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Structure and Stability of the Midsummer Fish Communities in Chequamegon Bay, Lake Superior, 1973–1996 a

Michael H. Hoff & Charles R. Bronte

a

a

U.S. Geological Survey, Biological Resources Division, Great Lakes Science Center , Lake Superior Biological Station , 2800 Lake Shore Drive East, Suite A, Ashland, Wisconsin, 54806-2427, USA Published online: 09 Jan 2011.

To cite this article: Michael H. Hoff & Charles R. Bronte (1999) Structure and Stability of the Midsummer Fish Communities in Chequamegon Bay, Lake Superior, 1973–1996, Transactions of the American Fisheries Society, 128:2, 362-373, DOI: 10.1577/1548-8659(1999)1282.0.CO;2 To link to this article: http://dx.doi.org/10.1577/1548-8659(1999)1282.0.CO;2

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Transactions of the American Fisheries Society 128:362–373, 1999 American Fisheries Society 1999

Structure and Stability of the Midsummer Fish Communities in Chequamegon Bay, Lake Superior, 1973–1996 MICHAEL H. HOFF*

CHARLES R. BRONTE

AND

Downloaded by [US Fish & Wildlife Service] at 09:45 09 April 2014

U.S. Geological Survey, Biological Resources Division, Great Lakes Science Center, Lake Superior Biological Station, 2800 Lake Shore Drive East, Suite A, Ashland, Wisconsin 54806-2427, USA Abstract.—We analyzed the structure and stability of the summer fish communities of Chequamegon Bay, Lake Superior, during 1973–1996 from data collected with bottom trawls at 39 stations. Fifty-three taxa were collected during the study, but we found that relative abundances for 20 taxa described most of the internal variability of the data for all taxa. Abundance data for the 20 species showed that two communities existed in the bay; one inhabited shallow water (#3.0 m) whereas the other inhabited deeper water (.3.0 m). No temporal patterns of change were found in the structure of the shallow-water community, whose variation was best described by abundances of 12 taxa. The deepwater community, whose variation was best described by eight taxa, underwent three periods ofstability; 1973–1978, 1979–1988, and 1989–1996. We conclude that the shallowwater community was stable throughout the 24 years studied. Dynamics of the deepwater community were greatly affected by changes in stocking rates of lake trout Salvelinus namaycush and splake (hybrid of brook trout S. fontinalis 3 lake trout) and by rehabilitation of populations of lake herring Coregonus artedi and lake whitefish C. clupeaformis. Information on the existence, structure, stability, and habitats of fish communities in the bay will be useful for assessing changes in those communities that result from further changes in the bay or lake ecosystems.

Communities are ecological units that function in an orderly manner, so their structures can be unique attributes (Odum 1969). Patterns in dynamics of fish communities can be used to evaluate effects of changes in population, community, and ecosystem management and then to adapt management to achieve objectives. Great Lakes fish communities have been perturbed by water quality degradation, physical habitat destruction, and species invasions (Spangler et al. 1987). Those perturbations caused Great Lakes fishery managers to recognize the need for a transition from species to community approaches that manage Great Lakes fishes (Christie et al. 1987; Evans et al. 1987; Steedman and Regier 1987). Holistic management of fish communities in the Great Lakes has been hampered by lack of information on fish community structure. Only one previous study (Henderson and Nepszy 1990) described Great Lakes fish communities. Interagency processes developed to determine status or coordinate management of Lake Superior fishes referred to only one fish community (Busiahn 1990; Hansen and Schorfhaar 1994; Lake Superior Work Group, Lake Superior Binational Program, unpublished) because no analysis of data from the lake * Corresponding author: [email protected] Received July 11, 1997

Accepted May 11, 1998

has shown the existence of more than one community. Fishery management agencies agreed that managing fish communities in the Great Lakes would require defining objectives for the structure of each fish community and developing a means of measuring progress toward achievement of those objectives (Great Lakes Fishery Commission 1994). Before objectives are developed, fish communities must be described. The objective of our study was to describe the structure and stability of fish communities in Chequamegon Bay, Lake Superior, during 1973–1996 so that community structures can be used to evaluate effects of changes in population, community, or ecosystem management practices. Methods Study site.—Chequamegon Bay is in southwestern Lake Superior (Figure 1). The bay has a surface area of approximately 16,000 ha, a mean depth of 8.6 m, a maximum depth of 23 m (Ragotzkie et al. 1969), and nine tributaries. Long Island isolates the bay from Lake Superior, although strong northeast and southwest winds activate thermal currents between the bay and the lake. The bay thermally stratifies from June to September. Most of the substrate in the bay is composed of silt and sand. Sampling and analyses.—Fishes were sampled annually in Chequamegon Bay during 1973–1996

