Geology topics

S.K. Brewer

Publications and source records attributed to S.K. Brewer.

8 recordsLinked to original sources

USGS2011

Patterns in young-of-year smallmouth bass microhabitat use in multiple stream segments with contrasting land uses

Young-of-the-year (YOY) smallmouth bass, Micropterus dolomieu Lacepede, were evaluated in streams from eight catchments with two contrasting land uses to determine their use of microhabitats under a variety of stream conditions. Step-wise discriminant function analyses revealed patterns of habitat use by discriminating used from available microhabitat conditions. Velocity was significant in 88% of streams sampled, whereas depth was significant in only the smallest stream in the forest-dominated catchments and 75% of stream segments located in pasture-dominated catchments. Mean velocities used by YOY bass were lower than available velocities, and mean depths used were greater than mean availability in all cases. Substrata varied significantly with availability in different stream segments. Error rates associated with classification ranged from 5 to 39%. Results indicate that YOY smallmouth bass are somewhat opportunistic, but use low-velocity habitats in most cases and deeper water when streams are impacted by pasture land use and associated physical changes.

Fisheries Management and Ecology↗

USGS2011

Spawning habitat associations and selection by fishes in a flow-regulated prairie river

We used histological features to identify the spawning chronologies of river-dwelling populations of slenderhead darter Percina phoxocephala, suckermouth minnow Phenacobius mirabilis, stonecat Noturus flavus, and red shiner Cyprinella lutrensis and to relate their reproductive status to microhabitat associations. We identified spawning and nonspawning differences in habitat associations resulting from I year of field data via logistic regression modeling and identified shifts in microhabitat selection via frequency-of-use and availability histograms. Each species demonstrated different habitat associations between spawning and nonspawning periods. The peak spawning period for slenderhead darters was April to May in high-velocity microhabitats containing cobble. Individuals were associated with similar microhabitats during the postspawn summer and began migrating to deeper habitats in the fall. Most suckermouth minnow spawned from late March through early May in shallow microhabitats. The probability of the presence of these fish in shallow habitats declined postspawn, as fish apparently shifted to deeper habitats. Stonecats conducted prespawn activities in nearshore microhabitats containing large substrates but probably moved to deeper habitats during summer to spawn. Microhabitats with shallow depths containing cobble were associated with the presence of spawning red shiners during the summer. Prespawn fish selected low-velocity microhabitats during the spring, whereas postspawn fish selected habitats similar to the spawning habitat but added a shallow depth component. Hydraulic variables had the most influence on microhabitat models for all of these species, emphasizing the importance of flow in habitat selection by river-dwelling fishes. Histological analyses allowed us to more precisely document the time periods when habitat use is critical to species success. Without evidence demonstrating the functional mechanisms behind habitat associations, protective flows implemented for habitat protection are unlikely to be effective. ?? Copyright by the American Fisheries Society 2006.

Transactions of the American Fisheries Society↗

USGS2007

Natural landscape and stream segment attributes influencing the distribution and relative abundance of riverine smallmouth bass in Missouri

Protecting and restoring fish populations on a regional basis are most effective if the multiscale factors responsible for the relative quality of a fishery are known. We spatially linked Missouri's statewide historical fish collections to environmental features in a geographic information system, which was used as a basis for modeling the importance of landscape and stream segment features in supporting a population of smallmouth bass Micropterus dolomieu. Decision tree analyses were used to develop probability-based models to predict statewide occurrence and within-range relative abundances. We were able to identify the range of smallmouth bass throughout Missouri and the probability of occurrence within that range by using a few broad landscape variables: the percentage of coarse-textured soils in the watershed, watershed relief, and the percentage of soils with low permeability in the watershed. The within-range relative abundance model included both landscape and stream segment variables. As with the statewide probability of occurrence model, soil permeability was particularly significant. The predicted relative abundance of smallmouth bass in stream segments containing low percentages of permeable soils was further influenced by channel gradient, stream size, spring-flow volume, and local slope. Assessment of model accuracy with an independent data set showed good concordance. A conceptual framework involving naturally occurring factors that affect smallmouth bass potential is presented as a comparative model for assessing transferability to other geographic areas and for studying potential land use and biotic effects. We also identify the benefits, caveats, and data requirements necessary to improve predictions and promote ecological understanding. ?? Copyright by the American Fisheries Society 2007.

North American Journal of Fisheries Management↗

USGS2001

Cholinergic and behavioral neurotoxicity of carbaryl and cadmium to larval rainbow trout ( Oncorhynchus mykiss )

Pesticides and heavy metals are common environmental contaminants that can cause neurotoxicity to aquatic organisms, impairing reproduction and survival. Neurotoxic effects of cadmium and carbaryl exposures were estimated in larval rainbow trout (RBT; Oncorhynchus mykiss ) using changes in physiological endpoints and correlations with behavioral responses. Following exposures, RBT were videotaped to assess swimming speed. Brain tissue was used to measure cholinesterase (ChE) activity, muscarinic cholinergic receptor (MChR) number, and MChR affinity. ChE activity decreased with increasing concentrations of carbaryl but not of cadmium. MChR were not affected by exposure to either carbaryl or cadmium. Swimming speed correlated with ChE activity in carbaryl-exposed RBT, but no correlation occurred in cadmium-exposed fish. Thus, carbaryl exposure resulted in neurotoxicity reflected by changes in physiological and behavioral parameters measured, while cadmium exposure did not. Correlations between behavior and physiology provide a useful assessment of neurotoxicity.

