MCSI develops new methods for tagging adult white sharks
Scientists at MCSI have been working to improve methods for SPOT tagging adult great white sharks. New methods developed, tested and implemented by MCSI involve a device to prevent gut hooking, soft fishing gear to prevent skin abrasions and constant forward movement to fully irrigate the gills. Sharks tagged in this manner, including the largest white shark to ever be SPOT tagged, were far more vigorous upon release than our previous method that lifted the sharks from the water. We strive to constantly improve our methods to do what is best for the sharks and the scientific community.
New publication reveals the 2-year migration for adult female white sharks in the northeastern Pacific
Expedition White Shark tracking app
The Marine Conservation Science Institute has launched an app focusing on great white sharks. The app, called Expedition White Shark, includes numerous features that let users learn more about these amazing animals, including the ability for users to track satellite-tagged great whites. The app displays a map with live tracking data for the sharks tagged with real-time tracking devices, so that users can follow these sharks at the same time as the research scientists! The Guadalupe Gallery shows images of all sharks in the Guadalupe Island photo-ID database and the photo gallery has photos and videos showing how the sharks were tagged.
For more information see expeditionwhiteshark.com
Montauk Sperm Whale Stirs SOFA Mystery
When I recently heard rumors that a sperm whale calf had washed ashore on the shores of Montauk, and that this calf had a massive shark bite on it, I became very interested. Adult White Sharks in the Eastern Pacific spend 6-16 months in the deep Pacific Ocean, halfway between the mainland and the Hawaiian Islands. This is an area we have termed the Shared Offshore Foraging Area, or SOFA, because Great White Sharks from both Guadalupe Island and Central California travel the this area to feed. The SOFA is a huge area, so big that White Sharks probably rarely encounter one another while they are offshore. But what are the Great White’s eating in the middle of the ocean? If I had a dollar for every time I’ve been asked that question I would be taking my vacations in a private jet! But it’s a great question, one that inspired me to mount the very first expedition to the SOFA to visually characterize the SOFA habitat and creatures that live there. Chris Fischer and the National Geographic Channel made that expedition possible and some of the events are portrayed on two episodes of Expedition Great White.
The expedition raised as many questions as it answered. First, I was able to determine that Great White Sharks in the SOFA are NOT feasting on seals, dolphin or porpoise…the SOFA was basically a huge zone with very little life at the surface. We saw very few seabirds and almost no pelagic fishes. However, at night hoards of squid would swarm under the lights; we even found a freshly killed giant squid (Architeuthis sp). Not surprisingly, we found the large squid biomass to be supporting a large number of sperm whale pods; sperm whales primarily feed on squid.
The absence of appropriately sized marine mammals in the SOFA forced me to speculate that White Sharks in the SOFA may be feeding on squid, or large fishes that eats squid; a notion that is contrary to current theories about adult White Shark diet. Swordfish, sharks, marlin and tuna all feed on squid and they likely occur in the SOFA. I had ruled out sperm whales as potential White Shark prey due to their huge size…but then this calf washes ashore in Montauk. Did I get it wrong? Can white shark truly feed on living sperm whales? Using rumors or information gathered from the media can get scientists in serious trouble, so I searched for a reliable source of information. I tracked down the scientist who did the necropsy on the sperm whale: Kimberley Durham, the Rescue Program Director at the Riverhead Foundation for Marine Research and Preservation, in Riverhead NY. Kimberley and I discussed the case at length, trying to determine if a Great White Shark may have attacked the sperm whale calf.
I learned that the sperm whale calf was a female, approximately 18 feet long and 5000 pounds. The teeth had not yet erupted in the mouth but squid beaks were found in the stomach, so this calf was still nursing but learning to catch squid as well. Yes, there was a large bite shaped wound on the right posterior flank, not too far from the caudal peduncle (area where the tail joins the body) measuring 71 cm wide by 37 cm high. A very large Great White could make a bite that large, even larger. Furthermore, predatory sharks often make their first attack at the caudal peduncle, to cripple their prey with the first bite. So my first thought was, yes, this could be the first case of a White Shark attempting to prey on a sperm whale! But stop there, Kimberly Durham explained that the wound had largely healed…and she sent me a photograph. The photo revealed that the wound was almost completely healed and there was no “divot” of missing muscle and tissue in the middle of the presumed bite mark. Instead, the wound was filled-in and skin was intact. If a White Shark had attacked I would expect some tissue to be removed and I would also expect to see scarring to match the ragged punctures that would have been made by the teeth.
