. It was not found at any site in 

1994-1995, and mean densities in 2000 were only 37/m2

, 25/m2, 0/m2, and 0/m2 at the four depth intervals, 

respectively. However, by 2005 mean densities increased to 6,125/m2

, 16,017/m2, 6,472/m2, and 13/m2

(Figure 9). Differences between the three sampling periods were significant (P < 0.01, year x interval 

interaction: P < 0.01). D .r. bugensis was found only in the northern region of the lake in 2000 and, 

although it was found throughout the lake by 2005, densities remained highest in that region in 2005 

(Figure 10). 

Densities of D. polymorpha increased between 1994/1995 and 2000, but then decreased between 2000 

and 2005 (Figure 11). Differences between these three periods were significant (P < 0.01; year x interval 

interaction: P < 0.01). D. polymorpha was mainly found at the two shallowest depth intervals (< 30 m and 

31-50 m) over the entire 10-year sampling period. Peak mean density was 1,836/m2

 at the < 30 m interval 

in 2000. Like D. r. bugensis, densities of D. polymorpha tended to be greater in the northern portion of 

the lake (Figure 12). 

In summary, Diporeia and D. polymorpha declined, while D. r. bugensis increased in Lake Michigan 

between 1994-1995 and 2005. The decline of Diporeia has been linked to the expansion of dreissenids, 

but exact mechanisms for the negative response are not entirely clear (Nalepa et al. 2006). Lower 

abundances of D. polymorpha in 2005 compared to 2000 were temporally coincident with the increase 

in D. r. bugensis, and similar declines relative to D. r. bugensis have been documented in Lake Ontario 

(Mills et al. 1999). Based on laboratory experiments, D. polymorpha has a lower assimilation rate and a 

higher respiration rate compared to D. r. bugensis, and is therefore likely to be outcompeted for available 

food resources (Stoeckmann 2003). In 2005, the D. r. bugensis population was still expanding at all depth 

intervals, so it is not yet apparent at what level the population will stabilize and reach an equilibrium 

with the surrounding environment. A lakewide survey planned for 2010 should provide an answer to this 

important question. 

4. REFERENCES

Mills E.L., J.R. Chrisman, B. Baldwin, R.W. Owens, R. O’Gorman, T. Howell, E.F. Roseman, and M.K. 

Raths. Changes in the dreissenid community in the lower Great Lakes with emphasis on southern Lake 

Ontario. Journal of Great Lakes Research 25:187-197 (1999).

Nalepa, T.F. Long term changes in the macrobenthos of southern Lake Michigan. Canadian Journal of 

Fisheries and Aquatic Sciences 44:515-524 (1987).

Nalepa, T.F., M.A. Quigley, K.F. Childs, J.M. Gauvin, T.S. Heatlie, M.P. Parker, and L. Vanover. 

Macrobenthos of southern Lake Michigan. NOAA Data Report ERL GLERL-28. Great Lakes 

Environmental Research Laboratory, Ann Arbor, MI (1985). 

Nalepa, T.F., D.J. Hartson, D.L. Fanslow, G.A. Lang, and S.J. Lozano. Declines in benthic 

macroinvertebrate populations in southern Lake Michigan, 1980-1993. Canadian Journal of Fisheries 

and Aquatic Sciences 55:2402-2413 (1998).
8

Nalepa, T.F., D.L. Fanslow, A.J. Foley, III, G.A. Lang, B.J. Eadie, and M.A. Quigley. Continued 

disappearance of the benthic amphipod Diporeia spp. in Lake Michigan: is there evidence for food 

limitation? Canadian Journal of Fisheries and Aquatic Sciences 63:872-890 (2006).

Nalepa, T.F., D.L. Fanslow, and G.A. Lang. Transformation of the offshore benthic community in 

Lake Michigan: recent shift from the native amphipod Diporeia spp. to the invasive mussel Dreissena 

rostriformis bugensis. Freshwater Biology (in press).

Stevens, D.L., Jr. Variable density grid-based sampling designs for continuous spatial distributions. 

