Transactions of the American Fisheries Society 133:984–1003, 2004 q Copyright by the American Fisheries Society 2004
Spatial Variation in Fish Species Richness of the Upper Mississippi River System TODD M. KOEL*1 Minnesota Department of Natural Resources, Mississippi Monitoring Station, 1801 South Oak Street, Lake City, Minnesota 55041, USA; and U.S. Geological Survey, Upper Midwest Environmental Sciences Center, La Crosse, Wisconsin 54603, USA Abstract.—Important natural environmental gradients, including the connectivity of off-channel aquatic habitats to the main-stem river, have been lost in many reaches of the upper Mississippi River system, and an understanding of the consequences of this isolation is lacking in regard to native fish communities. The objectives of this study were to describe patterns of fish species richness, evenness, and diversity among representative habitats and river reaches and to examine the relationship between fish species richness and habitat diversity. Each year (1994–1999) fish communities of main-channel borders (MCB), side channel borders (SCB), and contiguous backwater shorelines (BWS) were sampled using boat-mounted electrofishing, mini-fyke-nets, fyke nets, hoop nets, and seines at a standardized number of sites. A total of 0.65 million fish were collected, representing 106 species from upper Mississippi River Pools 4, 8, 13, and 26; the open (unimpounded) river reach; and the La Grange Reach of the Illinois River. Within pools, species richness based on rarefaction differed significantly among habitats and was highest in BWS and lowest in MCB (P , 0.0001). At the reach scale, Pools 4, 8, and 13 consistently had the highest species richness and Pool 26, the open-river reach, and the La Grange Reach were significantly lower (P , 0.0001). Species evenness and diversity indices showed similar trends. The relationship between native fish species richness and habitat diversity was highly significant (r2 5 0.85; P 5 0.0091). These results support efforts aimed at the conservation and enhancement of connected side channels and backwaters. Although constrained by dams, pools with high native species richness could serve as a relative reference. The remnants of natural riverine dynamics that remain in these reaches should be preserved and enhanced; conditions could be used to guide restoration activities in more degraded reaches.
Large flood plain rivers are among the most biologically productive and diverse ecosystems on Earth (Tockner and Stanford 2002). These ecosystems are threatened in North America and elsewhere due to habitat alterations, altered hydrologic regimes, exotic species invasions, and other stressors. Natural disturbance regimes and environmental gradients are required to maintain river–flood plain connectivity and habitat heterogeneity (Sparks et al. 1990; Ward 1998). Fish communities are an integral component of flood plain systems, helping to maintain ecosystem function and resilience and also supporting regionally and economically important fisheries (Holmlund and Hammer 1999). As North America’s temperate freshwater ecosystems are being depleted of species as rapidly as tropical forests (extinction rate of 4% per decade; Ricciardi and Rasmussen 1999), it is imperative that we better understand the spatial and temporal structure of our imperiled fish communities. * Corresponding author:
[email protected] 1 Present address: National Park Service, Center for Resources, Fisheries and Aquatic Sciences Section, Post Office Box 168, Yellowstone National Park, Wyoming 82190, USA. Received May 13, 2003; accepted January 14, 2004
The upper Mississippi River system (UMRS) is arguably the most biologically productive and economically important large flood plain river system in the United States. The UMRS extends from the confluence with the Ohio River upstream to St. Anthony Falls and includes the Illinois River (Figure 1). In 1986, the U.S. Congress designated the UMRS as a nationally significant ecosystem and a nationally significant commercial navigation system (McGuiness 2000). Although partially constrained by a series of locks and dams created mostly in the 1930s, the UMRS still retains some of its original character. The dynamic nature of longitudinal and lateral river flows throughout the flood plain have created a diversity of terrestrial and aquatic habitat types. The resulting flow of energy within this system is also spatially and temporally dynamic (Vannote et al. 1980; Junk et al. 1989; Thorp and Delong 1994; Johnson et al. 1995). During large floods, the flood plains of the Mississippi and Illinois rivers become part of the flowing river itself, conveying water slowly downstream through forests and marshes (Sparks 1995). Unless restricted by levees (constructed to isolate areas of the flood plain from the main-stem river), fishes have access to numerous primary and secondary channels and a variety of off-channel back-
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SPECIES RICHNESS OF THE MISSISSIPPI RIVER
FIGURE 1.—The upper Mississippi River system with the trend pools used to assess fish species richness. The upper and lower river kilometers (Rkm) are the locations of the upstream and downstream ends of the trend pools, respectively. For the upper Mississippi River, Rkm 0 occurs at the confluence with the Ohio River; for the Illinois River, Rkm 0 occurs at the confluence with the Mississippi River.
water lakes, sloughs, and ponds. These habitats and natural river flows (Poff et al. 1997) provide a variety of lentic and lotic conditions to support a diversity of fish species, many with highly specific life history strategies. Many UMRS fish species move among various habitats throughout the year to complete their life cycles. Even the main navigation channel, which is often dominated by powerful towboats, supports unique and highly productive fish communities (Galat and Zweimuller 2001; Dettmers et al. 2001a, 2001b). However, the unnatural hydrologic regimes caused by operations of locks and dams to support commercial navigation may result in increased numbers of undesired, tolerant, generalist fish species and heightened success of exotic fish invaders (Koel and Sparks 2002). The enhanced ecological integ-
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rity gained by naturalizing river flows should be beneficial for native species (Welcomme 1995). Recent significant invasions by aquatic exotic species have added additional stress to an already imperiled UMRS. The zebra mussel Dreissena polymorpha has resulted in the near extinction of several native mussel species (Ricciardi et al. 1998; Strayer 1999). Asian carp populations, including grass carp Ctenopharyngodon idella, silver carp Hypophthalmichthys molitrix, and bighead carp H. nobilis, are increasing and threaten many native fishes (Raibley et al. 1995; Pegg et al. 2002). Altered flow regimes facilitate the invasion and success of exotic and introduced species in rivers (Bunn and Arthington 2002). Additionally, the proposed modification to many UMRS locks and dams may result in an increase in commercial navigation and, in turn, the many impacts that result from this activity, including habitat degradation by dredge material placement (Koel and Stevenson 2002) and the loss of fish due to entrainment by towboats (Gutreuter et al. 2003). As UMRS stressors increase, it is imperative that we understand the potential value of channel and off-channel contiguous habitats and their use by native fish communities. The overall goal of the present study was to document systemic-level spatial patterns in fish species richness of the UMRS as determined by the multiple-gear-type approach of the Long Term Resource Monitoring Program (LTRMP; U.S. Fish and Wildlife Service 1993). The study is required as various ecosystem stressors threaten to further alter the structure of fish communities and natural ecosystem processes of the UMRS. Specific study objectives were to (1) describe patterns of fish species richness among representative aquatic habitats and river reaches using a standardized method, (2) determine overall trends in fish species evenness and diversity among habitats and river reaches, and (3) examine the relationship between fish species richness and habitat diversity of river reaches. Study Areas Navigation pools.—The UMRS is fragmented by a series of locks and dams used to maintain a 2.7m-deep channel for commercial navigation. The areas between two successive locks and dams are commonly referred to as navigation ‘‘pools.’’ In general, these pools are characterized by having an upper, riverine reach that is somewhat representative of the predam river, and a lower, lacustrine reach that is atypical of the predam river (U.S. Geological Survey 1999). Only where tributaries created large alluvial fans do natural impoundments occur on the UMRS (Lake Pepin of the Mississippi River and the Peoria Lakes of the Illinois
