Kyle J. Hartman

Evidence of a threshold level of fine sediment accumulation for altering benthic macroinvertebrate communities

When land use practices alter natural hydrologic and sediment delivery regimes, the effects usually are negative to macroinvertebrates. We hypothesized a threshold level of fine sediment accumulation in the substrate may exist where benthic macroinvertebrate abundance and diversity will be significantly reduced. We surveyed seven Appalachian streams with different levels of substrate fine sediment twice yearly from fall 1998 to spring 2000. Three riffles (with 2 replicates each) were sampled with a 0.25 mm Surber sampler in each season and stream. Simple linear regression was used to test relationships between substrate size classes and metrics, and nested ANOVA was used to test macroinvertebrate differences among streams. Consistent negative relationships with the finest substrate particles (<0.25 mm) were observed with EPT (Ephemeroptera, Plecoptera, and Trichoptera) taxa richness. In seasons of normal hydrology, EPT taxa richness significantly decreased (p<0.05) in streams where fine substrate particles (<0.25 mm) exceeded 0.8–0.9% of riffle substrate composition. In drought seasons, fine sediment (<0.25 mm) exceeded 0.8–0.9% in most surveyed streams, lowering macroinvertebrate diversity in all streams. In these streams, a threshold for EPT diversity appears to be in excess of 0.8–0.9% fine sediment (<0.25 mm) substrate accumulation. We suggest similar threshold levels exist in other streams where macroinvertebrate taxa are altered with potential effects on trophic webs and nutrient processing.

How much do valley fills influence headwater streams

AbstractValley fill mining has the potential to alter headwater stream habitat in many areas in the eastern United States. In valley fill mining, overburden is removed to expose underlying coal seams. The overburden is then deposited in the adjacent valley. The deposited overburden from mining increases sedimentation, increases stream conductivity, and alters hydrologic regimes downstream of the fill. Changes in downstream communities are not well documented. However, it was suspected the increased sedimentation and conductivity would have deleterious effects upon the downstream macroinvertebrate communities. In southern West Virginia, four pairs of streams, each consisting of a fill and a reference stream, were selected as representative of watersheds experiencing valley fill mining. Stream pairs were selected for similar environmental conditions, with one stream having a valley fill in its headwaters. Each stream was sampled by replicate Surber samples (n=9 per stream). Water chemistry and sediment measurements also were taken at each location. Valley fill streams experienced significantly higher specific conductance (p < 0.01), but did not have elevated levels of fine sediment. Fills exhibited elevated levels of Na, K, Mn, Mg, Ca, Ni and Fe relative to reference streams. Additionally, valley fill streams demonstrated significantly lower densities of Ephemeroptera, Coleoptera, Odonata, Non-insects, Scrapers, and Shredders (p < 0.03) than reference streams. Further, Ephemeroptera richness was negatively related to specific conductivity and many of the richness metrics were negatively related to metals, both of which were generally elevated in fill streams. It appears that at the minimum, valley fills increase specific conductance and metals in streams and this or some other unqualified factors structure the macroinvertebrate community downstream of the valley fill. However, given the level of disturbance in valley fills, it is surprising how little differences existed between fills and reference stream biota.

Influence of Turbidity on Brook Trout Reactive Distance and Foraging Success

Abstract Past research has focused on the effects of sediment action on stream morphology and the habitat of brook trout Salvelinus fontinalis. Throughout the Appalachian Mountains, the watersheds in which brook trout reside are being influenced by timber harvesting and related road construction. Although these streams may have gradients steep enough to prevent deleterious sediment deposition, elevated stream turbidity is nevertheless common. An understanding of the sublethal effects of increased sedimentation and turbidity is essential to further our knowledge of the effects of increased sediment loading on stream fish production and how these effects differ among species living in sympatry. The specific objectives of this study were to determine (1) the effects of turbidity on the reactive distance of brook trout, (2) how turbidity affects encounter rates between brook trout and their prey, and (3) how turbidity affects brook trouts foraging success. We used videographic techniques to study brook trout...

Reduction of Reactive Distance and Foraging Success in Smallmouth Bass, Micropterus dolomieu, Exposed to Elevated Turbidity Levels

We determined how turbidity affected the reactive distance and foraging success of smallmouth bass, Micropterus dolomieu. Smallmouth bass reactive distance decreased exponentially with increasing turbidity, from 65 cm in clear water to 10 cm at the highest turbidity. Turbidity significantly decreased the probability of a fish reacting to a prey item, but did not influence foraging success following reaction to the prey. Elevated turbidity may reduce stream fish foraging efficiency and decrease prey consumption.

A spatially-explicit approach for estimating carrying capacity: An application for the Atlantic menhaden (Brevoortia tyrannus) in Chesapeake Bay

