In-situ dynamics of tuna purse seine deployment in various operations and currents

Abstract

One of the greatest concerns for a successful catch in tuna fishing operations is the diving behavior of the purse seine. To analyze the integrated effect of fishing methods and sea currents on purse seine sinking depth, a multiple regression model was used. This improved model shows current speeds, shooting duration, the included angle between a two-layer current, and net mouth orientation relative to current direction (shooting angle) have an influence on maximum sinking depth. The current in the mid-layer is considered to significantly resist the seine’s vertical dive by a quadratic relation, but an increased shooting duration and shooting angle can be enhance the sinking. An obvious difference in terms of sinking depth is found between free-swimming school fishing and floating objects fishing, two common methods in tuna purse seine fisheries. It has been suggested that seine sinking dynamics respond to gear manipulation and, therefore, the model provides useful guidance in implementing net casting for an effective capture.