Spawning Intervals, Timing, and Riverine Habitat Use of Adult Atlantic Sturgeon in the Hudson River

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Abstract The Hudson River currently supports the largest population of Atlantic Sturgeon Acipenser oxyrinchus in the United States despite currently supporting less than 1% of historic abundance. Federally listed as endangered throughout much of their range, Atlantic Sturgeon are still impacted by multiple threats, resulting in habitat destruction or direct mortality that has inhibited the rebuilding of populations despite more than 20 years without direct fishing pressure. To assist in management and reduction in anthropogenic impacts to adult Atlantic Sturgeon in the Hudson River, we have examined sex‐specific patterns related to spawning. Utilizing hundreds of adult Atlantic Sturgeon telemetered along the Atlantic coast and an extensive passive acoustic array from 2010 to 2016, we were able to estimate arrival, departure, and duration of occupancy for four segments of the Hudson River for male, female, and unknown‐sex individuals. Male Atlantic Sturgeon arrived above river kilometer (RKM; RKM 0 = Battery Park, New York) 100 at an average date of May 27, 12 d prior to females on June 8. While there were only a few significant differences in the timing of departure, the average date from RKM 100 was July 11 for males, June 29 for females, and July 23 for unknown‐sex individuals, as such occupancy was significantly longer for male Atlantic Sturgeon. This study shows that female Atlantic Sturgeon often spawned in consecutive years and had much shorter mean intervals between spawning appearances (females 1.66 years, males 1.28 years) than the historical literature suggests. While the timing of spawning is consistent with the historic record, we provide a timeline with finer resolution and much greater detail for adults in the Hudson River, as well as update the historic estimate of spawning return rates. Conservation measures to reduce direct impacts to spawning habitat and mature Atlantic Sturgeon would likely provide the most benefit if conducted between mid‐May through the end of July.

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