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.