Geology topics

Richard L. Raesly

Publications and source records attributed to Richard L. Raesly.

3 recordsLinked to original sources

USGS2022

Life history strategies of stream fishes linked to predictors of hydrologic stability

Life history theory provides a framework to understand environmental change based on species strategies for survival and reproduction under stable, cyclical, or stochastic environmental conditions. We evaluated environmental predictors of fish life history strategies in 20 streams intersecting a national park within the Potomac River basin in eastern North America. We sampled stream sites during 2018–2019 and collected 3801 individuals representing 51 species within 10 taxonomic families. We quantified life history strategies for species from their coordinates in an ordination space defined by trade-offs in spawning season duration, fecundity, and parental care characteristic of opportunistic, periodic, and equilibrium strategies. Our analysis revealed important environmental predictors: Abundance of opportunistic strategists increased with low-permeability soils that produce flashy runoff dynamics and decreased with karst terrain (carbonate bedrock) where groundwater inputs stabilize stream flow and temperature. Conversely, abundance of equilibrium strategists increased in karst terrain indicating a response to more stable environmental conditions. Our study indicated that fish community responses to groundwater and runoff processes may be explained by species traits for survival and reproduction. Our findings also suggest the utility of life history theory for understanding ecological responses to destabilized environmental conditions under global climate change.

Maryland, Virginia, West Virginia↗

USGS2021

Comparative morphology of freshwater sculpin inhabiting different environmental conditions in the Chesapeake Bay headwaters

We compared body morphology of two freshwater sculpin taxa that inhabit distinct environmental conditions in the Chesapeake Bay watershed of eastern North America: Potomac sculpin ( C. girardi , Robins; PS) and checkered sculpin ( C. sp. cf. girardi ; CS). Both taxa are endemic to the study area, but PS are more broadly distributed than CS which are limited to karst groundwater-dominated streams in the central Potomac River basin. We examined preserved specimens from sites encompassing their geographic range (six sites per taxon) to evaluate taxonomic differences and environmental effects. Pelvic fin ray counts and body shape distinguished the study taxa. Morphological variation exhibited stronger relationships to environmental covariates (site elevation and basin size) in PS than CS as expected. In addition, the frequency of specimens with a united median chin pore increased with site elevation in PS (but not CS), suggesting thermal effects on preoperculomanibular canal development. However, contrary to expectation, PS did not exhibit greater among-population variation in body shape than CS, and this indicates the potential importance of unmeasured environmental differences among karst groundwater-dominated streams in the study area. Our study also indicated the utility of stream-level management units for CS, an undescribed species recognized as “critically imperiled” by state agencies.

Chesapeake Bay↗

USGS2016

First record of the bigeye shiner ( Notropis boops ) from West Virginia

We report a population of Bigeye Shiner Notropis boops in the South Fork Hughes River drainage of the Little Kanawha River, West Virginia. A total of 27 individuals of N. boops were collected during five sampling efforts from 1999 to 2005. These specimens represent an addition to the state fauna, a distributional record for the Little Kanawha River, and an eastern range extension for this species on the Appalachian Plateau, West Virginia. Notropis boops in the South Fork Hughes River drainage likely represents a native population.

West Virginia↗