Although I was intrigued that the Montauk case could suggest that Great White Sharks are capable of feeding on sperm whale calves in the SOFA, I personally do not believe the wound on this whale to be a result of a shark attack. Years ago I logically eliminated sperm whales, even the calves, due to their incredible size…how could a 3000-4000 pound shark eat a 5000 pound whale? Even a newborn sperm whale weighs 3000 pounds! Furthermore, adult sperm whales would aggressively defend their calf if confronted by a threat like a White Shark. Reluctantly I must retreat back to my first notion, albeit controversial, that Great White Sharks are not feeding on marine mammals while they inhabit the pelagic environment. This is not a trivial question to ponder, since on average, adult White Sharks in the Eastern Pacific spend more time in this habitat than they do in coastal habitats.
So what injured the sperm whale? Obviously the calf came into something solid, which is unusual in the sperm whale habitat, but I suspect it was struck by a boat or ship? And what do Great White Sharks eat in the SOFA?? Gotta dollar? If everyone connected to the internet sends me a dollar, I’ll answer that question next year…I promise!
I would love to hear comments about this topic from other experts (post on facebook).
Dr. Michael L. Domeier
Marine Conservation Science Institute
Update on Amy, the female white shark that traveled into the Sea of Cortez
Amy, one of the first mature female white sharks we tagged at Guadalupe Island, is a very significant shark in our quest to learn more about the complete life history of this species in the northeastern Pacific. Via her SPOT tag, Amy was the first shark to reveal where mature females are spending their time during their two year absence from the adult aggregation site at Guadalupe Island. She left Guadalupe Island in late January 2009 and spent the next 15 months living an entirely pelagic existence in the middle of the Pacific Ocean. For the first seven months she was between 250 and 900 miles west of Guadalupe Island, but once the males returned to Guadalupe in the fall of 2009, she headed deeper into the Pacific (up to 1700 miles from Guadalupe), to the Shared Offshore Foraging Area (SOFA). In April of 2010 she surprised us by entering the Sea of Cortez, traveling all the way to the northern reaches before exiting two months later. Pupping in southern California begins as early as April and peaks in July, so we cannot say for sure that she gave birth while she was in the Sea of Cortez, but we believe she was pregnant and therefore it is possible.
After rounding Cabo San Lucas her tag suddenly stopped transmitting about 260 miles southwest of the tip of Baja California. We have heard nothing from Amy for a year now and we suspect she may have met a tragic end. Although it is possible that the tag failed, we have had no reports that she returned to Guadalupe, as expected, in the fall of 2010. Unfortunately the disappearance of Amy is not unprecedented. Twenty-one of our known white sharks at Guadalupe Island have seemingly vanished since 2005; among them is a rather well known male named “Fat Tony.” The story of Amy reminds us of why we are working so hard to learn more about this magnificent species. The tracking work we conduct is critical, allowing us to unravel the life history and migratory patterns of white sharks so that we can identify the times and regions where they are most vulnerable. Through our work Mexican authorities now know that white sharks, which they protect at Guadalupe Island, are exposed to the longline and gillnet fleets that fish the waters surrounding Baja California.
These data are the property of MCSI and may not be reproduced or used without permission.
HOW MANY WHITE SHARKS ARE SWIMMING IN THE NORTHEASTERN PACIFIC?