362


FISH COMMUNITIES IN LAKE SUPERIOR

363

FIGURE 1.—Location of trawl stations in Chequamegon Bay, Lake Superior. Depth contours shown are 1.8, 3.7, 5.5, 7.3, and 9.1 m.

from mid-July to early August. Sampling was conducted at 38 stations in 1973 and 39 stations during 1974–1996 by taking one 10.0-min bottom trawl tow at each station (Figure 1). The locations of the stations were permanently established in the first year sampled by randomly selecting coordinates within ten 1.83-m depth strata. The proportion of stations in each stratum was equal to the proportion of the stratum area to that of the bay. In 1973– 1976 and 1978–1996, the trawl used was constructed with an 11.9-m headrope, 2.5-cm-barmesh body, and a 6.4-mm-bar-mesh cod end. In 1977, the trawl used was similar except that the headrope was 9.7 m. Catches for 1977 were expanded to compensate for the larger area swept by trawls in the other years. All fish captured were identified to species and counted. Hatchery lake trout was treated as a different taxon from wild lake trout because we wanted to detect if either group was more important than the other in community structural importance. We used four multivariate statistical methods to analyze the abundance data (number of fish/taxon per trawl tow). Hierarchical cluster analysis (Afifi and Clark 1990) was performed to reveal groups

and patterns in abundance data across space and through time. Standardized abundances of each taxon were used in the cluster analyses, and standardization was achieved by subtracting the mean (across years for analysis of spatial structure and across sampling stations for analysis of temporal stability) and dividing by the standard deviation. Euclidean distance was used to decide which stations or years were closest, and Ward’s and complete linkages were used to aggregate distances. Linear discriminant analysis (Afifi and Clark 1990) was performed on transformed abundances (log10 abundance 1 1) to determine whether stations were more accurately classified from cluster analysis groups or from a modification of those groups that pooled stations within specific depth strata. Accuracy of the group classifications was calculated by using the jackknife procedure, which excluded one station observation from computation of the discriminant function on the remaining observations. That procedure was repeated for each station observation, after which percentages of stations correctly classified in each group were computed. Principal component analysis (Jackson 1991)


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was first used to select a subset of the 53 fish taxa by keeping only those whose loading absolute values for the first three principal components were greater than 0.7. Principal component analysis was used again to reduce the dimensionality of the data by obtaining linear transformations of the remaining fish taxa variables and to summarize the major sources of variation in the abundance data. Both analyses used the correlation matrix derived from transformed abundances. Multivariate analysis of variance (ANOVA; Chatfield and Collins 1992) was used to test for differences in transformed abundances of fishes (dependent variables) across space (stations) and through time (years). Groups (factor) were selected from results of discriminant and principal component analyses. Student’s t-tests were used to test for differences between the transformed abundances of fishes in two depth strata (Zar 1984). One-way ANOVA and Bonferroni post hoc comparisons were used to test for differences in the transformed abundances among three time periods. Spatial structure of the fish community was examined by using the multivariate analyses after pooling the abundance data from all years. Temporal structure was examined after pooling the data from all stations. We define stability as the absence of patterns of discernible change in the fish abundance data across years.

TABLE 1.—List of common and scientific names of species captured in Chequamegon Bay, Lake Superior, during 1973–1996. Common name Sea lamprey Lake sturgeon Alewife Rainbow smelt Central mudminnow Northern pike Mukellunge Black bullhead Brown bullhead Tadpole madtom Burbot Brook stickleback Ninespine stickleback Trout-perch White perch Lake herring Bloater Lake whitefish Chinook salmon Coho salmon Rainbow trout Round whitefish Atlantic salmon Brown trout Brook trout Lake trouta Splakeb Common carp Longnose sucker White sucker Silver redhorse Northern redhorse Shorthead redhorse Emerald shiner Spottail shiner Mimic shiner Bluntnose minnow Creek chub Unidentified minnow Rock bass Pumpkinseed Bluegill Smallmouth bass Johnny darter Logperch Yellow perch Walleye Ruffe Mottled sculpin Slimy sculpin Spoonhead sculpin Deepwater sculpin

