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The Fishes of the Upper Moreau River Basin

Results


We found 21 species in headwater streams and 19 species in the upper mainstem (Table 1). Species found only in headwaters were Iowa darter (Etheostoma exile), brook stickleback (Culaea inconstans), brassy minnow, creek chub (Semotilus atromaculatus), bluegill (Lepomis macrochirus), and golden shiner (Notemigonus crysoleucas). The fathead minnow (Pimephales promelas) was the most widespread species, being found in seven of nine headwater streams. In the main river, cyprinids composed about 78% of the total catch, whereas ictalurids and catostomids each made up 10% of the catch. Species found only in the mainstem below the confluence of the North and South forks were emerald shiner (Notropis atherinoides), white bass (Morone chrysops), black crappie (Pomoxis nigromaculatus), and largemouth bass (Micropterus salmoides). We found no species that was listed as rare by the Federal or State government. The common carp (Cyprinus carpio), largemouth bass, white bass, bluegill, and black crappie were probably introduced species. On the mainstem, we captured 19 species in 1995 and 16 in 1996. We missed only the white bass, black crappie, and largemouth bass that were caught at one reach in 1995. Species richness was similar between years (χ² = 2.23, df = 1, P = 0.135) at mainstem reaches (Table 3).

Table 3. Fish density by station in 1995 and 1996 from seining riffles and runs in the Moreau River, South Dakota. Density expressed as fish per meter of stream seined.
Speciesa Year Station Number
1 2 3 4 5 6 7 8 9 10 11
Goldeye  1995 0.09 - 0.04 - - 0.02 0.01 0.01 - - 0.03
1996 0.04 0.06 0.03 0.14 0.02 0.05 - 0.10 0.04 0.02 -
Common carp  1995 - - 0.05 - 0.04 0.04 - - 0.04 - -
1996 0.01 - - 0.03 - - 0.01 - 0.02 - 0.01
Sand shiner  1995 0.63 0.42 2.76 2.38 2.21 0.63 1.90 0.29 1.33 0.28 0.13
1996 1.51 0.89 1.07 0.38 0.13 0.18 0.21 0.22 0.17 - 0.20
Fathead minnow  1995 0.09 0.14 0.35 0.12 0.16 0.11 0.31 0.04 0.02 0.01 0.04
1996 0.15 0.03 0.03 - 0.02 0.12 0.90 - 2.78 - 0.01
Flathead chub  1995 0.43 0.18 0.42 0.14 0.86 0.63 0.09 0.67 0.62 0.79 1.60
1996 0.43 0.11 0.79 0.14 0.87 0.37 0.12 0.10 0.44 0.16 0.76
Longnose dace  1995 0.51 0.01 0.21 - 0.23 0.17 0.31 0.10 0.23 0.07 0.03
1996 0.03 0.10 0.33 - 0.02 0.02 0.57 0.01 0.76 0.06 4.73
Plainsb minnow 1996 0.34 0.20 0.01 0.09 0.50 0.80 0.01 - 0.15 0.12 0.20
Westernb silvery minnow 1996 0.39 0.13 0.07 0.22 0.13 0.20 - 0.01 - 0.21 0.39
River carpsucker  1995 - - 0.15 0.06 0.06 0.05 0.01 0.04 0.05 - 0.19
1996 0.10 0.21 0.03 0.25 0.12 0.02 0.24 - 0.08 0.07 0.08
Shorthead redhorse 1995 0.20 0.14 0.16 0.18 0.13 0.19 - 0.36 0.19 0.01 0.05
1996 0.16 0.03 - 0.11 0.02 0.08 0.09 - 0.04 0.23 0.08
White sucker  1995 0.03 0.03 0.06 0.10 - 0.06 0.07 - 0.01 - 0.03
1996 0.03 0.03 - - 0.02 0.03 0.64 - - - -
Black bullhead  1995 - - 0.09 - - 0.02 - 0.01 0.01 - 0.01
1996 - - - - 0.05 - - - - 0.02 -
Channel catfish  1995 0.03 0.06 0.09 0.01 0.25 0.16 0.03 0.10 1.09 0.06 0.88
1996 0.51 0.16 - 0.08 0.07 0.14 0.03 0.01 0.04 0.20 0.18
Stonecat 1995 0.11 - 0.11 - - 0.15 0.01 0.03 0.04 0.01 0.07
1996 0.0 - 0.01 - - 0.02 0.01 0.01 0.02 0.14 -
Total number of species  1995 10 12 15 11 12 14 13 13 16 12 13
1996 16 14 11 11 13 13 12 12 12 10 9
a Not shown were data for one white bass, one largemouth bass, nine green sunfish (Station 1,2,8,9) and 10 emerald shiners (Station 4,5,8,9,10).
b No data for 1995 when these fish were not identifies to species.

