Reconstructing juvenile chinook salmon life history in the Salmon River Estuary, Oregon, using otolith microchemistry and microstructure

Publisher's PDF courtesy of the American Fisheries SocietyWe quantified the juvenile rearing and migratory patterns of individuals from a population of fall-spawning Chinook salmon Oncorhynchus tshawytscha in Oregon's Salmon River estuary using otolith microchemistry and microstructure. The study confirmed the daily periodicity of otolith growth increments in a natural fish population under field conditions and validated fundamental assumptions about increased otolith strontium: calcium values during entry into saline waters. The otolith results indicated that more than 75% of the subyearling Chinook salmon captured near the mouth of the Salmon River had entered the estuary during the summer and that two-thirds of these fish had spent more than a month in the estuary before capture. Unlike in other Oregon coastal estuaries, in which the fingerling-migrant portion of their life histories is dominant, approximately two-thirds of Salmon River Chinook salmon in upper-estuary marshes were early fry (