Benjamin J. Schall Matthew J. Ward Cody E. Treft Steven R. Chipps Christopher A. Cheek Justin M. Sturtz 2026 <p><span id="_mce_caret" data-mce-bogus="1" data-mce-type="format-caret"><span>Isotope values in fish eye lenses may be useful in differentiating rearing origins. We compared eye lens isotopic values of fall fingerling age-0 walleye (</span><i>Sander vitreus</i><span>) reared in a hatchery pond, a recirculating aquaculture system (RAS), and a natural lake. Using 10 fish per rearing source, we delaminated layers from one eye lens per fish to assess temporal changes in carbon (δ</span>¹³<span>C) and nitrogen (δ</span>¹⁵<span>N) and pulverized the whole second eye lens for δ</span>¹³<span>C, δ</span>¹⁵<span>N, and sulfur (δ</span>³⁴<span>S). RAS-reared walleye values exhibited high precision among individuals and were δ</span>³⁴<span>S enriched. Pond-reared walleye had lower δ</span>¹³<span>C and δ</span>¹⁵<span>N core values compared to other rearing sources. For δ</span>¹³<span>C and δ</span>¹⁵<span>N, values remained consistent among layers for RAS-reared walleye, δ</span>¹⁵<span>N slightly increased for pond-reared and lake-reared walleye, and δ</span>¹³<span>C increased substantially among subsequent layers in pond-reared walleye. Bayesian 95% ellipses did not overlap among rearing sources. These results demonstrate that eye lens stable isotope analysis may be a useful tool for differentiating hatchery-reared and wild large fingerling walleye, specifically from RAS- and pond-reared sources.</span></span></p> application/pdf 10.1111/fme.70057 en Wiley Using eye lens stable isotopes to identify the rearing origin of fall age-0 walleye (<i>Sander vitreus</i>) article