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TABLE 1.—Surface area (ha) of aquatic–geomorphic habitats for upper Mississippi River Pools 4, 8, 13, and 26; the open-river reach (OR); and the La Grange Reach of the Illinois River (LG). Aquatic habitats were the main navigation channel (MNC), main-channel border (MCB), tailwater (TWZ), secondary channel (SCH), tertiary channel (TCH), tributary channel (TRC), contiguous floodplain lake (CFL), contiguous floodplain shallow aquatic area (CFS), contiguous impounded area (CIM), terrestrial island (TIS), and contiguous terrestrial floodplain (CTF), with the total contiguous habitat area (TOC). H9 is Shannon’s index of aquatic area diversity. Data are from the habitat needs analysis for the upper Mississippi River system (DeHaan et al. 2000). Trend pool 4 8 13 26 OR LG
Aquatic habitat MNC
MCB
TWZ
SCH
TCH
TRC
CFL
CFS
CIM
TIS
CTF
TOC
H9
1,093 627 1,569 1,467 1,509 2,359
448 603 1,141 2,875 2,828 0
12 21 20 28 0 0
463 510 789 1,483 261 178
2 1 105 14 0 3
97 30 32 51 67 278
10,320 1,125 1,242 409 103 5,573
1,567 1,573 1,902 0 0 103
408 4,024 3,556 245 0 0
1,848 2,966 2,414 2,530 451 1,112
8,438 3,478 8,494 18,663 14,880 19,703
24,695 14,957 21,262 27,764 20,099 29,309
1.48 1.84 1.81 1.16 0.88 1.01
River). River pools and reaches used for fish community assessment included Pools 4, 8, 13, and 26; the unimpounded Mississippi River (open-river reach); and the La Grange Reach of the Illinois River (Figure 1). These river areas are the six regional trend analysis areas (trend pools) of the LTRMP chosen for intensive physical, chemical, and biological sampling to monitor the ecological status and trends of the UMRS (U.S. Fish and Wildlife Service 1993). Aquatic habitats.—Main-channel borders (MCB), side- (secondary) channel borders (SCB), and contiguous backwater shorelines (BWS; Wilcox 1993) were chosen for fish community assessment. These habitats were chosen because they are (1) representative of the predam river system and should theoretically support naturally occurring, large flood plain river fish communities and (2) present in all trend pools, making systemic-level comparisons among trend pools a possibility (with one exception: since backwaters have been isolated by levees from most of the unimpounded Mississippi River, there were no significant contiguous backwater habitats to sample at the open-river reach). The total area of contiguous aquatic habitats for trend pools are provided in Table 1 (DeHaan et al. 2000; Koel 2001) Methods Sampling Design Spatially randomized fish collections, stratified by natural aquatic–geomorphic habitats, were completed in all six LTRMP trend pools (Gutreuter et al. 1995). Fish collections were made during each of three seasonal time periods: period 1 (June 15–July 31), period 2 (August 1–September 15), and period 3 (September 16–October 31). For this study, a standardized total of 12 electrofishing, 12 mini-fyke-net, 18 fyke net, 24 hoop net, and 12
seine collections were randomly selected from each habitat, trend pool, and year, 1994–1999. Gear Protocols Electrofishing was conducted in MCB, SCB, and BWS using a boat-mounted, 3000-W, pulsed-DC electrofisher with two netters during daylight hours and standardized electrofishing power (Burkhardt and Gutreuter 1995). Mini-fyke-nets (3-mm-bar mesh) were set in MCB, SCB, and BWS for 24 h and had a 4.5-m lead (0.6 m high) attached to a 0.6-m 3 1.2-m frame with a 0.6-mdiameter cab; the frame and cab were 3 m long when fully extended. Fyke nets (1.8-cm-bar mesh) were set in BWS for 24 h and had a 15-m lead (1.3 m high) and a 0.9-m 3 1.8-m frame with a 0.9-m-diameter cab; the frame and cab were 6 m long when fully extended. The hoop nets were set in MCB and SCB by paired deployment of a small baited hoop net (3 m long, 0.6 m in diameter decreasing by 2.5 cm incrementally toward the cod end, 1.8-cm-bar mesh) and a large baited hoop net (4.8 m long, 1.2 m in diameter, decreasing by 2.5 cm incrementally toward the cod end, 3.7-cm-bar mesh) set parallel to the shoreline for 48 h. Seine nets (3-mm mesh) were 10.7 m long and 1.8 m high, with a square bag measuring 0.9 m on each side located in the center of the net. Seine hauls were made in MCB, SCB, and BWS in water less than 1.2 m deep, with one end anchored to the bank and the other deployed perpendicular to the bank and swept around a 908 arc (quarter haul) to the shoreline in the downstream direction. Samples by all gears were made through a wide range of river stage (flow) conditions. Deviations to basic gear allocations are presented in the Appendix. Data Analyses Species abundance model.—A Whittaker plot (Krebs 1999) of log10 abundance versus species
SPECIES RICHNESS OF THE MISSISSIPPI RIVER
rank was constructed to determine the shape of the dominance–diversity curve of UMRS fish communities. From this plot, the appropriate model of species abundance relations could be selected. The lognormal distribution (species–abundance curve) describing fish communities was fit using the maximum likelihood methods devised by Cohen (1959, 1961) and described by Pielou (1975). This distribution was then used to estimate the potential total number of species (ST 5 those species collected by the sampling program and the extremely rare species not yet collected) in each habitat and trend pool following the procedure of Krebs (1999). Additionally, the number of species represented by each geometric class (3X) based on total abundance (data from all samples combined) was determined to assess the proportion of species which may be rare (in low abundance) or very common (in high abundance) in a typical sample of fishes on the UMRS. For this analysis and all that follow, fish species known to be nonindigenous or exotic were not included for purposes of enhancing the interpretability of richness estimates and community metrics. Rarefaction.—All collections taken by LTRMP each year were assigned a random number and then samples were selected from this list randomly for inclusion in analyses. For each gear type, data from a standardized number of annual collections were combined to constitute a single sample for each habitat, trend pool, and year. The Hurlbert (1971) method of investigating species richness by rarefaction was used, that is,
O 51 2 [1N 2n n 2@1Nn 2]6 , S
E(S n ) 5
i
i51
where S is the total number of species, Sn is the number of species in the standardized sample of size n, N is the total number of individuals recorded, ni is the number of individuals in the ith species, and E(Sn) is the number of species that can be expected in a sample size of n individuals (Ludwig and Reynolds 1988). To make valid comparisons by this method, the size of the area covered to obtain each sample should remain relatively constant. Standardized protocols and a consistent number of electrofishing collections and/or net sets were used among habitats and trend pools and thus, except for a few cases, any effect of sampling area size on species richness was avoided to the greatest extent possible (Winston and Hawkins 1996). The Hurlbert (1971) method is less sensitive to differences in sample area sizes than other methods (Ludwig and Reynolds 1988; Ricklefs and Schluter 1993; Winston and Hawkins 1996). To develop rarefaction curves for electrofishing,
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FIGURE 2.—A Whittaker plot of the log10 transformed number of individuals of each fish species of the upper Mississippi River system in rank order with the number of fish species in each geometric (3X) class of number of individuals (geometric class I was 1–2 individuals, class II was 3–8 individuals, class III was 9–26 individuals, etc.).
