Shark Week Series: What We Don’t Know About Great Whites

Robin Just

Fun fact: Great white sharks (or white sharks, as scientists prefer) are migratory.

(Photo credit: kqedquest, flickr)

Scientists are just beginning to learn how far ranging an individual shark can be, and they are still puzzling over what motivates them to travel. In Devil’s Teeth, Susan Casey’s fascinating book about white sharks off the Farallon Islands near San Francisco, she describes some of their wanderings. The sharks completely disappear for several months, then return, thin and hungry, to fatten up on local seal and sea lion populations. Some of the Farallon sharks have been tracked to an area off the Pacific coast of Mexico.

What are they doing down there? Nobody knows, but researchers are working hard to find out.  Elsewhere in the book, Casey gives an account of orcas killing and eating one of the sharks. Almost immediately after the killing, dozens of other sharks fled the area. Researchers had been observing them daily, and were very surprised when they all disappeared. One of the sharks had a radio tag on; he turned up in Hawaii.

Our “local” white sharks migrate as well. Like many New Englanders, they head south when the temperature drops, and have been found off the southeast coastal states, and in the Gulf of Mexico.

There is a lot we don’t know about white sharks. But we do know that their numbers are declining throughout the world’s ocean. The average size of the animals is shrinking as well.

This is not good news. Sharks are an important part of a healthy, functioning ocean ecosystem. As we learn more about these mysterious animals, we will need flexible, ecosystem-based management strategies to ensure their survival.

Coastal Marine Spatial Planning (CMSP) is one tool that can help. It is a strategy that is paying off for the endangered North Atlantic right whales. There are very few of these animals left, but they are showing signs of recovery. Recently, shipping lanes were re-routed in Stellwagen Bank National Marine Sanctuary to avoid right whale feeding grounds, allowing for fewer whale/boat collisions. This is just one example of how a strong National Ocean Policy can help provide creative solutions for species conservation.

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