Donald J. Orth

Regional Applications of an Index of Biotic Integrity for Use in Water Resource Management

Abstract The index of biotic integrity (IBI) integrates 12 measures of stream fish assemblages for assessing water resource quality. Initially developed and tested in the Midwest, the IBI recently was adapted for use in western Oregon, northeastern Colorado, New England, the Appalachians of West Virginia and Virginia, and northern California. The concept also was extended to Louisiana estuaries. In regions of low species richness, the IBI proved difficult to apply and often required extensive modification. Adapting the 1BI to those regions required that metrics be replaced, deleted, or added to accommodate regional differences in fish distribution and assemblage structure and function. Frequently replaced metrics include: proportion of individuals as green sunfish (Lepomis cyanellus), proportion of individuals as insectivorous cyprinids, proportion of individuals as hybrids, and number and identity of sunfish and darter species. The proportion of individuals as top carnivore metric was often deleted. Metr...

Habitat Use by an Assemblage of Fish in a Large Warmwater Stream

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.

Application and Testing of an Index of Biotic Integrity in Small, Coolwater Streams

Abstract A recently proposed index of biotic integrity (IBI), which applies features of indigenous fish communities to assess watershed and stream quality, is based on the assumption that community features change consistently with stream degradation. In this study, the IBI was modified for and applied to small coolwater streams in the Appalachian Plateau region of West Virginia. Changes in fish community variables proposed for the IBI were tested in seven similar streams exhibiting a wide range of stream degradation due to sewage, mining, and urbanization. A consistent response with increasing stream degradation was found for the following variables: Total number of species, proportion of individuals as creek chubs Semotilus atromaculatus, species richness and composition of darters (Percidae), number of fish in sample, and proportion of fish with disease or anomalies. Proportions of omnivores, insectivorous cyprinids, and herbivore-detritivores yielded inconsistent results due to confounding interaction...

Microhabitat preferences of benthic fauna in a woodland stream

Estimates of numbers, biomass, and diversity of benthic macroinvertebrates were made quarterly over a two-year period to investigate microhabitat preferences. Although biomass of most taxa was significantly different among sampling times, physical factors also appeared to be important in determining abundance of many taxa. Optimum depth, velocity, substrate type, and turbulence were determined for major taxa. Optimum conditions for diversity appeared to be 34 cm depth, 60 cm s−1 velocity, and rubble and boulder substrate type. Habitat preference functions were derived for several taxa based on significant polynomial regressions of biomass on depth, velocity, substrate, and Froude number (turbulence). The relationship between abundance and physical habitat conditions was tested by using the product of the preference factors (range: 0–1) for depth, velocity and substrate type as a measure of habitat suitability (joint preference factor). There were significant correlations between biomass [transformed by loge (x + 1)] of 10 benthic species and the joint preference factor. The joint preference factors accounted for from 11 to 61% of the variation of biomass of the 10 benthic species. The intercepts of the relationships between biomass of individual species and the joint preference factor were not significantly different from zero for any species. Therefore, the joint preference factors appear to be valid indicators of biomass. The preference functions have utility in habitat assessment studies, specifically with regard to minimum instream flow determinations.

Trophic Basis of Production of Stream-Dwelling Smallmouth Bass, Rock Bass, and Flathead Catfish in Relation to Invertebrate Bait Harvest

Abstract We quantified annual consumption and annual production of the principal predatory fishes (smallmouth bass Micropterus dolomieu, rock bass Ambloplites rupestris, and flathead catfish Pylodictis olivaris) in a 62-hectare pool of the New River, West Virginia, to evaluate the potential for competition among these species and people for crayfish (Cambarus sciotensis, Orconectes sanbornii sanbornii, and Orconectes virilis) and hellgrammite (Corydalus cornutus) resources. Production of smallmouth bass (3.21 g·m−2·year−1), rock bass (2.00 g·m−2·year−1), and flathead catfish (0.56 g·m−2·year−1) was supported primarily by aquatic insects (age-0 and age-1 fishes) and crayfish (age-2 and older fishes). Hellgrammites were rarely eaten due to their secretive nature, and prey fishes were less numerous than crayfish in the diets and the environment. Diet overlap among the three species was relatively high (Schoeners overlap index = 0.74–0.93); species composition and sizes of crayfish eaten by the three fish sp...

