What is the difference as perceived by the old man etween the mako shark and the shovel- nosed sharks? Why does he respect one more than the other?

Santiago has his own hierarchy of ocean dwellers. The shovel-nosed sharks are destructive and without. They represent destructive laws of the universe. The mako shark holds a higher place in Santiago's world. It isn't a deceitful scavenger more than a representation of death; which Santiago knows he is close to facing.