Cape fur seal white shark research EDNA Science Dyer Island Conservation Trust

Infographic: How seals use subsurface structures to sneak by white sharks

Written by Michelle Jewell.  Follow her on twitter: @ExpatScientist

If you have ever avoided parking on a risky-looking street or taken a different route between classes to avoid a bully, your behaviour has been altered due to the perceived presence of ‘predators’.  In the wild, prey animals also change their behaviour when they think predators are around, and these altered anti-predator behaviours can often influence other species, and then influence more species, and eventually change the entire ecosystem.  This is an example of indirect effects predators have on ecosystems.

My research has focused on these principles of predator/prey interaction in the ocean, and a great place to study oceanic predators and their prey are Cape fur seal colonies in South Africa.  Every summer in the southern hemisphere (November), Cape fur seals give birth to thousands of pups.  For example, the seal colony Geyser Rock has a population of about 60,000 Cape fur seals and every year they give birth to 10,000 seal pups!  By winter (April – September) these 6 month old ‘young-of-the-year’ seals begin to venture off the colonies and swim offshore with the adults to the fishing grounds.  These young-of-the-years are typically slow, plump from months of a mostly fat milk diet, and – most importantly – naïve.  White sharks take advantage of this naivety and aggregate closely around seal colonies every winter to catch leaving/returning seals.  Young-of-the-year pups are forced to learn how to avoid sharks quickly or suffer some rather permanent consequences!  This means that during a full year, every seal colony goes through a period of high white shark presence (winter) and very low to no white shark presence (summer).  Therefore, we can see how seals act ‘normally’ during the summer when there are no/very few sharks and how they change their behaviour in the winter to avoid white sharks.

Dyer Island Geyser Rock Shark Alley South Africa Seal Island False Bay

A) The Western Cape of South Africa with B) Seal Island, False Bay and C) Dyer Island & Geyser Rock.

Also, there are many different kinds of seal colony islands along the coast, which lets us ask more questions about how seals use their environment to avoid sharks.  I conducted my study at the Dyer Island/Geyser Rock system, which is home to ‘Shark Alley’ as well as many shallow reefs, kelp forests, and shipwrecks.  About 100km to the east is another seal colony called Seal Island, which is a world-famous spot to see white sharks predate on seals, but this island system lacks the abundant nearby structures/reefs/kelp forests that are present at Geyser Rock.  By looking at these two different kinds of islands, we can also examine how structures – or ‘refugia’ – may alter how seals avoid white sharks at Geyser Rock from how seals avoid white sharks at Seal Island.

And here’s what we found…

Agents of seal cape fur white shark research dyer EDNA Science

Do all of these structures and anti-predatory tactics of Cape fur seals change white shark movements around Geyser Rock?  Most definitely!  Check out that study (and infographic!) here.

This project was funded by the Dyer Island Conservation Trust and supported by Marine Dynamics shark tours, Volkswagen South Africa, and OCEARCH.  The infographic was designed by EDNA Science.  You can read the detailed scientific publication on Behavioral Ecology & Sociobiology by clicking here.

Have a question?  Leave it in the comments and I will answer!


A Typical Day on this Research Cruise

Written by Helena Aryafar

*Helena tags and collects biological samples from juvenile and adult blue sharks on federal research cruises

5:30 a.m. (~sunrise)-6:30 a.m.  Set the longline gear (Set 1) 
Setting gear requires baiting the hooks (~200 per set), putting lightsticks above each hook (these attract fish to the bait in the deep dark waters), throwing the line out into the water, and attaching and releasing buoys to separate baskets of hooks.  This process usually takes around an hour to an hour and a half.  This will be set #1 and will soak (soak = stay in the water) for 10 hours before we haul it back on deck.  Immediately after set #1, we will motor to another area to do 1-2 shorter sets that will only soak for ~2 hours each before we haul the gear back. 
Buoys and radio beepers (used to find the longline gear for haulback)

Buoys and radio beepers (used to find the longline gear for haulback)

8:30 a.m.-9:30 a.m. Set the longline gear (Set 2)

9:30 a.m.-10:30 a.m Prepare tagging and sampling gear for haulback; deploy CTD (Conductivity, Temperature, and Depth device)–CTD provides us with information about the habitat in which we are fishing
The set-up for haulback and sampling

