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Comparison of Age and Growth Patterns of Flathead Catfish in Invasive and Native Populations: A Meta-analysis with Implications for Invasive Species Management

Flathead Catfish are a long-lived apex predator native to the Gulf Coast drainage including the Ohio Basin in Pennsylvania; however, they are invasive in the Atlantic Slope of Pennsylvania.  Large-scale range expansion and population increases were not realized until the late 1990s in the Delaware River drainage and the early 2000s in the Susquehanna River drainage. Since introduction, the range expansion of Flathead Catfish in the Atlantic Slope portions of Pennsylvania has not been adequately documented.  The primary objectives of the project are to (1) continue to collect Flathead Catfish abundance, distribution, and population characteristic data for both native and introduced populations in Pennsylvania initiated in 2016 and (2) perform meta-analysis of Flathead Catfish growth across much of its native and introduced range in the United States.

We found that since introduction, Flathead Catfish have expanded their range to a 185-km reach of the Delaware River, 132 km of the Schuylkill River and at least 5 km of the Lehigh River 20 years after their initial detection in the Schuylkill River.  In the Susquehanna River, Flathead Catfish are now known from lower 334 km, the lower 124 km of the Juniata River but have yet to be documented in the West Branch Susquehanna River.  We found that abundance of Flathead Catfish in portions of the Susquehanna River is similar to that of the waterbodies in its native range in Pennsylvania but lower in the non-tidal reaches of the Delaware River when compared to both the Susquehanna River and its native range in Pennsylvania.  We found through a meta-analysis of growth that the von Bertalanffy growth parameters theoretical maximum length (L∞) and Brody’s growth coefficient (K) varied among 21 native and introduced riverine populations of Flathead Catfish. Both the slowest (Three Rivers) and fastest (tidal Delaware River) growth rates, as measured by K, among the populations analyzed came from Pennsylvania populations. We also found that that the effects of the different drivers of growth varied among these populations and was related to whether they were native or introduced and how long these introduced populations have been established.  These differential effects could, in turn, impact how Flathead Catfish populations affect their environment. 

These data in combination also help to build the foundation for understanding for the impact of invasive Flathead Catfish populations.  Using distribution, abundance, and growth information in conjunction with diet (on going) and stable isotope and bioenergetics information, researchers will be able to calculate impact of Flathead Catfish on various prey items such as popular or economically important fish species or species that are the focus of restoration efforts.  More importantly, this information will aid in determining potential impacts for areas they have not yet invaded.

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