Results From 1973–1996, 935 trawl tows captured 1,879,329 fish from 53 taxa (Table 1). Cluster analyses performed by using Ward’s and complete linkages showed that all of the shallowest stations, where depths were 2 m, were in one cluster with other relatively shallow stations (Figure 2). Jackknifed discriminant analysis of the two clusters from the analysis correctly classified 64–97% of the stations into two to four groups, which were based on different clustering interpretations, derived from cluster analysis results or from modifications of those results. The highest correct classification was for stations grouped as less than or equal to 3.0 m deep and greater than 3.0 m deep, so we used those groupings in further multivariate analyses of spatial structure. Principal component analysis on the abundances of all taxa showed that 21 of the 53 taxa component loadings were greater than 0.7, so we used the abundance data for only those 21 taxa to further analyze community structure across space (Appendix Table A.1). Results from principal com-

Scientific name Petromyzon marinus Acipenser fulvescens Alosa pseudoharengus Osmerus mordax Umbra limi Esox lucius Esox masquinongy Ameiurus melas Ameiurus nebulosus Noturus gyrinus Lota lota Culaea inconstans Pungitius pungitius Percopsis omiscomaycus Morone americana Coregonus artedi Coregonus hoyi Coregonus clupeaformis Oncorhynchus tshawytscha Oncorhynchus kisutch Oncorhynchus mykiss Prosopium cylindraceum Salmo salar Salmo trutta Salvelinus fontinalis Salvelinus namaycush Cyprinus carpio Catostomus catostomus Catostomus commersoni Moxostoma anisurum Moxostoma sp. Moxostoma macrolepidotum Notropis atherinoides Notropis hudsonius Notropis volucellus Pimephales notatus Semotilus atromaculatus Cyprinidae Ambloplites rupestris Lepomis gibbosus Lepomis macrochirus Micropterus dolomieui Etheostoma nigrum Percina caprodes Perca flavescens Stizostedion vitreum Gymnocephalus cernuus Cottus bairdi Cottus cognatus Cottus ricei Myoxocephalus thompsoni

a

Stocked and wild lake trout were treated as separate taxa in our analyses. b Brook trout 3 lake trout hybrid.

ponent analysis on the abundance data for the 21 taxa grouped by station depth category showed that 79% of the total variance was explained by the first three principal components and that the 95% confidence ellipses from the centroids of the

365



FIGURE 2.—Result of hierarchical cluster analysis of abundances of 53 fish taxa in Chequamegon Bay by using (A) Ward’s linkage and data standardized by the standard deviation and (B) complete linkage and data standardized by the range.

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TABLE 2.—Component loadings, in descending order, of fish abundances for the first principal component.

FIGURE 3.—Plots of (A) 95% confidence ellipses from centroids of first two principal components (PC 1, PC 2) and (B) the first three principal components (PC 1, PC 2, PC 3) for abundances of 21 fishes in Chequamegon Bay.

first two principal components did not overlap (Figure 3). When the same data were plotted along the first three component axes, station depth categories did not overlap. Component loadings were highly positive and similar (0.55–0.91) for mimic shiners, logperch, smallmouth bass, johnny darters, black bullheads, yellow perch, spottail shiners, silver redhorses, emerald shiners, walleyes, rock bass, and bluntnose minnow; they were highly negative and similar (20.71 to 20.87) for bloaters, lake whitefish, hatchery lake trout, lake herring, spoonhead sculpin, splake, longnose suckers, and rainbow smelt; and the loading was negative but lower for mottled sculpin (20.22; Table 2). Multivariate ANOVA showed that the abundances of these 21 species were different between the shallow and deep stations (Pillai Trace 5 0.997; F 5 238.28, df 5 21, 17; P , 0.001). Thus, the complex interrelationships of species abundances were different in the two depth zones. Student’s t-tests

Taxon

Loading

Mimic shiner Logperch Smallmouth bass Johnny darter Black bullhead Yellow perch Spottail shiner Silver redhorse Emerald shiner Walleye Rock bass Bluntnose minnow Mottled sculpin Rainbow smelt Longnose sucker Splake Spoonhead sculpin Lake herring Stocked lake trout Lake whitefish Bloater

