1. Fish Assemblage in Different Habitats in the
Mississippi River
Kelsey Hoffmann, Johnna Miller, Ethan Sorenson
Limnology 520
Introduction
The Mississippi River is the largest river in North America. It starts in Lake
Itasca, Minnesota and flows approximately 2318 miles to the Head of Passes in Louisiana where
it splits into several distributaries and drains into the Gulf of Mexico (Fremling 1989). The upper
Mississippi river extends from the St. Anthony falls to the mouth of the Missouri River
(Fremling, 1986). The upper Mississippi River has a great variety of habitats including the main
channel, side channels, and backwaters, which results in having a great variety of fish species
(USGS, 2008). Fish are considered some of the most significant organisms in a river from both a
recreational and economic standpoint because their distribution and abundances are affected by
many different factors that can change their life cycles (Madejczk et. al 1998). More than 130
fish species have been observed in the Upper Mississippi River (Fremling et. al 1989).
Fish communities in the Upper Mississippi River have significant differences in species
distribution in the backwater and main channel habitats (Roach 2009). Fish species can be
grouped into different feeding classes; planktivores (eat zooplankton and phytoplankton),
benthivores (eat mainly benthic prey), omnivores (eat both plant and animals), and piscivores
(eat primarily fish).
There are many different habitats within the Mississippi river. Riprap is installed on shore
lines where there is a need to stop erosion and to stabilize the shoreline. Riprap is natural rock
that is randomly placed along the shoreline (MN DNR). A natural bank habitat is a habitat that
has had no restoration. A slack water habitat is a habitat that is in between tides and has no
current running through it.
The relative abundances in terms of both numbers of fish and biomass of benthivores,
and omnivores will be greater than that of piscivores in the 3 different habitats of the Mississippi
River during autumn.

2. Materials and Methods
A boat-mounted electrofisher was used to collect the fish from each of the 3 locations.
The electrofisher was a Coffelt boat mounted electrofisher that runs 600 volts direct current DC.
This electrofisher creates about a 5 ft. electrical field around the boat which temporarily shocks
the fish allowing for easier collection. During the cooler autumn months, many fish species
prefer to stay in the shallow areas of the lake, so electrofishing was focused close to shorelines
and shallower portions of the water systems. All fish captured were identified, weighed and
counted. All fish were collected on November 1st, 2015 in 3 different habitats in a small stretch
of the Mississippi River near Winona, MN. A transect was done in each of the three different
habitats of the Mississippi River. The different habitats consisted of a natural bank habitat, a
riprap habitat and a slack water habitat. The first transect was in Yeomen’s pond (slack water
habitat) and fish were captured for 1319 seconds (Figure, 1). The second transect was in the
straight slough (natural bank habitat) and fish were captured for 920 seconds (Figure, 2). The
third and final transect was in the straight slough (Riprap habitat) and fish were captured for 644
seconds (Figure, 3).
Data from all of 3 transects were collected and combined to compare the species in
various river habitats. The overall abundance of fish and the abundance of different species in all
of the habitats were determined by calculating the catch-per-effort (CPE), of fish per minute. The
total number of fish captured were categorized into fish feeding classifications and then
compared between different river habitats (Figure, 4). The total number of biomass from each
habitat were categorized into fish feeding classifications and then compared between different
river habitats (Figure, 5). The percentages of fishes based on their feeding classifications were
determined for the total number of fish and the total biomass of fish in the river habitats (Figure,
6-11). A Simpson Diversity test was conducted on each of the river habitats to determine if there
was significant species diversity between each habitat (Table, 1). A Bray-Curtis similarity test
was conducted to determine if there was a similarity in the amount of species collected at each
habitat (Table, 2).
Results
From all three habitats on the Mississippi River a total of 185 individual fish (13 different
species) were collected. The species that were collected included Small and Largemouth bass,
Walleye, Northern Pike, Bluegill, Gizzard Shad, Yellow and Log perch, Baitfish, Sauger,
Freshwater Drum, and Redhorse. The total biomass of all 185 fish collected was 13,141g.
Piscivores represented 15.70% (29/185) of total fish collected and 88.4% (11,616/13,141) of the
total biomass collected, benthivores were 80% (148/185) of the total fish collected and 9.70%
(1275/13,141) of the total biomass, and omnivores accounted for 4.3% (8/185) of the total fish
collected and 1.9% (250/13,141) of the total biomass collected from the 3 habitat sites on the
Mississippi River (Table, 3). Total catch per effort was calculated for all fish and their biomass
for the 3 different river habitats on the Mississippi River. The total CPE (per minute) of

