Dead tired: evaluating the physiological status and survival of neonatal reef sharks under stress

Abstract

Marine protected areas can protect sharks from targeted fisheries, but may not manage other stressors. We demonstrated species-specific physiological responses of newborn reef sharks upon brief gill-net capture during summer months. Carcharhinus melanopterus and Negaprion acutidens were resilient to stress within a narrow temperature range and under ideal capture conditions.

The acute physiological status of white sharks (Carcharodon carcharias) exhibits minimal variation after capture on SMART drumlines

“…Bronze whaler sharks ( Carcharhinus brachyurus ) with a blood lactate concentration exceeding 27.4 mmol l −1 were predicted to die post-release after long-line capture (Dapp et al ., 2016). Similarly, both sicklefin lemon sharks ( Negaprion acutidens ) and blacktip reef sharks ( Carcharhinus melanopterus ), respectively, experienced elevated blood lactate concentrations 6- and 14-times (to ~ 22 and 21 mmol l −1 ) baseline values after gill-net capture and air exposure (Bouyoucos et al ., 2018).…”

“…There is a range of known secondary physiological stress responses in elasmobranchs that may indicate deleterious impacts of capture (Skomal and Mandelman, 2012). For example, elevated blood potassium known as hyperkalemia (Mandelman and Farrington, 2007; Frick et al ., 2012; Butcher et al ., 2015; Dapp et al ., 2017), elevated blood glucose known as hyperglycaemia (Frick et al ., 2010; Skomal and Mandelman, 2012; Bouyoucos et al ., 2018), and elevated blood lactate (Wells and Davie, 1985; Gallagher et al ., 2014; French et al ., 2015) commonly accompany mortality after elasmobranchs are exposed to various types of capture. These, and a suite of other blood variables, were analysed in this study due to their prominence in past research and known relationships with capture.…”

Exercise intensity while hooked is associated with physiological status of longline-captured sharks

“…Nurse sharks caught at higher water temperatures had higher blood glucose and plasma potassium concentrations than animals captured at lower water temperatures. Positive relationships between SST and blood glucose have previously been reported for Atlantic sharpnose ( Rhizoprionodon terraenovae ), gummy and blacktip reef sharks ( C. melanopterus ) (Hoffmayer et al , 2012; Guida et al , 2016; Bouyoucos et al , 2018). Variation in water temperature ranging from 23.0 to 30.0°C has previously been demonstrated to influence metabolic rate in nurse sharks and increases in blood glucose concentrations at higher temperatures may reflect increased energetic demand (as an oxidative fuel source), or increased rates of anaerobic glycolysis if an increased standard metabolic rate reduces the available aerobic scope (Whitney et al , 2016).…”

Reef Shark Science – Key Questions and Future Directions

“…Specifically, climate-driven impacts are expected to generate: (i) changes in the distribution and movement of marine megafauna, (ii) changes in the timing and duration of migration, (iii) changes in the distribution and quality of food resources, and (iv) disruption of physiological and metabolic process linked to food intake, behavior, digestion rates, reproduction and growth (Pistevos et al, 2015;Johnson et al, 2016). To date there is limited research in this field, with most studies focused on small benthic reef species (e.g., Gervais et al, 2016;Heinrich et al, 2016), although those investigating larger carcharhinid species are starting to occur (Bouyoucos et al, 2018). Future research should focus on determining the impacts of warmer and more acidic oceans on shark species with different life-histories (e.g., slow vs. fastgrowing), species living at the edges of coral reef distributions, species with varying degrees of reef-association and dependency, and the interaction between climate-driven impacts and food webs.…”