The legendary white shark can grow over twenty feet in length and weigh more than three thousand pounds. And as a study to promote the conservation of this endangered species, the Monterey Bay Aquarium periodically exhibits juvenile white sharks in their collection for public display.
Many white sharks exhibited at the aquarium were incidental captures in the commercial (primarily halibut and white seabass) groundfish fishery in southern California. Once a white shark is captured, it is transported in a 3000 galloon pelagic fish tank that gives them enough room to swim. They are then moved to an ocean pen until they are fed and determined ready to be moved to the Monterey Bay Aquarium exhibit. While on display at the aquarium, these white sharks participate in multiple studies intended to broaden overall knowledge of the species, but primary research occurs on the wild population.
What’s it take to tag a white shark in the wild and bring it into the captive environment temporarily? “There are many challenges to keeping white sharks on public display – with collection of a healthy specimen as one of the main difficulties,” says Juan Manuel “Manny” Ezcurra, Associate Curator of Elasmobranchs, Monterey Bay Aquarium. “The exhibit needs to be large enough to allow the fish to swim and glide in a pattern that doesn’t burn too much energy. These sharks are regional endotherms, like tunas, and therefore have complex circulatory systems and elevated metabolic rates, so feeding in a captive setting needs to be initiated quickly, or the sharks will burn too much energy reserves. They sharks we display are less than 12 months old, and they look just like adults but they are only 1.2-1.5 m in length when born.”
Because sharks are heavily exploited globally – for shark fin soup, meat, jaws and teeth – the aquarium believes that hosting white shark “ambassadors” in their collection will help promote species conservation. Manny says that sharks “have life histories that are more like mammals, with generally long lives, long times to reach sexual maturity and relatively few, well developed young compared to fishes… Sharks and rays and not able to reproduce at the rates that they are being harvested and populations are decreasing at alarming rates around the world.”
The collected white sharks are only on display for a finite period of time. Three criteria are used to determine the appropriate time to release a shark: the health of the animal, its size, and the compatibility to the exhibit community. Manny explains that “we want to be sure that there is no serious degradation of the health of the shark, and each of our released sharks have survived as seen by satellite tagging results. The growth of the white sharks on display is 2 times faster in length and 3 times faster in mass than growth of sharks in the wild at that size, and we want to make sure that the sharks don’t grow so fast that we can’t safely release them. Of the 5 sharks we have displayed, two started to attack other sharks and rays in the exhibit, and we released them after this change in behavior occurred. We do use the three criteria together in making these decisions.”
The longest a white shark has stayed under the aquarium’s care was 198 days, and each of the sharks are tagged before they are released back in the wild while they are still juveniles. Because satellite tagging results have revealed that released young white sharks undergo long migrations – from Baja California to the sea of Cortez – the aquarium releases their ambassadors in Monterey Bay.
Currently the Monterey Bay Aquarium is renovating their Outer Bay exhibit, with plans to reopen next year. The Outer Bay exhibit is a “a semi-closed system with life support to keep pH, temperature and oxygen near values encountered in southern California, where the juveniles are found,” explains Manny. “Salinity is matched as we pump in a small amount of seawater from Monterey Bay continually, to maintain good water quality in addition to the work of our life support system.”
The Montery Bay Aquarium does not currently have a white shark on display during the exhibit renovation, but they plan to acquire another juvenile animal in summer of 2011.
Planet Carnivore: Sharks airs Friday October 1 at 8P et/pt on Nat Geo Wild.
Video preview: This great white shark waits in the depths of ocean waters to stalk seal prey, then quickly leaps up out of the water to attack.
Photo Credits: Monterey Bay Aquarium/Randy Wilder