A spatially-explicit methodology was developed for estimating system carrying capacities of fish stocks, and used to estimate the seasonal and spatial patterns of carrying capacity of Chesapeake Bay for Atlantic menhaden (Brevoortia tyrannus). We used a spatially-explicit three-dimensional (3-D) model that divided the heterogeneous habitat of Chesapeake Bay into over 4,000 cubes. Each cube represented a volume of water that was characterized by a specific set of environmental variables (phytoplankton biomass, temperature, and dissolved oxygen) driven by the 3-D water quality model. Foraging and bioenergetics models transformed the environmental variables into measures of potential growth rates of menhaden. Potential carrying capacity of menhaden was estimated as a function of phytoplankton production, menhaden consumption rate, and potential growth rate, combining phytoplankton production, thermal habitat, and menhaden physiology into one ecological value that is a measure of habitat quality from the perspective of the fish. Seasonal analysis of the Chesapeake Bay carrying capacity for Atlantic menhaden suggested two bottleneck periods: one in early June and a second during the fall. The bottleneck in carrying capacity was at about 10 billion age-0 fish. Annual recruitment of age-0 menhaden for the entire Atlantic coast of the U.S. ranged from 1.2–18.6 billion fish between 1955 and 1986. It appears that carrying capacity of, Chesapeake Bay does not limit the coastwide production of young menhaden. Any conditions such as nutrient reduction strategies, further eutrophication, or global climatic warming, that may influence the carrying capacity during the fall or early June periods, may ultimately alter coastwide abundance of menhaden through changes in Chesapeake Bay carrying capacity.

Gastric Evacuation Rates of Brook Trout

Abstract We estimated the gastric evacuation rate (GER) of brook trout Salvelinus fontinalis at five different temperatures (4.3, 9.1, 12.1, 15.6, and 17.0°C). Fish were fed a mixed meal of fly larvae and beetle larvae, and stomach contents were sampled by gastric lavage at various times over a 48–72-h period to determine the proportional dry weight of an initial meal remaining in the stomach after feeding. The relationship between the proportional amount of a meal remaining in the stomach and the time postfeeding was best described by a linear function over all temperatures. As temperature increased, the instantaneous rate of gastric evacuation increased, but the rate of increase slowed at temperatures greater than 12.1°C. Brook trout GERs were much lower than those reported in the literature for other species at similar temperatures. These data will be useful for future field studies attempting to estimate daily ration.

Refinement and Testing of a Brook Trout Bioenergetics Model

Abstract The brook trout Salvelinus fontinalis is an important species across North America, being the focus of restoration and conservation efforts in the eastern United States and considered a threat to native salmonids in the western part of the country. Bioenergetics models have emerged as useful tools for studying the ecology and management of fish species, but these models should be critically evaluated prior to widespread application. We conducted laboratory experiments to refine model parameters (metabolism and the activity multiplier) and to test a model for brook trout. Brook trout metabolic rates increased with temperature up to 20°C, then declined sharply. Specific metabolism declined with increasing fish size. Validation experiments conducted for 7, 21, and 31 d at 12-16°C showed that the model predicted consumption within 1.6 ± 3.6%, growth within 2.3 ± 12.5%, and final weight within 1.7 ± 5.1% of measured values. The results of this study will allow biologists to better use bioenergetics mo...

Density-dependent individual growth and size dynamics of central Appalachian brook trout (Salvelinus fontinalis)

Density-dependent aggression, emigration, mortality, and individual growth have been identified in wild lotic salmonid populations. However, most work is limited to fish in the genus Salmo, and few studies consider density dependency coupled with observations of energy acquisition. We attempt to quantify density-dependent growth, size, and energy acquisition for a population of brook trout (Salvelinus fontinalis) in Appalachia, where the species is food-limited and population densities are low. Brook trout populations were intensely monitored over the course of 2 years at several sites within a watershed in eastern West Virginia. Tagging provided specific growth estimates, and diet analyses allowed for estimation of energy acquisition relative to maintenance requirements for adult fish. Young-of-the-year (YOY) brook trout exhibited density-dependent size relationships, but the intensity of density dependency varied substantially among months, with progressively decreasing slopes. Adult individual growth a...

A Target Strength and Length Relationship for Striped Bass and White Perch

Abstract For hydroacoustic studies in which estimation of fish size and absolute abundance is desirable, researchers must either develop a relationship between target strength and fish length or borrow one from the literature. The purpose of this study was to provide a relationship between target strength and total length for two economically and ecologically important sympatric species: striped bass Morone saxatilis and white perch M. americana. We measured the dorsal aspect target strength of 12 white perch and 22 striped bass with a 120-kHz split-beam hydroacoustic system. The calculated target strength (TS (decibels)) to length (L cm (cm)) relationships were as follows: white perch TS = 26.48 log10 L cm − 69.45 (r 2 = 0.81, P < 0.001); striped bass TS = 15.37 log10 L cm − 56.26 (r 2 = 0.80, P < 0.001); and a combined model TS = 15.613 log10 L cm − 56.47 (r 2 = 0.82, P < 0.001). Each of these models differs substantially from the equations of Love (1971) and Foote (1987), which are commonly used in aco...

An Evaluation of the Precision of Fin Ray, Otolith, and Scale Age Determinations for Brook Trout

Abstract The ages of brook trout Salvelinus fontinalis are typically estimated using scales despite a lack of research documenting the effectiveness of this technique. The use of scales is often preferred because it is nonlethal and is believed to require less effort than alternative methods. To evaluate the relative effectiveness of different age estimation methodologies for brook trout, we measured the precision and processing times of scale, sagittal otolith, and pectoral fin ray age estimation techniques. Three independent readers, age bias plots, coefficients of variation (CV = 100 × SD/mean), and percent agreement (PA) were used to measure within-reader, among-structure bias and within-structure, among-reader precision. Bias was generally minimal; however, the age estimates derived from scales tended to be lower than those derived from otoliths within older (age > 2) cohorts. Otolith, fin ray, and scale age estimates were within 1 year of each other for 95% of the comparisons. The measures of precis...