Bomb radiocarbon dating reveals 40-year lifespan of Shovelnose Sturgeon (Scaphirhynchus platorynchus)—Implications for stock assessments of long-lived, primitive fishes

Abstract

Stock assessments for Shovelnose Sturgeon have largely been limited to age and growth analyses using pectoral fin rays despite potential underestimation of age and lack of age validation. Fisheries stock assessments rely on accurate estimates of vital rates for effective fisheries management, within which fish age and lifespan are of primary importance. Age was estimated using pectoral fin rays and otolith sections, and bomb radiocarbon (¹⁴C) dating was applied to otolith cores to determine lifespan and validate ages. Age reading of fin rays was straightforward, whereas most otolith thin sections provided two age-reading scenarios: lumping (primary increments) or splitting (finer increments) presumed annuli. While fin-ray estimates led to a maximum age of 14 years, otolith estimates led to maximum ages of 27 and 42 years. ¹⁴C dating provided support for a combination of lumping early in life, to splitting in later years, and validation of a ~40-year lifespan. Age reading of otoliths was imprecise and resulted in ~40% of thin sections that were not age scoreable. However, scoreable otolith sections, coupled with ¹⁴C dating, resulted in growth and lifespan information that are the most accurate to date for Shovelnose Sturgeon and can be used as a baseline toward stock assessment refinements.