Environmetrics 8:167-195 (1997).
9

Table 1. Location and depth of sites sampled in 1994-1995, 2000, and 2005. Station designations and 

locations were associated with the following sampling programs: EMAP = Environmental Monitoring 

and Assessment Program; LMMB = Lake Michigan Mass Balance; GLERL = Great Lakes Environmental 

Research Lab, southern basin monitoring; GLERL* = Great Lakes Environmental Research Lab, 5-year 

lake-wide survey. 

Survey Year

Station Program Depth Latitude Longitude 1994 1995 2000 2005

Southern Region

A-1 GLERL 18 42°06.50 86°32.00 X X

A-2 GLERL 35 42°06.00 86°37.00 X X

A-4 GLERL* 74 42°03.50 87°06.50 X X

B-2 GLERL 47 42°24.00 86°27.00 X X

B-3 GLERL 68 42°24.00 86°35.50 X X

B-4 GLERL 129 42°23.50 87°01.00 X X

B-5 GLERL 108 42°22.50 87°21.00 X X

B-6 GLERL 83 42°22.50 87°30.00 X X

B-7 GLERL 45 42°22.00 87°40.00 X X X

C-1 GLERL 20 42°49.67 86°14.83 X X

C-2 GLERL* 46 42°49.67 86°18.14 X X

C-3 GLERL 77 42°49.17 86°28.42 X X X

C-5 GLERL 157 42°49.00 86°50.00 X X

C-6 GLERL 93 42°47.67 87°26.83 X X

C-7 GLERL 55 42°47.50 87°34.50 X X X

C-45 GLERL* 45 42°09.56 87°30.20 X X

EG-12 GLERL 56 42°20.90 87°37.00 X X

EG-14 GLERL 95 42°22.70 86°46.50 X X

EG-18 GLERL 57 42°17.60 86°38.57 X X X

EG-22 GLERL 45 43°06.20 86°22.00 X X

F-2 GLERL* 45 42°30.05 86°21.86 X X

F-3 GLERL* 72 42°30.10 86°31.50 X X

G-45 GLERL* 45 41°56.96 87°13.44 X X

H-8 GLERL 19 42°23.92 87°46.25 X X

H-9 GLERL 37 42°26.75 87°42.35 X X

H-11 GLERL 73 42°33.25 87°35.83 X X

H-13 GLERL 19 41°55.58 87°29.42 X X

H-14 GLERL 37 42°04.33 87°27.17 X X

H-15 GLERL 55 42°09.50 87°26.00 X X

H-18 GLERL 19 41°59.00 86°36.00 X X

H-19 GLERL 37 42°00.00 86°41.08 X X

H-20 GLERL 55 42°00.83 86°45.17 X X X

H-21 GLERL 73 42°02.42 86°53.00 X X

H-22 GLERL 46 42°08.35 86°39.83 X X

H-24 GLERL 19 42°23.25 86°20.00 X X

H-28 GLERL 19 42°37.80 86°15.92 X X

H-29 GLERL 37 42°37.80 86°18.35 X X

H-30 GLERL 73 42°37.80 86°26.00 X X
10

Survey Year

Station Program Depth Latitude Longitude 1994 1995 2000 2005

H-31 GLERL 46 43°02.47 86°19.99 X X X

M-45 GLERL* 45 43°11.43 86°25.72 X X

N-2 GLERL* 40 41°53.50 86°52.00 X X

N-3 GLERL* 61 41°58.00 86°59.00 X X

Q-13 GLERL* 13 42°50.63 87°47.92 X

Q-30 GLERL* 30 42° 50.61 87°39.24 X

R-20 GLERL* 20 42°45.04 87°41.78 X

R-45 GLERL* 45 42°45.00 87°36.33 X X

S-2 GLERL 17 41°45.90 87°23.47 X X

S-3 GLERL 25 41°51.00 87°19.20 X X

S-4 GLERL 40 41°56.10 87°15.10 X X

SAU-45 GLERL* 45 42°41.14 86°18.90 X X

T-3 GLERL* 73 42°10.00 86°43.00 X X

V-1 GLERL 16 41°41.80 87°00.80 X X