0.909 0.891 0.858 0.848 0.801 0.793 0.776 0.753 0.729 0.724 0.717 0.551 20.219 20.712 20.764 20.804 20.817 20.855 20.872 20.873 20.873

showed that differences in abundances of 20 of the 21 taxa existed (P , 0.001) between shallow stations (#3.0 m) and deep stations (.3.0 m; Table 3). The 12 taxa that received highly positive loadings were more abundant at shallow stations than at deep stations, whereas the eight taxa that received highly negative loadings were more abundant at deep stations than at shallow stations, and the single species (mottled sculpin) with low negative loading was equally abundant (P . 0.05) at shallow and deep stations. Thus, the two different communities were separated based on depth strata inhabited in midsummer. Principal component analysis of abundances of the 12 shallow-water species showed no temporal structure (Table 4; Figure 4). The principal component analysis of the abundance data for the eight deepwater species suggested that the deepwater community underwent three periods of stability; 1973–1978, 1979–1988, and 1989–1996 (Table 4; Figure 5). Results of multivariate ANOVA also showed that the abundances of the eight deepwater species were different (Pillai Trace 5 0.283; F 5 19.08; df 5 16, 1852; P , 0.001) across the three periods. One-way ANOVA showed that rainbow smelt and longnose sucker abundances were not different (P . 0.05) across periods, but abundances of lake herring, lake whitefish, bloaters, stocked lake trout, splake, and spoonhead sculpin differed significantly (P , 0.001) among periods (Table 5). In 1973–1978, lake herring, splake, lake whitefish, and spoonhead sculpin populations were

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TABLE 3.—Results of Student’s t-tests comparing mean transformed abundances of fishes at shallow-water (#3.0 m) stations (N 5 215 fish) and deepwater (.3.0 m) stations (N 5 720 fish). Back-transformed mean 6 SD (number/trawl tow) at:


Taxon Black bullhead Silver redhorse Emerald shiner Spottail shiner Mimic shiner Bluntnose minnow Rock bass Smallmouth bass Johnny darter Logperch Yellow perch Walleye Rainbow smelt Lake herring Lake whitefish Bloater Stocked lake trout Splake Longnose sucker Spoonhead sculpin Mottled sculpin

Depth #3.0 m 0.4 0.2 2.3 16.9 3.4 0.2 0.3 0.4 3.6 0.6 17.9 0.7 6.4 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0

6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6

0.9 0.5 7.4 8.5 6.6 0.9 0.9 1.2 3.6 1.1 7.8 1.3 10.4 0.1 0.3 0.1 0.1 0.1 0.1 0.1 0.1

lowest, while populations of stocked lake trout and bloaters were high. In 1979–1988, populations of spoonhead sculpin and stocked lake trout were low, lake whitefish populations were moderate, and populations of lake herring, bloaters, and splake were high. In 1989–1996, the bloater population was lowest, the splake population was moderate, and lake herring, lake whitefish, stocked lake trout, and spoonhead sculpin populations were high. Discussion Our principal component analysis and multivariate ANOVA results showed that Chequamegon Bay contained a shallow-water (#3.0 m) and a deepwater (.3.0 m) fish community in summer. Not all species are equally important in determining the nature of the whole community (Odum 1969), and decomposition of the Chequamegon Bay shallow-water community showed that most of its internal variation was described by the abundances of 12 key species: mimic shiner, logperch, smallmouth bass, johnny darter, black bullhead, yellow perch, spottail shiner, silver redhorse, emerald shiner, walleye, rock bass, and bluntnose minnow. Decomposition of the deepwater community showed that most of its internal variation was described by the abundances of eight key species: bloater, lake whitefish, stocked lake trout,

Depth .3.0 m 0.0 0.0 0.3 1.4 0.1 0.0 0.0 0.0 0.7 0.1 3.8 0.2 281.7 0.9 0.8 0.3 0.3 0.1 0.2 0.3 0.0

6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6

0.1 0.1 1.3 3.5 0.6 0.0 0.1 0.1 1.7 0.3 4.0 0.6 15.0 3.2 1.7 1.1 0.9 0.4 0.5 0.8 0.1

t

P

143.34 78.37 89.04 234.43 276.74 35.95 77.56 115.39 124.14 131.98 103.03 51.81 302.70 43.36 62.56 23.41 43.30 22.47 27.11 35.71 0.07

