Daryl Pierce | Geology Reports

USGS2026

Longitudinal variability of demographics and life history in an anadromous spawning population within a large, unimpeded East Coast, USA, watershed

Objective The goal of this study was to characterize the variability in age, growth, and life history of sea-run fish throughout a large, East Coast, USA, watershed to improve the parameterization of longitudinal variation in demographics and spawning histories in an undammed river. Methods Both live and dead American Shad Alosa sapidissima were collected during spring 2020 and 2021. Sex, length, age, and repeat spawning information were recorded for all individuals ( n = 512). Growth curves were created to test hypotheses about the variables that were related to the growth rates of American Shad for this relatively unsampled portion of the spawning population in the Delaware River. Results We observed variation in size, age, repeat spawning probability and propensity, and sex ratios from downstream to upstream as well as during the spawning season. Individual traits also varied among the fish that died during migration and those that were collected alive. Conclusions This study expands the current knowledge about variability in the life history traits that are commonly used in assessing and managing an anadromous fish that spawns upstream in a large, undammed watershed. Our results have broad implications for the assessment and management of anadromous fish populations globally and contribute to understanding parity along a continuum. Some potential priorities for future work include using telemetry to understand the final disposition of live fish, investigating fine-scale genetic control for correlated life-history traits, and investigating the correlations between natal origin (i.e., genetic stock mixing) and longitudinal variation within spawning populations.

New York, Pennsylvania↗

USGS2021

Range expansion and factors affecting abundance of invasive Flathead Catfish in the Delaware and Susquehanna Rivers, Pennsylvania, USA

Flathead Catfish Pylodictis olivaris have been either intentionally or accidentally introduced into Atlantic Slope drainages extending from Florida to Pennsylvania and have quickly become established. In Pennsylvania, Flathead Catfish were first detected in the Schuylkill River at the Fairmont Dam in 1999 and in the Susquehanna River at Safe Harbor Dam in 2002. The species has since moved throughout the respective basins, with subsequent detections during 244 riverine surveys in these drainages. Fishway and electrofishing surveys in the tidal Schuylkill River, a Delaware River tributary, have documented an increase in abundances since 2004, when the surveys were first implemented. Hoop-net surveys in nontidal large-river reaches found mean (±SD) catch rates varying from 0.00 to 4.51 ± 4.38 fish/series. A Bayesian hierarchical Poisson regression model indicated that Flathead Catfish abundance decreased as the distance from the initial point of detection increased, demonstrating a general pattern of fish expansion upstream from the point of detection. The distance downstream of the nearest dam, although not significant, had a relatively high posterior probability of being negatively correlated with Flathead Catfish abundance. Ongoing and future targeted surveys should help to better understand changes in the distribution and abundance of Flathead Catfish in these systems.

Pennsylvania↗