Molecular Phylogenetics and Hybridization of Sander: Implications for Effective Management

Percidae is among the most specious families of freshwater fishes in the Northern hemisphere with more than 170 species in North America and 14 recognized species in Eurasia.  Within Percidae, two primary genera are the target of recreational and commercial fisheries, Sander (pikeperches, walleye, and sauger) and Perca (perches).   Currently, Sander is composed of five species the North American-dwelling sauger (S. canadense) and walleye (S. vitreus) and the European/Eurasian endemics of zander (S. lucioperca), Volga pikeperch (S. volgensis), and the estuarine perch (S. marinus).   Understanding the phylogenetic history of species allows us to better understand evolutionary processes resulting in extant diversity and provides valuable insight for future management/conservation issues.  The molecular systematics of Sander has been the target of various studies.  The molecular systematics of the genus recognizes two distinct lineages, the North American lineage and the Eurasian lineage.  Hybridization within these lineages has been documented including the well-known walleye x sauger hybrid, saugeye and artificial hybrids of zander and Volga pikeperch.  Previous studies have shown difficulties in identifying hybrids via morphological/field-based assessments and stressed the importance of using genetic methods to confirm hybrids, especially in post-F₁ hybrids.  The incidence of natural hybridization in sympatric systems ranges from 0-39% with several reports of introgression within the species.  This introgression is a long-term threat to the genetic integrity of native fish and of critical concern when management agencies have explicit goals of protecting the genetic integrity of populations.  The insights from the molecular phylogenetic studies and hybridization studies on the management and conservation of Sander will be discussed.