Corroborating otolith age using oxygen isotopes and comparing outcomes to scale age: Consequences for estimation of growth and reference points in northern pike (<i>Esox lucius</i>)

Abstract Accurate age estimates are crucial for assessing the life‐histories of fish and providing management advice, but validation studies rare many species. We corroborated with annual cycles oxygen isotopes (δ 18 O) in otoliths 86 northern pike ( Esox lucius ) from southern Baltic Sea, compared results visual scales otoliths, assessed bias introduced by different age‐estimation structures on von Bertalanffy growth models age‐structured population models. Age were accurate, while significantly underestimated older than 6 years to reference age. Asymptotic length () was larger, coefficient lower scale ages otolith estimates. Consequentially, scale‐informed overestimated maximum sustainable yield (), biomass at relative frequency trophy optimal minimum limit fishing mortality (). Using scale‐based inform regulations may therefore result conservative lost yield. The asymptotic instill unrealistic expectations potential recreational anglers targeting large pike, overestimation MSY would cause commercial fishers.