Haha it honestly would make a lot of work much easier. Instead we inject a little oxytetracycline into 1000s of fish which stains calcified structures and release them again in the hopes someone recaptures one or so x years later in the hopes they report it and there are y rings between the dark ring and the margin of the otolith/vertebrae.

Should be some type of nuke that would release weird isotopes but with minimal toxicity?