Shark Cannonball causes salmon to behave so aggressively around it. In nature, when predator fish like salmon encounter a school of bait fish, they corral the school into a tight bait ball by swimming circles around it. Salmon swim in circles around the Shark for the same reason: they think it is the bait ball.
Sound is the reason why salmon are attracted to the Shark Cannonball: they can hear it from a long way off. When they move in for the kill and get close to a Shark, the other factors such as light reflection, static discharge and vortex all converge to create additional stimulation causing the fish to strike the trailing lure.