Why It Matters

A recent Congressional Research Service (CRS) report, published July 15, examines how DNA methylation, a chemical modification that accumulates as organisms age, could reshape how federal agencies assess fish populations and other marine life. The technique offers a nonlethal alternative to traditional methods that require killing animals to examine hard parts like scales and ear bones, potentially opening new avenues for managing threatened species and improving fisheries data.

Federal agencies currently rely on lethal sampling to determine the age, sex, and maturity of fish and marine mammals, destroying the very organisms they aim to manage.

The Big Picture

Scientists have developed an epigenetic clock using DNA methylation patterns for commercially important species including Atlantic cod, cownose rays, deepwater scorpionfish, and European seabass. Studies suggest the approach would function similarly across shorter- and longer-lived fish species, though experts recommend further testing across fish with different body types and life histories.

Environmental factors complicate the picture. Some researchers propose that methylation predicts chronological age independent of environmental disruptions in certain species, but knowledge gaps remain about universal applications across diverse marine resources.

Nonlethal tissue biopsies have enabled researchers to age killer whales, pinnipeds, polar bears, beluga whales, and bottlenose dolphins. DNA methylation shows promise for determining relative age in sea turtles and detecting thermal stress in the species. Short-tailed shearwaters demonstrated increased methylation with estimated age in most cases, and most seabirds do not have external identifiers of chronological age.

The CRS has not identified examples where federal agencies have used DNA methylation for living marine resource surveys and assessments. The report identifies this gap, even as Congress has funded molecular and genomic technologies for disease detection and genome sequencing across federal programs.

The Bottom Line

DNA methylation represents a complement to, not a replacement for, traditional sampling methods.

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