Atlantic sturgeon growth responses to dual seasonal spawning, latitudinal thermal regimes, and Chesapeake Bay environmental stressors
Secor, David H
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ABSTRACT Title of Dissertation: ATLANTIC STURGEON ACIPENSER OXYRINCHUS GROWTH RESPONSES TO DUAL SEASONAL SPAWNING, LATITUDINAL THERMAL REGIMES, AND CHESAPEAKE BAY ENVIRONMENTAL STRESSORS Erin Lorraine Markin, Doctor of Philosophy, 2017 Dissertation directed by: Professor, Dr. David Secor, University of Maryland Center for Environmental Science Chesapeake Biological Laboratory Recovery of Atlantic sturgeon, Acipenser oxyrinchus, will depend on actions that improve assessment of habitat conditions, particularly during the first year of life. Here, evaluation of stressors included temperature, salinity, and nitrite effects on survival of age-0 Atlantic sturgeon. Performance of a principal Atlantic sturgeon bioenergetics models was evaluated first by describing trends in habitat suitability during a recent 20+ year span in the Chesapeake Bay, and then by testing model predictions against incidence data for an abbreviated period which included 1562 observations of Atlantic sturgeon. In common garden experiments, thermal performance of juveniles from two populations of Atlantic sturgeon was evaluated. Finally, a growing-degree-day (GDD) model was developed to evaluate the phenology of spawning and early growth across latitudinally distributed Atlantic sturgeon populations, some of which exhibit dual seasonal spawning. Lethal levels of nitrite observed in the laboratory (24-hr LC50: 4.1 mg L-1 nitrite in 2 mg L-1 chloride) do not occur in the Chesapeake Bay, indicating that early juvenile Atlantic sturgeon are presently not at risk for nitrite toxicity. Application of bioenergetics models to long-term Chesapeake Bay data predicted consistently higher juvenile growth in spring and fall seasons. During summer months, Atlantic sturgeon were frequently captured in regions that the bioenergetics model predicted nil or negative growth, indicating that older Atlantic sturgeon may not be as sensitive to these environmental parameters than younger juveniles, which have been the focus of past research and bioenergetics models. Common garden experiments performed on Saint Lawrence and Altamaha strain Atlantic sturgeon juveniles showed no population effect on growth performance among thermal regions, allowing development of a predictive equation of juvenile length from GDDs. Predicted sizes of age 1.0 juveniles were within the size ranges reported in literature. Thus, the GDD model holds promise in future assessments of juvenile presence, recruitment, and recovery. Findings suggest that Chesapeake Bay Atlantic sturgeon are more resilient than previously believed. The Chesapeake Bay offers an environment conducive to recovery and where dual-spawning may be a successful strategy, thus improving resilience to climate change.