Otoliths suggest lifespans more than 30 years for free-living bowfin Amia calva: Implications for fisheries management in the bowfishing era.

The bowfin Amia calva is an amiid (Amiiformes) relict native to North America. It is the last surviving member of the Halecomorphi, a group of fishes that evolved more than 250 million years ago. Despite the phylogenetic significance of the amiids in vertebrate evolution, little has been published about their age and growth. Recreational bowfin harvest is currently unregulated throughout most of the USA, yet new recreational fisheries are emerging. As such, bowfin are increasingly harvested by sport bowfishing without limit, in addition to their growing commercial harvest for caviar. From 2017 to 2021 we studied a total of 81 bowfin from 11 populations across the east-west gradient of Minnesota within a narrow latitudinal margin (<50 km) of the 46th parallel north. We compared the allometry and translucence of bowfin asteriscus, lapillus and sagittal otoliths and found the lapillus otoliths provide consistent readability for age estimation despite being the smallest of the set. Size-at-age data derived from otoliths indicated that bowfin are sexually dimorphic in asymptotic length and may live up to 33 years, which is 15 years longer than previously estimated in wild populations, but comparable to what has been reported in captivity. Overall, 28% of the otolith-aged fish were estimated as older than the previously reported maximum age for wild bowfin populations. Our findings suggest that the bowfin life history may exhibit slower growth, greater longevity, and more variable recruitment than previously recognized, which sets the stage for more otolith-derived population demographics across their range and age validation study. Our results have direct implications for conservation of bowfin, especially amidst the increasing rates of exploitation during the bowfishing era.