Range Expansion and Factors Affecting Abundance of Invasive Flathead Catfish in the Delaware and Susquehanna Rivers, Pennsylvania, USA

Abstract

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.

Catfish 2020, A Clear Vision of the Future

“…This pattern in nonnative catfish populations is seen with Blue Catfish I. furcatus (Fabrizio et al 2021;Hilling et al 2021;Nepal and Fabrizio 2021; all this special issue), bullheads Ameiurus spp. (Barabe 2021;Sikora et al 2021; both this special issue), Channel Catfish I. punctatus (Pennock et al 2018;Hedden et al 2021, this special issue), and Flathead Catfish Pylodictis olivaris (Hedden et al 2016;Massie et al 2018;Schmitt et al 2019;Smith et al 2021, this special issue), which was summarized by Montague and Shoup (2021, this special issue). The extent, ecology, and impacts of nonnative, invasive catfish populations are becoming better understood over time, and Fabrizio et al ( 2021) described the conflicts involved in managing invasive catfish.…”

Two Decades of Advancement in Flathead Catfish Research

“…Impoundments result in a decline in juvenile Flathead Catfish habitat and can alter their development (Heimann et al 2007*). Flathead Catfish are able to migrate upstream from barriers, such as fishways, and can use dams as a staging area to forage before migrating (Raabe and Hightower 2014;Raabe et al 2019;Smith et al 2021). Flathead Catfish populations are unaffected by boat traffic disturbance in commercial navigation channels (Gutreuter et al 2006).…”

“…However, studies addressing the effects of dams on Flathead Catfish have shown inconsistent findings. Aadland (2015*) found that Flathead Catfish were absent above dams in Minnesota, but Smith et al (2021) found that Flathead Catfish have the ability to disperse despite the presence of dams. Lastly, there has historically been some question regarding whether Flathead Catfish populations should be managed riverwide or by river reach (Travnichek 2004).…”

“…Since Jackson's (1999) article, Flathead Catfish have invaded the Great Lakes basin (originally by stocking in the 1800s; Fuller and Whelan 2018) and are now found in Lakes Erie, St. Clair, Huron, and Michigan, including nearly all Lake Michigan drainages on the Michigan side and the Fox/Wolf and Milwaukee River drainages on the Wisconsin side (Fuller and Whelan 2018). Flathead Catfish have also expanded into additional Chesapeake Bay tributaries (Schmitt et al 2019) and are now also more extensively established along the Atlantic Slope (USGS 2020; Rachels 2021; Smith et al 2021). The species' range also expanded from the native range along the Gulf Coast into parts of Alabama, Georgia, and Florida (USGS 2020).…”