mini-fyke-net, fyke net, and seine data, E(Sn) was calculated for n 5 1–1,200 individuals in increments of 10. For hoop netting data, E(Sn) was calculated for n 5 0–400 individuals in increments of 2. These were the numbers of individuals that allowed each to reach the maximum E(Sn) asymptote possible. For purposes of statistical comparisons among habitats and trend pools, E(Sn) for electrofishing, mini-fyke-net, fyke net, hoop net, and seine was calculated at a sample size of 460, 360, 220, 100, and 700 individuals, respectively. Total numbers of fish collected has varied, and these were the sample sizes that allowed for the maximum number of replicates (years) for among habitat and trend pool statistical comparisons. Statistical treatment of rarefaction estimates.— Comparisons of E(Sn) were made among habitats and among trend pools using a series of statistical tests conducted using SAS (Institute, Inc. 1999). For each gear type separately, a test of the E(Sn) frequency distribution for univariate normality was by the Shapiro–Wilk statistic W (Zar 1996). Sampling years (1994–1999) were considered replicates for model development, and the analyses assumed independence among years and across habitats within trend pools. The degree to which these assumptions were met is unknown, but violations may have occurred. The effects of habitat and trend pool on E(Sn) were determined using a three-factor analysis of variance (ANOVA; PROC GLM) with habitat (MCB, SCB, and BWS), trend pool (Pools 4, 8, 13, and 26; the open-river reach; and La Grange Reach), and gear type (electrofishing, mini-fyke-net, fyke net, hoop net, and seine) entered as the class variables for each analysis. Including gear type as a class variable al-
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TABLE 2.—Results of three-factor analysis of variance examining the significance of aquatic habitat, trend pool, sampling gear, and the interactions among these main effects on the expected species richness of upper Mississippi River system fish communities.
Source Habitat Pool Gear Habitat 3 pool Habitat 3 gear Pool 3 gear Habitat 3 pool 3 gear
df
Type IV sum of squares
Mean square
F-value
P-value
2 5 4 9 5 18 19
302.54 934.03 7,017.97 287.20 112.42 1,053.78 328.10
151.27 186.81 1,754.49 31.91 22.48 58.54 17.27
12.76 15.76 148.00 2.69 1.90 4.94 1.46
,0.0001 ,0.0001 ,0.0001 0.0051 0.0949 ,0.0001 0.1003
lowed for a synthetic measure of E(Sn) incorporating information from all gears into a single analysis for meaningful comparisons among habitats and trend pools. The hypothesis of (1) no habitat effect, (2) no pool effect, and (3) no habitat 3 pool interaction was investigated. Duncan’s tests (Zar 1996) were used to
FIGURE 3.—Expected species richness by rarefaction for upper Mississippi River system fish communities sampled by electrofishing.
determine statistical significance of differences among all habitat/pool E(Sn) means (a 5 0.05). Community heterogeneity.—To further characterize UMRS fish communities, a series of diversity and evenness indices were calculated based on all fish collections (all gear types, 1994–1999 combined) for each habitat and trend pool. The diversity indices included Simpson’s index (D; Simpson 1949), Shannon’s index (H9, natural logarithm base; Shannon and Weaver 1949), and
FIGURE 4.—Mean expected fish species richness (E[Sn]) by rarefaction (6SE) from main-channel borders (MCB), side-channel borders (SCB), and contiguous backwater shorelines (BWS) of the upper Mississippi River and Pool 4 (P4), Pool 8 (P8), Pool 13 (P13), Pool 26 (P26), the open-river reach (OR), and the La Grange Reach (LG). The total number of E(Sn) estimates on which each mean is based is in parentheses. Among aquatic habitats or among trend pools, means with different letters were significantly different (P , 0.05).
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Hill’s diversity numbers (N1 and N2; Ludwig and Reynolds 1988). The modified Hill’s ratio was used as an evenness index (E5; Ludwig and Reynolds 1988). Species richness–habitat diversity relationship.—The relationship between the diversity of contiguous habitats and native fish species richness was determined by regression. The independent variable was Shannon’s index (H9) of habitat diversity for each trend pool. Data used to calculate this index were from the Habitat Needs Assessment (HNA) query tool developed for the UMRS (DeHaan et al. 2000, Koel 2001; Table 1). Habitat surface areas were visually interpreted from 1:15,000 scale aerial photographs taken in 1989 with some degree of error and results should be interpreted with this knowledge. The dependent variable was the mean E(Sn) based on collections by all gears from all habitats and years. The hypothesis of no habitat diversity effect on fish species richness was investigated with this analysis. Results Species Abundances Collections for community assessment included 654,734 fish, representing 106 of the 139 species previously reported from the sampled trend pools (Appendix). Total fish collected by trend pool ranged from 43,189 for the open-river reach to 193,936 for the La Grange Reach (mean 5 109,122; but note that BWS were not sampled at the open-river reach). The most common species (.30,000 individuals) included gizzard shad (29%), emerald shiner (22%), bluegill (8%), freshwater drum (6%), and spotfin shiner (5%). Thirtyeight species were only rarely collected and represented by less than 100 individuals from all trend pools combined. The Whittaker (reversed S-shaped curve) and geometric classes plots indicated a lognormal species abundance distribution pattern (Figure 2). This pattern indicated that UMRS fish communities were composed of many species represented by relatively few individuals, and a few species represented by many individuals. The greatest number of species were represented by geometric classes VI and VII, 243–728 and 729–2186 individuals, respectively. The geometric classes plot suggests that in a typical sample on the UMRS, approximately 2% of the species may comprise 50% of the fishes present in the collection (in this analysis, these species were represented by geometric classes XI and XII). Estimates of ST in each habitat–trend pool by
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the lognormal model predicted a relatively high total number of species in all areas; estimates ranged from 54 species in BWS of Pool 26 to 98 species in MCB of the open-river reach (Appendix). The actual observed species richness (So) based on all samples (all years/gears) in each habitat–trend pool varied from ST the most in MCB of the open-river reach. Expected Species Richness Rarefaction curves of E(Sn) (e.g., see Figure 3) varied among gears, with electrofishing providing the greatest consistency and overall ability to detect differences among habitats and pools. When considering fish collections from all trend pools and gear types combined, a significant difference in mean E(Sn) was noted among habitats (P , 0.0001; Table 2). Mean E(Sn) was 21.6 in BWS, 18.0 in SCB, and 16.4 in MCB habitats (Figure 4). At the reach scale, when considering fish collections from all habitats and gear types combined, a significant difference in mean E(Sn) was noted among trend pools (P , 0.0001). Mean E(Sn) was higher in Pools 4, 8, and 13 than in Pool 26, the open-river reach, or the La Grange Reach and ranged from 21.3 in Pool 8 to 15.7 in the openriver reach (Figure 4). Furthermore, E(Sn) of a particular aquatic habitat type was somewhat dependent on trend pool (and vice versa) as the interaction between these two variables was significant (P 5 0.0051; Table 2). The interaction was investigated by examining a habitat 3 pool E(Sn) means matrix. Within all trend pools, a similar pattern in mean E(Sn) was noted among habitats with MCB being consistently lowest, except at Pool 13 where mean E(Sn) of SCB was lowest. For each of the three habitat types, a similar pattern in mean E(Sn) was noted among pools, with the La Grange Reach being consistently lowest, except in BWS where mean E(Sn) at Pool 26 was lowest. Community Heterogeneity Species diversity and evenness indices based on collections of native UMRS fishes by all gears, 1994–1999, indicated a high degree of variation across habitats and trend pools (Appendix; Figure 5). In most cases, however, fish communities of MCB exhibited the lowest species diversity and evenness. For example, in the La Grange Reach of the Illinois River, Simpson’s diversity index (D), Shannon’s diversity index (H9), and modified Hill’s ratio (E5) was 0.31, 0.83, and 0.34 in MCB, compared with 0.66, 1.75, and 0.41 in SCB and 0.84, 2.38, and 0.52 in BWS, respectively. Across trend pools, species diversity and evenness indices were generally high in Pool 8 and
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FIGURE 5.—The potential total number of fish species (ST) in each habitat and trend pool as derived from the lognormal species abundance model. Diversity indices included Simpson’s index (D), Shannon’s index (H9), and Hill’s numbers (N1 and N2). The evenness index was the modified Hill’s ratio (E5). See the caption to Figure 4 for habitat and trend pool designations.
