Evaluation of Genetic Population Structure of Smallmouth Bass in the Susquehanna River Basin, Pennsylvania

Abstract

The Smallmouth Bass Micropterus dolomieu was introduced into the Susquehanna River basin, Pennsylvania, nearly 150 years ago. Since introduction, it has become an economically and ecologically important species that supports popular recreational fisheries. It is also one of the most abundant top predators in the system. Currently, there is no information on the level of genetic diversity or genetic structuring that may have occurred since introduction. An understanding of genetic diversity is important for the delineation of management units and investigation of gene flow at various management scales. The goals of this research were to investigate population genetic structure of Smallmouth Bass at sites within the Susquehanna River basin and to assess genetic differentiation relative to Smallmouth Bass at an out-of-basin site (Allegheny River, Pennsylvania) located within the species’ native range. During spring 2015, fin clips (n = 1,034) were collected from adults at 11 river sites and 13 tributary sites in the Susquehanna River basin and at one site on the Allegheny River. Fin clips were genotyped at 12 polymorphic microsatellite loci. Based on our results, adults sampled throughout the Susquehanna River basin did not represent separate genetic populations. There were only subtle differences in genetic diversity among sites (mean pairwise genetic differentiation index F_ST = 0.012), and there was an overall lack of population differentiation (K = 3 admixed populations). The greatest genetic differentiation was observed between fish collected from the out-of-basin site and those from the Susquehanna River basin sites. Knowledge that separate genetic populations of Smallmouth Bass do not exist in the Susquehanna River basin is valuable information for fisheries management in addition to providing baseline genetic data on an introduced sport fish population.

Received August 25, 2016; accepted May 4, 2017 Published online July 11, 2017

ACKNOWLEDGMENTS

This research was made possible through collaborative efforts among multiple research groups and partners. A research grant was received through the R. K. Mellon Freshwater Research Initiative at Susquehanna University to cover laboratory processing costs. Graduate research support was provided through the U.S. Geological Survey’s (USGS) Chesapeake Bay Priority Ecosystems and Fisheries programs. Field assistance for fin clip collections was provided by personnel from the Pennsylvania Department of Environmental Protection, Pennsylvania Fish and Boat Commission, Susquehanna River Basin Commission, Susquehanna University, and USGS. We thank Shannon Julian and Jeffrey Kalie for technical assistance during laboratory work at the USFWS Northeast Fishery Center. We are grateful to Stephanie Dowell and Luke Iwanowicz for reviewing and providing advice on a previous manuscript draft. All fish handling was conducted in accordance with Protocol Number 42544 approved by the Institutional Animal Care and Use Committee at Pennsylvania State University. Use of trade names is for identification purposes only and does not imply endorsement by the U.S. Government. The findings and conclusions in this article are those of the author(s) and do not necessarily represent the views of the USFWS.