Black Bullhead Otolith Annual and Daily Increment Validation

Otolith age validation studies are essential to identify the accuracy of using otoliths to age fish; however, black bullhead (Ameiurus melas) otolith validation studies have not been conducted for either adult or age-0 individuals. Therefore, the objective of this study was to validate annu- lus and daily ring formation in lapilli otoliths of black bullheads. We assessed timing of annulus formation using marginal increment analysis on 409 black bullheads caught monthly from July 2015–June 2016 in Lake Carl Etling, Oklahoma. We evaluated daily growth increment deposition by batch-marking 253 age-0 black bullhead by immersion in a solution of 700 mg L–1 oxytetracycline (OTC) for 6 hrs to provide a date stamp; thereafter, 10 fish were pulled from the tank every 10 days and had otoliths removed for analysis. We observed that black bullhead produced a single annulus in their lapillus otolith in June. Daily ring deposition was observed in age-0 black bullhead; between reader precision was high for estimates pre-OTC mark, and known ages were accurately estimated up to 37 days post-OTC mark representing fish up to 70 days old. Results of this study demonstrated that lapilli otoliths are reliable aging structures for black bullhead in Oklahoma to determine population characteristics such as recruitment, growth, spawning time, and mortality.

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