FIGURE 6.—Relationship between habitat diversity (Shannon’s index, H9) and the mean expected fish species richness (E[Sn]) based on fish collections in mainchannel borders, side-channel borders, and contiguous backwater shorelines of six trend pools, 1994–1999, for multiple gear types on the upper Mississippi River system.
Pool 13 and especially low in Pool 4 (MCB and SCB) and the La Grange Reach (Appendix; Figure 5). In MCB, Hill’s effective number of species N1 and N2 were 9.65 and 5.78 in Pool 8 and 9.33 and 5.74 in Pool 13, compared with 3.73 and 1.81 in Pool 4 and 2.30 and 1.45 in the La Grange Reach, respectively. In SCB, Hill’s effective number of species N1 and N2 was 13.88 and 7.67 in Pool 8 and 12.60 and 7.61 in Pool 13, compared with 4.15 and 1.96 in Pool 4 and 5.78 and 2.96 in the La Grange Reach, respectively. Fish species diversity and evenness indices of BWS were consistently lower in Pool 26 than in other trend pools. Regression analysis identified a significant relationship between the diversity of trend pool contiguous habitats (H9) and native fish E(Sn) (Figure 6). As aquatic habitat diversity of trend pools increased, the mean E(Sn) of fish communities also increased (P 5 0.0091).
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Discussion Species richness by the rarefaction method provided a means for comparing this important metric among aquatic habitats and trend pools even though there has been a high degree of variability in the sample sizes (catch) for each. The estimates of E(Sn) were based on 0.65 million fish representing 106 species over a period of 6 years. Information of this magnitude should be representative of the fish communities found in the riverine habitats of the six trend pools studied. This should be especially true given that a multiple gear-type approach was used. Trends as presented should be interpreted with consideration of the sampling bias (i.e., toward fishes of a particular species or size) that is normally associated with each specific gear type. In addition, statistical power to detect change is different among gear types and is known to vary among habitats and trend pools (Lubinski et al. 2001). Chick and Pegg (2002) described the need for at least 2,000 individuals to effectively estimate fish species richness of LTRMP trend pools. Computation of community heterogeneity indices (including ST, diversity, and evenness) were based on more than 15,000 individuals collected by several gear types; these indices should theoretically be highly representative of the fish communities in these trend pools. One assumption made by rarefaction is that conspecifics (individuals within a species) are randomly dispersed and that species are dispersed independently (intra- and interspecific dispersion patterns are both random; Collins 1998; Krebs 1999). Clumping of individuals and species is typical of fish communities. The clumping tends to overestimate species richness by the rarefaction method, and the only way to reduce this bias is to use large samples spread widely throughout the community (Krebs 1999); any missing samples (see gear allocation summary, Appendix) may have inflated E(Sn) as calculated by rarefaction in this study. Additionally, statistical comparisons of species richness among habitats and trend pools were made by the use of type IV sums of squares in ANOVA. This was done due to missing cells in these data, but caution in interpretation is advised. Although the results of these analyses are probably robust and not greatly affected, the type IV hypotheses are dependent upon the pattern of the filled cells and not necessarily upon the statistician; variation in the input of the data can slightly change the results of analyses in these instances (Searle 1987; SAS Institute, Inc. 1999). Habitat Scale Influences on Species Richness Of great importance was the finding of significant differences in native fish species richness among
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the river–flood plain habitats of the UMRS. Results showed that SCB and the off-channel, contiguous BWS had higher species richness than MCB habitats. Also, community heterogeneity indices indicated high ST, species diversity, and evenness in many SCB and BWS habitats. This is significant because the UMRS has lost a great amount of SCB and BWS habitats due to the construction of locks, dams, and other structures to support commercial navigation (U.S. Geological Survey 1999). The locks and dams have created large, unnatural impounded areas; the once diverse river–flood plain habitats no longer exist in most reaches for great distances above the dams; islands have been lost, wind and currents have redistributed sediments, and the bottom topography has been simplified (U.S. Geological Survey 1999). In addition, in the upper, riverine sections of most UMRS navigation pools, there are many places where side channel closing structures, wing dams, and revetments have diverted river flows toward the main channel and away from secondary and tertiary channels and backwaters of the flood plain (Nielsen et al. 1984). These manipulations have prevented the river–flood plain system from functioning naturally, particularly in downstream reaches of the UMRS where levees are more prominent and flood plain isolation is greatest. The distribution of levees among major UMRS river reaches is 3% for Pools 1–13, 50% for Pools 14–26, 83% for the unimpounded Mississippi River, and 60% for the lower Illinois River (C. Theiling, U.S. Army Corps of Engineers, personal communication). The ST of MCB and SCB was high relative to that of BWS in most cases; especially at the open-river reach and the La Grange Reach, ST deviated greatly from So in MCB and SCB habitats. This suggests that the potential for fish species richness is not being realized in these reaches, possibly due to these detrimental environmental factors. Other recent studies have compared species richness among habitats of the UMRS and other large-river systems. Johnson and Jennings (1998) found no difference in the species richness of small fishes (15–60 mm) by rarefaction among MCB, SCB, and BWS habitats along islands on Pools 5– 10 of the UMRS. Similarly, no difference was found in the use of larval fish in a backwater lake of Pool 8 among sites near and far from the main channel (Dewey and Jennings 1992). Instead, vegetation abundance was considered the primary factor in influencing densities of small fishes by these studies, with sites having abundant submersed vegetation supporting diverse fish communities. In contrast, flood plain aquatic habitats that maintained at least a seasonal, natural connectivity to the main-stem Missouri River were shown to sup-
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KOEL
