Life history and status of Shortnose Sturgeon (Acipenser brevirostrumLeSueur, 1818)

Abstract

Summary Shortnose Sturgeon = SNS (Acipenser brevirostrum) is a small diadromous species with most populations living in large Atlantic coast rivers and estuaries of North America from New Brunswick, Canada, to GA, USA. There are no naturally land‐locked populations, so all populations require access to fresh water and salt water to complete a natural life cycle. The species is amphidromous with use of fresh water and salt water (the estuary) varied across the species range, a pattern that may reflect whether freshwater or saltwater habitats provide optimal foraging and growth conditions. Migration is a dominant behaviour during life history, beginning when fish are hatchling free embryos (southern SNS) or larvae (northeastern and far northern SNS). Migration continues by juveniles and non‐spawning adult life stages on an individual time schedule with fish moving between natal river and estuary to forage or seek refuge, and by spawning adults migrating to and from riverine spawning grounds. Coastal movements by adults throughout the range (but particularly in the Gulf of Maine = GOM and among southern rivers) suggest widespread foraging, refuge use, and widespread colonization of new rivers. Colonization may also be occurring in the Potomac River, MD–VA–DC (mid‐Atlantic region). Genetic studies (mtDNA and nDNA) identified distinct individual river populations of SNS, and recent range‐wide nDNA studies identified five distinct evolutionary lineages of SNS in the USA: a northern metapopulation in GOM rivers; the Connecticut River; the Hudson River; a Delaware River–Chesapeake Bay metapopulation; and a large southern metapopulation (SC rivers to Altamaha River, GA). The Saint John River, NB, Canada, in the Bay of Fundy (north of the GOM), is the sixth distinct genetic lineage within SNS. Life history information from telemetry tracking supports the genetic information documenting extensive movement of adults among rivers within the three metapopulations. However, individual river populations with spawning adults are still the best basal unit for management and recovery planning. The focus on individual river populations should be complemented with attention to migratory processes and corridors that foster metapopulation level risks and benefits. The species may be extirpated at the center of the range, i.e., the mid‐Atlantic region (Chesapeake Bay, MD–VA, and probably, NC), but large rivers in VA, including the James and Potomac rivers, need study. The largest SNS populations in GOM and northeastern rivers, like the Kennebec, Hudson, and Delaware rivers, typically have tens of thousands of adults. This contrasts with southern rivers, where rivers typically have much fewer (<2500) adults, except for the Altamaha River (>6000 adults). River damming in the 19th and 20th Centuries extirpated some populations, and also, created two dysfunctional segmented populations: the Connecticut River SNS in CT–MA and the Santee‐Cooper rivers–Lake Marion SNS in SC. The major anthropogenic impact on SNS in marine waters is fisheries b...

Temperature, discharge and development shape the larval diets of threatened green sturgeon in a highly managed section of the Sacramento River

“…Larvae have 4-5 days to find food before starvation, and this critical period is one of the primary drivers of sturgeon population growth rate (Gross, Repka, Robertson, Secor, & Van Winkle, 2002). Studies on other sturgeon species, such as shortnose sturgeon (Acipenser brevirostrum) and white sturgeon (Acipenser transmontanous), have found that larvae consume primarily drifting prey (Buckley & Kynard, 1981;Kynard, Parker, Kynard, & Horgan, 2014;Kynard et al, 2016), while juveniles shift to benthic prey (Radtke, 1966). Optimal growth of early life stage green sturgeon has been found to occur between temperatures of 15-19°C (Mayfield & Cech, 2004).…”

“…Based on ontogenetic diet shifts in white sturgeon and shortnose sturgeon (Buckley & Kynard, 1981;Kynard et al, 2014Kynard et al, , 2016Radtke, 1966), we hypothesise that as larval green sturgeons increase in total length, they shift from zooplankton to benthic macroinvertebrates (BMI). Based on ontogenetic diet shifts in white sturgeon and shortnose sturgeon (Buckley & Kynard, 1981;Kynard et al, 2014Kynard et al, , 2016Radtke, 1966), we hypothesise that as larval green sturgeons increase in total length, they shift from zooplankton to benthic macroinvertebrates (BMI).…”

“…Optimal growth of early life stage green sturgeon has been found to occur between temperatures of 15-19°C (Mayfield & Cech, 2004). Studies on other sturgeon species, such as shortnose sturgeon (Acipenser brevirostrum) and white sturgeon (Acipenser transmontanous), have found that larvae consume primarily drifting prey (Buckley & Kynard, 1981;Kynard, Parker, Kynard, & Horgan, 2014;Kynard et al, 2016), while juveniles shift to benthic prey (Radtke, 1966). However, the diet of larval green sturgeon in the Sacramento River is not known.…”

Sturgeon and paddlefish life history and management: Experts' knowledge and beliefs

“…Spawning behavior in most sturgeon species is difficult to observe, because spawning occurs in deep and sometimes turbid rivers . Polyandrous spawning, represented by several males following a single female and competing for an optimum spawning position, was reported in a number of species such as Atlantic sturgeon (A. o. oxyrinchus; Hilton, Kynard, Balazik, Horodysky, & Dillman, 2016), Gulf sturgeon , shortnose sturgeon (A. brevirostrum; Kynard et al, 2016), and white sturgeon . However, males also tend to remain near the spawning grounds, and spawn several times with different females .…”

“…There is abundant evidence of spawning site fidelity in various sturgeon species (Bruch, Haxton, Koenigs, Welsh, & Kerr, 2016;DeHaan, Libants, Elliott, & Scribner, 2006;Forsythe et al, 2012;Kynard et al, 2016;Pollock et al, 2015;Sulak et al, 2016;Welsh, Hill, Quinlan, Robinson, & May, 2008). In addition, differentiated genetic structure observed in some populations with no visible fragmentation is considered to be another indication of strong spawning site fidelity (Bruch et al, 2016;Hildebrand et al, 2016;Pollock et al, 2015;Sulak et al, 2016).…”