,0.001 ,0.001 ,0.001 ,0.001 ,0.001 ,0.001 ,0.001 ,0.001 ,0.001 ,0.001 ,0.001 ,0.001 ,0.001 ,0.001 ,0.001 ,0.001 ,0.001 ,0.001 ,0.001 ,0.001 .0.05

lake herring, spoonhead sculpin, stocked splake, longnose sucker, and the nonindigenous rainbow smelt. Taxa loadings to the first principal component were of similar sign and size within each community, which indicated that the component was a depth metric affected by abundance sizes (e.g., Bookstein et al. 1985) and that the important taxa within each community were equally important to the structures of their communities. Thus, the smallest, most statistically descriptive dimension of each community was that described by the structurally important taxa, so management of those taxa should best manage the structure and variability of each community. No temporal pattern in structural variation was found for the shallow-water community in Chequamegon Bay, and the stability found there was probably the result of the presence of 12 equally important taxa in the community. Because a large assemblage dominated that community, it could not be easily destabilized by a change in abundance of one species. The deepwater community underwent three periods of stability. In 1973–1978, lake herring, lake whitefish, splake, and spoonhead sculpin populations were lowest, while stocked lake trout and bloater populations were high. In 1979–1988, spoonhead sculpin abundance remained low, stocked lake trout abundance declined to its lowest

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TABLE 4.—Abundances of 20 fish taxa captured with bottom trawls at 39 stations, pooled across stations, during annual midsummer sampling in Chequamegon Bay, Lake Superior, 1973–1996. Shallow-water taxa


Year

Black bullSilver Emerald head redhorse shiner

Spottail shiner

Mimic shiner

Bluntnose minnow

Rock bass

Smallmouth bass

Johnny darter

Logperch

Yellow perch

Walleye

1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

3 20 3 1 3 22 9 2 5 2 8 10 20 20 0 3 1 9 21 43 0 0 0 0

13 23 3 2 10 3 4 1 4 4 0 5 2 0 0 3 0 0 0 0 8 0 6 0

0 7 730 2,789 4,089 1,209 2,974 286 420 590 37 1,216 1,265 1,099 20 5 24 117 335 5 412 665 0 141

419 1,088 795 2,063 1,923 2,155 1,729 1,578 1,093 2,384 264 3,799 1,342 893 652 3,520 1,229 1,280 1,206 814 744 3,574 242 853

0 752 0 204 105 278 54 1,506 154 1,182 0 957 372 239 21 753 26 1,502 1,385 424 711 4,392 225 66

0 0 0 0 1 4 0 0 68 4 0 0 0 0 0 8 98 0 87 30 0 6 0 0

0 8 0 0 2 3 7 2 4 2 11 11 7 3 49 2 19 3 5 51 3 9 0 1

0 4 2 1 1 0 2 1 2 2 0 3 2 0 108 1 0 16 5 8 9 45 152 85

4 51 1 24 32 28 466 20 126 53 20 439 36 217 501 862 58 186 487 772 206 678 485 211

2 55 2 3 26 2 11 7 7 14 3 11 6 33 55 31 2 23 32 15 4 127 11 7

339 931 1,026 1,328 4,907 1,601 2,351 2,403 1,041 1,190 838 1,267 601 687 628 1,763 611 2,086 15,090 5,318 172 3,961 723 1,720

10 84 3 21 70 38 27 18 9 11 59 21 25 23 9 21 10 45 31 48 18 93 1 42

Total

205

91

18,435

35,639

15,308

306

202

449

5,963

489

52,582

737

level, lake whitefish populations increased to a moderate level, the bloater population remained high, and populations of lake herring and splake increased to very high levels. In 1989–1996, the bloater population declined to its lowest level, the splake population declined to a moderate level, the lake herring population remained high, and lake whitefish, stocked lake trout, and spoonhead sculpin populations increased to their highest levels. Populations of rainbow smelt and longnose suckers did not change across those three periods. Abundances of stocked lake trout and splake in Chequamegon Bay changed during the study period as the likely result of reduction in survival of lake trout (Hansen et al. 1996) and stocking rates that fluctuated from 101,000 to 731,000/year for lake trout and from 0 to 296,000/year for splake in Chequamegon Bay and the Wisconsin waters of Lake Superior (Keim and Hulse 1997). Lake herring abundance changed as the result of 2,000-fold annual variation in first-year recruitment during the study period, and lake whitefish recruitment increased in the 1980s and early 1990s (MacCallum et al. 1994; Selgeby et al. 1994). Bloater and spoonhead sculpin abundances changed during the study period as the likely result of changes in

predation rates by lake trout (MacCallum and Selgeby 1987; Selgeby et al. 1994). Most of the rainbow smelt in Chequamegon Bay in summer were yearlings; the bay is a nursery area for the species, and recruitment rates there have been relatively stable through time. Communities have functional unity with characteristics beyond those of the individuals or populations composing them, and have sometimes been considered ‘‘super-organisms’’ in ecological organization (Odum 1969). In Chequamegon Bay, we described structural characteristics that can be used to assess effects of major changes in the ecosystem or its components. Regulations on smallmouth bass harvest in Chequamegon Bay have recently changed from no minimum length limit in 1988 to a 559-mm minimum length limit in 1994, and mean length and mean catch per effort of smallmouth bass in angler catches there have increased significantly from 1994 to 1996 (Great Lakes Science Center, Lake Superior Biological Station, unpublished data). If more and larger smallmouth bass continue to inhabit the shallowwater community, then resulting changes in the shallow-water community will be evaluated by comparing structures of the shallow-water fish

369


TABLE 4.—Extended.


