Experimental validation of otolith-based age and growth reconstructions across multiple life stages of a critically endangered estuarine fish

PeerJ

article

Wilson Xieu¹  Levi S. Lewis¹  Feng Zhao¹  Rachel A. Fichman¹  Malte Willmes²  Tien-Chieh Hung⁴  Luke Ellison⁴  Troy Stevenson⁴  Galen Tigan⁴  Andrew A. Schultz⁵  James A. Hobbs¹ 

[1] Department of Wildlife, Fish, and Conservation Biology, University of California;Institute of Marine Sciences, University of California;Southwest Fisheries Science Center, National Marine Fisheries Service;Department of Biological and Agricultural Engineering, University of California;Bay-Delta Office;Bay-Delta Region, California Department of Fish and Wildlife

关键词: Otolith;    Fish;    Estuarine;    Freshwater;    Growth;    Validation;    Delta Smelt;    San Francisco;   

DOI  :  10.7717/peerj.12280

学科分类：社会科学、人文和艺术（综合）

来源: Inra

【 摘 要 】

BackgroundThe application of otolith-based tools to inform the management and conservation of fishes first requires taxon- and stage-specific validation. The Delta Smelt (Hypomesus transpacificus), a critically endangered estuarine fish that is endemic to the upper San Francisco Estuary (SFE), California, United States, serves as a key indicator species in the SFE; thus, understanding this species’ vital rates and population dynamics is valuable for assessing the overall health of the estuary. Otolith-based tools have been developed and applied across multiple life stages of Delta Smelt to reconstruct age structure, growth, phenology, and migration. However, key methodological assumptions have yet to be validated, thus limiting confidence in otolith-derived metrics that are important for informing major water management decisions in the SFE.MethodsUsing known-age cultured Delta Smelt and multiple independent otolith analysts, we examined otolith formation, otolith-somatic proportionality, aging accuracy and precision, left-right symmetry, and the effects of image magnification for larval, juvenile, and adult Delta Smelt.ResultsOverall, otolith size varied linearly with fish size (from 10–60 mm), explaining 99% of the variation in fish length, despite a unique slope for larvae < 10 mm. Otolith-somatic proportionality was similar among wild and cultured specimens. Aging precision among independent analysts was 98% and aging accuracy relative to known ages was 96%, with age estimates exhibiting negligible differences among left and right otoliths. Though error generally increased with age, percent error decreased from 0–30 days-post-hatch, with precision remaining relatively high (≥ 95%) thereafter. Increased magnification (400×) further improved aging accuracy for the oldest, slowest-growing individuals. Together, these results indicate that otolith-based techniques provide reliable age and growth reconstructions for larval, juvenile, and adult Delta Smelt. Such experimental assessments across multiple developmental stages are key steps toward assessing confidence in otolith-derived metrics that are often used to assess the dynamics of wild fish populations.

【 授权许可】

CC BY