3. piscivores was .6 fish and 241.8 g. of biomass, CPE (per minute) of benthivores was 3.1 fish and
26.54 g. of biomass, and CPE (per minute) of omnivores was .17 fish and 5.2 g. of biomass
(Table, 4).
CPE (per minute) was also calculated for number of fish and biomass in each of the
individual river habitats. In Yeomen’s pond, benthivores had the highest CPE for number of
individual fish caught and piscivores had the highest CPE for biomass. The natural bank habitat,
benthivores had the highest CPE for number of individual fish caught and piscivores had the
highest CPE for biomass. In the rip-rap habitat piscivores had the highest CPE for both number
of individual fish caught and biomass (Table, 5).
Pie charts were created to analyze the total number of fish in each habitat, categorized by
feeding classification. Pie charts were also created to analyze the total biomass (g) in each
habitat, categorized by feeding classification. Benthivores were higher in abundance and biomass
in Yeomen’s Pond (Figure, 6,9). In the Natural Slough habitat, Benthivores were higher in
abundance but Piscivores were significantly higher in total biomass (Figure, 7,10). In the rip-rap
habitat an equal amount of benthivores and piscivores were collected but the benthivores had a
higher total biomass (Figure, 8,11).
A Simpson diversity test was conducted and compared amongst all of the individual sites.
The habitat that was weighted the most was rip-rap habitat. This concludes that the rip-rap
habitat had the highest number of species and evenness among all of the habitats. The natural
bank habitat had the lowest Simpson diversity index (Table, 1). A Bray-Cutris community
similarity index was conducted to compare the fish communities of each possible site pair. It was
determined that each site was significantly different than each other (Table, 2).
Discussion:
This lab concluded that individual fish from the benthivore and omnivore feeding class
accounted for 84.3% (156/185) however they only accounted for 11.6% (1525/13141) of the
total biomass collected. This is because the benthivores and omnivores are generally fish that are
smaller in size than piscivores.
This lab also concluded that there were more individual fishes in the Natural bank habitat
of Straight Slough than any of the other habitats. Yeomen’s Pond had the overall highest grams
of biomass. River habitats are very diverse because their runoffs provide more inputs of
sediments, nutrients and runoffs (Lakescientist). Fish tend to prefer diverse habitats rather than
locations with fewer habitat types (Madejczk et.al 1998).
The boat-mounted electrofisher had limits on how deep it was able to collect fish. Fishes
collected in littoral zones are in higher abundances than fishes collected in profundal zones
(Whitfield, 1993). The river habitats were mostly collected along the banks of the river.
However in the rip-rap habitat, the river was a little deeper. This may have affected how many
fish were caught.
Fish feeding classifications were used when categorizing fish. Benthivores were captured
the most. Benthivores are usually bottom feeders and would be in shallower parts of the river

4. habitats. Omnivores were collected the least. Omnivores eat everything and can sometimes be
found in deeper parts of the river.
In some of the habitats while electrofishing, there many fish that many were missed. This
could have an effect on our results. Another human error to be considered is that the fish were
being weighed on an unstable boat. This may have caused inaccurate readings of the biomasses.
Acknowledgments
We would like to thank Dr. Mundahl for taking us out electrofishing on a very lovely
Sunday when he likely had better things to do than boat around three obnoxious graduate
students. We would also like to thank Nathan Hoffmann and Jesse Owen for their enthusiastic
help scooping up fish. Kelsey Hoffmann would also like to apologize to Nathan Hoffmann for
accidently throwing one of the better fish he scooped up off the boat. Sorry!
Literature Cited:
Fremling, C.R., J.L Rasmussen, R.E. Sparks, S.P Cobb, C.F. Bryan and, T.O. Claflin. 1989.
Mississippi River, fisheries: a case history. Can. Spec. Publ. Fish. Aquat. Sci. 106:1
Fremling, Calvin R., and Glenn A. Heins. A Lake Winona Compendium: Information concerning
the Reclamation of a Winter-kill Lake at Winona, Minnesota. 2nd ed. Winona, Minn.: Winona
State U, 1986.
Madejczyk, Jeffrey C., Neal D. Mundahl, and Richard M. Lehtinen. "Fish Assemblages Of
Natural And Artificial Habitats Within The Channel Border Of The Upper.." American Midland
Naturalist 139.2 (1998): 296. EBSCO MegaFILE. Web. 9 Dec. 2015
Status and Trends of Selected Resources of the Upper Mississippi River System a Synthesis
Report of the Long Term Resource Monitoring Program. La Crosse, Wis.: U.S. Geological
Survey, Upper Midwest Environmental Sciences Center, 2008.
ROACH, K. A., THORP, J. H. and DELONG, M. D. (2009), Influence of lateral gradients of
hydrologic connectivity on trophic positions of fishes in the Upper Mississippi River. Freshwater
Biology, 54: 607–620. doi: 10.1111/j.1365-2427.2008.02137
"What Can I Do to Keep My Shoreline from Washing Away?" Minnesota Department of Natural
Resources. Web. 9 Dec. 2015.
"How Lakes Differ - Lake Scientist." Lake Scientist. Web. 9 Dec. 2015.

