White Sharks at Point Reyes

 

Have you ever seen a white shark at Point Reyes? How about one feeding on seal carcasses near the headlands? Would you like to know where and how often white sharks are seen, and what they are usually seen doing? This may be useful information if you dive or surf in open water here!

Scot Anderson, Ben Becker and Sarah Allen published an article in the January 2008 edition of California Fish and Game on observational sightings of white sharks at Point Reyes National Seashore (PRNS) over 23 years and decoy surveys over 11 years.

 
Two photos of a white shark feeding on a seal as a couple sea birds fly above the blood-filled water.
A white shark is seen here feeding on a seal just off shore.

© Scot Anderson

 

Where are they seen?

Most observations were clustered in three areas: Point Reyes Headlands, McClures Rock, and Tomales Point. White sharks are mostly seen close to shore, in water depths from 5 meters to 30 meters. This is likely because they need to keep sight of the surface where they capture their prey.

When are they seen?

White sharks are observed at Point Reyes most frequently in the late summer and fall (August, September, October), which coincides with the seasonal peaks of pinnipeds—California sea lions congregate in the area when males migrate north in the fall, and juvenile northern elephant seals haul out in the fall. When Scot Anderson used decoys to track the frequency of white shark appearances, he found that they were seen approximately once every six hours at Point Reyes National Seashore! However, this frequency is still less than the frequency in which they are sighted at the Southern Farallon Island: once every 1.9 hours.

What do they eat?

At Point Reyes, white sharks prey on pinnipeds that congregate onshore and they also scavenge on marine mammal carcasses (especially whales). At the Farallones and Año Nuevo, the pinniped population that white sharks primarily feed on are the northern elephant seals. However, this is not what Scot Anderson found at Point Reyes—the white sharks here seem to be feeding mostly on harbor seals and California sea lions.

White sharks also scavenge off of marine mammal carcasses. Large dead marine mammals such as sperm whales, baleen whales, and northern elephant seas can leave an odor trail that can be carried for many kilometers. White sharks can track these "odor corridors" and follow them to the source. In 2004, when a dead sperm whale drifted to Point Reyes, as many as four white sharks came to feed on the carcass at one time. A large white shark (~943 kg) can survive up to 45 days after feeding on 30 kg of blubber from a dead cetacean!

Should I be concerned about attacks on humans?

There has been five human attacks by white sharks at Point Reyes over 23 years (as of 2008), all of which occurred in the fall season close to shore in water less than 10 meters deep. All the victims survived. Those highest at risk appear to be people who dive for abalone, spearfish, or surf in open water in or near areas where sharks have been sighted, or near seal colonies. Please be careful, and report any white shark attacks to a park ranger.


This page has been adapted from Ocean Updates: Vol. 1, Issue 6: "White Sharks at Point Reyes National Seashore" published on May 20, 2008.

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Additional Information

White Shark Information from the California Department of Fish and Wildlife
White Shark species profile from NOAA Fisheries

 

Learn More About White Sharks

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    Multimedia Presentations

    From 2007 to 2012, Pacific Coast Science and Learning Center Science Communication Interns produced a series of podcasts, videos, and audio-slide shows exploring science from Bay Area national parks. Two of these The Natural Laboratory multimedia products focused on white sharks. View the videos or listen to the podcasts below. Visit our Multimedia Presentations: The Natural Laboratory page for additional videos and podcasts.

     

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    Transcript

    [Introduction]

    This is the Natural Laboratory, a podcast exploring science for Bay Area National Parks. I'm Cassandra Brooks.

    [music]

    Today, I'm with Scot Anderson, a local researcher who's studied great white sharks here off Point Reyes Seashore and at the Farallons for more than two decades. In the fall of 2009, Anderson and his colleagues with Stanford University's Tagging of Pacific Predators Program, UC Davis and others published a paper on the sharks. Their study revealed new information about where the sharks travel to, how they spend their time, and showed that the shark population here off California's genetically different from great white shark populations throughout the world.

    I sat down with Anderson to find out more about the study and what it tells us about these iconic and revered animals.

    [Scot Anderson Interview]

    Cassandra Brooks: Maybe you could tell me a little bit about what at typical day is like for you out in the field.

    Scot Anderson: Yeah, okay, so a typical day, uh, going out looking for sharks, let's say, on the Farallon Island runs, we leave out of San Francisco, now, on a big sailboat called the Derek M. Baylis. It has this launch and we, uh, go to the island and we launch the launch and we work out of that for six hours on the water looking for sharks. Um, usually what we do is we put a decoy out that's about the size of a small sea lion and a small piece of whale blubber next to the boat, that's tied to the boat. And what that does is provides a area of scent around the boat that gets the sharks interested in sticking around. And then, if the shark comes around, we videotape them first, try to document what the shark looks like, who it is, and what their sex is, and then we go ahead and either tag them.

    CB: How do you actually tag a great white shark?

    SA: [cross talk] tag a white shark. [Brooks chuckles] Um, it sounds like it'd be a complicated process, but it's actually quite simple. You wait for the right moment, which is when the shark is at a 90-degree angle to you, swimming by the boat. So, then, the tag is on the end of a long pole and it has a harpoon-like dart on the end. Once it's embedded in the shark's skin, it's going to stay there until it finally pulls out, in a year to two years, or something like that.