V-2 GLERL 29 41°49.00 87°02.90 X X

X-1 GLERL 36 43°08.25 86°21.70 X X

X-2 GLERL 93 43°12.00 86°31.00 X X

100 LMMB 100 43°01.02 86°37.02 X

822 LMMB 52 42°08.52 86°39.72 X

9211 LMMB 73 43°00.96 86°24.42 X

9222 LMMB 124 42°29.76 86°49.74 X

9224 LMMB 73 42°30.18 86°31.74 X

9511 LMMB 87 42° 07.20 87°03.12 X

9531 LMMB 145 42°40.14 87°15.06 X

9534 LMMB 157 42°46.26 87°04.56 X

9544 LMMB 93 42°57.12 87°18.54 X

20148 LMMB 54 42°00.81 86°45.18 X

31916 LMMB 26 41°49.98 86°54.36 X

73452 EMAP 17 42°50.09 86°14.76 X

73472 EMAP 45 42°22.02 86°26.58 X

73492 EMAP 17 41°54.00 86°38.98 X

75000 EMAP 28 43°06.72 86°19.74 X

75010 EMAP 58 42°52.74 86°21.42 X

75030 EMAP 70 42°23.10 86°35.46 X

75040 EMAP 79 42°10.50 86°44.04 X

75050 EMAP 47 41°56.58 86°49.74 X

75060 EMAP 6 41°42.78 86°55.98 X

76570 EMAP 104 43°03.54 86°39.72 X

76580 EMAP 108 42°49.68 86°45.54 X

76590 EMAP 145 42°35.22 86°51.36 X

76611 EMAP 65 42°59.04 87°00.84 X

76620 EMAP 43 41°53.16 87°09.24 X

76622 EMAP 20 41°47.40 87°17.58 X

78150 EMAP 89 43°00.30 86°59.22 X

78190 EMAP 51 42°03.96 87°22.80 X

Table 1. (Continued).
11

Survey Year

Station Program Depth Latitude Longitude 1994 1995 2000 2005

79752 EMAP 80 42°37.14 87°33.24 X

79760 EMAP 88 42°28.86 87°30.60 X

79781 EMAP 8 41°52.32 87°35.88 X

81340 EMAP 46 42°53.70 87°38.46 X

89195 LMMB 52 42°17.10 86°37.92 X

Central Region

E-1 GLERL* 44 44°37.50 86°18.20 X X

K-2 GLERL* 45 43°20.10 86°29.80 X X

KE-1 GLERL* 20 44°23.30 87°28.52 X X

KE-2 GLERL* 30 44°23.30 87°27.64 X X

KE-3 GLERL* 45 44°23.30 87°26.34 X X

KE-5 GLERL* 80 44°23.30 87°23.98 X X

L-220 GLERL* 20 43°30.05 86°30.14 X X

L-230 GLERL* 30 43°30.05 86°31.12 X X

L-245 GLERL* 45 43°30.05 86°31.88 X X

L-260 GLERL* 60 43°30.05 86°33.29 X X

L-280 GLERL* 80 43°30.05 86°36.22 X X

LU-1 GLERL* 20 43°56.64 86°32.10 X X

LU-3 GLERL* 45 43°56.64 86°36.49 X X

LU-4 GLERL* 60 43°56.64 86°37.60 X X

LU-5 GLERL* 80 43°56.64 86°39.00 X X

MAN-1 GLERL* 20 44°24.78 86°16.93 X X

MAN-2 GLERL* 30 44°24.78 86°17.18 X X

MAN-3 GLERL* 45 44°24.78 86°19.91 X X

MAN-4 GLERL* 60 44°24.78 86°20.37 X X

MAN-5 GLERL* 80 44°24.78 86°20.82 X X

PW-2 GLERL* 30 43°26.82 87°46.92 X X

PW-3 GLERL* 45 43°26.82 87°46.19 X X

PW-4 GLERL* 60 43°26.82 87°44.04 X X

PW-5 GLERL* 80 43°26.82 87°41.90 X X

SY-1 GLERL* 20 43°55.09 87°39.83 X X

SY-2 GLERL* 30 43°55.09 87°38.86 X X

SY-4 GLERL* 60 43°55.09 87°30.32 X X

SY-5 GLERL* 80 43°55.09 87°22.54 X X

9552 LMMB 86 43°11.10 87°12.54 X X X

9554 LMMB 114 43°14.28 86°53.22 X X X

9556 LMMB 71 43°18.30 87°46.32 X X X

