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

Area of Science:

• Marine Biology
• Fisheries Science
• Animal Physiology

Background:

• Shark populations are declining due to fisheries impacts like targeted capture and by-catch.
• Understanding the physiological stress response of sharks during capture is crucial for effective fisheries management and conservation.

Purpose of the Study:

• To investigate the relationship between exercise intensity during longline capture and the physiological status of nurse sharks (Ginglymostoma cirratum) and Caribbean reef sharks (Carcharhinus perezi).
• To inform management strategies aimed at reducing the negative impacts of longline fishing on shark populations.

Main Methods:

• Quantified shark exercise intensity using digital cameras and accelerometers during longline capture.
• Collected blood samples immediately post-capture to measure physiological metrics.
• Analyzed associations between exercise intensity, capture duration, environmental factors, and physiological parameters.

Main Results:

• Nurse sharks exhibited increased blood pH and altered glucose/potassium levels with longer capture times and lower exercise intensity, with temperature influencing some metrics.
• Caribbean reef sharks showed equivocal results, with increased blood lactate and decreased plasma chloride correlating with capture duration.
• Caribbean reef sharks appeared less able to regulate blood pH, suggesting greater vulnerability to physiological impairment compared to nurse sharks.

Conclusions:

• Exercise intensity during longline capture is associated with physiological status in nurse and Caribbean reef sharks, though species-specific responses vary.
• Caribbean reef sharks may be more vulnerable to physiological stress due to a limited ability to modulate blood pH.
• Fisheries management should consider shark exercise intensity during capture to develop strategies for mitigating by-catch and physiological stress, though further research is needed to link exercise to mortality outcomes.