An investigation of reactive behavior of yellowfin tuna schools to the purse seining process

The movement parameters of yellow fin tuna schools were analyzed by means of scanning sonar in tuna purse seine capture situations in the Oman Sea in June 2010. There was significant difference in swimming speed and radial swimming direction between the escaped and captured schools. In escaped cases, the fish schools swam faster with mostly horizontal avoidance behavior to the sound stimuli from the surrounding vessel and escaped capture under the sinking net at last. The swimming speed of the schools in two occasions was correlated to the vessel’s speed. Some alternatives of new constructions of the nets with regard to the sinking speed are discussed that may reduce the potential problem of escape capture during purse seining process.