RADIOCHEMICAL DETERMINATION OF LONGEVITY IN FLYINGFISH HIRUNDICHTHYS-AFFINIS USING TH-228 RA-228/

Radiochemical assays of fish otoliths using the radioisotope pair Pb-2 10/Ra-226 have proven successful in determining the longevity of sever al long-lived fish species, but are unsuitable for determining ages le ss than about 3 yr. We tested the utility of the radioisotope pair Th- 228/Ra-228 for determining the longevity of the four-winged flyingfish Hirundichthys affinis of the eastern Caribbean. A new decay equation was developed for interpreting radioactivity in whole otoliths charact erized by a nonlinear growth history. Assay results on both whole otol iths and otolith cores indicated that the mean age of adult flyingfish was about 1 yr, and significantly less than 2 yr. The Th-228/Ra-228 r adiochemical dating technique appears to be well suited for age determ inations of fish up to age 5.