A few months ago a population estimate for northeastern Pacific white sharks was published by Chapple et al. in the Proceedings of the Royal Society of London . In summary, the researchers used unique dorsal fin markings to identify individual white sharks, and then they conducted surveys to search for known and unknown white sharks. This is a classic example of tagging data (mark/recapture) being used to generate a population estimate, except instead of physically marking the animals they relied upon natural markings. They estimated the number of adult and sub-adult white sharks in waters off central California to be 219. They went even further to speculate that the adult and sub-adult population in the entire northeastern Pacific is approximately 438 animals. This alarmingly low number soon gained traction among the conservation community and the media. But wait a minute…is this estimate really representative of the white shark population in the entire Northeastern Pacific? I have not seen a single discussion of the merits of the methods used to derive this population estimate. Any model is only as good as the assumptions used to build the model; if the assumptions are wrong than the results are invalid. Let’s have a look at the assumptions that were used to generate this population estimate.
The details of the model cannot be found in the paper, instead the reader must get access to the supplementary materials. The meat of the paper is really in this supplement. Their first assumption is that the population is closed, meaning no new white sharks migrate into the population and no members of the population die or migrate away from this population. Immediately I see a red flag. Our long term monitoring at Guadalupe Island has shown individuals to disappear (Fat Tony was a very popular example, and our tagged shark Amy is another); these sharks either died or migrated elsewhere. We have also seen the sudden appearance of new sharks that are so big it is unlikely they have been present for many years and never before observed. Furthermore, some of the same authors that published this population estimate presented data to the Gulf of the Farallones National Marine Sanctuary (naturalist training meeting) that documented the migration of a white shark from central California to Guadalupe Island. This shark did not return to central California. So, this first assumption has been violated in both directions….sharks leaving and joining the population. The population is not closed.
The second assumption is that every individual has an equal probability of being spotted during any given sampling period. Some of the same authors of the population estimate published a previous paper that invalidates this assumption. In this earlier paper it was demonstrated that individual white sharks show some preference for particular sites within central California, and yet sampling for the population estimate only occurred at two sites (Southeast Farallon Island and Tomales Point). A third important site, Año Nuevo, was not included. So a shark initially identified at Tomales Point would not have the same probability of being re-identified at Southeast Farallon Island, when compared to a shark originally identified at Southeast Farallon Island. Sharks identified at Año Nuevo, if included in this estimate (it is not clear from the methods) would have been less likely to be re-identified during this study because that site was not included.
The next three assumptions seem valid: 1)Marking individuals does not alter their survival probability; 2) Individuals do not lose their marks; and 3) Sampling time is instantaneous.
The final assumption is that the white sharks do not leave the population and return. Another red flag. Our photo-ID work, as well as our SLRT/SPOT tagging, have proven that mature female white sharks undergo a 2-year migration pattern that typically causes them to be absent from the aggregation site for a period of 2 years. In fact, Anderson and Pyle (2003) documented this very same pattern for the central California sharks. There are times when a particular female may rest a year between mating cycles, and in these cases a female may return to the aggregation site in two successive years, but nonetheless, during the white shark season 50% of the females may be absent and therefore have a zero probability of being observed. The fact that females do not annually visit the coastal aggregation sites also invalidates the assumption that every individual has an equal probability of being spotted during any given sampling period. This alone would result in a population estimate 25% lower than reality. A final concern is that the white sharks sampled in this study were not broken down into age or size classes, but instead it was assumed that the observed sharks represented the entire adult and subadult population. It is very hard to age and/or measure white sharks in the field, so I know why the model was set up this way, but I do believe that sub-adults are spread out over a much larger geographic area than adults during the adult aggregation season, so the vast majority of the population of sub-adults are way under-represented in this study. Also, to simply double the population estimate derived from their study sites and assume this number can represent the entire northeastern Pacific population, without the analysis of any additional data, is not rational.
It is clear that the population estimate was based upon several faulty assumptions and therefore this estimate is not valid. The actual population is likely dramatically larger than the values presented in this paper. The study described above is flawed, but it has tremendous value as an index of abundance. An index of abundance does not provide an absolute population estimate, but it does allow us to track whether the population is going up or down if the study is repeated on a regular basis. The good news is that white sharks are protected along the coastal regions of the United States and Mexico, and recent research by those working on juveniles suggests the population may be increasing. The bad news is that juvenile sharks are still accidentally killed by commercial fishing practices and it is not known how much this impacts the populations recovery. Furthermore, white sharks become primarily pelagic in the later stages of their lives and the regions they visit do not have protective measures in place. Therefore it is important to understand where these adults are going so that we can identify potential threats they may face.