port twice as many fish species as those which remained isolated; adult fish assemblages were similar, but the composition of larval and juvenile fishes were markedly different between connected and isolated basins (Galat et al. 1998). On the UMRS, backwaters are known to be important nursery areas for many fish species (Holland and Huston 1985; Holland 1986, Sheaffer and Nickum 1986; Zigler and Jennings 1993). In the present study, small-bodied fishes were primarily collected by mini-fyke-nets and seines; comparisons by mini-fyke-nets did not indicate differences among habitats. However, E(Sn) by seining was lower in MCB than in SCB or BWS habitats. Reach Scale Influences on Species Richness Pools 4, 8, and 13 consistently had the highest fish species richness; species richness of Pool 26, the open-river reach, and the La Grange Reach was significantly lower. Of considerable interest, however, was the low overall diversity and evenness of Pool 4 (in MCB and SCB) by comparison to that of Pools 8 and 13, not detected by comparison of species richness by rarefaction. The low diversity in MCB and SCB habitats of Pool 4 appears to be driven by low evenness, as the 63 and 64 species collected in these areas, respectively, are comparable to the other trend pools. Emerald shiner, a pelagic planktivore found in large lakes and rivers, comprised 72% of the total catch in these habitats, and most other species were collected in relatively low abundance by comparison. Lake Pepin was not sampled by LTRMP and possibly represents a significant source of emerald shiner collected in the riverine habitats upstream and downstream. Emerald shiners are the second most abundant species sampled by shoreline seining in Lake Pepin by the Minnesota Department of Natural Resources (Hoxmeier 2003). Flood plain isolation and highly altered hydrologic regimes are likely causes of the low native fish species richness of Pool 26 and the open-river reach. The water levels of Pool 26 are managed using a midpool control point, resulting in drawdown near the dam of up to 1.8 m during periods of moderate to high river discharge. These drawdowns dewater extensive shallow areas in the downstream half of the pool, effectively reversing the stage-to-discharge relationship of the hydrologic regime (simulating a drought when the system is experiencing natural floods). Much of the flood plain has been isolated from the main-stem river in Pool 26 and the open-river reach; fewer fish species were collected in the remaining contiguous BWS of Pool 26 (So 5 51) than in all other trend pools and habitats; the potential total number
of species here as predicted by the lognormal model was also low (ST 5 54). These backwaters are silt laden and have low abundances of submersed aquatic vegetation (Yin et al. 2001). Also, in several areas, side channels have been ‘‘closed’’ by the U.S. Army Corps of Engineers to divert river flows toward the main channel; these side channels have acted as sediment traps and lost their integrity (Simons et al. 1975). The life history patterns of many UMRS fish species require that the annual hydrologic regime occur naturally with a predictable spring flood (Junk et al. 1989). Many of the species also require a diversity of interconnected off-channel habitats; disturbance by pool drawdown has the potential to strand fishes in backwater areas. The losses of secondary channels and backwaters have likely influenced the low species richness, evenness, and diversity detected by the present study in Pool 26 and the open-river reach. The La Grange Reach of the Illinois River was also low in native fish species richness. While water level variability and flood plain isolation have had significant impacts in this trend pool, agricultural runoff of sediments and pesticides have also likely had profound effects here. Agriculture presently dominates approximately 60% of the UMRS landscape (U.S. Geological Survey 1999) but is especially prevalent in the Illinois River watershed. At the La Grange Reach, relatively large tributaries (e.g., the Mackinaw and Spoon rivers) enter and deliver heavy sediment loads and other agriculturally derived influences (Soballe et al. 2002). High ambient suspended solids, limited underwater light, and high water content sediments, combined with extremely unpredictable and widely fluctuating water levels (Koel and Sparks 2002), have resulted in the suppression of submersed aquatic vegetation in the La Grange Reach (Yin et al. 2001). The average volume loss of Illinois River backwaters is 75%, and remaining backwaters are projected to fill over the next 50–100 years (Bellrose et al. 1983; Demissie et al. 1992). The La Grange Reach contrasts with that of Pools 4, 8, and 13, which are in a region of the UMRS that is moderate in its degrees of pollution and agricultural runoff effects, side channel and flood plain isolation, hydrologic alteration, and invasive species impacts (U.S. Geological Survey 1999). A recent comparative study on the sediment dynamics of Pool 13 and the La Grange Reach indicated that Pool 13 exported nearly all the sediment that entered from upstream and tributary sources. The La Grange Reach, with a watershed one-third the size of Pool 13 and a discharge less than half that of Pool 13, received almost one-and-one-half times the suspended sediment and stored a signif-
SPECIES RICHNESS OF THE MISSISSIPPI RIVER
icant portion of it (U.S. Geological Survey 1999). Trend Pools 4, 8, and 13 have retained a great amount and diversity of habitats, possibly explaining the higher native fish richness, evenness, and diversity of these reaches. Implications for Monitoring The results of this study highlight the importance and benefits of coordinated, consistent monitoring among state and federal agencies. Bonar and Hubert (2002) called for the standardization of protocols for sampling inland fish populations. The LTRMP provides an excellent example of such a standardized program, developed and maintained by five state and two federal agencies. A multiple gear-type approach was invaluable for examining patterns in species richness among habitats and trend pools of the UMRS. The shapes of the Whitaker and geometric classes plots indicated adequate sample sizes for these broad spatial and temporal comparisons. In several cases, however, E(Sn) (as detected by LTRMP gears each year) has not been reaching asymptote (e.g., Pool 13, SCB by electrofishing). This may reflect an effect of water year and flow conditions on gear efficiency and resulting catch as the LTRMP fish collections are made through a wide range of hydrologic and thermal conditions. The program may benefit by implementing river stage–flow criteria to reduce catch variation caused by these factors. Conclusions This study demonstrates the need for restoring, preserving, and/or enhancing UMRS secondary channel and contiguous backwater habitats because of their fish species richness and their interaction with the main channel. Of the trend pools considered by this study, evidence based upon fish communities suggests that the priorities for river–flood plain restoration activities should target Pool 26, the open-river reach, and the La Grange Reach. This would likely include activities within the watershed; agricultural practices have disrupted the magnitude and frequency of large floods and accelerated the delivery of agriculturally derived sediment to floodplain and backwater environments of the UMRS (Knox 2001). Reestablishing the functional heterogeneity (e.g., hydrologic and successional processes) across the river–flood plain corridor could serve as a focus of river conservation activities (Ward and Tockner 2001). The life cycles of many large river fishes rely upon a dynamic river–flood plain landscape; in many cases, the alteration of habitat use corresponds to the rise and fall of the flood (Robinson et al. 2002). Although constrained by dams, trend Pools 4, 8, and 13 (where fish communities
993
