**Macroinvertebrate sampling in the Missouri River below Fort Randall
and**

**Gavins Point dams during 2005 and 2006**

Kristen Berg -- SCEP Student

and

Robert Klumb -- Fisheries Biologist

U.S. Fish and Wildlife Service

Great Plains Fish and Wildlife Management Assistance Office

420 South Garfield Avenue, Suite 400

Pierre, South Dakota 57501

![](media/image1.jpeg){width="5.129861111111111in"
height="3.8472222222222223in"}

April 27, 2007

Prepared for

U.S. Fish and Wildlife Sevice - Region 6

Lakewood, Colorado

**Introduction**

A field project initiated in 2005 and completed in 2006 focused on the
relative prey use by juvenile pallid sturgeon *Scaphirhynchus albus*,
and species composition and diversity of macroinvertebrates in the
Missouri River below Fort Randall and Gavins Point dams, South Dakota
and Nebraska. Macroinvertebrates are an important component in aquatic
food chains (Wilhm et al. 1978) and previous diet studies have shown
juvenile pallid sturgeon rely heavily on macroinvertebrates throughout
the year, especially caddisfly larvae and chironomids (Kallemeyn 1983;
Wanner et al. 2007). However, little information has been collected on
macroinvertebrate diversity and distribution concurrently with pallid
sturgeon food habits. Also, this project, along with previous pallid
sturgeon diet studies, will assist in current bioenergetics modeling and
spatial analysis studies on pallid sturgeon and their habitat. The main
objective of this study was to quantify habitat associations and
densities of macroinvertebrates. Macroinvertebrate assemblage,
abundance, and diversity will be compared between the Fort Randall and
Gavins Point reachs, as well as between upstream and downstream sites
within each reach. Cross-sectional spatial distribution and abundance
along bankline to bankline transects and temporal trends during summer
will also be compared. Lastly, macroinvertebrates collected in pallid
sturgeon stomachs will be compared to those collected in the field.

Although the motivation behind this macroinvertebrate survey was the
determination of prey available to juvenile hatchery-reared pallid
sturgeon, a concurrent benefit of this project included an active
monitoring program for macroinvertebrate aquatic nuisance species,
particularly zebra mussels *Dreissena polymorpha*. Although zebra mussel
veligers have been identified in plankton samples from the Missouri
River downstream of Fort Randall Dam (near Verdel, NE), no adult zebra
mussels have yet been found. Extensive sampling, in upstream and
downstream locations of the Missouri River below both dams will help
elucidate whether adult zebra mussel populations have become
established.

**Study Area**

The study area includes two unchannelized reaches of the Missouri River.
The Fort Randall reach is located below Fort Randall Dam (river
kilometer \[RK\] 1,416) downstream to Springfield, South Dakota (Figure
1). The Gavins Point reach is located below Gavins Point Dam (RK 1,305)
downstream to Ponca, Nebraska (Figure 2). Habitat types at both sites
included inside bends, outside bends, secondary connected channels,
channel crossovers, and braided areas. Four transects for each site were
randomly selected from topographic maps sectioned off into 250-m
intervals for a 6 km area surrounding each boat ramp. Each transect
formed a cross-section of the river (Figure 3).

The Fort Randall reach included three sites (Figure 1). The most
upstream site was located at Sunshine Bottoms, 3 km upstream and
downstream of the Boyd County boat ramp. The middle site was located
upstream of the Verdel boat ramp to downstream of the Ponca Creek
confluence. The most downstream site was located 3 km upstream and
downstream of the Santee boat ramp on the Nebraska side, and 3 km
upstream and downstream of the Springfield boat ramp on the South Dakota
side. This most downstream site, referred to as the Santee/Springfield
site, is unique because it represents the braided section of the
Missouri River formed from sedimentation into Lewis and Clark Lake
downstream of the confluence with the Niobrara River. This study was the
first macroinvertebrate survey within this braided habitat of the
Missouri River.

The Gavins Point reach also included three sites (Figure 2). The most
upstream site was located 3 km upstream of the St. Helena boat ramp to
the downstream tip of James River Island. The middle site was located
upstream of the Clay county boat ramp to Goat Island and downstream to
the Clay County boat ramp. The most downstream site was located 3 km
upstream and downstream of the Ponca State Park boat ramp in Nebraska.
Ponca State Park is just upstream of where the Missouri River becomes
channelized for navigation at Sioux City, Iowa. Downstream of Sioux City
is the location where the first adult zebra mussel was found in the
Missouri River in 1999 (USGS-NAS 2006).

