Temperature and photoperiod strongly influence the timing of Atlantic Sturgeon volitionally spawning in captivity
James P Henne, James A Crossman, Molly A H Webb, Roman L Crumpton, Kent M WareAbstract
Objective
Understanding how environmental variables influence the timing of spawning is important for the conservation of imperiled fishes like the endangered Atlantic Sturgeon Acipenser oxyrinchus. We observed mature Atlantic Sturgeon volitionally spawning in captivity over a 14-year period to evaluate the change in how both spawn timing and the daily probability of spawning changed in response to environmental (temperature, photoperiod, lunar cycle) and biological (individual females) variables.
Methods
Adults were held at Bears Bluff National Fish Hatchery in seminatural conditions mimicking the Altamaha River temperature profile and under natural photoperiod. We fit Bayesian linear regression models using a suite of covariates to represent patterns in environmental conditions across several time periods in advance of when spawning was observed.
Results
A total of 35 volitional spawning events were observed over the study period, with 31 assigned to individual females. The average interval between spawning events for individual females was 1.7 years (range = 1–9 years). Atlantic Sturgeon responded more to cumulative thermal conditions in the lead-up to spawning compared with fluctuations in temperature closer to the observed event, with mean water temperature the 30 d prior to spawning and accumulated thermal units over the same period being the strongest predictors of spawning time. Median spawning time was August 21 at an average temperature of 22.7°C (range = 20.9–25.3°C), and with each 1°C increase in the mean temperature over the preceding 30 d, spawning advanced by 16.7 d. The cumulative probability that spawning would occur increased sharply as photoperiod declined past 14 h and reached its maximum near a day length of 13.2 h.
Conclusions
Volitional spawning produced viable offspring, and the approach could be considered for conservation efforts. Individual females spawned volitionally in captivity in consecutive years, which is not well documented for any sturgeon species. Results add to our understanding of the reproductive ecology of the species that can supplement results from monitoring in the wild. For fall-spawning Atlantic Sturgeon, our results help to shed light on uncertainties related to long-term implications of climate change on thermal conditions for spawning and early life stage rearing.