It’s elemental, my dear Watson: validating seasonal patterns in otolith chemical chronologies

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Hüssy, Karin, Krüger-Johnsen, Maria, Thomsen, Tonny Bernt, Heredia, Benjamin Dominguez, Naeraa, Tomas, Limburg, Karin E., Heimbrand, Yvette, McQueen, Kate, Haase, Stefanie, Krumme, Uwe, Casini, Michele, Mion, Monica, Radtke, Krzysztof
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2021
• Subjects: Text; article; ddc:570; Age validation > elements > microchemistry > otolith > physiology > seasonal patterns; Gadus morhua
• Online Access: https://doi.org/10.1139/cjfas-2020-0388; https://www.openagrar.de/receive/openagrar_mods_00073796; https://www.openagrar.de/servlets/MCRFileNodeServlet/openagrar_derivate_00041377/dn063187.pdf

Accurate age data are essential for reliable fish stock assessment. Yet many stocks suffer from inconsistencies in age interpretation. A new approach to obtain age makes use of the chemical composition of otoliths. This study validates the periodicity of recurrent patterns in 25Mg, 31P, 34K, 55Mn, 63Cu, 64Zn, 66Zn, 85Rb, 88Sr, 138Ba, and 208Pb in Baltic cod (Gadus morhua) otoliths from tag–recapture and known-age samples. Otolith P concentrations showed the highest consistency in seasonality over the years, with minima co-occurring with otolith winter zones in the known-age otoliths and in late winter – early spring when water temperatures are coldest in tagged cod . The timing of minima differs between stocks, occurring around February in western Baltic cod and 1 month later in eastern Baltic cod; seasonal maxima are also stockspecific, occurring in August and October, respectively. The amplitude in P is larger in faster-growing western compared with eastern Baltic cod. Seasonal patterns with minima in winter – late spring were also evident in Mg and Mn, but less consistent over time and fish size than P. Chronological patterns in P, and to a lesser extent Mg and Mn, may have the potential to supplement traditional age estimation or to guide the visual identification of translucent and opaque otolith patterns used in traditional age estimation. Si des données exactes sur l’âge revêtent une importance fondamentale pour l’évaluation fiable des stocks de poissons, l’interprétation des âges pour de nombreux stocks est minée par des incohérences. Une nouvelle approche d’estimation des âges repose sur la composition chimique des otolites. La présente étude valide la périodicité de motifs récurrents des concentrations de 25Mg, 31P, 34K, 55Mn, 63Cu, 64Zn, 66Zn, 85Rb, 88Sr, 138Ba et 208Pb dans des otolites de morue (Gadus morhua) de la mer Baltique tirés d’échantillons de marquage–recapture et d’âges connus. Les concentrations de P des otolites montrent la plus grande cohérence sur le plan de la saisonnalité au fil ...