Alligator gar as a centenarian species: extending lifespan estimates using bomb radiocarbon and laser ablation–accelerator mass spectrometry

Abstract

Context The potential lifespan of alligator gar (Atractosteus spatula) is currently unknown. A previous study applied bomb radiocarbon (14C) dating to establish ages >60 years, but maximum age was limited by the rise of bomb-produced 14C in the 1950s. Aims An exceptionally large specimen (2.6 m, 148 kg) was captured in Mississippi and otolith growth zones revealed an age estimate of 95 years. This specimen provided an opportunity to apply new technology to validate the lifespan of alligator gar. Methods Developments in accelerator mass spectrometry (AMS) led to technology that measures 14C continuously from carbonates (laser ablation-AMS), as opposed to single sample 14C analysis. Key results Use of laser ablation AMS on the 2.6-m alligator gar otolith, and two smaller fish aged >60 years, supported ages that were older than original estimates by 5–20 years. Conclusions Our study indicates that alligator gar age can be underestimated for the largest fish, maximum recorded length is 2.6 m based on a historical photograph, and lifespan is at least 75–95 years with support for an age of 100 years for the 2.6-m fish. Implications An increase in lifespan of this magnitude would affect our understanding of population dynamics and recovery efforts.