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BiologyFound in mud burrows in upper reaches of coastal streams for the first four years of life until metamorphosis and subsequent downstream migration to the sea (Ref. 44894). Adults inhabit the sea for an undetermined period and are parasitic on other fishes. Migrate upstream which may last for 16 months and spawn in freshwater (Ref. 5154). Adults are often found below weirs and dams during their spawning migration which may take them 60 km or more upstream of the coast (Ref. 44894). Migration mostly takes place in rainy nights when water levels are rising, with temperatures between 12-14.5°C and when there is extensive cloud cover or during the dark phase of the moon (Ref. 5154). Stones with a volume of 144 ml, equivalent in size to a tennis ball, can be transported by adults using their oral disc (Ref. 89241). Sometimes they exit the water by wriggling up the bank to bypass obstacles to migration (Ref. 44894). Adults stop feeding while in freshwater and die shortly after spawning. Maximum length reported to reach 62 cm TL (Ref. 5154). Common length is 45-50 cm SL. Status of abundance decreased due to proliferation of obstacles such as dams and weirs to upstream spawning runs (Ref. 44894). Fecundity, 48,004 to 68,212 eggs/female (Ref. 89241).In New Zealand, the Maori use the pouched lamprey at the beginning of their upstream migration for human consumption and ceremonial purposes (McDowall, 1990). These are caught using weirs built along river edges or collected by hand as they are making their way up the rocky face of falls. They are then dried for human consumption (Ref. 89241).