Effects of historic flooding on fishes and aquatic habitats in a Missouri River delta

Figures & data

Figure 1. Missouri River basin and location of the Lewis and Clark Delta along the South Dakota–Nebraska border, USA. The upstream end of the Delta is located near its confluence with the Niobrara River (576907 N, 4734800 E). The downstream end of the Delta is located where the reservoir portion of Lewis and Clark Lake begins (594446 E, 4743533 N).

Figure 2. Gage height in the Lewis and Clark Delta at Springfield, South Dakota, from 1980 to 2012. The 2011 flood was the most severe hydrological disturbance in recent history. Gage height was measured by the United States Geological Survey (USGS gage 06466700, 408905 E, 4745408 N).

Table 1. Numbers of introduced, native, sport, and small-bodied fishes collected from 2004 to 2012 in the Lewis and Clark Delta.

Species	Scientific name	EF	Pre	Post	MFN	Pre	Flood	Post
Introduced
Common carp	Cyprinus carpio	244	159	85	192	97	25	70
Rock bass	Ambloplites ruprestris	39	19	20	50	26	15	9
Native
River carpsucker	Carpiodes carpio	115	60	55	422	107	17	298
Smallmouth buffalo	Ictiobus bubalus	37	31	6	32	14	0	18
Green sunfish	Lepomis cyanellus	2	2	0	98	66	17	15
Shorthead redhorse	Moxostoma macrolepidotum	135	81	54	39	23	2	14
Black bullhead	Ameiurus melas	4	4	0	97	15	79	3
Freshwater drum	Aplodinotus grunniens	84	24	60	339	267	67	5
Shortnose gar	Lepisosteus platostomus	24	20	4	274	209	42	23
Sport
Bluegill	Lepomis macrochirus	109	85	24	347	238	5	104
Black crappie	Pomoxis nigromaculatus	60	47	13	340	127	96	117
Channel catfish	Ictalurus punctatus	79	10	69	196	93	101	2
White crappie	Pomoxis annularis	3	3	0	384	358	26	0
Yellow perch	Perca flavescens	4	4	0	58	15	13	30
Largemouth bass	Micropterus salmoides	97	71	26	334	233	58	43
Northern pike	Esox lucius	29	6	23	30	5	22	3
Sauger	Sander canadensis	170	102	68	42	37	1	4
Smallmouth bass	Micropterus dolomieu	63	48	15	384	321	5	58
Walleye	Sander vitreus	29	25	4	94	93	1	0
White bass	Morone chrysops	98	84	14	311	269	34	8
Small-bodied
Emerald shiner	Notropis atherinoides	1389	1201	188	–	–	–	–
Red shiner	Cyprinella lutrensis	109	83	26	–	–	–	–
Spotfin shiner	Cyprinella spiloptera	366	333	33	–	–	–	–

Electrofishing (EF) data include catches of small-bodied (i.e., typical adult length < 100 mm TL) and adult large-bodied species arranged by pre-flood (Pre; 2005, 2008, 2009) and post-flood (Post; 2012) periods. Mini-fyke net (MFN) data include catches of juvenile large-bodied species arranged by pre-flood (Pre; 2004-2010), flood (Flood; 2011), and post-flood (Post; 2012) periods. The entire species pool was reduced to common species (>1% of total catch per sampling event) to remove effects of rare species and species difficult to collect.

Table 2. Structural indices (species richness [S], evenness [J′], diversity [Fisher's α]) of common fishes collected during pre-flood (2005, 2008, 2009) and post-flood (2012) periods in the Lewis and Clark Delta.

Index	2005	2008	2009	2012	p
Richness	25^.a	15^.c	22^.b	21^.b
	25	15			<0.01
		15	22		<0.01
			22	21	0.07
	25		22		<0.01
	25			21	<0.01
		15		21	<0.01
Evenness	0.88^.a	0.80^.b	0.73^.c	0.84^.b
	0.88	0.80			<0.01
		0.80	0.73		<0.01
			0.73	0.84	<0.01
	0.88		0.73		<0.01
	0.88			0.84	<0.01
		0.80		0.84	0.08
Diversity	4.56^.a	2.17^.d	3.48^.b	3.27^.c
	4.56	2.17			<0.01
		2.17	3.48		<0.01
			3.48	3.27	0.03
	4.56		3.48		<0.01
	4.56			3.27	<0.01
		2.17		3.27	<0.01

Different letters indicate significant differences among flood periods for particular structural indices. p values denote whether indices were significantly different (p < 0.05) between years as inferred from a bootstrapping procedure in program PAST (PAleontological STatistics).

Figure 3. Nonmetric multidimensional scaling (NMS) ordinations of mean catch per unit effort (CPUE) for juvenile native and sport fishes during pre-flood (2004–2010), flood (2011), and post-flood (2012) periods in the Lewis and Clark Delta, South Dakota–Nebraska, USA. Multivariate heterogeneity is explained by changes in CPUE of individual species (bottom panel). Different letters indicate significant differences in mean CPUE among time periods for particular species. CAP = common carp; FRD = freshwater drum; RIC = river carpsucker; BGL = bluegill; BLC = black crappie; SMB = smallmouth bass; WHC = white crappie.

Figure 4. Nonmetric multidimensional scaling (NMS) ordinations of mean catch per unit effort (CPUE) for adult native and sport fishes and small-bodied species during pre-flood (2004–2010), flood (2011), and post-flood (2012) periods in the Lewis and Clark Delta, South Dakota–Nebraska, USA. Multivariate heterogeneity is explained by changes in CPUE of individual species (bottom panel). Different letters indicate significant differences in mean CPUE between time periods for particular species. CAP = common carp; FRD = freshwater drum; RIC = river carpsucker; SHR = shorthead redhorse; BGL = bluegill; CCF = channel catfish; LMB = largemouth bass; SAR = sauger; EMS = emerald shiner; RES = red shiner; SFS = spotfin shiner.

Figure 5. Pre-flood (June 2010) and post-flood (October 2011) frequency of side channels, backwaters, and sandbars in the Lewis and Clark Delta between the Niobrara River confluence and the downstream limit of the Delta in Springfield, SD. Habitat features were enumerated on 30 equidistantly spaced transects (perpendicular to the main channel) between the Niobrara River confluence and the downstream end of the Delta in ARCMap 10.1 using aerial photographs taken during months with comparable gage height (∼4.5 m).