A Tale of Two Rivers; Atlantic Sturgeon Spawning in the Delaware and Hudson Rivers

Five Distinct Population Segments (DPS) of Atlantic Sturgeon (Acipenser oxyrinchus oxyrinchus) were listed under the Endangered Species Act in 2012. The New York Bight DPS is comprised of the Delaware, Hudson, and Connecticut Rivers; of which the Delaware and Hudson contain extant spawning populations.  From 2009 – 2014, we estimated relative run size and reproductive cycles utilizing 256 adult (>150cm FL) Atlantic Sturgeon implanted with long lived acoustic transmitters.  Extensive passive receiver networks were maintained in the Delaware and Hudson Rivers to monitor the periodicity of river returns, while spawning activity was inferred from both timing and movement patterns. We found no evidence of interbasin straying; individuals returned to the same rivers in subsequent years. The majority of males appeared to spawn annually, while females returned at 2-4 year intervals; both of these estimates are markedly lower than suggested by the literature. Our findings suggest that run size estimates for both male and female Atlantic Sturgeon  are higher for the Hudson compared to the Delaware River (3.4 and 3.1 times greater respectively).  These relative run size estimates and insights on spawning periodicity provide much needed information on the status of these two rivers as managers struggle to recover this species.