Deepwater taxa

Year

Rainbow smelt

Lake herring

Lake whitefish

1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

49,627 213,298 25,650 43,793 51,362 51,324 76,479 17,102 49,177 124,453 61,938 53,162 54,958 56,445 171,271 70,336 40,701 18,573 38,248 31,354 29,043 232,767 54,755 13,770

15 14 23 7 38 24 121 10 17 38 0 118 6,292 1,036 301 3 714 4,075 1,662 245 207 33 3 5

19 37 3 11 16 10 48 73 41 77 48 42 30 33 52 90 41 113 253 406 257 273 188 130

Total

1,629,586

15,001

2,291

Stocked lake trout

Splake

Longnose sucker

Spoonhead sculpin

28 7 31 10 55 71 166 22 2 54 5 10 709 153 0 1 6 0 0 5 0 0 0 0

25 187 35 4 11 15 17 3 16 4 7 15 27 22 0 6 11 18 34 56 42 70 39 9

0 1 0 0 0 0 21 9 13 7 11 23 17 8 30 8 7 1 0 0 9 15 0 5

24 12 16 4 7 9 15 8 6 8 9 19 8 19 5 12 0 5 6 7 4 14 5 4

9 17 0 9 0 1 15 6 11 2 6 0 1 24 13 21 7 26 38 97 30 160 20 9

1,335

673

185

226

522

Bloater

FIGURE 4.—Principal component (PC) ordinations of 12 shallow-water fish abundances by year.


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HOFF AND BRONTE

FIGURE 5.—Principal component (PC) ordinations of eight deepwater fish abundances by year and year-group.

community before and after changes occurred in smallmouth bass population size and structure. The deepwater community of the bay will probably be affected by elimination of stocked lake trout, which will occur as a result of the termination after 1995 of stocking lake trout in eastern Wisconsin waters (including Chequamegon Bay). Wild lake trout have not been abundant in Chequamegon Bay, so they will probably not replace stocked lake trout as an important taxon in the deepwater community there. We will assess the effects of that change on the structure and stability of the deepwater community. In 1987, consensus was reached that the species approach to management of Great Lakes fishes needed to be replaced by the community approach (Christie et al. 1987; Evans et al. 1987; Spangler et al. 1987; Steedman and Regier 1987). Since then, only our study and that by Henderson and Nepszy (1990) described the structure of fish com-

munities in the Great Lakes, so more descriptions of fish community structures are needed. Those descriptions will provide ecosystem managers with information on the existence, structure, stability, and habitats of fish communities needed to manage the communities. Community structure information will be useful in managing fish communities (Great Lakes Fishery Commission 1994) and ecosystems of the Great Lakes (Lake Superior Work Group, unpublished). Acknowledgments The sampling program in Chequamegon Bay was initiated by J. Selgeby; and D. Swedberg, G. Curtis, G. Cholwek, C. Bresette, T. Edwards, K. Peterson, K. Mayo, W. Brown, A. Edwards, E. Buckner, and J. Bratley participated in the field work. This is contribution 1038 of the USGS Great Lakes Science Center.

TABLE 5.—Results of analysis of variance (ANOVA) and Bonferonni post hoc paired comparisons of transformed abundances for eight deepwater fishes in Chequamegon Bay by year-group (1973–1978, 1979–1988, 1989–1996). Back-transformed mean 6 SD for: Taxon Rainbow smelt Lake herring Lake whitefish Bloater Stocked lake trout Splake Longnose sucker Spoonhead sculpin

