Whither the White Shark?

Last November, we released a young great white shark that had been with us for more than two months. During that time, she served as an ambassador to tens of thousands of visitors, helping convey the awesome beauty of these animals and letting us tell the story of the dangers they face in the wild.

So where is she now? The good news is that she did very well on release, traveling from Monterey Bay to Baja California, a distance of more than 500 miles. The last time we heard from her, she was near Ensenada, Mexico.

But about two months ago, her satellite tracking tag “started talking on land,” according to John O’Sullivan, the Aquarium’s curator of field operations. The white shark had been incidentally caught in a gillnet and died. She is the only one of the five white sharks exhibited at the Aquarium known to have died following its release.

Still, that shark, and the more than 180 others that have been tagged and tracked as part of the Aquarium’s White Shark Program, have provided invaluable information on where juvenile and adult great white sharks are traveling and how we might better protect them from overfishing, habitat destruction and other human activities.

Future Plans

So what can white shark watchers expect this summer, the time when we normally collect and display seasonal “young of the year?” The million-gallon Outer Bay exhibit is scheduled for renovation starting in August, and that means we won’t be hosting another white wonder until 2011 at the earliest.

For the Aquarium’s White Shark Project, however, it’s full speed ahead. “Our field research continues even though there will be no exhibit white shark this year,” says John.  

Working with colleagues at Tagging of Pacific Predators, as well as colleagues in Mexico and southern California, Aquarium staff hopes to answer one looming question: Where do young white sharks go? “Many of our released sharks have gone south to Mexico,” says John. “But we don’t know where they came from before that, and we don’t know where they’re bred or pupped.” Further tagging efforts can help answer these questions.

Data from other tagged sharks indicate that there are “two major population centers in the Eastern Pacific—one in central California, off the Farallon Islands; and one off of Guadalupe Island in southern California,” says John. The adults of these two distinct populations appear to travel back and forth to Hawaii and the “Shark Café,” a remote area between Baja and Hawaii known as winter and spring habitat for adult great whites.

“It’s a huge migration, and there must be an important reason they’re doing it, possibly related to feeding or breeding,” says John. “But no one knows for sure. Continued tagging will help us determine that.”

Tagging Technology

To help solve these mysteries, researchers will employ satellite tagging technologies. Currently, before a shark is returned to the wild, it’s fitted with two types of electronic tags. The first is an externally attached pop-up satellite (PAT) tag that eventually pops off, floats to the surface and transmits data via satellite. A second type, the smart position-only (SPOT) tag, sends data every time the shark’s dorsal fin breaks the surface. But these tags have limited lifespans and don’t supply information past six months. 

Now, to track shark movement for periods up to five years and closer to shore, researchers will be using implanted acoustic tags. This technology requires underwater “listening stations” to record the “pings” emitted by the tags. “The adult white shark program uses these extensively off the Farallones and Point Reyes, near San Francisco Bay,” says John. “But we’ll be deploying 11 more listening stations off southern California and Mexico’s Baja Peninsula in the next year.”

A fourth type of tag, the archival tag, may also be used. These are surgically implanted and can record temperature, compass heading and depth, and last up to seven years. The shark must be caught in order to recover the tag and its storehouse of data.

It’s all part of solving the mystery of the white shark.

“They’re a big piece of the ecosystem, and yet we know so little about them,” says Dr. Chris Harrold, the Aquarium’s director of conservation research. “What we do know is that there are not many of them. And that alone is cause for concern.  We’re trying to learn as much as we can, so we know their role in the marine ecosystem, and what kind of protection they need.”

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Comments

[עדה לזורגן]

Wow amazing, what a grate stuff. And this is really hard work. Hands on for all the researchers.

[Patric Douglas]

That's entirely believable. Scott Cassel has been working in the Sea of Cortez with those critters for a while and has been saying these animals are now inhabiting the niche left behind from blue sharks and other predatory species taken out by rampant fishing all along the west coast.

If you want the truth about a fishery ask a fisherman.

[Ken Peterson]

Patric, that's disturbing news. I'll share with our juvenile white shark research team and our Mexican colleagues.

We're pretty sure that this was truly accidental catch. The fisherman took his ponga (small boat) father offshore than usual to avoid Humboldt squid preying on his catch, and left his gillnet in the water for a week when bad weather prevented him from getting back out to check it.

[Patric Douglas]

Whites in Ensenada are targeted by long liners and small co-ops, the meat is then sold as swordfish in local markets.

After speaking with one family run operation two years ago I was told they often catch young of the year and have two choices. Put the dead shark back into the water or make a few pesos from the animal at market.

Images here:

http://sharkdivers.blogspot.com/2009/11/ensenada-fish-market-mexicos-white.html

[mike mulligan]

More sea farming is needed which will decrease the need for indiscriminate fishing practices like gill nets.

Sea farming is the future.

[Ken Peterson]

Great white sharks are protected in California and Mexico, and still they are caught accidentally in gillnets.

By working with commercial fishermen, we're helping to document how significant an issue this is, and what kind of impact it's having on the regional population of great white sharks.

Fisheries managers in both countries regulate use of gillnets (such as the seasons when they can be used, and the locations where they're permitted). Ideally, the data we're gathering will inform those regulations and better protect young white sharks.

For now, follow our Seafood Watch guidelines to make sustainable seafood choices. Unwanted catch of protected animals (like great white sharks) is one of the key factors that affects whether something winds up on our Red list to avoid.

[Maggie Rufo]

What, if any, efforts are being made to do something about the gill nets? It's heartbreaking to know that these sharks continue to killed like this! Especially a long-lived shark like the Great White that is in trouble. This shark will never breed now. I wish we could do move to stop this endless exploitation and corruption of the sea. Is there really anything we can eat from the sea that doesn't have an environmental cost, your seafood card quide notwithstanding?