**Methods**

Substrate and deep main channel benthos were sampled using two gears.
The main gear used in the deep water of the main channel was a ponar
dredge with a scoop volume of 8.2 L, and a sampling area of 58.1 cm^2^
(9 in^2^). Samples were collected at 0.25-x channel width, 0.50-x
channel width, and 0.75-x channel width (Figure 3). In areas where the
ponar dredge did not adequately sample benthos after three attempts the
substrate sample was collected using a hess sampler. The hess sampler is
a large metal tube of 10.2 cm (4 in) diameter used to sample integrated
sediment by dragging the tube along the bottom. All ponar and hess
samples were preserved in the field with 10% formalin. Additional
habitat variables measured include: water temperature, depth, dissolved
oxygen, turbidity, and surface water velocity.

Deep-water sampling for macroinvertebrates was conducted using a 0.5-m
diameter 1.5-m long conical zooplankton drift net with 500 µm mesh. The
drift net had a lead weight attached to the bottom and a flow meter
attached in the center that calculated the volume of water filtered. Two
types of drift samples were collected: bottom and column drifts. Bottom
drift collections consisted of deploying the drift net to the bottom and
allowing it to set for three to five minutes; soak time varied due to
turbidity, detritus load, and presence of macrophytes. Column drifts
consisted of deploying the drift net to the bottom and immediately
retrieving the net to the surface. Column drift was collected to see if
deploying and retrieving the net significantly affected the sample
compared to the net resting on the bottom. Time was recorded as the net
is deployed to the bottom and retrieved to the surface. All drift
samples were preserved in the field with 70% ethanol.

Active sampling of deep main channel benthos and placement of
colonization plates in the Missouri River resulted in a spatially
expansive monitoring program for zebra mussels in South Dakota and
Nebraska. Macroinvertebrates were sampled in shallow water using
hester-dendy 14-plate artificial substrate sampler (pictured on the
title page) and a surber sampler. Hester-dendy samplers were wired to
stable logs along the shore or wired to a t-bar stake and placed at an
adequate sampling depth. The hester-dendy has a total exposed surface
area of approximately 1,300 cm^2^ and were deployed for 50 to 60 days to
allow adequate colonization (Turner and Trexler 1997; Hilsenhoff 1969;
and Wilhm et al. 1978) and invertebrates were preserved with 10%
formalin. A standard surber sampler, with a sampling area of 0.09 m^2^
(one square foot), was modified with a PVC pipe handle which allowed
sampling in waist deep waters. The surber sampler was deployed facing
upstream allowing the collection net to deploy and an extendable
three-pronged rake was used to disrupt the substrate to collect the
sample which was then preserved in 70% ethanol. Substrate was sampled in
shallow waters simply by grabbing a handful of the substrate (i.e., a
hand grab) near the location where invertebrates were collected.

Samples for 2005 and 2006 were processed the in lab at South Dakota
State University (Tables 1-4). Ponar dredge sediment samples and hess
samples were processed utilizing a sugar solution to float the
invertebrates to the surface of the sample. Samples were soaked in a
sugar solution for approximately 20 minutes then the invertebrates were
collected out of the sample (Anderson 1959). While the ponar and hess
samples were soaking in the sugar formalin solution, the sample was
stirred and visually checked for the presence of mussels. Hester-dendy
samples were scraped to collect colonized macroinvertebrates. Surber and
drift samples were rinsed in a sieve and placed in a sorting tray.
Invertebrates in all samples, both aquatic and terrestrial, were picked,
placed in vials, labeled, and preserved in 70% ethyl alcohol.
Invertebrates will be identified to genus with some exceptions (i.e.,
Family Chironomidae). To date, all samples have been sorted and over 50%
of macroinvertebrates have been indentified.

**Results**

Macroinvertebrate and substrate samples were collected in the Missouri
River downstream of the Fort Randall and Gavins Point Dams on three
occasions during 2005: June 2-17th, August 1-12th, and September 26th
through October 6th (Tables 1 and 2). A total of 1,208 samples were
collected of which, 625 were collected below Fort Randall Dam and 583
were collected below Gavins Point Dam. During the June sample period,
192 samples were collected below Fort Randall Dam and 176 samples were
collected below Gavins Point Dam. In August, 209 samples were collected
below Fort Randall Dam and 205 samples were collected below Gavins Point
Dam. For the late September through October sample period, 224 samples
were collected below Fort Randall Dam and 202 samples were collected
below Gavins Point Dam. In 2005, 84% of samples downstream of Fort
Randall Dam and 86% of samples downstream of Gavins Point Dam collected
macroinvertebrates. A total of 224 substrate samples were collected
below Fort Randall Dam and 204 samples were collected below Gavins Point
Dam. Substrate samples were dried and sieved to determine the percent
composition of gravel, sand, and silt. The sampling goal was to average
8-10 bankline samples per site and 12-14 main channel samples per site
three times during the summer. However, the number of hester-dendy
samples varied due to the public finding and disposing of them, the
river claiming them, or drastic water level fluctuations rendering the
samples useless.

