Pygmy whitefish
The pygmy whitefish ("Prosopium coulterii") is a freshwater whitefish of the genus "Prosopium" in the family Salmonidae. Found in the mountain streams and lakes in western North America, it also has isolated populations in Lake Superior and in Ekityki Lake, Chukchi Peninsula. Description. The pygmy whitefish is a small herring-like fish with a long and cylindrical body by comparison to other whitefishes. Silvery in colour, it has a brownish back, and a whitish belly. Black spots on the side called "parr marks", which are present on young trout or "parrs", are present on the young of this  species, and on adults in some Alaskan populations. Commonly ranging from in length, it is typically long, and reaches a maximum length of . It is identified by its small size, and its large eye, which has a greater length than its blunt snout. Its dorsal fin and pectoral fin are usually clear, and its tail is clear with a faint dark spot. Its anal fin and pelvic fin are plain whitish. It has large scales with only 56–70 on its lateral line, fewer gill rakers, all characteristics that indicate a degree of differentiation from the other "Prosopium" fishes. Because of  this, it is considered an early offshoot (basal) species in its genus, and it is the most trout-like member of a genus considered the most trout-like and primitive whitefish group. Taxonomy. The pygmy whitefish was first described by Carl H. Eigenmann and Rosa Smith Eigenmann in 1892, as "Coregonus coulteri". they named the species after the prominent botanist John Merle Coulter. Since its initial description as a "Coregonus", it has been placed in the genus "Prosopium" of more primitive whitefishes. The members of this genus are distinguished from the other whitefishes by several characteristics, such as a single  flap of skin over the nostril, rather than one; "parr marks" as on trout and char; a round body; and a small toothless mouth. The genus name "Prosopium", meaning "mask" in Greek, refers to the large bones in front of its eyes. Distribution. The pygmy whitefish is found mostly in the northern Rocky Mountains, with three other disjunct populations. One is in Lake Superior, another is in southwestern Alaska, and the third is in the Ekityki Lake, Chukchi Peninsula, Russia. The pygmy whitefish's range probably was continuous until the late Pleistocene. In the Rocky Mountains it is found in  cold and rapid streams, and in cool lakes at depths of over . In Lake Superior it is found in cooler water, at depths of . Ecology. In Lake Superior, the pygmy whitefish spawns during November and December at depths of . Females lay an average of 362 orange eggs, with a diameter of . Elsewhere, the pygmy whitefish migrates upstream to spawn, usually spawning in November or December in gravelly streams. Pygmy whitefish feed primarily on the aquatic larvae of insects, and crustaceans. In Lake Superior, the amphipod "Pontoporeia" and various other crustaceans, mostly ostracods, form 77 percent of the pygmy whitefish's  diet. The burbot, kingfishers, and terns, and pikes have been recorded preying on the pygmy whitefish.