demonstrated the highest ecological integrity) could serve as a relative reference condition. There are remnants in these pools of natural habitat variability, environmental gradients, lateral migratory pathways, and overall riverine dynamics that should be preserved and enhanced; these conditions could be used to guide restoration activities in more degraded reaches. Acknowledgments During the period that fish collections were made and the author was with the LTRMP, Field Station Team Leaders providing overall support were K. Douglas Blodgett, Terry Dukerschein, Robert Hrabik, Timothy Mihuc, Walter Popp, and Mike Steuck. Fisheries Specialists that led sampling efforts were Andy Bartels, Mel Bowler, Frederick Cronin, Steve Delain, David Herzog, Kevin Irons, Eric Kramer, T. Matt O’Hara, Michael Petersen, Eric Ratcliff, Dirk Soergel, and Mark Stopyro. Thanks also to the many fisheries technicians, interns, and volunteers that worked countless hours collecting, recording, archiving, and verifying the LTRMP fisheries data. Randy Burkhardt served as fish component leader. David Hansen was fisheries database manager. This research was supported by the Illinois Natural History Survey, the Iowa Department of Natural Resources, the Minnesota Department of Natural Resources, the Missouri Department of Conservation, the U.S. Geological Survey Upper Midwest Environmental Sciences Center, the U.S. Army Corps of Engineers, and the Wisconsin Department of Natural Resources, through the Environmental Management Program for the Upper Mississippi River System (INT 1445-98-HQAG2003). Special thanks to the many river professionals that reviewed an earlier draft of this manuscript. This research would not have been accomplished without the kind support provided by Walter Popp and all the staff of the Mississippi Monitoring Station, Lake City, Minnesota. References Bellrose, F. C., S. P. Havera, F. L. Paveglio, Jr., and D. W. Steffeck. 1983. The fate of lakes in the Illinois River valley. Illinois Natural History Survey Biological Notes 119. Bonar, S. A., and W. A. Hubert. 2002. Standard sampling of inland fish: benefits, challenges, and a call for action. Fisheries 27(3):10–16. Bunn, S. E., and A. H. Arthington. 2002. Basic principles and ecological consequences of altered flow regimes for aquatic biodiversity. Environmental Management 30:492–507. Burkhardt, R. W., and S. Gutreuter. 1995. Improving electrofishing catch consistency by standardizing
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power. North American Journal of Fisheries Management 15:375–381. Chick, J. H., and M. A. Pegg. 2002. Long Term Resource Monitoring Program outpool fisheries analysis. Final report of the Illinois Natural History Survey to U.S. Geological Survey, Biological Resources Division, Upper Midwest Environmental Sciences Center, La Crosse, Wisconsin. Cohen, A. C. J. 1959. Simplified estimators for the normal distribution when samples are singly censored or truncated. Technometrics 1:217–237. Cohen, A. C. J. 1961. Tables for maximum likelihood estimates: singly truncated and singly censored samples. Technometrics 3:535–541. Collins, M. D. 1998. The effect of spatial autocorrelation on rarefaction. Master’s thesis. University of Florida, Tallahassee. DeHaan, H. C., T. J. Fox, C. E. Korschgen, C. H. Theiling, and J. J. Rohweder. 2000. Habitat needs assessment GIS query tool users manual. U.S. Geological Survey, Upper Midwest Environmental Sciences Center, La Crosse, Wisconsin. Demissie, M., L. Keefer, and R. Xia. 1992. Erosion and sedimentation in the Illinois River basin. Illinois State Survey Water Report ILENR/RE WR 92/04, Champaign, Illinois. Dettmers, J. M., S. Gutreuter, D. H. Wahl, and D. A. Soluk. 2001a. Patterns in abundance of fishes in the main channels of the upper Mississippi River System. Canadian Journal of Fisheries and Aquatic Sciences 58:933–942. Dettmers, J. M., D. H. Wahl, D. A. Soluk, and S. Gutreuter. 2001b. Life in the fast lane: fish and food web structure in the main channel of large rivers. Journal of the North American Benthological Society 20:255–265. Dewey, M. R., and C. A. Jennings. 1992. Habitat use by larval fishes in a backwater lake of the upper Mississippi River. Journal of Freshwater Ecology 7: 363–372. Galat, D. L., L. H. Fredrickson, D. D. Humburg, K. J. Bataille, J. R. Bodie, J. Dohrenwend, G. T. Gelwicks, J. E. Havel, D. L. Helmers, J. B. Hooker, J. R. Jones, M. F. Knowlton, J. Kubisiak, J. Mazourek, A. C. McColpin, R. B. Renken, and R. D. Semlitsch. 1998. Flooding to restore connectivity of regulated, large-river wetlands. Bioscience 48:721–733. Galat, D. L., and I. Zweimuller. 2001. Conserving largeriver fishes: is the highway analogy an appropriate paradigm? Journal of the North American Benthological Society 20:266–279. Gutreuter, S., R. Burkhardt, and K. Lubinski. 1995. Long Term Resource Monitoring Program procedures: fish monitoring. National Biological Service, Environmental Management Technical Center, LTRMP 95-P002-1, Onalaska, Wisconsin. Gutreuter, S., J. M. Dettmers, and D. H. Wahl. 2003. Estimating mortality rates of adult fish from entrainment through the propellers of river towboats. Transactions of the American Fisheries Society 132: 646–661. Holland, L. E. 1986. Distribution and early life history of fishes in selected pools of the upper Mississippi River. Hydrobiologia 136:121–130.
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Strayer, D. L. 1999. Effects of alien species on freshwater mollusks in North America. Journal of the North American Benthological Society 18:74–98. Thorp, J. H., and M. D. Delong. 1994. The riverine productivity model: an heuristic view of carbon sources and organic processing in large-river ecosystems. Oikos 70:305–308. Tockner, K., and J. A. Stanford. 2002. Riverine flood plains: present state and future trends. Environmental Conservation 29:308–330. U.S. Fish and Wildlife Service. 1993. Operating plan for the Upper Mississippi River System Long Term Resource Monitoring Program. Environmental Management Technical Center, EMTC 91-P002R, Onalaska, Wisconsin. U.S. Geological Survey. 1999. Ecological status and trends of the upper Mississippi River system, 1998: a report of the Long Term Resource Monitoring Program. U.S. Geological Survey, Upper Midwest Environmental Sciences Center, LTRMP 99-T001, La Crosse, Wisconsin. Vannote, R. L., G. W. Minshall, K. W. Cummins, R. D. Sedell, and C. E. Cushing. 1980. The river continuum concept. Canadian Journal of Fisheries and Aquatic Sciences 37:130–137. Ward, J. V. 1998. Riverine landscapes: biodiversity patterns, disturbance regimes, and aquatic conservation. Biological Conservation 83:269–278. Ward, J. V., and K. Tockner. 2001. Biodiversity: towards a unifying theme for river ecology. Freshwater Biology 46:807–819. Welcomme, R. L. 1995. Relationships between fisheries and the integrity of river systems. Regulated Rivers: Research and Management 11:121–136. Wilcox, D. B. 1993. An aquatic habitat classification system for the upper Mississippi River system. U.S. Fish and Wildlife Service, Environmental Management Technical Center, EMTC 93-T003, Onalaska, Wisconsin. Winston, M. R., and C. P. Hawkins. 1996. Effects of sampling area and subsampling procedure on comparisons of taxa richness among streams. Journal of the North American Benthological Society 15:392– 399. Yin, Y., H. Langrehr, T. Blackburn, M. Moore, J. Winkelman, R. Cosgriff, and T. Cook. 2001. 1998 annual status report: submersed and rooted floating leaf vegetation in Pools 4, 8, 13, 26, and La Grange Pool of the upper Mississippi River system. U.S. Geological Survey, Upper Midwest Environmental Sciences Center, LTRMP 2001-P001, La Crosse, Wisconsin. Zar, J. H. 1996. Biostatistical analysis. Prentice-Hall, Inc., Englewood Cliffs, New Jersey. Zigler, S. J., and C. A. Jennings. 1993. Growth and mortality of larval sunfish in backwaters of the upper Mississippi River. Transactions of the American Fisheries Society 122:1080–1087.