In the mainstem, 5572 fish of 18 species were captured in seines and 727 fish of 13 species were captured in traps. Trap netting missed species of small fish, i.e. fathead minnow, emerald shiner, sand shiner (Notropis stramineus), and longnose dace (Rhinichthys cataractae), and also missed the one (each) white bass and largemouth bass that were collected by seining. Traps were most effective on river carpsucker (158 fish), channel catfish (111 fish), and shorthead redhorse (Moxostoma macrolepidotum) (88 fish). In the seine catch, the sand shiner usually had the highest CPUE values, which exceed 2 fish/m in some reaches (Table 3). Shorthead redhorse, flathead chub (Platygobio gracilis), longnose dace, plains minnow, and western silvery minnow usually had CPUE values ranging from 0.1 to 1.0 fish/m, but the CPUE for the remaining 12 species was usually less than 0.1 fish/m. The CPUE values varied greatly for most species by reach and between years (Table 3). For example, CPUE for channel catfish ranged from 0.01 at reach 4 to 1.09 at reach 9 in 1995. In 1996, CPUE at reach 4 increased to 0.08, but at reach 9 declined to 0.04.

Mean Wr values by size category for channel catfish were 103 ± 1 (substock lengths), 81 ± 1 (stock to quality lengths), and 92 ± 3 (quality to preferred lengths). The skewed U-shaped Wr pattern for river carpsucker was similar to that of channel catfish (Fig. 3), but mean Wr values for most size categories were lower: 88 ± 2 (substock lengths), 84 ± 1 (stock to quality lengths), 78 ± 1 (quality to preferred lengths), and 80 ± 2 (preferred to memorable lengths). The Wr pattern for white sucker was opposite that of the channel catfish and river carpsucker (Fig. 3). The Wr values for white sucker were 78 ± 4 (substock lengths), 81 ± 3 (stock to quality lengths), 71 ± 2 (quality to preferred lengths), and 67 ± 2 (preferred to memorable lengths).

Figure 3 - Plotted graphs showing actual and predicted weights for three species of Moreau River fish

Figure 3.  Actual and predicted relative weights for channel catfish, white sucker, and river carpsucker collected in seines and trap nets from the Moreau River, South Dakota in 1995 and 1996. Arrows indicate ranges for substock length group (SS), stock to quality length group (S-Q), quality to preferred length group (Q-P), preferred to memorable length group (P-M), memorable to trophy (M-T), and trophy (T).

  River flow characteristics varied somewhat among reaches and between years. Three river width measurements increased in the downstream direction. Between 1995 and 1996 the mean water surface width increased by 0.1 to 4.2 m at reaches 2 through 11. The change in width was probably a result of discharges that were about 0.4 m³/s higher in 1996 than in 1995 (Fig. 2). Discharges during our study were about the same as the historical mean during the months of June, July, and August. High discharges during February and May during our study were similar to the maximum historical discharges. Thus, we were working during a relatively wet period. For example, the maximum historical mean monthly discharge in May is 62 m³/sec, and the mean monthly discharge during May of 1996 was 60 m³ /sec. Water quality was similar among reaches and between years at the mainstem reaches (Table 2). Secchi disc depths ranged from 11 to 69 cm and were negatively correlated to discharge (r = 0.60, df = 20, P < 0.01). Reach gradient ranged from 2 to 24 cm/ 100 m in 1995 and from 3 to 23 cm/100 m in 1996. The dominant macrohabitat in the main river was the run, an area of relatively uniform depth and velocity, which made up 77 to 78% of our sample reaches depending on year. From 10 to 13% of the transects crossed riffle macrohabitats, 5 to 7% crossed pools, and about 4% were classified as mixed macrohabitats each year. A mix of clay, silt, and sand (termed "fines") covered 34 to 77% of the river bottom depending on station (Fig. 4). Silt made up most of the fines in 1995 (51%), whereas sand made up most in 1996 (56%). Very fine to very course gravel was the next most common substrate class (37% in 1995 and 29% in 1996), followed by the cobble-boulder category (Fig. 4).

In-stream and riparian vegetation was sparse. Emergent macrophytes were usually rushes (Juncus spp.) occurring in stands covering less than 1 m², but there were no emergent macrophytes at 65% of transects. Banks were primarily vegetated with grasses and forbs (57%), sedges (Carex spp.) and rushes (20%), and willows (Salix spp., 7%), but 16% of the banks had no vegetation. This vegetation community of grasses and forbs, interspersed with occasional cottonwood (Populus deltoides) and willow trees extended from the top-of-bank into the upland vegetation community. In 1995, 55% of the transects showed no livestock use. Where grazing was apparent that year, 16% of the transects were classified as heavily grazed, 6% moderately grazed, and 78% lightly grazed. In 1996, all transects were grazed; 82% were judged to be lightly grazed and 18% moderately grazed.


Figure 4 - Graph: Percent substrate type by station number; Top layer = Cobble, Middle layer = Gravel, Bottom layer = Fines
Figure 4.  Percentage of three size categories of substrate at 11 stations on the upper Moreau river in South Dakota in 1995; fines are particles less than 1 mm in diameter, gravel diameter is between 2 and 64 mm, cobble is greater than 64 mm in diameter.


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