Acoustic accelerometry reveals diel activity patterns in premigratory Port Jackson sharks

Area of Science:

• Marine Biology
• Animal Behavior
• Biotelemetry

Background:

• Understanding species-specific activity patterns is crucial for ecology and behavior.
• Continuous marine observation is challenging; biotelemetry offers detailed movement analysis.
• Accelerometers provide data on animal activity, but calibration is key for interpretation.

Purpose of the Study:

• To investigate how calibrating accelerometers with video footage enhances understanding of Port Jackson shark activity patterns.
• To quantify diel activity patterns in male and female captive sharks.
• To validate captive data by comparing it with free-ranging shark movement data.

Main Methods:

• Linear regression was used to correlate root mean square (RMS) acceleration with time-matched video-recorded behaviors.
• Diel activity patterns of captive sharks were quantified using calibrated accelerometer data.
• Passive acoustic tracking data from free-ranging sharks were used for validation.

Main Results:

• Calibrated RMS acceleration data revealed nocturnal diel patterns in captive Port Jackson sharks, with activity peaking in the late evening.
• Activity patterns in captive sharks showed strong correlation with those of free-ranging individuals.
• Elevated nocturnal activity in captive sharks during the breeding season suggested migratory restlessness, aligning with wild migration timing.

Conclusions:

• Calibrated RMS acceleration is a promising method for detailing activity patterns in cryptic marine species.
• Sex, time of day, and seasonal behaviors significantly influence activity levels in Port Jackson sharks.
• Validated captive data can provide reliable insights into the behavior of free-ranging marine animals.