Response in Growth, Scute Development, and Whole-Body Ion Composition of Acipenser fulvescens Reared in Water of Differing Chemistries

Simple Summary In fishes, the relationship between environmental concentration of ions and internal availability is closely linked. Environmental ion limitation can have substantial effects on early life stages and growth and potentially reduce development of predatory defenses. This study examined whether different environmental ion levels affect the growth and development of protective structures in a species of conservation interest, the Lake Sturgeon (Acipenser fulvescens). We hatched sturgeon eggs in water from two sources varying in ionic composition: the Warm Springs National Fish Hatchery and the Coosa River. Each water type had a stable pH (7.3 ± 0.09) and temperature (15 ± 1 °C) throughout the experiment, and the environmental concentrations of calcium, magnesium, potassium, sodium, and zinc were quantified for collected water samples. These same ions were also quantified in the tissue of the larval fish during the first eight weeks of development post-hatch. Results indicate that the ion content of larval fish mirrors the environmental differences, and that the growth rate is slower in natural river water, which has lower levels of calcium (14.0 ± 0.24 mg/L) and higher amounts of zinc (0.13 ± 0.02 mg/L). Understanding environmental impacts on growth rate and development of defensive structures is important to re-establishing a self-recruiting A. fulvescens population in Georgia waterways. Abstract In fishes, environmental ion availability can have substantial effects on growth and development. This study examined the development of Lake Sturgeon in response to the varying environmental ion availability that they experience as part of a conservation stocking program. We reared sturgeon in natural water from the Coosa River, which had higher concentrations of Mg2+, Na+, and Zn2+ than standard hatchery conditions, while [Ca2+] at the Warm Springs National Fish Hatchery was 2× higher than in the Coosa River. Eggs were hatched in each water type and the larvae were sampled at time points before and after yolk absorption during the first 8 weeks of development. Total length and weight in WSNFH larvae were significantly higher than larvae in Coosa River water starting at 8 dph, indicating that growth was dependent on the different environmental ion levels. Concentrations of the ions of interest were also determined for whole-body acid digests of the exposed Lake Sturgeon. We found that Lake Sturgeon reared in Coosa River water had significantly higher magnesium and zinc than Lake Sturgeon reared in WSNFH water (p < 0.05), while calcium was significantly higher in WSNFH than Coosa River water. This difference shows that different environmental ion concentrations also impact the overall development of larval Lake Sturgeon.