No abstract

We assessed salmon id production in summer in a second-and third-order montane stream in eastern Tennessee in 1987. We sampled three stream sections, one containing exclusively brook trout Salvelinusfontinalis. one containing exclusively rainbow trout Oncorhynchus mykiss. and a third with a mixture of both species. Population estimates for July and October 1987 revealed reductions in biomass over the 4-month period that ranged from 31 to 49%, whereas population densities declined by 32-46% during the same period. Total net production during the 4-month period was low and ranged from 0.38 to 0.45 g/m 2 . From June through September, the mean number of prey items per stomach ranged from 4.2 to 29.9, whereas the mean relative weight of stomach contents ranged from 0.12 to 1.34 mg dry weight per gram wet weight offish flesh. There was a strong positive correlation between the mean relative weight of stomach contents and the mean condition factor for a given date. Calculated energy intake was below the level necessary to provide energy for maintenance metabolism.

Visual estimation of stream salmonid abundance using strip transect sighting models has become commonplace. Application of visual estimation to other stream fishes, particularly benthic forms, has been limited. Examination of the distribution of sighting distances for the Roanoke darter (Percina roanoka), Roanoke logperch (P. rex), and black jumprock (Moxostoma cervinum) indicates that strip transect sighting models that assume probability of sighting remaining constant out to the limits of observer visibility are not appropriate for these benthic species. Our datasets indicate that distance sampling models that assume decreased sighting probability with increasing distance of the target from the observer provide a reasonable alternative to strip transect sighting models. There was a strong positive correlation between abundance estimates calculated using two alternative distance sampling models, as well as between the distance sampling model estimates and an estimate of abundance obtained with a backpack electroshocker.

Abstract.-We examined fish distribution and abundance in erosional habitat units in South Fork Roanoke River, Virginia, following a fish kill by using a reachwide sampling approach for 3 species and a representative-reach sampling approach for 10 species. Qualitative (presence-absence) and quantitative (relative abundance) estimates of distribution and abundance provided consistent measures of fish recovery for 2 of 3 species at the reachwide scale and 8 of 10 species at the representative-reach scale. Combining results across scales and estimator types showed that distributions and abundances of 5 of I1 species in the reach affected by the kill were similar to those observed in unaffected upstream and downstream reaches 8-1 I months following the perturbation. Differences in distribution and abundance between the affected reach and unaffected reaches indicate that 4 of 1 I species had not fully recovered during the same time period; results were equivocal for 2 other species. We attribute differences in recovery rates between these two groups to differences in parental investment in offspring. Species exhibiting rapid recovery either engage in extensive spawning site preparation or guard the spawning site following egg deposition and Fertilization; species that had not recovered in the year following the kill show limited spawning site preparation and do not guard the spawning site.Stream fish are exposed to both natural and anthropogenic disturbances that can alter population distribution and abundance. We need to understand the factors that influence population recovery following disturbances in order to effectively manage stream fish resources (Cairns et al. 1971; Hughes et al. 1990;Detenbeck et al. 1992). Factors determining recovery rates can be viewed in a hierarchical fashion (Detenbeck et al. 1992). Regional variations in climate, geomorphology, and hydrologic regime provide the large-scale habitat L Present address:

Forested riparian corridors are thought to minimize impacts of landscape disturbance on stream ecosystems; yet, the effectiveness of streamside forests in mitigating disturbance in urbanizing catchments is unknown. We expected that riparian forests would provide minimal benefits for fish assemblages in streams that are highly impaired by sediment or hydrologic alteration. We tested this hypothesis in 30 small streams along a gradient of urban disturbance (1-65% urban land cover). Species expected to be sensitive to disturbance (i.e., fluvial specialists and "sensitive" species that respond negatively to urbanization) were best predicted by models including percent forest cover in the riparian corridor and a principal components axis describing sediment disturbance. Only sites with coarse bed sediment and low bed mobility (vs. sites with high amounts of fine sediment) had increased richness and abundances of sensitive species with higher percent riparian forests, supporting our hypothesis that response to riparian forests is contingent on the sediment regime. Abundances of Etheostoma scotti, the federally threatened Cherokee darter, were best predicted by models with single variables representing stormflow (r(2) = 0.34) and sediment (r(2) = 0.23) conditions. Lentic-tolerant species richness and abundance responded only to a variable representing prolonged duration of low-flow conditions. For these species, hydrologic alteration overwhelmed any influence of riparian forests on stream biota. These results suggest that, at a minimum, catchment management strategies must simultaneously address hydrologic, sediment, and riparian disturbance in order to protect all aspects of fish assemblage integrity.