Appendix follows
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Appendix: Species and Collection Data TABLE A.1.—The total number of individuals collected, gear allocations, and fish community metrics from mainchannel borders (MCB), side channel borders (SCB), and contiguous backwater shorelines (BWS) of upper Mississippi River Pools 4, 8, 13, and 26; the open-river reach; and the La Grange Reach of the Illinois River, 1994–1999. Metrics are as follows: So is the observed number of species; ST is the potential total number of species in the community estimated from the lognormal distribution; D is Simpson’s diversity index; H9 is Shannon’s diversity index; N1 and N2 are Hill’s effective-number-of-species indices; and E5 is the modified Hill’s ratio (evenness). Pool 4 Species and metric Petromyzontidae Chestnut lamprey Ichthyomyzon castaneus Silver lamprey I. unicuspis Acipenseridae Lake sturgeon Acipenser fulvescens Shovelnose sturgeon Scaphirhynchus platorynchus Polyodontidae Paddlefish Polyodon spathula Lepisosteidae Spotted gar Lepisosteus oculatus Longnose gar L. osseus Shortnose gar L. platostomus Amiidae Bowfin Amia calva Hiodontidae Goldeye Hiodon alosoides Mooneye H. tergisus Anguillidae American eel Anguilla rostrata Clupeidae Skipjack herring Alosa chrysochloris Gizzard shad Dorosoma cepedianum Threadfin shad D. petenense Cyprinidae Central stoneroller Campostoma anomalum Red shiner Cyprinella lutrensis Spotfin shiner C. spiloptera Blacktail shiner C. venusta Western silvery minnow Hybognathus argyritis Mississippi silvery minnow H. nuchalis Plains minnow H. placitus Speckled chub Macrhybopsis aestivalis Silver chub M. storeriana
MCB
1
SCB
1
Pool 8 BWS
MCB
SCB
Pool 13 BWS
MCB
1
7
6
11
1
3
8
11
4
4
SCB
BWS
1 1
1 1
1
1
11
8
25
27
30
103
17
9
22
7
7
57
18
20
373
48
17
233
6
29
158
4
11
155
5
1
122
6
2
2
2
1
1 7
16
2
1,125
3
7
2
1,063
1
2,430
1,761
719
2,283
1,374
536
7,657
173
7,522
8,674
5,911
619
188
172
1
2
1
2
3
5
1
115
78
1
2,538
4,198
4
231
21
34
1 2
16
5
1
190
997
SPECIES RICHNESS OF THE MISSISSIPPI RIVER
TABLE A.1.—Extended.
Open river
Pool 26 MCB
SCB
BWS
1
MCB 10
La Grange Reach
SCB
MCB
SCB
BWS
5
Total 43
1
34
1 2
2
7
1
3
2
49
4
14
4
146
163
854
1
1
51
72
22
3
64
21
1
1
1
3
1
3
23
84
14
11
9
11
21
340
95
244
53
58
566
2,959
9
2
2
54
611
783
350
7
4
3
1,245
32
19
2
3
183
1
12
190
74
12
70
11
634
89
45
1,125
9,439
6,039
14,945
5,188
7,189
89,134
22,470
14,987
188,339
5
20
34
45
22
1,137
532
386
2,181
3
3
3
3
2
13
1
6
35
88
126
11
212
1,471
125
394
113
2,540
223
940
360
1
1
31,520
13
7
20
7 88
95
8
13
47
71
7 21
24
64
36
313
1
1
2
15
16
294
19
21
84
51
12
791
998
KOEL
TABLE A.1.—Continued Pool 4 Species and metric Golden shiner Notemigonus crysoleucas Pallid shiner Notropis amnis Emerald shiner N. atherinoides River shiner N. blennius Bigeye shiner N. boops Bigmouth shiner N. dorsalis Spottail shiner N. hudsonius Silverband shiner N. shumardi Sand shiner N. stramineus Weed shiner N. texanus Mimic shiner N. volucellus Channel shiner N. wickliffi Pugnose minnow Opsopoeodus emiliae Suckermouth minnow Phenacobius mirabilis Southern redbelly dace Phoxinus erythrogaster Bluntnose minnow Pimephales notatus Fathead minnow P. promelas Bullhead minnow P. vigilax Blacknose dace Rhinichthys atratulus Creek chub Semotilus atromaculatus Catostomidae River carpsucker Carpiodes carpio Quillback C. cyprinus Highfin carpsucker C. velifer White sucker Catostomus commersoni Blue sucker Cycleptus elongatus Northern hog sucker Hypentelium nigricans Smallmouth buffalo Ictiobus bubalus Bigmouth buffalo I. cyprinellus Black buffalo I. niger Spotted sucker Minytrema melanops Silver redhorse Moxostoma anisurum
MCB
SCB
3
Pool 8 BWS
MCB
SCB
33
12
21
Pool 13 BWS
MCB
SCB
BWS
600
17
14
231
1 34,697
35,116
4,247
14,460
4,687
5,372
11,507
4,264
9,577
796
252
8
6,316
1,303
1,198
8,009
2,019
2,205
2
40
75
269
210
226
204
234
107
52
143
79
87
52
2
1
4
2
10
12
67
46
1,426
1,272
79
5,363
923
1,663
15
52
179
66
699
2,113
1
1,195
752
844
4,201
2,353
3,902
10
5
99
3 1 4
9
2 626
1,714
25
2
2
42
40
1
1
16
5
4
2
3
1
341
1,382
1,983
4,141
495
887
1,493
1
8
18
25
3
8
17
1,003
130
810
121
409
58
509
852
281
18
9
16
1
1
51
7
14
13
8
1
4
9
8
2
1
247
168
52
344
245
168
302
345
199
5
17
9
3
2
6
24
17
35
2
3
1
4
159
118
33
20
1 3
2 2
9
203
4
41
417
161
547
260
308
358
2
2
999
SPECIES RICHNESS OF THE MISSISSIPPI RIVER
TABLE A.1.—Extended (Continued) Open river
Pool 26 MCB 2
SCB 6
BWS
MCB
La Grange Reach
SCB
7
MCB
SCB
BWS
Total
45
120
258
1,369 1
2,663
4,274
1,649
940
845
7,829
3,530
1,115
146,772
372
1,447
40
247
92
3
1
48
24,356
5
5
2
44
4
5
22
60
246
17
19
7
154
1
52
47
67
1,696
334
98
70
13
997
2
7
2
27
303 141 13,517
928
2,048
95
1,102
2,428
17,057 3,238
2
6
2
1
14 1
3
8
5
6
8
35
22
4 62
184
180
20
26
15
227
1
39
91
141
511
14,277
2
1
1
5
1
2
465
3,402
1
129
105
147
125
258
81
9
10
2
2
3
3
14
2,316
2
9
85
2
79
4
4
70
3
30 1
12
941
669
439
358
313
794
921
1,363
7,868
10
12
117
8
134
99
386
801
1,685
15
38
75
66
113
23
43
57
436 837
3
18
1,777
1000
KOEL
TABLE A.1.—Continued Pool 4 Species and metric
MCB