1973–1978 (N 5 233) 124.8 0.2 0.2 0.3 0.3 0.0 0.1 0.1

6 6 6 6 6 6 6 6

20.8 0.7 0.6 0.8 0.9 0.1 0.5 0.4

1979–1988 (N 5 390) 121.8 0.8 0.4 0.4 0.1 0.2 0.1 0.1

6 6 6 6 6 6 6 6

25.8 3.0 1.1 1.4 0.5 0.5 0.5 0.4

ANOVA

1989–1996 (N 5 312) 117.2 1.0 1.3 0.0 0.4 0.1 0.1 0.4

6 6 6 6 6 6 6 6

16.9 3.4 2.2 0.2 0.9 0.3 0.3 1.0

Mean square df 0.05 4.21 6.11 1.57 0.73 0.44 0.04 1.30

2 2 2 2 2 2 2 2

F

P

0.03 13.96 43.12 19.38 12.45 23.50 1.67 27.26

.0.05 ,0.001 ,0.001 ,0.001 ,0.001 ,0.001 .0.05 ,0.001

Bonferroni paired comparisons 78–88 89–96 73–78 73–78 79–88

and 89–96 . 73–98 . 79–88 . 73–78 and 79–88 . 89–96 and 89–96 . 79–88 . 89–96 . 73–78

89–96 . 73–78 and 79–88



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associations. Transactions of the American Fisheries Society 119:741–756. Jackson, J. E. 1991. A user’s guide to principal components. Wiley, New York. Keim, S. A., and S. R. Hulse. 1997. Wisconsin’s Lake Superior salmonid stocking summary. Wisconsin Department of Natural Resources, Bureau of Fisheries Management and Habitat Protection, Madison. MacCallum, W. R., S. T. Schram, and R. G. Schorfhaar. 1994. Other species. Pages 63–76 in M. J. Hansen, editor. The state of Lake Superior in 1992. Great Lakes Fishery Commission, Special Publication 94–1, Ann Arbor, Michigan. MacCallum, W. R., and J. H. Selgeby. 1987. Lake Superior revisited 1984. Canadian Journal of Fisheries and Aquatic Sciences 44(Supplement 2):23–36. Odum, E. P. 1969. Fundamentals of ecology. Saunders, Philadelphia. Ragotzkie, R. A., W. F. Ahrsbrak, and A. Synowiec. 1969. Summer thermal structure and circulation of Chequamegon Bay, Lake Superior—a fluctuating system. Proceedings of conference on Great Lakes Research. 12:686–704. Selgeby, J. H., C. R. Bronte, and J. W. Slade. 1994. Forage species. Pages 53–62 in M. J. Hansen, editor. The state of Lake Superior in 1992. Great Lakes Fishery Commission, Special Publication 94–1, Ann Arbor, Michigan. Spangler, G. R., K. H. Loftus, and W. J. Christie. 1987. Introduction to the international symposium on stock assessment, and yield prediction (ASPY). Canadian Journal of Fisheries and Aquatic Sciences 44(Supplement 2):7–9. Steedman, R. J., and H. A. Regier. 1987. Ecosystem science for the Great Lakes: perspectives on degradative and rehabilitative transformations. Canadian Journal of Fisheries and Aquatic Sciences 44(Supplement 2):95–103. Zar, J. H. 1984. Biostatistical analysis. Prentice-Hall, Englewood Cliffs, New Jersey.

Appendix follows

372

HOFF AND BRONTE

Appendix: Fish Data TABLE A.1.—Abundances of 21 fish taxa captured with bottom trawls at 39 stations, pooled across years, from annual midsummer sampling in Chequamegon Bay, 1973–1996. Station


Depth Number (m)