9559 LMMB 80 43°25.14 87°06.54 X

9561 LMMB 138 43°28.26 86°47.04 X

9562 LMMB 129 43°30.00 87°37.02 X X X

9564 LMMB 140 43°36.06 87°20.46 X X X

9570 LMMB 174 43°53.16 86°54.48 X

9574 LMMB 148 44°04.08 87°08.82 X X X

9576 LMMB 175 44°09.06 86°37.26 X X X

9577 LMMB 63 44°14.58 87°22.44 X X X

Table 1. (Continued).
12

Survey Year

Station Program Depth Latitude Longitude 1994 1995 2000 2005

9582 LMMB 128 44°24.48 86°22.14 X X X

9587 LMMB 207 44°37.26 86°21.18 X

19163 LMMB 116 43°12.00 86°42.00 X

76560 EMAP 90 43°17.70 86°33.48 X

78110 EMAP 30 43°56.64 86°34.72 X X X

78140 EMAP 112 43°14.35 86°53.18 X

79730 EMAP 84 43°11.10 87°12.96 X

79732 EMAP 67 43°05.34 87°21.48 X

81330 EMAP 88 43°07.80 87 32.70 X

82882 EMAP 60 44°23.30 87°25.40 X X X

82902 EMAP 40 43°55.09 87°37.44 X X X

82922 EMAP 8 43°26.82 87°48.54 X X X

Northern Region

EA-7 GLERL* 43 45°17.00 85°20.06 X X

FR-1 GLERL* 20 44°49.00 86°08.36 X X

FR-2 GLERL* 30 44°49.00 86°09.31 X X

FR-3 GLERL* 45 44°49.00 86°10.13 X X

FR-4 GLERL* 60 44°49.00 86°11.07 X X

FR-5 GLERL* 80 44°49.00 86°11.77 X X

PET-1 GLERL* 17 45°26.74 85°04.26 X X

PET-2 GLERL* 32 45°26.74 85°04.53 X X

PET-3 GLERL* 43 45°26.74 85°11.21 X X

SB-2 GLERL* 30 44°51.44 87°10.04 X X

SB-3 GLERL* 45 44°51.44 87°09.06 X X

SB-4 GLERL* 60 44°51.44 87°08.21 X X

SB-5 GLERL* 80 44°51.44 87°05.19 X X

SC-2 GLERL* 30 45°50.47 86°06.32 X X

SC-3 GLERL* 45 45°49.03 86°06.32 X X

SC-4 GLERL* 60 45°47.41 86°06.32 X X

SC-5 GLERL* 82 45°45.37 86°06.32 X X

WI-1 GLERL* 20 45°14.85 86°54.30 X X

WI-2 GLERL* 30 45°14.85 86°52.57 X X

WI-3 GLERL* 45 45°14.85 86°49.80 X X

WI-5 GLERL* 80 45°14.85 86°38.20 X X

9597 LMMB 164 44° 58.32 86°22.20 X X X

9599 LMMB 208 45° 00.24 86°43.44 X

74880 EMAP 23 45°54.54 85°01.50 X X X

74900 EMAP 55 45°26.74 85°13.31 X X X

76442 EMAP 20 46°00.06 85°24.60 X X X

76451 EMAP 17 45°43.36 85°19.89 X X X

76462 EMAP 55 45°32.10 85°38.16 X X X

76471 EMAP 32 45°14.52 85°33.36 X X X

76482 EMAP 28 45°04.14 85°51.42 X X X

78030 EMAP 35 45°48.72 85°43.08 X X X

79612 EMAP 21 45°54.00 86°06.32 X X X

Table 1. (Continued).
13

Survey Year

Station Program Depth Latitude Longitude 1994 1995 2000 2005

81220 EMAP 39 45°42.60 86°24.54 X X X

81240 EMAP 57 45°14.85 86°40.11 X X X

82851 EMAP 81 45°00.03 86°55.38 X X X

82862 EMAP 12 44°51.44 87°11.40 X X X

95116 LMMB 37 45°24.00 85°35.46 X

95118 LMMB 89 45°28.32 86°31.02 X

95120 LMMB 140 45°31.44 86°10.14 X

95122 LMMB 92 45°34.44 85°49.50 X

95126 LMMB 96 45°45.36 86°03.48 X

Green Bay

BBDN-1 GLERL* 12 45°42.00 86°44.50 X X

