By Blaise Jones
Sharks can be found all over the world with only a few exceptions. There are no sharks in the Southern Ocean, and sharks do not inhabit the deepest benthic depths of the ocean.
The majority of all shark species inhabit The Sunlight Zone (Epipelagic Zone), which ranges from the surface to 650 feet (200 m). As ectothermic animals (cold-blooded), sharks need the warmth these waters retain from the sun, not to mention the vast amount of prey that live in these waters that the sharks need. Some of the most common sharks like the bull shark and the blacktip reef shark remain in this highest portion of the water column.
The Twilight Zone (Mesopelagic Zone) is the second zone in the water column and reaches 3,300 feet (1,000 m). Many large shark species inhabit this zone such as the great hammerhead, whale shark and the basking shark.
The third and last layer in the water column that sharks inhabit is The Midnight Zone (Bathypelagic Zone) that extends to 13,100 feet (4,000 m) where no sunlight exists. The fewest numbers of sharks inhabit this cold, dark realm. Ancient sharks like the frilled shark and the Portuguese dogfish call these waters home.
No sharks have been found in The Abyss (Abyssopelagic Zone), that reach the ocean floor at approximately 19,700 feet (6,000 m). Nor have any been discovered in the Hadal Zone (The Trenches) that plunges to 36,100 feet (11,000 m) in the Marianas Trench.
As ectothermic animals, most sharks prefer tropical regions, which typically have temperatures of 69° F (21° C) and higher. These regions also rich in marine life, which means plenty of prey items for sharks. In the Indo-West Pacific tropical area alone you can find 1.5 times as many shark and stingray species as there are in the Eastern Pacific and the Tropical Atlantic combined.
In the Southern Ocean, in the cold waters surrounding Antarctica, there are no sharks.
Every spring, thousands of blacktip sharks migrate to Florida at the same time that tourists start pouring in for vacation with as many as 12,000 sharks were seen at one time only a few yards off the beach. Unsurprisingly, Florida is the No. 1 state on the U.S. list for shark attacks with 273 official attacks reported between 2000 to 2015. While that may sound like a lot, remember that this averages out to around 18 attacks per year, and when you have 12,000 sharks and anywhere between 40,000,000-97,000,000 tourists sharing the same space each year, 18 bites doesn’t seem so bad.
Blacktip sharks aren’t the only ones who migrate in massive numbers. The blue shark has been known to migrate as well, sometimes in schools as large as one thousand individuals off the Maryland coast.
Gigantic Galapagos Gatherings
While the Florida numbers are impressive, they don’t compare to the density and diversity of the scalloped hammerhead’s migration destination. The Galapagos has a massive protected marine park, protecting more than 18,000 square miles (46619.786 km2). For every hectare of sanctuary there is an average of 17.5 tons of fish, 70 percent of which are sharks.
In other words, the Galapagos is home to 12.25 tons of sharks. The kinds of species you find there range in size and shape from the massive whale shark, hammerhead, and the aptly names Galapagos shark.
While the Galapagos has both the largest amount and highest species diversity of sharks in the world, it doesn’t have the highest density of sharks. That unique distinction goes to the atoll of Fakarava in French Polynesia.
While lacking in the diversity quotient, Fakarava has the highest concentration of grey reefs sharks in the work. Just the southern pass of the atoll alone is home to approximately 700 shark species. They’re so densely packed that in a 500-foot square there may be as many as 34 shark species. There are so many sharks there that they actually outweigh their prey items, in terms of biomass. This is only because Fakarava has a constant supply of migrating fish that come there to spawn at all times of the year, providing the reef sharks with a constant supply of food.
“The Encyclopedia of Sharks” by Steve Parker
“Sharks: The Animal Answer Guide” By Gene Helfman and George H. Burgess.
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