Smolt Transformation and Seaward Migration in 0-Age Progeny of Adult Spring Chinook Salmon (Oncorhynchus tshawytscha) Matured Early with Photoperiod Control

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Abstract
Maturation of hatchery-held adult spring-run chinook salmon (Oncorhynchus tshawytscha) was accelerated by decreasing photoperiods. Spawning occurred 1 mo earlier than with nontreated fish. Because of early hatching, progeny from the photoperiod regulated adults were larger and exhibited signs of parr–smolt transformation such as changes in coloration and behavior, elevation of gill Na+-K+ ATPase activity, and active seaward migration at age 0, nearly 1 yr prior to usual releases of juveniles from normally spawned adults.