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BiologyAnadromous. A permanent freshwater resident population is believed to occur in Morrison Creek, British Columbia. In marine waters, they inhabit surface waters. In fresh waters, they occur in lakes, rivers, and creeks. They leave rivers to enter the sea in late spring or early summer, where they actively feed throughout the summer, and return to the rivers in the fall (Ref. 89241). Parasitic adults are found in estuaries and the ocean, migrating to clear gravel riffles of streams to spawn (Ref. 5723). Ammocoetes burrow into the mud where they live for an unknown period and migrate to the sea only after transformation (Ref. 1998). Adults feed by ripping flesh from other fishes (Ref. 2850), ammocoetes feed on microscopic plants and animals just like other members of this family (Ref. 1998). Parasitism can take place at a length of 16.2 cm TL (Ref. 1998). Preyed upon by a number of fishes, e.g. lingcod, and birds (Ref. 1998). In the Sacramento River, California, the spawning season is thought to be from late April into May. Fecundity, 11,398-37,288 eggs/female. Egg diameter, 0.6-0.7 mm (Ref. 89241). Because of its small size, it is unlikely to pose a threat to economically important fish (Ref. 1998). Utilized fresh or smoked by some cultures (Ref. 27436).