Michael L Domeier, Ph.D.
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Tiger Shark Film Wins First MacGillivray Freeman Award at Newport Film Festival
With great pleasure we attended the premiere of the film This Is Your Ocean: Sharks, at the Newport Film Festival on Friday 29 April. The film was a collaboration between Director George Schellenger, Dr. Guy Harvey, Jim Abernethy and Wyland. All of these people are established artists in their respective mediums, and their collaboration will help to change the public’s perception of sharks as well as highlight the great peril our ocean’s sharks face today. The film won the first MacGillivray Freeman Films Special Achievement Award in Environmental Filmmaking.
Dr. Michael Domeier met Jim Abernethy during an incredible submersible expedition to Guadalupe Island in 2008 (hosted by their late mutual friend, Steve Drogin). During this trip Jim became very impressed with what MCSI had accomplished with white sharks via photo-ID and satellite tagging; as a result Jim and Michael hatched plans to collaborate on a similar project with Jim’s tiger sharks at Tiger Beach in the Bahamas. Guy Harvey funded the first tagging expedition to Tiger Beach where Dr. Domeier and Dr. Mahmood Shivji (Guy Harvey Research Institute) surgically implanted the first electronic tag on a tiger shark in the Bahamas. Since then Guy Harvey’s team has returned and SPOT tagged more tiger sharks at this site. In a few years this project will very likely be as productive as our existing white shark project. For more information on the movie see the This is your Ocean website.
April 10, 2011 is the premier of Shark Men on the National Geographic Channel. This show features the tagging and tracking of great white sharks by scientists from MCSI in collaboration with Fischer Productions and the crew of the M/V Ocean.
Sept. 3, 2010 The two sharks tagged with SPOT tags at the Farallon Islands by MCSI in the fall of 2009 have now been successfully tracked out into the middle of the Pacific Ocean and back to central California. One of the sharks returned July 26 and the other Aug 4. The first shark was offshore 225 days, traveling approximately 4,000 miles, and the second shark was offshore for 269 days covering 3,000 miles. This information was printed in an online article in the Marin Independent Journal September 3, 2010. For more information on our white shark research program click here.
MCSI and the National Geographic Channel series Expedition Great White were featured on the front page of the San Diego Union Tribune Saturday July 17. For more information on our white shark research program click here. For more information on the Expedition Great White series click here. To read the online article click here.
June 6, 2010 is the premier of Expedition Great White on the National Geographic Channel. This show features the tagging and tracking of great white sharks by scientists from MCSI in collaboration with Fischer Productions and the crew of the M/V Ocean.
Here are a few quotes by Dr. Michael Domeier directly from the Expedition Great White series…
“The public really needs to pay attention and care about sharks. What we do know about sharks is that they’re being overfished all over the world. If we continue to fish sharks as heavily as we do now, sharks are going to disappear from the planet”
and “It’s really important that the public knows that sharks occupy an important niche… if we loose sharks, our ecosystem is going to change for the worse”
and explaining why tracking these sharks is important…“we know great white sharks aggregate in a few areas around the world…we’re not exactly sure why they’re there, we’re not exactly sure where they go or what they’re doing when they’re not there… we need to know where they’re going so that we can protect them… hopefully one day we can put together a comprehensive management plan so that we can protect great whites wherever they go”
Tune in Sunday nights all summer on the National Geographic Channel for more information on the tagging and tracking of great white sharks!
MCSI organized an International white shark symposium: Resetting Research and Conservation Objectivesin Honolulu Hawaii.
For more info visit www.whitesharkscience.com
Paxson Offield and his crew aboard the Kelsey Lee successfully surgically implanted 50 archival tags into striped marlin at Bahia Magdelena, Mexico. This project will provide multi-year data which are important for defining marlin. stocks.
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