Nocomis platyrhynchus. Northern hog sucker. Hypentelium nigricans. Spotfin shiner. Notropis spilopterus. Central stoneroller. Campostoma anomalum. Spotted ...
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Habitat Use by an Assemblage of Fish in a Large Warmwater Stream a
M. Delbert Lobb III & Donald J. Orth
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Department of Fisheries and Wildlife Sciences , Virginia Polytechnic Institute and State University , Blacksburg, Virginia, 24061-0321, USA Published online: 09 Jan 2011.
To cite this article: M. Delbert Lobb III & Donald J. Orth (1991) Habitat Use by an Assemblage of Fish in a Large Warmwater Stream, Transactions of the American Fisheries Society, 120:1, 65-78, DOI: 10.1577/1548-8659(1991)1202.3.CO;2 To link to this article: http:// dx.doi.org/10.1577/1548-8659(1991)1202.3.CO;2
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Transactions of the American Fisheries Society 120:65-78, 1991 €> Copyright by the American Fisheries Society 1991
Habitat Use by an Assemblage of Fish in a Large Warmwater Stream M. DELBERT LOBB III1 AND DONALD J. ORTH
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Department of Fisheries and Wildlife Sciences Virginia Polytechnic Institute and State University Blacksburg, Virginia 24061-0321. USA Abstract. —We examined habitat-use patterns in a fish assemblage in a large warmwater stream in West Virginia. Fish species and life stage composition and densities differed among habitat types, and five habitat-use guilds (edge pool, middle pool, edge channel, riffle, and generalist) were proposed. Larger centrarchids used deep habitats with slow velocities, whereas young centrarchids used shallower habitat. Juvenile and adult smallmouth bass Micropterus dolomieui were nearly ubiquitous in the habitats of the study area, although densities were highest among snags. Minnows and darters used shallower areas, but the range of velocity used differed among species and life stages. Vegetated and channel edge habitats served as nursery areas. Total fish densities were highest in edge pool, backwaters, snags, edge riffles, and riffles. Nearshore, structurally complex habitats seem important in influencing the assemblage structure of fishes of large streams. In warmwater streams the large number of fish species and the lack of reliable habitat suitability criteria make assessments of flow alterations difficult (Leonard and Orth 1988). Recent studies of habitat needs of warmwater fishes typically have concentrated on single species (Probst et al. 1984; Rankin 1986; Sechnick et al. 1986). A broader, community-level perspective is needed to protect stream resource values (Orth 1987; Miller et al. 1988). For example, Bain et al. (1988) documented differential responses of several stream fishes to fluctuating streamflows. The influence of habitat factors on fish assemblages has been studied in small and mediumsized streams, but few comparable studies exist for large streams (StaufFer et al. 1976). Many factors (abiotic and biotic) interact to determine the structure of fish assemblages in streams. Studies in small warmwater streams reveal that physical habitat structure (depth, current velocity, and substrate) influences species composition, and species diversity is correlated with habitat diversity (Schlosser 1982). Although physical structure creates suitable habitat for fishes, biotic factors such as food availability and predation influence growth, survival, and abundance. For example, woody debris and snags provide both food and cover for fishes in warmwater streams (Angermeier and Karr 1984; Benke et al. 1985), predation risk sometimes restricts certain small fishes to shallow hab-
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Present address: Missouri Department of Conservation, 2500 South Halliburton, Kirksville, Missouri 63501, USA.