Black bullhead

Silver redhorse

Emerald shiner

Spottail shiner

Mimic shiner

Bluntnose Rock minnow bass

Smallmouth bass

Johnny darter

Logperch

Yellow perch

Walleye

300 301 302 303 304

3 18 15 6 5

0 0 0 0 1

0 0 0 0 2

3 0 0 4 25

115 5 2 304 118

1 0 0 4 8

0 0 0 0 0

1 0 0 1 0

1 0 0 0 0

197 1 1 15 11

0 0 0 3 4

166 19 3 495 228

0 0 0 3 2

305 306 307 308 309

5 4 3 2 3

1 0 22 126 3

3 2 2 7 7

30 9 1,838 146 293

499 165 3,456 1,753 562

42 15 4,166 5,699 165

0 0 14 287 0

0 3 11 134 1

1 0 4 205 7

136 132 288 1,329 34

11 11 12 140 21

770 367 18,562 6,848 193

4 4 23 66 9

310 311 312 313 314

4 5 6 9 13

0 0 0 0 0

7 0 0 0 0

48 2 6 8 26

322 87 84 485 38

85 11 8 3 0

0 0 0 0 0

0 1 0 0 1

2 0 0 0 0

48 101 15 7 1

7 2 0 1 0

627 889 681 160 20

4 8 5 2 0

315 316 317 318 319

15 6 5 4 5

0 0 0 0 0

0 0 0 2 0

0 12 2 53 59

9 159 35 281 690

3 9 9 13 11

0 0 0 0 0

0 0 1 0 6

0 1 0 0 5

1 20 90 215 140

0 2 0 2 4

0 574 914 953 723

0 4 14 21 11

320 321 322 323 324

3 2 5 6 9

7 25 1 0 0

7 11 0 0 0

441 3,384 42 88 17

4,648 3,162 2,857 160 55

374 989 46 4 3

0 5 0 0 0

4 10 2 0 0

21 107 11 0 0

269 465 244 16 0

12 56 74 0 0

3,500 3,200 1,045 216 52

106 32 39 8 0

325 326 327 328 329

10 2 8 6 6

0 4 0 1 0

0 9 0 1 0

21 3,238 61 102 22

341 3,878 93 681 49

1 363 1 8 2

0 0 0 0 0

0 23 0 1 0

0 27 0 0 0

3 514 5 101 6

1 50 0 1 0

222 4,550 174 895 191

1 42 0 60 2

330 331 332 333 334

3 6 5 4 7

0 0 0 0 1

0 0 0 0 0

39 13 116 296 59

628 230 856 728 216

17 25 30 8 61

0 0 0 0 0

0 0 1 0 0

0 0 1 2 0

379 22 182 159 2

1 0 0 1 0

168 319 487 686 137

38 14 14 57 19

335 336 337 338

5 5 3 2

0 6 0 7

0 0 25 6

1,228 5,155 241 1,308

907 4,172 44 2,765

24 458 159 2,483

0 0 0 0

0 1 0 0

0 1 4 49

45 441 62 266

4 7 39 23

248 1,337 275 1,688

21 80 3 21

205

91

18,435

35,639

15,308

306

202

449

5,963

489

52,582

737

Total

373


TABLE A.1.—Extended.

Station


Depth Number (m)

Rainbow smelt

Lake herring

Lake whitefish

Bloater

Stocked lake trout

Splake

Longnose Spoonhead Mottled sucker sculpin sculpin

300 301 302 303 304

3 18 15 6 5

10,203 7,092 18,500 104,064 51,225

11 1,159 1,653 2,522 120

8 383 229 29 15

4 81 252 12 20

1 89 30 5 3

1 8 6 3 3

14 10 1 4 1

18 52 13 4 6

0 0 0 0 0

305 306 307 308 309

5 4 3 2 3

62,177 22,549 6,330 76 831

1,068 388 0 0 1

21 16 0 0 22

4 1 0 0 0

1 0 1 0 0

0 2 0 0 0

0 1 0 0 0

0 1 0 0 0

0 0 0 0 0

310 311 312 313 314

4 5 6 9 13

3,455 27,217 43,185 82,871 21,715

0 385 1,319 301 1,885

25 72 22 111 116

0 1 41 70 233

4 3 123 12 56

0 0 13 13 4

2 1 2 2 11

1 1 1 4 22

0 0 0 0 0

315 316 317 318 319

15 6 5 4 5

26,631 107,813 47,084 11,410 29,065

584 179 145 4 0

118 30 4 1 0

125 47 23 0 0

79 10 3 0 1

6 11 3 1 2

14 6 2 0 1

58 7 7 0 1

0 0 0 0 0

320 321 322 323 324

3 2 5 6 9

2,194 3,094 33,551 60,362 58,129

0 0 0 37 493

0 0 15 10 71

0 0 0 2 18

0 0 0 7 33

1 0 0 5 10

0 0 0 1 6

0 0 0 7 36

0 0 0 0 0

325 326 327 328 329

10 2 8 6 6

50,527 1,226 76,571 83,108 69,321

492 0 260 214 842

129 2 321 50 206

33 0 60 4 132

36 0 50 12 34

33 1 20 5 5

12 0 33 2 11

46 0 38 5 22

2 0 2 1 1

330 331 332 333 334

3 6 5 4 7

19,634 104,857 113,494 75,084 65,234

77 589 112 101 22

21 90 19 34 79

2 89 12 33 28

3 24 12 6 25

2 4 8 3 8

2 26 33 8 11

1 47 11 0 70

0 1 1 0 1

335 336 337 338

5 5 3 2

79,331 49,627 637 112

34 4 0 0

16 1 4 1

6 2 0 0

9 1 0 0

4 0 0 0

8 1 0 0

40 3 0 0

0 4 0 0

1,629,586

15,001

2,291

1,335

673

185

226

522

13

Total