ABSTRACT
Recent estimates suggest that there are approximately 33,200 species of fi sh in the world, 7000 of which have been described since 1995 (Eschmeyer 2014). Of those, approximately 12,000 species strictly occupy fresh water habitats (Nelson 2006). The order Perciformes represents the largest group of vertebrates, consisting of some 18 suborders of fi sh, the largest of which is Percoidei, which contains some 71 families representing about 530 genera and 3000 species (Nelson 2006). One of those families, Percidae, consists of 10 genera of fi shes limited to fresh water, particularly in the Northern Hemisphere. The focus of the present volume is on the three extant members comprising the genus Perca: P. fl avescens Mitchill, 1814, P. fl uviatilis Linnaeus, 1758, and P. schrenkii Kessler, 1874.
