Integrating side-scan sonar and acoustic telemetry to estimate the annual spawning run size of Atlantic sturgeon in the Hudson River

Abstract

There is considerable interest in evaluating the status and trends of sturgeon populations, yet many traditional approaches to estimating the abundance of fishes are intractable due to their biology and rarity. Side-scan sonar has recently emerged as an effective tool for censusing sturgeon in rivers, yet challenges remain for censusing open populations that may visit specific habitats over periods of time (e.g., spawning runs). We use a hierarchical model to integrate side-scan sonar with acoustic telemetry, to estimate the proportion of a spawning run fitted with acoustic tags (12%; 95% CrI = 8%–16%) and extrapolate to the total run size in 2014. Our investigation represents a novel approach to generating run size estimates in a large river and provides the first estimate of Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) spawning run size for the Hudson River ([Formula: see text] = 466; 95% CrI = 310–745) since the fishery moratorium in the 1990s. Our estimate suggests that the Hudson River holds one of the largest contemporary populations of Atlantic sturgeon, but also indicates that it remains sharply depleted relative to virgin conditions.

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

“…Despite a moratorium prohibiting all take in U.S. waters in 1998 and listing under the Endangered Species Act in 2012, recovery has been minimal (Kazyak et al 2020), with population estimates remaining extremely low in comparison to historic estimates at the end of the 19th century (Secor and Waldman 1999; O’leary et al 2014; ASMFC 2017). To address drastic declines in sturgeon populations, it is recommended to reduce harvest, improve river conditions, habitat, and reduce direct impediments to spawning (Billard and Lecointre 2001; Pikitch et al 2005; ASSRT 2007; ASMFC 2017).…”

“…Dredging, bottom disturbance, or other activities that may directly or indirectly impact Atlantic Sturgeon, including the early life stages, near the spawning areas should be minimized or avoided from mid‐May through September. Despite the historically low abundance, the Hudson River still boasts the largest population of Atlantic Sturgeon in the USA (ASMFC 2017; Kazyak et al 2020), and these findings should be considered when making management decisions for other river systems where less information is available.…”

“…The Hudson River is no exception, with the lower ~100 kilometers of the river being brackish or seasonally brackish, which precludes it from successful spawning, while upper ~145 kilometers of the tidal river remain fresh and is available for spawning (Bain 1997). The lower ~100 kilometers of the Hudson River still plays a critical role in pre-spawning behavior (Kazyak et al 2020;Breece et al In Prep) and as habitat for early stage juveniles (Bain 1997).…”

“…This article is protected by copyright. All rights reserved Hudson River still boast the largest population of Atlantic Sturgeon in the U.S. (ASMFC 2017, Kazyak et al 2020) and these findings should be considered when making management decisions for other river systems where less information is available.…”

“…Atlantic Sturgeon Acipenser oxyrinchus are endangered throughout much of their U.S. range (USOFR 2012) as a result of multiple threats where the associated risks are dependent on life history phase. The Hudson River is estimated to support the largest population of Atlantic Sturgeon in the United States, with an estimate of less than 1,000 spawning adults (Kahnle et al 2007; Kayzak et al 2020). Despite being the largest population, the Hudson River Atlantic Sturgeon are listed as endangered under the New York Bight distinct population segment and continually face threats such as disturbances from the shipping industry (USOFR 2016), energy development (USDE 2013), and poaching (ASSRT 2007) when occupying the river.…”