Category: General Article
Not all sharks live in coastal waters or in the Sunlit Zone, although many of them spend some time in these shallower, well-lit areas because of the abundance of food. Of the Oregon shark species, coastal waters are home it both the largest (Basking Shark) and the smallest (Spiny Dogfish). Below, you’ll find some general information about sharks in our area. There will also be a downloadable information packet which provides you with great detail on each of Oregon’s native shark species.
When a predator’s been around for millions of years, it makes hunting look effortless. And this is definitely the case for sharks. Every part of them, from the tiny sensors which cover their snouts to the very design of their bodies, has been perfectly adapted to locating, killing and eating other animals. But finding a tasty snack isn’t just a matter of seeing or smelling another animal. Sharks use a variety of senses to locate prey.
Hundreds of yards: Sharks can smell another animal.
Tens of yards: The shark’s lateral line gathers information from the water ripples, movements and eddies made by prey.
Yards: The shark may now see the prey, depending on the clarity of the water.
Inches: Tiny receptors in the shark’s head called ampullae of Lorenzini allow it to identify the electrical signature of prey.
Contact: The shark can can touch and taste the prey animal.
Although sharks are often called “the ultimate predator,” this doesn’t make them invulnerable. In Oregon waters, even the largest and most dangerous shark can be hunted and killed by other species.
Dolphins, Porpoises and Sperm Whales are all known to kill sharks, although mostly in self-defense. When threatened by sharks, these marine mammals will ram into the fish’s sensitive body areas, including their gills, genitals and anus. A Short-Beaked Common Dolphin can launch through the water at speeds reaching 25 mph (40 km/h), making it a virtual torpedo. When it impacts with the shark, the results can be painful – even fatal. A smart shark will quickly retreat before challenging a pod of dolphins.
Some Orcas actively hunt large sharks like the Great White, apparently feeding on the fish’s large, oil-rich liver. Orcas and Great Whites may be an even match in terms of ferocity and power, but the whales have some advantages – their intelligence and ability to work as a team. Recent studies have shown some Orcas know how to immobilize sharks using a technique called tonic immobility in which they hold the big fish upside-down. Unable to move, the shark eventually drowns and then feeding on the big fish is, well, a piece of cake. Apparently sharks instinctively know Orcas are a real threat, as they will often flee an area when the whales appear. Scientists played recorded Orca sounds to a group of Bull Sharks – causing them to become immediately agitated and aggressive. Despite this fearsome reputation, none of the Orca pods in Oregon waters are known to target sharks for food, preferring instead to feed on smaller fish like Coho Salmon.
In the wild, the key to taking down a shark doesn’t always have anything to do with power or even intelligence. Like any other living creature, sharks can be killed by very small, simple animals too. Parasites like small crustaceans and tapeworms often live inside sharks, robbing them of nutrients until they die.
By far, the most dangerous predators to sharks are human beings. It’s not known exactly how many sharks humans kill every year – mostly for food or as bycatch to commercial fishing operations – but the numbers are in the millions.
Yeah, that’s right. Millions.
As a result of this unchecked killing, many shark species are now fighting to survive. Legislation and enforcement are providing new protection for sharks, but progress is often slow and hampered by human bias against these animals.
Related Information: Great White Wonder
Photo credit: Mark Rothman, used with permission.