The set-up for haulback and sampling

Electronic tags

Electronic tags

10:30 a.m.-12:00 p.m Haulback of Set 2

When we are ready to haul the gear back on deck, the main line will be pulled back onto the spool and each hook is removed and put back into a large bin to be used for setting the gear next time.  As the animals come up, we assess the condition of the fish, pull them onto a cradle that gets hoisted onto the deck with a hydraulic winch, and begin working up the animal.  Sharks will immediately get a ventilator (hose with specially fitted mouth piece) to run water over their gills, a wet chamois or towel is used to cover their eyes (which keeps them calm), and the hook is removed.  We take length measurements and determine sex of the animal (claspers vs. no claspers).  A small corner of the dorsal fin is clipped and saved in alcohol as a DNA sample, and depending on the size of the shark and which project we want to use that sample for, either a conventional tag (a thin piece of plastic that contains a unique ID number and contact information for fishermen to use in the event of recapture of the animal) or an electronic tag (that provides data on location and movement patterns) is inserted near the dorsal fin.  We will also be taking blood samples to measure lactate levels, which can give us information on the stress level (condition) of the fish. Some of the sharks will also receive a secondary tag (with reward information for recapture) and antibiotics that function as a marker of when they were captured and can be used to determine age and associated growth of the shark if it is recaptured in the future and the vertebrae are returned to our lab.  Once the sharks have been tagged and/or sampled, we return them to the water and assess condition once again.  Sharks that are not alive upon haulback of the longline will be processed for biological samples that include: stomach (can be used to determine what the shark has been eating and which habitats it exploits), liver/muscle/heart tissues (used for stable isotope analysis which can tell us about its movements and where it spends a lot of its time), and gonads (used to determine maturity and provide information on reproduction).      



Ventilated male shark with a roto tag and conventional tag just before release

Ventilated male shark with a roto tag and conventional tag just before release

1:00 p.m.- 2:00 p.m. Set the longline gear (Set 3)
3:00 p.m.- 4:30 p.m. Haulback of Set 3
5:30 p.m.-7:00 p.m. Haulback of Set 1

Repeat for 10 days and pepper in some tagging of opah and swordfish. Rough seas, long days, hard work, and lots of fun!

My bunk for 10 days...pretty cozy

My bunk for 10 days…pretty cozy

Science Saving Sharks

Written by Dr. Michelle Heupel

How are scientists helping to save sharks?

There is a lot of information on the internet about sharks and how to save them. Some of it is good, some of it is bad, some of it has a purpose, some of it has none. I’m starting to sound like Dr.Suess with all of this, but this is how things are in our world of increasing internet and social media. So there seems to be a lot happening and a lot of people involved in the cause. This is great because getting people to understand the problem is one way to create solutions, as long as what we tell them is correct.

So what is my role in all of the workings of shark (and ray!) conservation? My job is to create information. This is one of the best parts of my job – getting to learn things that maybe no one else in the world knows. What then? Then I need to get the information written up and published so others can use it and learn from it. This isn’t just about telling other scientists what I learned, this is also about making sure people who make decisions about management get the new information if they need it.

There are so many questions about sharks and rays. So many things we don’t know. For some species we don’t know how long they live, how many pups they have, how far they swim, and even how many are there. We need all of this information. People who decide if it is ok to fish sharks and rays, or whether we need to make a marine protected area, need this information. If they don’t know these answers they can’t make good decisions because sometimes they’ll have to guess what to do. My job is to give them the answers so they don’t have to guess (as often, we still have to guess sometimes). This same information is also used by conservation groups. If a manager makes a decision that doesn’t match the scientific information then the conservationists can use the information I provide to try to change the decision.

So, it seems like I sit outside of all the action doesn’t it? I don’t make the decisions and I usually don’t challenge the people who make the decisions. Those are other people’s jobs. My job is to get the information or ammunition needed to argue or make decisions. So, does someone like me ever really make a difference? You bet. Work I did to define what a shark nursery is has been used to save habitat for Endangered smalltooth sawfish. My science is listed in the Federal Register in the protections for sawfish, a real world result of my science! My data from studying mortality rates of blacktip sharks has been used to adjust the number of blacktip sharks caught in US fisheries. This was an unexpected outcome of one of my projects, but one that proved very useful to managers. These two examples are not the things my research is most known for, but they are some of the bits I am most proud of – times when science made a difference.

Times are complicated and our oceans are damaged, but with hard work and good science I hope to continue to make a difference where I can. We need more answers to save sharks and rays, and that means we need more science.

Dr. Michelle Heupel releasing a young blacktip shark in Florida

Dr. Michelle Heupel releasing a young blacktip shark in Florida

An endangered smalltooth sawfish from southern Florida

SHARKS INTERNATIONAL 2014: A pivotal forum for science and conservation collaboration

Written by Hannah Medd


Hannah Medd

Approximately 275 students and professionals from 40 countries descended upon Durban, South Africa, during the first week of June, 2014, to talk SHARK! The 2nd annual SHARKS INTERNATIONAL scientific conference was recently held over 4 days of about 80 talks on all aspects of elasmobranch research including acoustic telemetry, physiology, tourism, genetics, tagging, age and growth, fisheries, sensory biology, population ecology, Baited Remote Underwater Video Systems (BRUVS), trophic ecology, sawfish, social research, management, and shark control. It was a shark nerd’s dream and I jumped at the chance to go! Having attended graduate school in South Africa, it was a long awaited homecoming but also a rare opportunity to network with peers working around the globe, exchange ideas, collaborate, and finally meet face to face.

