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

Abstract

Summary The critical thermal maximum (CTmax) and the associated hematological response of juvenile (~145 g, n = 8 for both species) Atlantic Acipenser oxyrinchus and shortnose Acipenser brevirostrum sturgeons acclimated to 15°C were determined using a heating rate of 8°C h−1. The critical thermal maximum averaged 30.8°C and 31.6°C for Atlantic and shortnose sturgeon, respectively, and values fell within the range noted for other sturgeon species. Oxygen‐carrying capacity (hemoglobin and hematocrit) measures were generally unaffected by thermal stress. Plasma lactate levels increased from 0.5 mm to 4 mm following temperature stress in both species. Both plasma glucose and potassium levels increased following CTmax, however, these levels were about double in the shortnose sturgeon. Lastly, plasma sodium and chloride levels were significantly depressed (by more than 10%) following thermal stress in shortnose sturgeon, whereas only chloride levels decreased in Atlantic sturgeon. Taken together, while CTmax values were similar, thermal stress resulted in different hematological profiles; these differences are consistent when compared to other stressors, and may be related to the phylogenetic position and thus could reflect the evolutionary history of these two species.

The effects of repeat acute thermal stress on the critical thermal maximum (CTmax) and physiology of juvenile shortnose sturgeon (Acipenser brevirostrum)

“…constant rate ~9°C hour -1 (see below) throughout the study. This heating rate was chosen as it was within the range of heating rates (6-15 o C hour -1 ) used in our previous studies (Zhang D r a f t and Kieffer 2014; Spear and Kieffer 2016;Zhang et al 2017). Since heating rate does not affect CT max values in shortnose sturgeon (Zhang et al 2017), the use of a heating rate of 9 o C hour -1 allows for a comparison of CT max values between studies conducted in our laboratory.…”

“…(calculated from each CT max test; 9.28±0.05) at a constant rate until loss of equilibrium (LOE) occurred. Loss of equilibrium as an endpoint is indicated when the fish rolled dorso-ventrally and is unable to right itself within 10 s (Ziegeweid et al 2008;Zhang and Kieffer 2014;Spear and Kieffer 2016). We manually righted individuals three times to ensure that each fish reached its CT max (Spear and Kieffer 2016).…”

“…From previous studies on shortnose sturgeon, it has been demonstrated that acclimation temperature (Ziegeweid et al 2008;Zhang and Kieffer 2014) and body size (Zhang and Kieffer 2014) significantly affect thermal tolerance (as assessed using a critical thermal maximum, CT max , test), but heating rate has little impact (Zhang et al 2017). Through the measurement of various physiological endpoints, such as plasma lactate and ion concentrations, the physiological response following a CT max thermal stress test has also been documented for shortnose sturgeon (Zhang and Kieffer 2014;Spear and Kieffer 2016;Zhang et al 2017). Other studies have examined the thermal tolerance of sturgeon species (see Spear and Kieffer 2016, for a summary;…”

“…The majority of thermal tolerance studies focused on other fish species (Lutterschimdt and Hutchison 1997;Beitinger et al 2000;Deslauriers et al 2016) will subject individuals to a singular thermal stressor (i.e., a single CT max test), without any assessment of post-test physiology (Zhang and Kieffer 2014;Spear and Kieffer 2016). Furthermore, thermal tolerance studies are largely concentrated on the effects of acclimation temperature in freshwater and/or game fish, such as rainbow trout (Oncorhynchus mykiss Walbaum 1792), channel catfish (Ictalurus punctatus, Rafinesque 1818) and largemouth bass (Micropterus salmoides, Lacépède, D r a f t 5 1802) (Cheetman et al 1976;Field et al 1987;Bennett et al 1997;Currie et al 1998).…”

Short‐Term Physiological Disruption and Reflex Impairment in Shortnose Sturgeon Exposed to Catch‐and‐Release Angling

“…The physiological responses of sturgeons to stressors such as critical thermal tolerances (Ziegeweid et al. ; Spear and Kieffer ), hypoxia (Baker et al. ), and exhaustive exercise (Baker et al.…”