BBDN-2 GLERL* 24 45°37.25 86°44.50 X X

BBDN-3 GLERL* 24 45°32.50 86°44.50 X X

LBDN-2 GLERL* 15 45°30.00 87°00.00 X X

LBDN-3 GLERL* 25 45°30.00 87°05.83 X X

82842 EMAP 37 45°19.62 87°00.54 X X X

84450 EMAP 11 45°36.18 87°05.82 X X X

84470 EMAP 23 45°08.04 87°18.36 X X X

86101 EMAP 16 44°56.40 87°36.12 X

86112 EMAP 8 44°44.82 87°53.70 X

Grand Traverse Bay

EA-1 GLERL* 45 44°47.00 85°31.00 X X

EA-2 GLERL* 45 44°47.00 85°33.00 X X

EA-3 GLERL* 40 44°51.00 85°27.80 X X

EA-4 GLERL* 40 44°54.00 85°26.12 X X

EA-5 GLERL* 47 44°54.00 85°29.00 X X

EA-6 GLERL* 20 45°02.00 85°23.65 X X

EA-61 GLERL* 45 45°02.00 85°24.43 X X

EA-62 GLERL* 70 45°02.00 85°25.01 X X

GT-1 GLERL* 98 44°50.00 85°37.00 X X

GT-3 GLERL* 112 44°59.00 85°34.80 X X

GT-11 GLERL* 60 44°50.00 85°38.48 X X

GT-12 GLERL* 45 44°50.00 85°38.63 X X

GT-13 GLERL* 30 44°50.00 85°38.70 X X

GT-31 GLERL* 75 44°59.00 85°35.30 X X

GT-32 GLERL* 55 44°59.00 85°35.45 X X

GT-33 GLERL* 45 44°59.00 85°35.47 X X

GT-34 GLERL* 25 44 59.00 85°35.50 X X

GT-35 GLERL* 17 44°59.00 85°35.62 X X

SG-5 GLERL* 120 44°57.40 85°34.00 X X

SG-38 GLERL* 115 45°01.75 85°32.80 X X

74920 EMAP 51 45°07.86 85°27.24 X X X

Table 1. (Continued).
14

d. Green Bay

a. Southern Region

b. Central Region

c. Northern Region

e. Grand Traverse Bay

Chicago

Muskegon

Milwaukee

Green

Bay

Figure 1. All sites sampled 

in Lake Michigan in 1994-

1995, 2000, and 2005. 

The sites were divided into 

various regions as follows: 

a = southern region, 

b = central region, 

c = northern region, 

d = Green Bay, and 

e = Grand Traverse Bay. 

46o

45o

44o

43o

42o

88o 87o 86o 85o
15

Figure 2. Designation of sites sampled in 1994-1995, 2000, and 2005 that were located 

in the southern region of Lake Michigan. Site coordinates are given in Table 1. 

A-2

A-4

B-3 B-2 B-4 B-6 B-5 B-7

C-1

C-2 C-5 C-3

C-7 C-6

C-45

EG-12

EG-14

EG-18

EG-22

F-3 F-2

G-45

H-8

H-9

H-11

H-13

H-14

H-15

H-18 H-19 H-20

H-21

H-22

H-24

H-28

H-30 H-29

H-31

M-45

N-2

N-3

Q-13 Q-30

R-20 R-45

S-2

S-3

S-4

SAU-45

T-3

V-1

V-2

X-1

X-2

100

822

9211

9222 9224

9511

9531

9534

9544

20148

31916

73452

73472

73492

75000

75010

75030

75040

75050

75060

76570

76580

76590

76611

76620

76622

78150

78190

79752

79760

79781

81340

89195

a. Southern Region

Chicago

Milwaukee

Muskegon

St, Joseph

Waukegan
16

Figure 3. Designation of sites sampled in 1994-1995, 2000, and 2005 that were located in 

the central region of Lake Michigan. Site coordinates are given in Table 1. 

