As humans, we are hard-wired to fear top predators, such as bears, lions, tigers, sharks, and other toothy beasts capable of helping to speed us and other lower species toward our deaths. As humans, we also have the capacity to understand just how important these fearsome species are to our survival, and to the survival of the world as a whole. Without predators, our world is thrown out of balance. Unfortunately, this is something which is happening right now, and it is a problem we can do something about. Here, we'll take a closer look at the important role predators play, using sharks as an example - after all, as divers, these are animals we strive to understand better.
Oceans Need Sharks
Sharks and other top predators, including killer whales, dolphins, porpoises, tuna, and other animals with few natural enemies, play a vital role in ocean health - more so than the average fish or marine mammal does. Their position at the top of the food chain helps keep other marine populations healthy and balanced. They do this by eating efficiently, with a tendency to select the prey that is easiest to catch - that is, fish that are old, sick, or injured are eliminated, thus providing more resources for healthy fish to consume. And, in turn, when fish populations are in balance, so are other species throughout the ecosystem.
A number of intricate, delicately balanced food webs make up the ocean ecosystem. Sharks are a keystone species, so named because without them the entire structure can collapse. While some fish may thrive for a short time in the absence of apex predators, their decline is rapid once food runs out, and once the health of coral reefs is adversely impacted.
Sharks and other predators also help maintain kelp, sea grass beds, and other habitats. They scavenge, consuming carcasses rapidly, and they regulate prey species so these vital habitats do not become overgrazed. In Hawaii, for example, sharks keep turtle populations in check naturally; since turtles graze on sea grass beds and sponges, an overabundance of sea turtles would lead to destruction of habitat, which in turn would lead to the demise of the sea turtles and other species that depend on sea grass and sponges for food and shelter.
The lesson is this: when sharks are eliminated, areas they once hunted quickly fall out of balance. We see this occurring over and over again in areas where sharks have been fished and finned out of existence. Humans consuming sharks don't rely on them for immediate survival, but once sharks are removed, and ocean habitats decline, everyone is at risk. After 450 million years, these predators are at risk of extinction in many areas, and if they disappear, our oceans, which cover an astounding two thirds of our planet, will be the next to decline.
As divers, we have an intimate relationship with the ocean; it is important that we recognize that the seas and oceans we love depend on us for their very survival, and in turn, our planet relies on us, too. Share what you know. Support organizations that protect sharks and other predators worldwide. Our world, and our legacy, depends on the choices we make each day.