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

Abstract

The shortnose sturgeon (Acipenser brevirostrum Lesueur, 1818) is a species of special concern in Canada, but little is known about their thermal biology. Information on the upper thermal tolerance of shortnose sturgeon becomes valuable for predicting future survival particularly with climate change and improving species management. Using a modified critical thermal maximum (CTmax) methodology, the objective is to determine whether previous thermal stress affects the thermal tolerance of juvenile shortnose sturgeon when exposed to a second thermal stress event. Prior exposure to thermal stress (CTmax1) did not affect the thermal tolerance (CTmax2) of juvenile shortnose sturgeon when a 24 h recovery period was allotted between tests. However, a significant increase in thermal tolerance occurred when the recovery time between the two thermal challenges was 1 h. Plasma glucose, lactate, and osmolality were all significantly affected by thermal stress, but values returned to control levels within 24 h. Hematocrit and plasma chloride concentrations were not significantly affected by thermal stress. All fish survived the CTmax testing. The data indicate that the thermal tolerance of juvenile shortnose sturgeon is modified when multiple thermal stresses occur closer together (1 h) but not if separated by a longer time period (24 h).

Critical thermal maximum and minimum of juvenile shortnose sturgeon ( Acipenser brevirostrum ) acclimated to 12 and 18°C

“…Our findings for shortnose sturgeon CT max values are similar to previously published data (Bard & Kieffer, 2019; Spear & Kieffer, 2016; Zhang et al, 2017; Zhang & Kieffer, 2014; Ziegeweid et al, 2008), and further confirms the relationship between acclimation temperature and CT max across fish species, including shortnose sturgeon (Chatterjee et al, 2004; Currie et al, 1998; Das et al, 2004, 2005; Dülger et al, 2012; Ford & Beitinger, 2005; Martìnez et al, 2016; McKenzie et al, 2021; Peng et al, 2014; Zhang & Kieffer, 2014; Ziegeweid et al, 2008). In the current study, we found that the acclimation response ratio was 0.81 in shortnose sturgeon, which indicates that for each 1°C in environmental temperature, the CT max of shortnose sturgeon increased by 0.81°C.…”

“…The arena was then covered with a fitted piece of plexiglass to prevent the fish from escaping. The fish was held in the test arena for 1 h to recover from handling stress (Bard & Kieffer, 2019; Spear & Kieffer, 2016; Zhang & Kieffer, 2014). Then individual fish were subjected to a thermal stress (i.e., heating or cooling) (see Table 1).…”

“…CT max or CT min were determined by a loss of equilibrium (LOE), where the fish is unable to maintain upright dorsal‐ventral positioning for at least 10 s (Bard & Kieffer, 2019; Zhang & Kieffer, 2014; Ziegeweid et al, 2008). Once the LOE was reached, the final temperatures were recorded.…”

Temperature increase and its effects on fish stress physiology in the context of global warming

“…Cortisol responses during and after an acute temperature rise have been described for multiple species (Table 1), with only a few exceptions [e.g., LeBlanc et al (2012) and Chadwick et al (2015)]. Secondary stress responses are also observed on acute temperature increase; glucose and lactate generally rise during acute thermal challenge, along with alterations in blood osmolality and other haematological variables (Bard & Kieffer, 2019;Dengiz Balta et al, 2017). In addition, inhibitory effects on the fish immune system may be observed (Dengiz Balta et al, 2017).…”

“…(2015)]. Secondary stress responses are also observed on acute temperature increase; glucose and lactate generally rise during acute thermal challenge, along with alterations in blood osmolality and other haematological variables (Bard & Kieffer, 2019; Dengiz Balta et al ., 2017). In addition, inhibitory effects on the fish immune system may be observed (Dengiz Balta et al ., 2017).…”