Movement and Out‐Migration of Juvenile Atlantic Sturgeon in Georgia, USA

Abstract

Atlantic Sturgeon Acipenser oxyrinchus, a federally endangered anadromous fish, persist along the East Coast of North America. Despite two decades of federal protection, many populations have yet to fully recover and major knowledge gaps remain, especially in the southern portion of the species’ range. The seasonal movement patterns of river‐resident juveniles (RRJs) are not well understood, and little is known about the transition from the RRJ life stage to the marine‐migratory juvenile (MMJ) life stage. During the summers of 2014–2016 we captured and acoustically tagged age‐1 RRJ Atlantic Sturgeon in the Ogeechee, Altamaha, and Satilla rivers, Georgia, to (1) describe and quantify seasonal movements of RRJ Atlantic Sturgeon in order to identify important estuarine nursery areas and (2) examined temporal patterns of out‐migration in order to better understand the critical transition from RRJ to MMJ in Georgia rivers. Movements of 79 fish were monitored using an array of stationary receivers deployed downstream from the heads of tide in each river system. During the summer months in each river, the fish congregated in upriver, freshwater reaches, but during the winter months they moved downriver and became more broadly distributed. Some fish (36.7%; n = 29) migrated back up their natal river in the spring and remained there as age‐2 RRJs. We observed the out‐migration of 30.4% (n = 24) of age‐2 MMJs only during December–March, based on detections outside their natal river. The results of this study support the assumption of the closure of age‐1 populations that underpins recent quantitative studies of Atlantic Sturgeon recruitment.

Evaluating population trends of juvenile Atlantic Sturgeon at low abundance in a dynamic estuarine environment (Hudson River, New York)

“…Our final model indicated a positive trend in catch rates associated with temperature, with mean posterior predicted catch rates more than doubling over the sampling range (0–15°C), which supports the importance of temperature as a cue for movement and distribution of juvenile Atlantic Sturgeon within estuaries (Fox & Peterson, 2019; Niklitscheck & Secor, 2005). Temperature‐related migratory behavior that redistributes fish populations can affect their availability to standardized surveys, thereby biasing abundance indices (DuFour et al, 2019; Harley et al, 2001; Maunder et al, 2006).…”

“…The impact of cold temperature‐related susceptibility is an important consideration in northern DPS but may decline with latitude in southern DPS (Chesapeake Bay, Carolina, and South Atlantic). However, southern DPS regularly experience temperatures greater than 25°C (Fox et al, 2018; Fox & Peterson, 2019; Moser & Ross, 1995; Niklitscheck & Secor, 2005; Schueller & Peterson, 2010), which could also reduce susceptibility to a survey. Higher temperature, lower dissolved oxygen, and increased metabolic rate could lead to restricted movement (Niklitscheck & Secor, 2005, 2009) and a higher proportion of structural zeroes in passive survey gears (e.g., gill nets) at high temperature.…”

“…Adult fish primarily occupy coastal marine waters (Dunton et al, 2010; Erickson et al, 2011; Laney et al, 2007) and migrate into freshwater portions of coastal rivers to spawn (ASSRT, 2007). Upon hatching, young‐of‐year fish migrate downstream to brackish nursery habitats to spend the first 1–6 years of life, with clinal variation, in estuarine portions of rivers (Bain et al, 2000; Fox & Peterson, 2019; Peterson et al, 2000). Atlantic sturgeon populations that were negatively affected by habitat degradation, harvest, bycatch mortality, laxed regulatory mechanisms, and other human‐induced issues were protected by a 1998 coastwide fishing moratorium and an intensive population status review begun in 2003 (ASSRT, 2007).…”

Long‐Term Trends in Juvenile Atlantic Sturgeon Abundance May Signal Recovery in the Hudson River, New York, USA

“…Fortunately, juvenile populations of Atlantic Sturgeon remain in their natal rivers for 1–6 years (Dovel and Berggren 1983; Hilton et al. 2016; Fox and Peterson 2019), providing a window for stock‐specific monitoring prior to emigration to the Atlantic Ocean (Bain et al. 1999; Kahnle et al.…”

“…Additionally, Atlantic Sturgeon mature late (10-28 years; Hilton et al 2016) and may only spawn periodically in major freshwater rivers (Van Eenennaam et al 1996;Hilton et al 2016); therefore, population recovery may not be evident in the spawning stock for several decades. Fortunately, juvenile populations of Atlantic Sturgeon remain in their natal rivers for 1-6 years (Dovel and Berggren 1983;Hilton et al 2016;Fox and Peterson 2019), providing a window for stock-specific monitoring prior to emigration to the Atlantic Ocean (Bain et al 1999;Kahnle et al 2007;Sweka et al 2007).…”