Presently, there are four species of native esocids, Esox masquinongy, E. lucius, E. niger and E. americanus and one exotic species, E. reicherti, at large in North America. The four native species now include five named forms, intergrades and natural hybrids. Taxonomic divisions within species are under study. Post-Wisconsin, natural distribution patterns have been changed by man and man is again adjusting the distributional limits of some species by extensive introductions.
Changes in taxonomic concepts of the family and species are traced. The present distribution of each species is given in detail and suggestions are made concerning their distributions in the past and future.