A comparison of single and multiple stressor protocols to assess acute stress in a coastal shark species, Rhizoprionodon terraenovae

Abstract

Elasmobranch stress responses are traditionally measured in the field by either singly or serially sampling an animal after a physiologically stressful event. Although capture and handling techniques are effective at inducing a stress response, differences in protocols could affect the degree of stress experienced by an individual, making meaningful comparisons between the protocols difficult, if not impossible. This study acutely stressed Atlantic sharpnose sharks, Rhizoprionodon terraenovae, by standardized capture (rod and reel) and handling methods and implemented either a single or serial blood sampling protocol to monitor four indicators of the secondary stress response. Single-sampled sharks were hooked and allowed to swim around the boat until retrieved for a blood sample at either 0, 15, 30, 45, or 60 min post-hooking. Serially sampled sharks were retrieved, phlebotomized, released while still hooked, and subsequently resampled at 15, 30, 45, and 60 min intervals post-hooking. Blood was analyzed for hematocrit, and plasma glucose, lactate, and osmolality levels. Although both single and serial sampling protocols resulted in an increase in glucose, no significant difference in glucose level was found between protocols. Serially sampled sharks exhibited cumulatively heightened levels for lactate and osmolality at all time intervals when compared to single-sampled animals at the same time. Maximal concentration differences of 217.5, 9.8, and 41.6 % were reported for lactate, osmolality, and glucose levels, respectively. Hematocrit increased significantly over time for the single sampling protocol but did not change significantly during the serial sampling protocol. The differences in resultant blood chemistry levels between implemented stress protocols and durations are significant and need to be considered when assessing stress in elasmobranchs.

Plasma 1α-Hydroxycorticosterone as Biomarker for Acute Stress in Catsharks (Scyliorhinus canicula)

“…In all, these data provide evidence for an activated glycolytic pathway and subsequent increased plasma glucose levels after an acute stressor such as air exposure as seen in our study, but also after capture and/or transport (Cliff and Thurman, 1984; Hoffmayer and Parsons, 2001; Skomal and Mandelman, 2012). However, other studies on elasmobranchs and chondrichthyan species reported lower or even no changes in plasma glucose levels coinciding with higher plasma lactate after an acute stress situation (Manire and Hueter, 2001; Brill et al, 2008; Kneebone et al, 2013; Martins et al, 2018).…”

Individual personality differences in Port Jackson sharks Heterodontus portusjacksoni

“…Such studies should incorporate analysis of blood stress variables (e.g. lactate, blood glucose or osmolality; Hoffmayer et al, 2015) to more confidently assess the link between bold v. shy stress responses and examine other correlates within proactive-reactive coping styles, such as aggressiveness/dominance, response to contest outcomes, foraging behaviour, exploratory behaviour and activity rates (Sih et al, 2004a;Conrad et al, 2011). Moreover, there has been a recent impetus to research the physiological stress response of elasmobranchs to fishing techniques.…”

Effects of delayed phlebotomy on plasma steroid hormone concentrations in two elasmobranch species

“…While there was a trend toward decreasing Hct with time, no statistically significant changes were found in Hct in either species over the sampling period. Similarly, Hoffmayer, Hendon, and Parsons () and Hoffmayer, Hendon, Parsons, Driggers, and Campbell () did not observed significant changes in hematocrit in serially sampled R. terraenovae . Despite not being statistically significant, the trend of decreasing Hct could be indicative of a hemodilution.…”