5. Whitfield, Alan K.. “Fish Biomass Estimates from the Littoral Zone of an Estuarine Coastal
Lake”.Estuaries 16.2 (1993): 280–289.
Tables and Figures
Figure 1. Yeomans Pond
Figure 2. Natural Bank habitat

6. Figure 3.RipRap habitat

7. Figure 4. A comparison of the total number of fish collected on November 1st 2015.
Figure 5. A comparison of the total biomass of fish collected on November 1st 2015.
Table 1. Simpson diversity of fish structure in 3 different sites near Winona, MN. Sites were
electrofished in November 1st, 2015.
Site # individuals biomass(g)
Yeomen’s pond 0.75 0.62
Natural bank 0.05 0.62
Rip-rap bank 0.92 0.64

8. Table 2. Bray-Curtis results of fish structure in 3 sites around Winona, Mn in October, 2015.
Highlighted values are significantly different.
Yeomen’s Natural Rip-rap
Yeomen’s 0
Natural 0.096 0
Rip-rap 0.22 0.014 0
Table 3. Totals Number of fish and biomass collected in the 3 different river habitats on the
Mississippi river on November 1st, 2015
Number of Fish Biomass
Piscivores 29 15.70% 11616 88.40%
Benthivores 148 80% 1275 9.70%
Omnivores 8 4.30% 250 1.90%
Totals 185 13141
Table 4. Catch-per-effort per minute of fish and biomass collected in the 3 different river
habitats on the Mississippi river on November 1st, 2015
CPE Fish CPE
Biomass (g)
Piscivores 0.603663614 241.80
Benthivores 3.08 26.54038301
Omnivores 0.166527893 5.20
Table 5. Catch-per-effort (by minuets) for total numbers of fish and total biomass from each of
the Yeomen’s pond, straight slough natural bank, and straight slough rip-rap on the Mississippi
River
CPE of Number of
Fish
CPE of Biomass
(g)
Yeomen’s Pond
Piscivores 0.59144677 290.0363967
Benthivores 1.137397634 39.12647862

9. Omnivores 0.363967243 11.37397634
Straight Slough
Natural Bank
Piscivores 0.195694716 290.2804958
Benthivores 7.697325506 2.609262883
Straight Slough
Rip-rap
Piscivores 1.211556384 73.71854613
Benthivores 0.465983225 34.94874185
Figure 6. A comparison of the total number of fish collected in Yoemens Pond. Fish were
categorized by feeding classification. All data were collected on November 1st 2015.
Figure 7. A comparison of the total number of fish collected in the Natural slough habitat. Fish
were categorized by feeding classification. All data were collected on November 1st 2015.

10. Figure 8. A comparison of the total number of fish collected in the RipRap habitat. Fish were
categorized by feeding classification. All data were collected on November 1st 2015.
Figure 9. A comparison of the biomass (g) of fish collected in Yeomens Pond. Fish were
categorized by feeding classification. All data were collected on November 1st 2015.

11. Figure 10. A comparison of the biomass (g) of fish collected in the Natural slough habitat. Fish
were categorized by feeding classification. All data were collected on November 1st 2015.
Figure 11. A comparison of the biomass (g) of fish collected in the RipRap habitat. Fish were
categorized by feeding classification. All data were collected on November 1st 2015.