The data logger recorded swim speed at 1/8 s, 1 s, or 2 s intervals
(depending on the individual sharks), depth and temperature at a
1 s interval, and acceleration along lateral and longitudinal axes (to
detect tail-beat activity and pitch angle, respectively) at a 1/32 s interval.
A miniature camera was also attached to sharks C and E; however,
the images obtained were too dark to be analysed. The total mass of
the packages (data loggers and recovery system) were 188 g (accelerometer
only) and 311 g (accelerometer and camera) (0.06–0.15%
of the estimated body mass of the sharks). The buoyancies of the two types of packages were 0.53 N and 0.74 N in seawater, respectively.
Frontal areas of the packages were 0.7–1.8% of that of the sharks (estimated
from the girth measurements, assuming that sharks are circular
in cross section). These small values indicate that mass, buoyancy, or
hydrodynamic drag of the sharks was changed little by the attached
package.