Surely the first rule of survival for fish must be: “Stay away from sharks.” But it seems that pilot fish not only ignore that rule but also benefit greatly from the company of sharks.
These small striped fish often swim alongside sharks. In fact, their name comes from the belief that they used to guide sharks to their prey. Today, we know that sharks have better detection systems than pilot fish, so this seems unlikely. In fact, there is no clear argument for how this companionship benefits the shark. However, there are good reasons that benefit the pilot fish.
Sharks cannot chew their food, so they cut large chunks of their prey and swallow them whole. This generates a significant amount of food particles in the water, which the pilot fish voraciously feed on. Another benefit for the pilot fish is that they keep their own predators away. These predators would hesitate to attack a fish that remains so close to a shark, as they would risk becoming prey themselves.
When two large sharks approach each other, the pilot fish change color. Their black stripes disappear, and their bodies become uniformly silver. This is an aggressive behavior of the fish, which becomes less visible among the shimmering water. This aggressive behavior is often seen when two pilot fish fight. It is believed that, in the encounter between sharks, the pilot fish from each group are signaling each other, as if each group is defending its own territory. In this case, the “territory” is nothing less than a shark.
Of course, in this relationship, there are still some unanswered questions: If sharks were to stop and sleep, they would drown (see Sleeping Sharks), so how do pilot fish rest? Or worse yet, the most logical question… if the shark doesn’t benefit from the presence of pilot fish, and a shark can swim three times faster than its traveling companions, why doesn’t it eat them?
We don’t have an answer to this question. Perhaps the shark becomes accustomed to seeing them by its side, or perhaps it does derive some benefit. It would be logical to think that a successful shark in finding food would be accompanied by a larger number of pilot fish. In that case, such a procession could indicate a certain power over other sharks or even a higher social rank when it comes to mating with females. These are just theories after all, who really knows sharks?
“You cannot defend what you do not love, and you cannot love what you do not know.”