Growth‐Increment Formation Using Otoliths and Scales for Age‐0 Chinook Salmon

Retrospective analysis is used to reconstruct fish body size at previous ages, with size and growth assumed to be accurately reflected by scale circuli and otolith increments. Using a 122‐d laboratory experiment, this study validated the relationship between fish body size and growth with scale circuli and otolith daily growth increments for age‐0 Chinook Salmon Oncorhynchus tshawytscha. Somatic growth was accurately reflected by growth in scale radius and growth in otolith diameter, indicating that growth in these two measures was proportional to growth in fish length. Although the width between scale circuli reflected somatic growth, daily growth was not accurately reflected by the width between corresponding otolith daily increments. Study results showed that fish deposited new otolith increments on a daily basis, but that new scale circuli were deposited at each successive increase of 5 to 6 mm in total length. These findings provide a foundation for future retrospective growth analyses involving Chinook Salmon and allow for the conversion of otolith and scale measurements into fish lengths, which are meaningful in studies of growth and survival. Received November 5, 2015; accepted April 8, 2016 Published online August 26, 2016