    CB: And during that year to two years, it's collecting data the whole time about where the shark is going and...?

    SA: Yeah…okay so there's two kinds of tags we use. The first kind of tag is a satellite tag and that we put on the shark and then it...it records data, like, uh, the depth of the water, the temperature of the water, and light levels, and things like that. And that's on the shark until a pre-programmed date that it's, uh, released. When it releases, it floats to the surface and starts downloading data.

    The other kind of tag's called an acoustic tag and, um, it makes a sound that's a signature sound for each individual shark, comes out to a number. If they swim within a quarter mile of the receiver, it logs them in. Now these receivers are placed on the bottom and we have one at Tomales Point, one at Point Reyes, two at the Farallons, and two at Año Nuevo.

    CB: Wonderful, so people will just have these underwater devices that are just constantly picking up these pings that are individual to each shark, and, then, you know when they are there and when they are not there.

    SA: Yeah.

    CB: I was hoping you could tell me a little bit about the recent study that was published in the Proceedings of the Royal Society. And you were co-author on this study.

    SA: Well, it's a study that, sort of pulls together a lot of different kinds of data. And, so, what we did was we took DNA data and looked at that and what we found is that the sharks are very closely related. And then you start looking at where the sharks have migrated to and from and it's actually a...an area that's well defined. They don't go much past Hawaii—maybe 500 miles beyond that—and they don't go past Midway, and they don't go north of in a line with Canada, and they are pretty much in this zone.

    CB: But why do they even migrate as far as past Hawaii?

    SA: So why do they go there?

    CB: Yeah.

    SA: Well, that still remains a question to be answered. But it really looks like it has to do more with breeding than feeding, because this population, when they're on the coast, is feeding on an abundance of food. So, why would you go somewhere where there is very little food?

    CB: You were talking that the study also shows that this population is genetically distinct. Does that...so it means that they’re not breeding with sharks from South Africa, obviously, or other areas...

    SA: Right, yeah, because of the genetics, we know they're isolated up here and it's its own distinct population, so...

    CB: And that seems like a very important finding in terms of understanding their role in the ecology here in the North Pacific.

    SA: Yeah, you know, when you look at the role animals have in the environment, they're either going to be a producer or a consumer. Obviously, white sharks are apex predators; they're at the top of the game here. The role they play in the environment is...has yet to be totally understood, because we know they eat seals and sea lions—during certain times of year—and we know that they scavenge on dead whales and things and...but so do other animals. Whether they're actually, you know, keeping the environment healthy and all that, it's yet to be seen, but probably. They must play some role.

    [Conclusion]

    Looking out over the ocean from Tomales Point, it's surprising to think that great white sharks, among the most massive and mobile predators in the world, don't use the whole Pacific as their playground and that they don't mate with other white sharks in the world. Instead, they follow a strict and isolating migration path between California and the Hawaii region, which, as winter rapidly approaches, they are soon to embark on. Why, exactly, they make these vast migrations remains to be seen, but until then, Anderson and colleagues will be out every fall doing more observational and tagging studies.

    [music]

    With the Pacific Coast Science and Learning Center, I'm Cassandra Brooks.

    Visit our keyboard shortcuts docs for details
    Duration:
    5 minutes, 5 seconds

    Casandra Brooks interviews Scot Anderson, a local researcher who has studied white sharks off of Point Reyes Seashore and at the Farallon Islands for more than two decades.

     
     
     

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    Research Journal Articles

    Anderson, Scot D. 2011. "Long-term individual identification and site fidelity of white sharks, Carcharodon carcharias, off California using dorsal fins." Marine Biology 158: 1233–1237. Available at https://rd.springer.com/article/10.1007/s00227-011-1643-5 (accessed on 11 June 2022).

    Anderson, Scot D., Benjamin H. Becker, and Sarah G. Allen. 2008. "Observations and Prey of White Sharks, Carcharodon carcharias, at Point Reyes National Seashore: 1982-2004." California Fish and Game 94(1):33–43. Available at https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=47405 and https://www.researchgate.net/publication/234130258_Observations_and_prey_of_white_sharks_Carcharodon_carcharias_at_Point_Reyes_National_Seashore_1982_-_2004 (accessed on 11 June 2022).

    Curtis, Tobey H., John T. Kelly, Karl Menard, and R. Karl Laroche. 2006. "Observations on the Behavior of White Sharks Scavenging from a Whale Carcass at Point Reyes, California." California Fish and Game 92(3):113-124. Available at https://www.researchgate.net/publication/264992898_Observations_on_the_Behavior_of_White_Sharks_Scavenging_from_a_Whale_Carcass_at_Point_Reyes_California (accessed on 11 June 2022).

    Kelly, John T., and A. Peter Klimley. 2003. "The Occurrence of the White Shark, Carcharodon carcharias, at the Point Reyes Headlands, California." California Fish and Game 89(4):187–196. Available at https://www.researchgate.net/publication/282777974_The_occurrence_of_the_white_shark_Carcharodon_carcharias_at_the_Point_Reyes_Headlands_California (accessed on 11 June 2022).

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    Last updated: July 18, 2022

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