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Stock assessors commonly use models that incorporate biological data such as fish length and age to determine the status of fish stocks and how different management scenarios affect stock size. Ages used in assessment models need to be accurate and precise because ageing error can affect many model inputs and potentially result in stock mismanageme...
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The paper investigates the possibility of determining the age of dub Limanda limanda Linnaeus, 1758, by the length, width, thickness and mass of the otolith. The purpose of the study is to evaluate the possibility of using this method. A total of 247 otoliths (172 females and 75 males) were processed. The age of the dub in the Chupa Bay ranged from...
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... individuals for a single species; Hoie & Folkvord, 2006;Kastelle et al., 2017;Kimura et al., 2006;Terwilliger et al., 2023;Weidman & Millner, 2000). In response to our first hypothesis, we found F I G U R E 5 Von Bertalanffy growth curves for isotope-based age, otolith age, and scale age estimates of two age readers (reader 1 and reader 2) on 86 northern pike sampled from three coastal lagoon chains and several tributaries around Rügen island in Germany between June 2019 and November 2020. ...
Accurate age estimates are crucial for assessing the life‐histories of fish and providing management advice, but validation studies are rare for many species. We corroborated age estimates with annual cycles of oxygen isotopes (δ ¹⁸ O) in otoliths of 86 northern pike ( Esox lucius ) from the southern Baltic Sea, compared results with visual age estimates from scales and otoliths, and assessed bias introduced by different age‐estimation structures on von Bertalanffy growth models and age‐structured population models. Age estimates from otoliths were accurate, while age estimates from scales significantly underestimated the age of pike older than 6 years compared to the corroborated reference age. Asymptotic length () was larger, and the growth coefficient was lower for scale ages than for corroborated age and otolith age estimates. Consequentially, scale‐informed population models overestimated maximum sustainable yield (), biomass at (), relative frequency of trophy fish (), and optimal minimum length limit but underestimated fishing mortality at (). Using scale‐based ages to inform management regulations for pike may therefore result in conservative management and lost yield. The overestimated asymptotic length may instill unrealistic expectations of trophy potential in recreational anglers targeting large pike, while the overestimation in MSY would cause unrealistic expectations of yield potential in commercial fishers.
Marine mollusk shells continuously incorporate oxygen isotope signatures during growth that are representative of their surrounding environment and thus produce valuable records of seawater temperature and oxygen isotopic composition. These records of past environmental conditions can be measured in situ at length-scales down to sub-daily growth increments using high resolution ion microprobes (SIMS). However, the determination of oxygen isotope ratios in aragonite, the most common shell mineral, is hampered by a lack of ideal reference materials, limiting the accuracy of isotope calibrations and temperature reconstructions. Here, we cultured marine Anadara trapezia bivalves under controlled environmental conditions at four seawater temperatures ranging from 13 to 28 °C. The start of the growth period was marked in the crossed-lamellar shell ultrastructure using strontium labelling, enabling precise targeting of the SIMS analyses. A novel calibration method, specifically tailored to analyses of biogenic aragonites with organic-inorganic architectures, has been developed to correct matrix biases that affect the accuracy of all such SIMS oxygen isotope analyses. The matrix fractionation bias calibration was achieved by combining two aragonite reference materials in a linear relationship, pinning the SIMS biases to the true composition as a function of calcium abundances. The oxygen isotope calibration provided a novel seawater temperature versus seawater-corrected oxygen isotope fractionation relationship of T (°C) = 23.31 ± 0.34 - 4.31 · (δ18Oaragonite [‰ VPDB] - δ18Oseawater [‰ VSMOW] ± 0.22) that improves the applicability of in-situ oxygen isotope-based paleo-environmental reconstructions of marine bio-aragonite proxy archives.
