Taxonomy and distribution

Abstract

This is a family of freshwater fish distributed throughout the world in the Northern Hemisphere (section 1.4). The general body form is long, and subcylindrical in the young and smaller species but laterally compressed and deep bodied in older representatives of the larger species. The head is characterized by a long, flattened snout, large gape, mouth well armed with teeth on jaws, vomer, palatines and tongue. The eyes are moderately large, as is typical in shallow-water sight predators. The unpaired fins (dorsal, caudal and anal) are concentrated at the rear as an adaptation to sprint predation, usually, but not always, on other fish and other vertebrates. The caudal fin is forked, and the paired fins are not large. Nelson (1994) summarized characters of the family as follows: caudal fin with 40 to 50 rays, 17 (rarely 16) branched; infraorbital sensory canal with eight or more pores, nasal bones present, branchiostegal rays 10 to 20, vertebrae 43 to 67. The gill rakers are reduced to patches of small, very sharp denticles. The lateral line is complete and straight, all scales are cycloid, but scales on the lateral line, and elsewhere on some species, are characteristically notched or heart-shaped (cardioid). Maximum size (muskellunge, Esox masquinongy) approximately 165 cm. Maximum age in that species in excess of 30 years, and maximum weight approaching 32 kg, but the smallest species (redfin pickerel, E. americanus americanus) not exceeding 330 mm length, 200 g weight and 8 years of age.