Use of Habitat Guilds of Fishes to Determine Instream Flow Requirements

Abstract We grouped eight warmwater fishes, each represented by one to four life stages, into habitat-use guilds (i.e., groups of species) to select target species for instream flow studies. Cluster analysis of depth, velocity, substrate, and cover use identified four primary habitat-use guilds, which were distinguished largely on the basis of water velocity. Habitat-suitability criteria were developed for each species and life stage combination, and these criteria were used in physical habitat simulations to determine relations between weighted usable area (WUA) and discharge for three streams in the upper James River basin, Virginia. Weighted usable areas for species within each habitat-use guild generally exhibited similar responses to discharge except those for some stream-margin inhabitants and for strongly cover-oriented species. Four types of habitat–discharge relations, which were consistent among streams, were identified. Curves of WUA versus discharge for habitat generalists and some specialists...

Formulation of Habitat Suitability Models for Stream Fish Guilds: Do the Standard Methods Work?

Abstract Habitat suitability index (HSI) models for seven fish guilds in two segments of the upper Roanoke River drainage, Virginia, were formulated for the summer seasons of 1989 and 1990. We considered five habitat variables as potential limiting factors: depth, average and demersal velocities, average substratum size, and percent cover. These physical variables were modeled both separately and as composite HSI indices. Composite models were built from linear regression equations (both simple and multiple) in which the observed guild density in quadrats was regressed against physical microhabitat variables or individual suitability indices (SIs = predicted fish densities). There were five major findings. First, habitat variables were used independently by most fish guilds, as statistical interactions were weak and inconsistent for regression models predicting guild densities from physical variables. That is, fish-microhabitat relations for target habitat variables were typically unaffected by the condit...

Factors Affecting Nesting Success of Smallmouth Bass in a Regulated Virginia Stream

Abstract We examined the influences of habitat, temperature, stream discharge, and the timing of spawning on the nesting success of smallmouth bass Micropterus dolomieu. Smallmouth bass began spawning when temperatures reached 15°C, and high flow disrupted spawning five times. Larger males spawned earlier than smaller males; a log-linear relation between male length and degree-days accumulated was significant (r = –0.63, P 305 mm total length) accounted for the highest production of free-swimming larvae and also made the most renesting attempts, which suggests that large males can have a strong influence on year-class strength. Stepwise discriminant analysis distinguished successful nests from unsuccessful nests by higher flow at time of nest construction, higher mean temperatur...

Habitat Use of Fish Communities in A Virginia Stream System

Fish habitat use during summer was examined at micro- and meso-levels, to determine species associations in the upper Roanoke River watershed, Virginia. Based on multivariate-mesohabitat analysis and examination of mean microhabitat use, seven habitat-use guilds were apparent. These included four rheophilic (fast-riffle, riffle/run, fast-generalist, and shallow-rheophilic) and three limnophilic guilds (pool/run, open-pool, and pool-cover) that were reasonably robust across two river segments and two years. Although simple-hydraulic, bottom-topographic, and turbulence variables all segregated fish habitat-use guilds, turbulence variables were redundant with simple-hydraulic variables, substratum use by limnophilic fishes was related to availability, and only one guild consistently selected high cover levels. At the family level, suckers, darters, and especially minnows were notable for occupying several habitat-use guilds, because of species differences in habitat preferences. Such formulation of guilds can simplify habitat-impact analyses in biodiverse, warmwater streams, via focus on habitat needs of guilds rather than on individual species.

A New Technique for Estimating the Abundance and Habitat Use of Stream Fishes

ABSTRACT An open-sampling technique that employed seining and AC electroshocking with a downstream block net was compared with enclosure sampling in a small river. Relative abundance of species, species diversity and richness, total numbers and densities of fish, and median fish size were examined. The two sampling techniques provided concordant fish-assemblage patterns for riffles and runs. Pool samples showed differences in species diversity and/or dominant species between sampling methods, which resulted from fish mobility or sample bias. Fish size did not differ significantly between the two methods, and only runs showed noticeably higher fish densities for the enclosure samples.