Transects at each study area were re-randomized and samples were
collected on three occasions during 2006: June 5-13th, July 31st through
August 6th, and September 28th through October 15th (Tables 3 and 4). A
total of 1,097 samples were collected of which, 615 were collected below
Fort Randall Dam and 482 were collected below Gavins Point Dam. During
the June sample period, 191 samples were collected below Fort Randall
Dam and 162 samples were collected below Gavins Point Dam. In August,
214 samples were collected below Fort Randall Dam and 184 samples were
collected below Gavins Point Dam. For the late September through October
sample period, 210 samples were collected below Fort Randall Dam and 136
samples were collected below Gavins Point Dam. Similar to 2005, 84% of
samples downstream of Fort Randall Dam and 85% of samples downstream of
Gavins Point Dam collected macroinvertebrates during summer of 2006.
Also, a total of 223 substrate samples were collected below Fort Randall
Dam and 177 samples were collected below Gavins Point Dam. Fewer
hester-dendy colonization samplers were successfully recovered in 2006
due to lowered water levels, especially below Gavins Point dam, during
late summer.

Preliminary results of percent composition by number was calculated for
macroinvertebrate samples collected during summer 2006 for the Fort
Randall and Gavins Point Reaches for the Surber sampler, drift net, and
ponar dredge. Fort Randall Surber samples were primarily composed of
Diptera (46%) and Ephemeroptera (27%), while Gavins Point samples were
composed of several taxa including Diptera (29%), Ephemeroptera (16%),
Trichoptera (20%), and larval fish (15%) (Figure 4). Fort Randall drift
net samples were primarily composed of Diptera (54%) and larval fish
(14%), while Gavins Point samples were composed mostly of Diptera (30%),
Trichoptera (29%), and larval fish (33%) (Figure 5). Ponar dredge
samples were primarily composed of Diptera for both Fort Randall (94%)
and Gavins Point (80%) samples (Figure 6). Furthermore, downstream of
Gavins Point Dam, Trichopterans composed 20% of the samples, however, a
smaller percent was found in the Fort Randall Reach (4%). The lower
prevalence of caddis flies downstream of Fort Randall Dam, especially
for the Surber samples, may have resulted from diurnal water level
fluctuations (\> 1 m) for power generation compared to the more
consistent discharges from Gavins Point Dam.

Zebra mussels were targeted using three gears: the ponar dredge, hess
sampler, and hester-dendy substrate samplers in 2005 and 2006. A grand
total of 344 samples were collected below Fort Randall Dam and 295
samples were collected below Gavins Point Dam during this study (Tables
1-4). However, no zebra mussels were found during the processing of
these samples. Current evidence suggests that there is not an
established adult zebra mussel population in the Missouri River below
Fort Randall and Gavins Point dams. Either the original veliger samples
were mis-identified (i.e. false positive) or the source of the veligers
may be from other upstream sections of the Missouri River or the
reservoir, Lake Francis Case, which were not sampled in this study.
Colonization by zebra mussels may not be conducive in these reaches of
the Missouri River due to the water fluctuations below Fort Randall Dam
and the prevalence of shifting sand substrates below both dams.

**Literature Cited**

Anderson, R.O. 1959. A modified flotation technique for sorting bottom
fauna samples. Limnology and Oceanography 4:223-225.

Hilsenhoff, W.L. 1969. An artificial substrate device for sampling
benthic stream invertebrates. Limnology and Oceanography 14:465-471.

Kallemeyn, L. 1983. Status of the Pallid Sturgeon *Scaphirhynchus
albus*. Fisheries

> 8:3-9.

Turner; A.M., and J.C. Trexler. 1997. Sampling Aquatic Invertebrates
from Marshes: Evaluating the options. Journal of the North American
Benthological Society 16: 694-709.

U.S. Geological Survey (USGS), Nonindigenous Aquatic Species (NAS)
website <http://nas.usgs.gov/> Accessed June 24, 2006.

Wanner, G. A., D. A. Shuman, D. W. Willis. 2007. Food habits of juvenile
pallid sturgeon and adult shovelnose sturgeon in the Missouri River
downstream of Fort Randall dam, South Dakota. Journal of Freshwater
Ecology 22: 81-92.

Wilhm, J., H. Namminga, and C. Ferraris. 1978. Species composition and
diversity of benthic macroinvertebrates in Greasy Creek, Red Rock Creek
and the Arkansas River. American Midland Naturalist 99:444-453.