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itats in small streams (Schlosser 1987), and interspecific interactions among individuals within the same habitat-use guild can influence the habitat use patterns of stream minnows (Gorman 1988). Because many factors influence associations between fish species and habitat features, these patterns often vary among streams and years (Angermeier 1987). Furthermore, the degree of association between habitat and fish assemblages may be less predictable in streams subjected to more severe physicochemical conditions (Matthews and Hill 1980), and some studies indicate very generalized patterns of habitat use (Bart 1989). The recent increase in licensing of hydropower plants on large warmwater streams underscores the need for similar studies of fish-habitat associations in larger streams. Also, the concept of habitat guilds has potential to simplify instream flow assessments (Leonard and Orth 1988), provided that the existence of such guilds is adequately tested before acceptance (Hawkins and MacMahon 1989). Our study was conducted within the New River Gorge National River, a unit of the National Park Service. Previous studies on the feasibility of hydropower development at Bluestone Dam, immediately upstream, were limited because of the lack of basic knowledge of the habitat requirements of the fish fauna. Here we describe habitatuse patterns in the fish assemblage in the New River, a large warmwater stream. Specifically our objectives were to (1) describe the assemblages of species and life stages associated with the major habitat types, (2) identify nursery habitats, and (3) compare fish densities among the major habitat
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LOBB AND ORTH
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types and correlate densities with habitat characteristics. Study Site The New River in southern West Virginia is a sixth-order stream, which was 60-^400 m wide in the study reach. Streamflow was regulated by Bluestone Dam (37°39'N, 80°53'W), a flood control reservoir. Average discharge measured at the upstream end of this reach (Hinton, West Virginia) was 230 m3/s (1949-1983);, August and September flows averaged 85 and 78 mVs, respectively. The stream gradient was 1.7 m/km; much of the drop occurred at several large falls and rapids. Stream substrate was dominated by bedrock outcrops and large cobbles. In shallow areas, river
weed Podostemum ceratophyllum colonized the bedrock outcrops and immovable cobbles. Beds of water willow Justicia americana were common in depositional areas along stream margins and islands. Submerged vegetation included Elodea canadensis, Heteroanthera dubia, Potomogeton spp., and Vallisneria sp. Water temperatures averaged 22-27°C in midsummer. In 1984, electrofishing collections were made extensively along the river from the town of Hinton to the mouth of Ephraim Creek (5-70 km downstream from Bluestone Dam). In 1985, we made intensive observations at two sites, Brooks Island (11.5-15.5 km downstream from Bluestone Dam) and Tug Creek rapids (7 km downstream from Bluestone Dam). At the Brooks Island site, the main and secondary channels along the island contained riffle and run habitats. The middle portion of the site contained shallow to deep pool habitat, and the downstream area was riffle habitat. The Brooks Island site ranged from 150 to 300 m wide and was representative of the habitats in the 17-km section of the New River between Bluestone Dam and Sandstone Falls. Methods Electrofishing.—Electrofishing collections were made to determine species richness in each habitat, identify habitats most used by young fishes, and positively identify species of cyprinids that could not be reliably identified in underwater surveys. We identified 11 habitat types (similar to those of Bisson et al. 1982) and selected 100 sampling stations distributed in proportion to the area represented by each habitat type. We sampled with pulsed DC electrofishing between July 3 and October 10, 1984. The most frequently used (43 of 100 samples) equipment
(variable voltage pulsator [Coffelt Model WP-2C] with two hand-held anodes, powered by a 120-V, 1,500-W Homelite generator) was used in areas less than about l . l m deep. Sampling was accomplished by wading upstream, parallel to the current, for 15 min. In shallow habitats (average depth, 400 mm). We also employed random swim counts; divers swam in a specific habitat type and only counted rarely seen species. After a count was completed, divers swam downstream along the transect and recorded depth (four categories), velocity (six categories), substrate type (four categories), vegetation (four categories), and woody debris (two categories) by 25-m sections. The abundance of large cobble and boulder substrate was used to simplify substrate type description and as an indicator of the amount of cover provided. Statistical analyses.—We calculated total fish density and densities of each species-life stage for 45 underwater transects at which area was determined. A chi-square goodness-of-fit test was used to compare actual number of fish seen with the expected (based on percent of area sampled) number of fish in a habitat type. In addition, 95% simultaneous Bonferroni confidence intervals for the actual number of fish in each habitat were calculated to compare with habitat available (Byers etal. 1984). We used a Kruskal-Wallis nonparametric analysis of variance (Hollander and Wolfe 1973) to compare the mean densities of all fish, and youngof-year and juvenile smallmouth base (see Table 1 for species names of fish) in the four dominant habitat types: edge pool, middle pool, riffle, and run. Comparisons for other species-life stages were not made because there were too many zero densities (45-92% of transects). Because there were significant differences among the dominant habitats, a Wilcoxon rank-sum test was used to make pairwise comparisons among the four habitats. We used canonical correlation analysis (SAS Institute 1985) to determine the relations between densities of 20 species-life stages and habitat variables for 43 of 45 transects. Two transects, located in snag habitats, were not included because these habitats were rare and had extremely high fish densities. Species that occurred on fewer than three of the transects were not included in this analysis. Species of Notropis and unidentified darters were
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not included because they were not identified to species and differences in habitat use among the species within these groups are potentially great. Young-of-year bigmouth chubs (
