The Vicsek's model (VM) IT. Viesek, ct. al., Phys. Rev. Lett. 15 (1995) 1226} is a popular approach to study nature of the phase tmnsition of self-propelling system. In this model, the direction of motion of each particle depends on the averege velocity of its neighboring particles within a circle of radius R. In this work, the authors consider a group of fishes as the particles, but the authors assumed that only the individuals of its neighbors within a cirde sector with central angle p (is called angle of view) and radius R, an
taken into account the average direction of motion. The authors used a similar model as the well known XY spin model on a squar'e lattice of ,linear size L, the particles can move freely on the plane (an off-lattice model). A phase diagram in the space ('P, e) has been established where P = p/2 E [0,pi] and e being the critical noise. The authors showed that e strongly depends on the view's angle P /= 0.5pi, but slightly varies with P 0.5pi. So, the authors can conclude that the schooling behavior of animal is only of the prey species, but not of the predator.