Active nuclease inhibition over passive freezing secures the genomic archive of fish eye lenses

Fish eye lenses offer a chronological archive of individual life histories and preserve genomic DNA. However, integrating ecological and genetic data is hindered by post‐mortem nuclease degradation, and standardized DNA preservation protocols for this tissue remain undefined. We evaluated chemical and thermal preservation methods to maximize DNA yield and integrity from fish lenses. Using a paired experimental design across three marine species, we demonstrate that chemical stabilization with TRIzol yields significantly higher DNA quantities (2654.7 ± 331.5 ng) than ultra‐low temperature freezing at −80°C (1425.4 ± 866.6 ng) or standard freezing at −20°C. TRIzol denatures endogenous nucleases upon contact, preventing the enzymatic fragmentation associated with passive freezing. This optimized protocol establishes a methodological standard for eco‐isotopic genomics, enabling the direct coupling of phenotypic chronologies with genotypes to assess marine population resilience.