![](media/image2.png){width="6.000694444444444in"
height="3.3958333333333335in"}

Figure 1: Three locations where macroinvertebrates were collected in the
Missouri River downstream of Fort Randall Dam during the summers of 2005
and 2006.

![](media/image3.png){width="5.627083333333333in"
height="3.1944444444444446in"}

Figure 2: Three locations where macroinvertebrates were collected in the
Missouri River downstream of Gavins Point Dam during the summers of 2005
and 2006.

![](media/image4.jpeg){width="6.122916666666667in"
height="4.432638888888889in"}

Figure 3: Map of summer 2005 sampling design for the Sunshine Bottoms
site of the Missouri River below Fort Randall Dam. Cross-sectional
transects included the main channel and bankline habitats. Main channel
habitats were sampled at approximately 0.25, 0.50, and 0.75-X channel
width using a ponar dredge to collect benthic macroinvertebrates and a
conical zooplankton net collected drifting macroinvertebrates. Bankline
habitats were sampled using hester-dendy substrate samplers and surber
samplers. New transects were randomly selected for summer 2006.

![](media/image5.wmf)Figure 4: Percent composition by numbers of
macroinvertebrates collected with a Surber sampler during summer 2006
below Fort Randall and Gavins Point dams, South Dakota and Nebraska.

![](media/image6.wmf)

Figure 5: Percent composition by number of macroinvertebrates collected
with a drift net during summer 2006 below Fort Randall and Gavins Point
dams, South Dakota and Nebraska.

![](media/image7.wmf)Figure 6: Percent composition by number of
macroinvertebrates collected with a ponar dredge during summer 2006
below Fort Randall and Gavins Point dams, South Dakota and Nebraska.

Table 1: Total samples collected on three occasions in summer of 2005 at
four sites downstream of Fort Randall Dam for each gear type used. For
Hester-dendy, numbers in parentheses are the total samplers deployed.
Not all hester-dendy samplers were recovered.

  -------------- -------------- ------------- ------------- --------------
  Sample type    Study site                                 

                 Sunshine       Verdel        Santee        Springfield

                                                            

  Hester-Dendy   14 (20)        12 (15)       10 (13)       13 (13)

  Surber Sampler 29             25            24            24

  Hand Grab      27             23            24            24

  Bottom Drift   41             36            24            24

  Column Drift   41             36            24            24

  Ponar Dredge   40             35            24            24

  Hess Sampler   1              2             0             0

                                                            
  -------------- -------------- ------------- ------------- --------------

Table 2: Total samples collected on three occasions in summer of 2005 at
three sites downstream of Gavins Point Dam for each gear type used. For
Hester-dendy, numbers in parentheses are the total samplers deployed.
Not all hester-dendy samplers were recovered.

  ------------------ ----------------- ----------------- -----------------
  Sample type        Study Site                          

                     James             Clay              Ponca

                                                         

  Hester-Dendy       18 (21)           20 (20)           13 (20)

  Surber Sampler     33                28                27

  Hand Grab          33                26                25

  Bottom Drift       42                42                36

  Column Drift       42                42                36

  Ponar Dredge       40                40                34

  Hess Sampler       2                 2                 2

                                                         
  ------------------ ----------------- ----------------- -----------------

Table 3: Total samples collected on three occasions in summer of 2006 at
four sites downstream of Fort Randall Dam for each gear type used. For
Hester-dendy, numbers in parentheses are the total samplers deployed.
Not all hester-dendy samplers were recovered.

  -------------- -------------- ------------- ------------- --------------
  Sample type    Study site                                 

                 Sunshine       Verdel        Santee        Springfield

                                                            

  Hester-Dendy   11 (18)        10 (16)       10 (16)       15 (16)

  Surber Sampler 28             24            24            24

  Hand Grab      28             24            24            24

  Bottom Drift   39             36            24            24

  Column Drift   39             36            24            24

  Ponar Dredge   39             36            24            24

  Hess Sampler   0              0             0             0

                                                            
  -------------- -------------- ------------- ------------- --------------

Table 4: Total samples collected on three occasions in summer of 2006 at
three sites downstream of Gavins Point Dam for each gear type used. For
Hester-dendy, numbers in parentheses are the total samplers deployed.
Not all hester-dendy samplers were recovered.

  ------------------ ----------------- ----------------- -----------------
  Sample type        Study Site                          

                     James             Clay              Ponca

                                                         

  Hester-Dendy       9 (18)            4 (20)            6 (16)

  Surber Sampler     22                29                25

  Hand Grab          22                27                23

  Bottom Drift       31                41                33

  Column Drift       31                41                33

  Ponar Dredge       31                41                33

  Hess Sampler       0                 0                 0

                                                         
  ------------------ ----------------- ----------------- -----------------