Enters freshwater during advanced stage of sexual development and spawning occurs almost immediately (Ref. 1998). Spawning occurs at depths of ~3 meters, current speeds of ~20cm/sec. near the head waters over sand and pebbles at 4-11° C water temperature. At spawning time the female excavates a hole of around 1 meter diameter and 50 cm depth before spawning can occur (Ref. 12218). Nest building is done by the female by lying on one side and lashing its tail to displace the sand and silt on the river bed. The pair then settles in the nest, mouths gape, and with rapid vibration of the pair, eggs and milt are released. The female then covers the nest. Males are aggressive and may spawn with different females; females likewise may spawn with other males and therefore builds different nests. Adults die after a week (Ref. 1998). A fish spawns 700-7,000 eggs in two to three egg releases. Eggs are ~300-3,500 per spawn. Egg size is ~6.7 mm, water temp. is 8-10°C at 60 days before hatching. Larva size is around 16 mm. Come springtime the juveniles go to the ocean and come back 3-4 years later to their exact birthplace. This fish reaches maturity in 2-4 years. Larvae are found around the spawning site, Juveniles are found around the coast. Juveniles migrate to the ocean at ~27-45 mm during February at water temperatures around 4° C (Ref. 12218).Reproductive strategy: synchronous ovarian organization, determinate fecundity (Ref. 51846).