The busy vessel traffic has already caused a negative impact on the animals. For example, Jefferson (2000) reported that six dolphins (representing 2.8% in the animal catalog) indicated unmistakable evidence of propeller cuts on their bodies and 12.5% of stranding specimens had evidence of death from vessel collision. Apart from causing death and injury, vessel traffic can seriously divert and distort the behaviors of resident cetaceans. For example, humpback dolphins demonstrated a strong tendency to chase fishing vessels for food