Oxygen consumption and haematology of juvenile shortnose sturgeon Acipenser brevirostrum during an acute 24 h saltwater challenge

Abstract

This study focused on the acute physiological responses to saltwater exposure in juvenile shortnose sturgeon Acipenser brevirostrum. In two separate laboratory experiments, 2 year-old A. brevirostrum were exposed to either full (32) or half-strength (16) seawater for up to 24 h. First, oxygen consumption rates were used to estimate the metabolic costs over 24 h. Secondly, blood and muscle samples were analysed at 6, 12 and 24 h for water loss, various measures of osmoregulatory status (plasma osmolality and ions) and other standard haematological variables. Juveniles exposed to full-strength seawater showed significant decreases in oxygen consumption rates during the 24 h exposure. Furthermore, seawater-exposed fish had significantly increased plasma osmolality, ions (Na(+) and Cl(-)) and a 17% decrease in total wet mass over the 24 h exposure period. To a lesser extent, increases in osmolality, ions and mass loss were observed in fish exposed to half-strength seawater but no changes to oxygen consumption. Cortisol was also significantly increased in fish exposed to full-strength seawater. While plasma protein was elevated following 24 h in full-strength seawater, haemoglobin, haematocrit and plasma glucose levels did not change with increased salinity. These results imply an inability of juvenile A. brevirostrum to regulate water and ions in full-strength seawater within 24 h. Nonetheless, no mortality occurred in any exposure, suggesting that juvenile A. brevirostrum can tolerate short periods in saline environments.

Critical thermal maxima and hematology for juvenile Atlantic (Acipenser oxyrinchusMitchill 1815) and shortnose (Acipenser brevirostrumLesueur, 1818) sturgeons

“…A portion of whole blood was used to determine hematocrit (HCt) and hemoglobin concentrations (Hb) following standard procedures (Baker et al, 2005a;Penny and Kieffer, 2014;Zhang and Kieffer, 2014). The mean erythrocytic hemoglobin content (MEHC) was calculated = 100 9 (hemoglobin/hematocrit) (Houston, 1990).…”

“…Most sturgeon species inhabit a wide variety of waterways, including estuaries, rivers, lakes and oceans (Beamesderfer and Farr, 1997). Both shortnose and Atlantic sturgeon can tolerate a variety of salinities (Gilbert, 1989;Penny and Kieffer, 2014), and as such can travel between fresh and brackish water. This lifestyle exposes sturgeon to many environmental conditions, including changes in salinity, turbidity, flow/current speed, and temperature (Beamesderfer and Farr, 1997).…”

Does body size affect the response to exercise in shortnose sturgeon (Acipenser brevirostrum)?

“…Lactate concentrations were determined using a standard colorimetric assay and appropriate standards (lactate reagent: 735–10; lactate standard: 735–11; Trinity Biotech). Sodium, potassium, and chloride concentrations were determined using a Smartlyte ion analyzer (Diamond Diagnostics, USA) and plasma glucose concentrations were determined using a hand‐held blood glucose meter (OneTouch Ultra 2, code 25 test strips; http://www.onetouch.ca) (Downie & Kieffer, ; Penny & Kieffer, ).…”