White Shark - Terry Gross

A simple wrong turn, no doubt by one or two pregnant females, somewhere in the vicinity of 450,000 years ago during climate changes, could have caused sharks to show up in a place they were no supposed to be. This is according to research which was Published this past Wednesday, in Proceedings of the Royal Society B. (It should however be noted that we don´t necessarily agree with the findings here at AC as competition for space is an easier explanation on why some fish first swam into the Mediterraneanan.)

And of course liking the area, they have stayed on in the Mediterranean – albeit in small groups – because much like salmon they go back to where they were born. It is also believed that the narrow channels in the Mediterranean have made it nigh impossible for the sharks to get back out again.

Researchers believe this “wrong turn” happened due to a mixture of climate change, high sea levels, and changing currents at the time, and as a result the sharks gained a permanent foothold in the Mediterranean.

Thanks to genetic analysis and tagging, researchers now know that sharks do indeed swim between Australia and Africa, and actually have a tendency to swim towards the east to where they were born, making their way using cues from the ocean currents they swim through.

However, in the case of long long ago, scientists still believe that some sharks simply became confused, and wound up a little bit off course, and as a result, permanently made a change in the way the world we live in today is.

After being exhibited for two months at the Monterey Bay Aquarium, a young female white shark was released back into the ocean Wednesday this week.

“I’ve always said that these animals will tell us when it’s time to put them back to the ocean. Now was clearly the time,” said Randy Hamilton, vice president of husbandry for the aquarium.

The release was prompted by a change in behaviour; she started acting aggressive towards other sharks in the million-gallon aquarium and during the Halloween weekend she received a superficial bite wound. She also injured a galapagos shark by biting it and was observed chasing the scalloped hammerhead sharks.

“We monitor the behavior of great white sharks very closely while they’re on exhibit,” Hamilton explained. “When we saw a new pattern of aggressive behavior, we decided it was best to release her.”

The young female was the fifth great white shark exhibited and successfully released back into the wild by the aquarium. Monterey Bay Aquarium is the only institution to keep a great white shark on exhibit for more than 16 days, get the shark to consistently take food from the staff, and document the animal’s successful return to the sea.

Just like this young female, the four previously released great white sharks were fitted with electronic tracking tags which make it possible to confirm the shark’s successful adaptation back into the wild. Two of the sharks travelled to the southern tip of Baja California and beyond after being released, while the third one opted for Santa Barbara waters. The fourth shark also stayed near Santa Barbara where it was caught and released by a commercial fisherman just a few days after being released from the aquarium and it was then reportedly in good health.

The female shark released this week has been fitted with two tracking devices; one that will deliver real-time data on her location and one that will collect and store information about her travels, the depths she dives to and the water temperatures she favours for about six months, before it pops free and delivers those data to scientists via satellite.

You can find the real-time data emitted by the first device on the TOPP website (Tagging of Pacific Predators): http://www.topp.org .

The shark was released in offshore waters near the southern tip of Monterey Bay shortly after sunrise.

“Her health is excellent, and we learned a lot while she was with us. Based on past experience, we have every expectation that she’ll do well after release,” said Hamilton.

During her two month long stay (69 days to be exact) in the aquarium, she grew from 5-foot 3-inches to 5-foot 5-inches and put on an extra 20 pounds. She ate mackerel only and would happily gulp down up to three percent of her body weight in a day.

The exhibit of young great white sharks is part of the Monterey Bay Aquarium’s effort to change public attitudes towards the feared white sharks and raise awareness about the threats facing them in the wild. The first white shark was exhibited in 2004/2005 and was seen by over a million visitors before being released after six months in captivity. Collectively, the four sharks exhibited before the newest addition has been seen by almost 2.5 million visitors.

“I can’t overstate the impact of this single animal on advancing our mission to inspire conservation of the oceans,” aquarium Executive Director Julie Packard said of the first white shark the aquarium had on exhibit.

The million-gallon Outer Bay exhibit will undergo renovations starting late August 2010 and it will therefore not be possible to see any great white shark at the aquarium until summer 2011 at the earliest.

A research group[1] studying the hunting ability of the great white shark has found evidence indicating that this notorious predator actually has a fairly weak bite. In several movies – including the legendary Spielberg film “Jaws” – the great white shark has been portrayed as a hunter blessed with an exceptionally strong bite, but the allegedly fierce jaw power of Carcharodon carcharias is now being questioned.

According to research leader Dr Daniel Huber of the University of Tampa in Florida, sharks actually have very weak jaws for their size and can bite through their prey mainly thanks to their extremely sharp teeth – and because they can grow to be so large.

Photo by Terry Goss, copyright 2006

“Pound for pound, sharks don’t bite all that hard,” says Dr Huber. Compared to mammals, sharks have amazingly weak bites for their size. Lions and tigers are for instance equipped with much more jaw strength than sharks when you account for body size. According to Huber, mammals have evolved much more efficient jaw muscles.

During the study, Dr Huber and his team studied 10 different shark species. The bites of small sharks were fairly easy to measure, while large sharks had to be knocked out and subjected to mild electricity in order to stimulate their jaw muscles.

As mentioned above, sharks don’t really need strong jaws since they can grow so large and are fitted with extraordinarily sharp teeth. In addition to this, they also benefit from having very wide jaws. When they tear an animal apart, they frequently use a sawing motion.

Dr Huber hopes that their study will lead to the development of protective swim wear and other types of shark-proofing gear.

If you wish to read more, you can find the study “Is Extreme Bite Performance Associated with Extreme Morphologies in Sharks?” in the journal Physiological and Biochemical Zoology.

http://www.journals.uchicago.edu/doi/abs/10.1086/588177?prevSearch=(shark)+AND+[journal%3A+pbz]

The young white shark brought to the Monterey Bay Aquarium on August 27 has now been released back into the wild after 11 days on exhibit. She was captured on August 16 in Santa Monica Bay and has now been safely returned to the same waters. During her stay at the Monterey Bay Aquarium she lived in their million-gallon Outer Bay exhibit, but despite her relatively roomy accommodation she only fed once and the staff decided that she would be better of in the wild.

A white shark

“These decisions are always governed by our concern for the health and well-being of these animals under our care,” says Jon Hoech, director of husbandry for the Monterey Bay Aquarium.

On September 7, the young female was released in offshore waters in the Santa Barbara Channel at 1:30 p.m. (Pacific Time). Before being released, she was tagged with a tracking device that will provide researchers with data on her life in the ocean. For 148 days, the pop-up tag will collect information about geographical location, depths, and water temperature. After this period, the tag will pop free and deliver the collected data via satellite.

As of now, a total of four White Sharks with tracking tags have been released from the Monterey Bay Aquarium. The three other sharks did however stay longer at the aquarium before going a back to the wild; between four and six months. Together with their research partners, the Monterey Bay Aquarium has tagged and tracked 18 juvenile white sharks off Southern California as a part of their “White Shark Conservation Research Project”. The aquarium is also involved in the project “Tagging of Pacific Predators” (TOPP) led by Stanford University’s Hopkins Marine Station, which has tracked 143 adult white sharks off the Central Coast using data-collecting tags.

If you wish to know more about the white shark research at the Monterey Bay Aquarium you can visit www.montereybayaquarium.org/whiteshark/.