Relationship Between Thickness of Daily Growth Increments in Sagittae and Change in Body Weight of Sockeye Salmon (Oncorhynchus nerka) Fry

Sixty-four laboratory-reared sockeye salmon (Oncorhynchus nerka) fry were marked to enable identification as individuals. Each was weighed initially on June 6 or 8, 1979; and again on July 6; and surviving fish were weighed a third time on July 20. After the final weighing, sagittae were removed and a standard otolith radius, corresponding to each weight, was determined by counting back from the otolith edge the appropriate number of daily increments. The regression of ln otolith radius on ln fish weight was linear, with r2 = 0.92, demonstrating a relationship between mean thickness of a daily increment in sagittae, and mean daily change in weight of the fry. Using this regression line, previous weights were back calculated from corresponding otolith radii with errors in the order of 15%.Key words: otoliths, daily growth increments, back calculation, sockeye salmon