River redhorse M. carinatum 51 Golden redhorse M. erythrurum 51 Shorthead redhorse M. macrolepidotum 271 Ictaluridae Black bullhead Ameiurus melas 1 Yellow bullhead A. natalis 1 Brown bullhead A. nebulosus Blue catfish Ictalurus furcatus Channel catfish I. punctatus 258 Stonecat Noturus flavus Tadpole madtom N. gyrinus 6 Freckled madtom N. nocturnus Flathead catfish Pylodictis olivaris 43 Esocidae Grass pickerel Esox americanus vermiculatus Northern pike E. lucius 40 Umbridae Central mudminnow Umbra limi Percopsidae Trout-perch Percopsis omiscomaycus 20 Aphredoderidae Pirate perch Aphredoderus sayanus Gadidae Burbot Lota lota Cyprinodontidae Blackstripe topminnow Fundulus notatus Poeciliidae Western mosquitofish Gambusia affinis Atherinidae Brook silverside Labidesthes sicculus 11 Gasterosteidae Brook stickleback Culaea inconstans 1 Percichthyidae White bass Morone chrysops 1,456 Yellow bass M. mississippiensis Centrarchidae Rock bass Ambloplites rupestris 115 Flier Centrarchus macropterus
SCB
Pool 8 BWS
MCB
SCB
Pool 13 BWS
MCB
SCB
BWS
41
8
5
5
2
56
51
130
169
95
10
1
2
335
201
449
434
390
112
75
91
3
7
4
45
1
62
355
59
2
1
9
1
1
1
292
32
1 1
609
870
37
641
1 11
9
7
22
42
11
29
58
25
7
52
26
53
47
31
16
40
118
8
46
176
9
9
57
120
38
1,315
150
1,398
1
40
4
1
1
6
3
1
1
2
1
7
1
58
1
202
275
2
1
727
369
1
575
682
314
1
800
856
2
197
220
73
300
38
275
4
4
4
1001
SPECIES RICHNESS OF THE MISSISSIPPI RIVER
TABLE A.1.—Extended (Continued) Open river
Pool 26 MCB
SCB
BWS
MCB
La Grange Reach
SCB
MCB
SCB
BWS
1 5
1
9
17
1
113
1
2
10
2
23
6
1
1 1
12 5
15
7
919
1,448
117
1
80
29
694
970
29
603
47
247
2,713
18
10
112
208
8
2
155
255
10
12
237
266
1 2,056
1
129
3,110
1 1
1 84
18
Total
10
10
1
129
132
49
1
132 300
12,767
1
7
2
199 22
64
23
928
1
5
7
1
504
11
65
1
1
5
9
11
2
17
12
37
79
147
114
171
5,631
11
71
167
224
1,204
7,593
30
34
25
8
26
16
80
204
2,757
6
1,039
542
757
433
1
1
9
1
271
1,780
1,223
4,711
17,769
2
3
51
108
1,192 1
1
1002
KOEL
TABLE A.1.—Continued Pool 4 Species and metric Green sunfish Lepomis cyanellus Pumpkinseed L. gibbosus Warmouth L. gulosus Orangespotted sunfish L. humilis Bluegill L. macrochirus Longear sunfish L. megalotis Redear sunfish L. microlophus Smallmouth bass Micropterus dolomieu Spotted bass M. punctulatus Largemouth bass M. salmoides White crappie Pomoxis annularis Black crappie P. nigromaculatus Percidae Western sand darter Ammocrypta clara Mud darter Etheostoma asprigene Bluntnose darter E. chlorosoma Iowa darter E. exile Johnny darter E. nigrum Yellow perch Perca flavescens Logperch Percina caprodes Blackside darter P. maculata Slenderhead darter P. phoxocephala River darter P. shumardi Sauger Sander canadensis Walleye S. vitreus Sciaenidae Freshwater drum Aplodinotus grunniens Total fish collected Percent of total Gear allocation 1994–1999 Electrofishing Mini-fyke-netting Fyke netting Hoop netting Seining Community metrics So ST D H9 N1 N2 E5
MCB
SCB
Pool 8 BWS
Pool 13
MCB
SCB
BWS
MCB
SCB
BWS
15
9
8
20
63
90
5
2
1
2
4
35
7
40
261
24
35
305
31
2
3
43
2
1
1
21
228
486
59
303
1,612
561
700
3,727
918
3,617
10,130
1,561
1,125
14,523
458
337
84
488
353
117
19
12
3
145
238
703
102
1,435
1,279
363
247
4,197
5
22
60
2
9
75
24
19
754
143
139
1,204
99
200
2,422
39
53
1,947
34
14
374
82
5
1
2
7
4
7
26
115
163
46
12
68 1
1
4
144
265
95
350
351
464
76
152
506
131
200
340
70
118
547
3
2
140
451
266
183
445
273
287
91
73
138
1
1
30
51
7
3
1
3
1
2
251
99
4
53
54
20
156
258
53
118
196
109
73
89
153
88
46
100
71
67
87
58
38
92
59
23
52
173 222 342 47,010 49,659 17,250 7.2 7.6 2.6 72 71
71 72
144 144
144 144
63 72 0.45 1.32 3.73 1.81 0.30
64 70 0.49 1.42 4.15 1.96 0.30
72 72 108
58 62 0.86 2.52 12.48 7.21 0.54
715 277 440 44,544 30,667 44,690 6.8 4.7 6.8 71 72
72 72
144 144
144 70
67 77 0.83 2.27 9.65 5.78 0.55
62 65 0.87 2.63 13.88 7.67 0.52
72 72 108 72 66 73 0.90 2.76 15.81 9.60 0.58
1,347 705 5,599 35,086 15,551 61,321 5.4 2.4 9.4 72 72
35 36
144 144
108 72
61 68 0.82 2.23 9.33 5.47 0.54
62 75 0.87 2.53 12.60 7.61 0.57
72 72 108 144 58 62 0.88 2.56 12.96 8.44 0.62
1003
SPECIES RICHNESS OF THE MISSISSIPPI RIVER
TABLE A.1.—Extended (Continued) Open river
Pool 26 MCB 6
SCB 5
BWS 15
MCB 1
La Grange Reach
SCB
MCB
SCB
32
18
8
BWS
Total
95
393
2
715
10
12
35
8
12
2
9
106
273
11
44
1,291
8
57
2
12
152
4,290
123
268
1,525
254
417
1,053
2,121
8,197
50,820
2
15
5
22
2
2
2
1,877
1 6
20
1
2
26
54
66
75
2
4
131
259
1,237
10,537
17
16
220
46
61
140
236
1,053
2,759
30
65
1,186
20
45
145
255
4,632
12,624
2 2
3
1 2
515
1
2
1
2
35
10
24
527 4 5
7
7
2
2
5
6
2
3
4
4
9
3
1
64
76
17
31
28
2
4
1 1,548 19,709 3.0
1,906 21,293 3.3
72 34
72 72
144 144
144 144
61 78 0.74 2.00 7.39 3.79 0.44
60 68 0.85 2.34 10.36 6.61 0.60
1
477 30,829 4.7 72 72 72
51 54 0.72 1.92 6.79 3.58 0.45
13,563 24,932 3.8
2,042 18,257 2.8
38
3
5
7
2,422
1
1,552
23
86
2,376
1
2
5
1
3
111 969
168
113
143
1,612
6
3
20
583
1,520 107,785 16.5
3,336 40,180 6.1
71 72
70 72
72 72
72 72
144 68
140 52
144 144
144 144
63 98 0.65 1.67 5.34 2.90 0.44
61 71 0.80 2.23 9.31 5.02 0.48
58 70 0.31 0.83 2.30 1.45 0.34
56 72 0.66 1.75 5.78 2.96 0.41
1,835 45,971 7.0
36,047 654,734 100.0
72 72 108
1110 1077 396 1688 1630
144 66 71 0.84 2.38 10.77 6.07 0.52
106 109 0.85 2.58 13.14 6.68 0.47