Ecotoxicology and Environmental Safety↗

USGS2001

Behavioral dysfunctions correlate to altered physiology in rainbow trout (Oncorynchus mykiss) exposed to cholinesterase-inhibiting chemicals

We selected four metrics of swimming behavior (distance swam, speed, rate of turning, and tortuosity of path) and the commonly used biochemical marker, brain cholinesterase (ChE) activity, to assess (1) the sensitivity and reliability of behavior as a potential biomarker in monitoring work, (2) the potential for these endpoints to be used in automated monitoring, and (3) the linkage between behavior and its underlying biochemistry. Malathion-exposed fish exhibited large decreases in distance and speed and swam in a more linear path than control fish after 24 h exposure. By 96 h exposure, fish still swam slower and traveled less distance; fish fully recovered after 48 h in clean water. Diazinon-exposed fish exhibited decreases in distance, speed, and turning rate compared to controls. After 48 h recovery in clean water, fish exposed to diazinon had not recovered to control levels. The behavioral responses provided measures of neurotoxicity that were easily quantifiable by automated means, implying that the inclusion of behavior in monitoring programs can be successful. Furthermore, correlations between behavior and biochemical endpoints, such as ChE inhibition, suggest that this approach can provide a meaningful link between biochemistry and behavior and can provide useful information on toxicant impacts.

Archives of Environmental Contamination and Toxico↗

USGS2000

Physiological measures of neurotoxicity of diazinon and malathion to larval rainbow trout ( Oncorhynchus mykiss ) and their correlation with behavioral measures

Relations between neurotoxicants and changes in physiological parameters and behavior were investigated in larval rainbow trout (RBT; Oncorhynchus mykiss ) exposed to sublethal concentrations of two organophosphate pesticides (OPs). Fish were exposed to diazinon and malathion in static-renewal experiments. After exposures for 24, 96, or 96 h, followed by 48 h of recovery, individual RBT were videotaped to assess locomotory behaviors. Brain tissue from the same fish was assayed for the physiological endpoints, cholinesterase (ChE) activity, muscarinic cholinergic receptor (MChR) number (B max ), and MChR affinity (K D ). Cholinesterase activity decreased significantly with increasing concentrations of both diazinon and malathion and differed significantly among exposure durations, with 24- and 96-h means less than 48-h recovery means. Decreases in B max with OP concentration were not significant for either chemical, and K D was unaffected. Changes in swimming speed and distance were significantly correlated with changes in ChE activity for both chemicals; rate of turning was significantly correlated with ChE activity in malathion exposures. These results suggest that correlations between physiological and behavioral changes previously seen in mammals also occur in fish.

Environmental Toxicology and Chemistry↗

USGS1999

The effects of chlorpyrifos on cholinesterase activity and foraging behavior in the dragonfly, Anax junius (Odonata)

We examined head capsule cholinesterase (ChE) and foraging behavior in nymphs of the dragonfly, Anax junius, exposed for 24 h to 0.2, 0.6 and 1.0 ??g l-1 of the organophosphorus (OP) insecticide, chlorpyrifos [O,O-diethyl O-(3,5,6-trichloro-2-pyridyl) phosphorothioate]. The invertebrate community is an important component of the structure and function of wetland ecosystems, yet the potential effects of insecticides on wetland ecosystems are largely unknown. Our objectives were to determine if exposure to environmentally realistic concentrations of chlorpyrifos affected foraging behavior and ChE activity in head capsules of dragonfly nymphs. Nymphs were exposed to different concentrations of chlorpyrifos and different prey densities in a factorial design. ChE activities and foraging behaviors of treated nymphs were not statistically different (p ??? 0.05) from control groups. Prey density effects exerted a greater effect on dragonfly foraging than toxicant exposures. Nymphs offered higher prey densities exhibited more foraging behaviors but also missed their prey more often. High variability in ChE activities within the control group and across treated groups precluded determination of relationships between ChE and foraging behaviors. It appears that A. junius is relatively tolerant of chlorpyrifos, although the concentrations we tested have been shown in other work to adversely affect the prey base; therefore the introduction of this insecticide may have indirect adverse affects on top invertebrate predators such as Odonata.

Hydrobiologia↗

USGS1999

Use of automated monitoring to assess behavioral toxicology in fish: Linking behavior and physiology

We measured locomotory behaviors (distance traveled, speed, tortuosity of path, and rate of change in direction) with computer-assisted analysis in 30 day posthatch rainbow trout (Oncorhynchus mykiss) exposed to pesticides. We also examined cholinesterase inhibition as a potential endpoint linking physiology and behavior. Sublethal exposure to chemicals often causes changes in swimming behavior, reflecting alterations in sensory and motor systems. Swimming behavior also integrates functions of the nervous system. Rarely are the connections between physiology and behavior made. Although behavior is often suggested as a sensitive, early indicator of toxicity, behavioral toxicology has not been used to its full potential because conventional methods of behavioral assessment have relied on manual techniques, which are often time-consuming and difficult to quantify. This has severely limited the application and utility of behavioral procedures. Swimming behavior is particularly amenable to computerized assessment and automated monitoring. Locomotory responses are sensitive to toxicants and can be easily measured. We briefly discuss the use of behavior in toxicology and automated techniques used in behavioral toxicology. We also describe the system we used to determine locomotory behaviors of fish, and present data demonstrating the system's effectiveness in measuring alterations in response to chemical challenges. Lastly, we correlate behavioral and physiological endpoints.

Conference Paper↗