Alaska blackfish (Dallia pectoralis) are found only in Alaska and eastern Siberia. They typically live in the densely vegetated areas of lowland swamps, ponds, rivers, and lakes.
Alaska blackfish are seldom longer than 8 inches, although individuals up to 13 inches have been found. They are distinguishable from other fish by their large paddle-like lower front fins and tail, tiny ventral lower middle fins, backward placement of their upper and anal fins, and rather broad, flat heads. Their color is dark green or brownish on the upper sides and pale below, with irregular blotchy areas on their side. Mature males can be distinguished from females by the presence of a reddish fringe along the dorsal, tail, and anal fins. Also, in mature males the tips of the ventral fins extend well beyond the front of the anal fin, whereas in females they do not.
Spawning occurs from May to August, with the possibility of individual fish spawning several times and females releasing only a portion of their eggs each time. Depending on her size, a female may release a total of 40 to 300 eggs at intervals throughout the entire spawning period. The eggs adhere to the heavy vegetation and hatch in a short time in temperate waters of about 54 degrees. The young, depending on water temperature, live off their yolk sacs for about ten days.
The Alaska Blackfish are rather sluggish, bottom-dwelling fish that use their large pectoral fins to paddle slowly about the vegetation in search of food. Once a prey organism is spotted, they capture it with a quick dart, much like a northern pike.