Effect of swimming on fish target strength
Original version
This report is not to be cited without prior reference to the authorAbstract
The influence of the swimming movement on fish target strength is
investigated through a modelling exercise. In this, several gadoid
specimens are represented as acoustic scatterers through their
triangulated swimbladder surfaces, assumed to be perfectly pressurereleasing.
The swimming movement is described as a periodic deformation
in swimbladder shape consistent with actual measurements of whole-body
movements of swimming gadoids. Results of computations of target
strength as would be observed with a vertical echo sounder are
expressed through the probability density function. This is found to
be nearly identical to that of the same fish with normal extended
posture. The inconsequentiality of swimming movement to the target
strength in typical echo-sounding applications is thereby demonstrated.