E-1

K-2

KE-1 KE-2 KE-3 KE-5

L-280 L-260 L-245L-230 L-220

LU-5 LU-4 LU-3 LU-1

MAN-5MAN-4MAN-3MAN-2MAN-1

PW-2PW-3 PW-4 PW-5

SY-1 SY-2 SY-4 SY-5

9552

9554

9556

9559

9561

9562

9564

9570

9574

9576

9577

9582

9587

19163

76560

78110

78140

79730

79732

81330

82882

82902

82922

Ludington

Muskegon

Milwaukee

b. Central Region
17

Figure 4. Designation of sites sampled in 1994-1995, 2000, and 2005 that were located in the 

northern region of Lake Michigan. Site coordinates are given in Table 1. 

EA-7

FR-5 FR-4 FR-3 FR-2 FR-1

PET-3 PET-2 PET-1

SB-2 SB-3 SB-4 SB-5

SC-2

SC-3

SC-4

SC-5

WI-1WI-2WI-3 WI-5

9597

9599

74880

74900

76442

76451

76462

76471

76482

78030

79612

81220

81240

82851

82862

95116

95118

95120

95122

95126

Traverse City

Petoskey

Manistique

c. Northern Region
18

Figure 5. Designation of sites sampled in 1994-1995, 2000, and 2005 that were located in 

Green Bay, Lake Michigan. Site coordinates are given in Table 1.

BBDN-1

BBDN-2

BBDN-3

LBDN-3 LBDN-2

82842

84450

84470

86101

86112

d. Green Bay

Green Bay

Sturgeon

Bay

Escanaba
19

Figure 6. Designation of sites sampled in 1994-1995, 2000, and 2005 that 

were located in Grand Traverse Bay, Lake Michigan. Site coordinates are 

given in Table 1.

EA-2 EA-1

EA-3

EA-5 EA-4

EA-62 EA-61 EA-6

GT-1

GT-3

GT-13 GT-12 GT-11

GT-35 GT-34 GT-33GT-32 GT-31

SG-5

SG-38

74920

e. Grand Traverse Bay

Traverse City
20

Figure 7. Mean (± SE) density (no. per m2) of Diporeia at each of four depth intervals (< 30 

m, 31-50 m, 51-90 m, > 90 m) in 1994-1995, 2000, and 2005. 
21

Figure 8. Distribution of Diporeia in Lake Michigan in 1994-1995, 2000, and 2005. 

Values given as mean density (no. per m2

). Small crosses denote sampling sites. 

1

1

1

1

1

2

2

2

2

3

3

3

3

3

3

3

4

4

4

4

4 4

4

4

4

4

5

5

5

5

5

5

5

6

6

6

6

6

6

6

7

7

7

7 7

7

8

8

8

8

8

8 9

9

10

11

12

1

1

1

2

2

2

2

2

3

3

3

4

4

4

5

5 5

5

1

1

2

 0 3 6 9 12 15 

Density (No. m -2 x10 3 ) 

 1994-95 2000 2005
22

Figure 9. Mean (± SE) density of Dreissena r. bugensis at each of four depth intervals (< 30 m, 

31-50 m, 51-90 m, > 90 m) in 1994-1995, 2000, and 2005. 
23

Figure 10. Distribution of Dreissena r. bugensis in Lake Michigan in 1994-1995, 2000, and 2005. 

Values given as mean density (no. per m2). Small crosses denote sampling sites. For 2005, 

contours were manipulated slightly in the northern, mid-lake region to reflect more realistic 

patterns. Although not thoroughly sampled, this region would have few individuals because of 

extreme depths. 

Quagga Mussel Distribution

1994/95 2000 2005

Density (No. per m2

)

101 102 103 104 105
24

Figure 11. Mean (± SE) density (no. per m2) of Dreissena polymorpha at each of four depth 

intervals (< 30 m, 31-50 m, 51-90 m, > 90 m) in 1994-1995, 2000, and 2005.
25

Figure 12. Distribution of Dreissena polymorpha in Lake Michigan in 1994-1995, 2000, and 

2005. Values given as mean density (no. per m2). Small crosses denote sampling sites. 

For 2000 and 2005, contours were manipulated slightly in the northern, mid-lake region to 

reflect more realistic patterns. Although not thoroughly sampled, this region would have 

few to no individuals because of extreme depths.

Zebra Mussel Distribution

1994/95 2000 2005

Density (No. per m2

)

101 102 103 104 105