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

[This corrects the article DOI: 10.1093/conphys/coz042.].

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

Drumlines incorporating SMART (Shark-Management-Alert-in-Real-Time) technology are a new tool used in several bather protection programmes globally. In New South Wales (NSW), Australia, the white shark (Carcharodon carcharias) is a target species for SMART drumlines because they are often involved in attacks on humans. To understand white shark sensitivity to capture and to establish protocols around acceptable timeframes for responding to alerts, 47 juvenile and subadult white sharks were caught on SMART drumlines at five locations off the east coast of Australia. There was no at-vessel mortality during the sampling period. After capture, blood was sampled from each shark to assess its acute physiological status. Of the 18 metabolites investigated, only lactate and aspartate aminotransferase exhibited significant positive relationships with the capture duration on SMART drumlines. These results indicate that the capture process is relatively benign and that the current response times used here are appropriate to minimize long-term negative impacts on released white sharks. Where white sharks are likely to interact negatively with beachgoers, SMART drumlines can therefore be a useful addition to bather protection programmes that also aim to minimize harm to captured animals. Other shark species captured on SMART drumlines should also be investigated to gain broader understanding of potential physiological consequences of using this new technology.

Effect of weight and frontal area of external telemetry packages on the kinematics, activity levels and swimming performance of small-bodied sharks

This study sought to observe the effects of submerged weight and frontal cross-sectional area of external telemetry packages on the kinematics, activity levels and swimming performance of small-bodied juvenile sharks, using lemon sharks Negaprion brevirostris (60-80 cm total length, L_T ) as a model species. Juveniles were observed free-swimming in a mesocosm untagged and with small and large external accelerometer packages that increased frontal cross-sectional area of the animals and their submerged weight. Despite adhering to widely used standards for tag mass, the presence of an external telemetry package altered swimming kinematics, activity levels and swimming performance of juvenile N. brevirostris relative to untagged individuals, suggesting that tag mass is not a suitable standalone metric of device suitability. Changes in swimming performance could not be detected from tail-beat frequency, which suggests that tail-beat frequency is an unsuitable standalone metric of swimming performance for small N. brevirostris. Lastly, sharks experienced treatment-specific changes in activity level and swimming kinematics from morning to afternoon observation. Therefore, the presence of external telemetry packages altered the kinematics, activity levels and swimming performance of small young-of-the-year N. brevirostris and these data may therefore be relevant to other similar-sized juveniles of other shark species.

Validation of the i-STAT system for the analysis of blood gases and acid-base status in juvenile sandbar shark (Carcharhinus plumbeus)

Accurate measurements of blood gases and acid-base status require an array of sophisticated laboratory equipment that is typically not available during field research; such is the case for many studies on the stress physiology, ecology and conservation of elasmobranch fish species. Consequently, researchers have adopted portable clinical analysers that were developed for the analysis of human blood characteristics, but often without thoroughly validating these systems for their use on fish. The aim of our study was to test the suitability of the i-STAT system, the most commonly used portable clinical analyser in studies on fish, for analysing blood gases and acid-base status in elasmobranchs, over a broad range of conditions and using the sandbar shark (Carcharhinus plumbeus) as a model organism. Our results indicate that the i-STAT system can generate useful measurements of whole blood pH, and the use of appropriate correction factors may increase the accuracy of results. The i-STAT system was, however, unable to generate reliable results for measurements of partial pressure of oxygen (PO2) and the derived parameter of haemoglobin O2 saturation. This is probably due to the effect of a closed-system temperature change on PO2 within the i-STAT cartridge and the fact that the temperature correction algorithms used by i-STAT assume a human temperature dependency of haemoglobin-O2 binding; in many ectotherms, this assumption will lead to equivocal i-STAT PO2 results. The in vivo partial pressure of CO2 (PCO2) in resting sandbar sharks is probably below the detection limit for PCO2 in the i-STAT system, and the measurement of higher PCO2 tensions was associated with a large measurement error. In agreement with previous work, our results indicate that the i-STAT system can generate useful data on whole blood pH in fishes, but not blood gases.

The blood chemical status of Atlantic cod Gadus morhua following capture by jig and demersal longline with differential hook removal methods

Common haematological [haematocrit (Hct)], primary (serum cortisol) and secondary (serum glucose and plasma lactate) analytes were utilized to compare blood biochemical status of Gadus morhua captured rapidly by jig with that of G. morhua captured by commercial demersal longline. In general, the physiological status of G. morhua, despite blind hook times, was significantly more disrupted (pronounced haemo-concentration and significantly elevated concentrations of cortisol, glucose and lactate) following longline capture relative to capture by jig, while no differences were detected among longline-caught fish as a function of dehooking method (or concomitant extent of overt physical trauma). Blood profiles from the more stressed G. morhua, a possible function of more extended longline hook times, were similar to the most stressed values reported for this species. The results also demonstrate that, although acute blood biochemical status is an effective gauge of relative stress, it does not reflect physical injury status, which has been shown to exert a strong influence on delayed mortality in previous studies in this species. Thus, acute blood chemical status alone may not be the most complete predictor of mortality. Future studies should evaluate physiological repercussions from capture-handling against physical trauma during more extended post-release periods for this species.