The talks were only 15 minutes long, which is not a lot of time to present the breadth of your work that for many is decades in the making so most presenters focus on their innovative methodologies or the latest results or most impactful applications. To further inspire the Gills Club members (not that the guys didn’t perform admirably) I noticed some impressive presenters that just happened to be ladies! Dr. Alison Kock, a Gills Club Scientist and Research Manager at Shark Spotters based in Muizenberg, South Africa, gave an impressive talk on her research on the white sharks of False Bay, South Africa, revealing the sharks demonstrate high levels of site fidelity (they really like to hang out in specific spots) to inshore areas which will affect how Marine Protected Areas will be designed. Charlene da Silva, shark researcher for the South African Fisheries Department, gave a funny and dynamic talk on the chondrichthyan fisheries of South Africa, the lack of data on economically important species and the immediate need for sustainable management. Rachel Graham, Executive Director of Mar Alliance, spoke on monitoring sharks using many different methods in Belize to establish a baseline which is incredibly important in informing conservation planning. Lauren De Vos, a PhD student from the University of Cape Town, spoke about her work using BRUVS (Baited Remote Underwater Video Systems) to assess abundance of sharks in different habitats. Alison Towner, a PhD student, described her work tagging and tracking great whites in Gansbaai, South Africa, to determine what environmental factors influence the sharks’ movements by collecting data on cage diving boats. Ana Sobral, a Portuguese researcher, represented the rays by presenting her work on the aggregating Mobula tarapacana near the Azores. Ana is developing a photo identification program based on the color patters on the rays’ stomachs to better understand the population dynamics of these little-studied rays. Sarah Fowler, the Vice-chair of the IUCN Shark Specialist Group, a legend in shark research and conservation, demystified the seemingly overwhelming process of listing vulnerable species on international treaties such as the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). The formidable Sonja Fordham of Shark Advocates International clarified some common misconceptions about global shark conservation that can be spread by reporters and well-meaning concerned citizens, while encouraging a focus on the real threats to the vulnerable species, charismatic or not. These ladies represent a snippet of the incredibly impressive and inspirational female talent demonstrated at this conference.


Charlene Da Silva

DSC_1273                                                                          Ana Sobral 


                                                                                       Alison Kock 

The take home message was that shark research needs to focus on species other than the big, charismatic species like whale and white sharks and it needs to employ innovative techniques to achieve goals for broader conservation impacts. It was so encouraging to see and meet new fresh faces that are so dedicated to understanding the importance of sharks and rays to our ocean ecosystems as well as to learn from those professionals that have plowed the way for better research and conservation. From the welcome cocktail party, including fabulous Zulu dancers, to the each evening’s event, through the manic tea breaks, Sharks International 2014 was definitely considered a success!


Rays need love too

Written by Dr. Michelle Heupel

I learned something new last year. I love learning new things, but I sort of wish I didn’t have to learn this. The International Union for Conservation of Nature (IUCN) has something they call the Red List. This is a list of all the species of plant and animal (or as close as we can get to all of them) and their conservation status. Scientists volunteer their time to assess species and the results are listed with IUCN. An analysis of the IUCN data for sharks, skates and rays last year revealed that 5 of the 7 most threatened families were rays, not sharks. And on top of that there are more threatened ray (107) than shark (74) species. Wow, who knew?

This result was published in a paper by Nick Dulvy and a slew of us who contributed to the listings ( I think all of us were stunned to see that the rays were so much more threatened than the sharks. So what does this mean in the real world? It means we have been catching and removing a lot of rays without realising the damage we are doing to their populations.

imageA figure from Dulvy et al. 2014 indicating the families of greatest and least conservation concern.

How did this happen? Great question. Skates and rays are not as well studied as sharks. Maybe they aren’t as cool? Maybe they aren’t as obvious? The reasons why vary, but the reality is not many people have or do study them. One reason these species aren’t well studied is that they have never really been the target of fisheries. They are typically taken as bycatch, meaning they just come up in the nets or lines when fishers are trying to catch something else. Historically bycatch species were usually not well studied because they weren’t high value or important species. Many of the rays that are killed each year may not even be harvested for food. They may simply be caught in nets, die during the fishing process and get tossed overboard. This means we haven’t really understood how many were being affected by fishing. Another, and possibly very important factor, is money. It is easier to get research money to study a target or high value species, it is much more difficult to get money to study bycatch, although that is changing as we grow more and more aware of the importance of bycatch species.


A giant shovelnose ray, one of the species with high value fins.

We haven’t done a good job of keeping track of what is happening with rays for a variety of reasons. In the meantime some rays have become pretty important to fisheries. For example, sawfish and guitarfish have some of the most valuable fins in the shark fin market. This means there is a lot of money to be made which provides incentive to fish these species, especially guitarfish. Sawfish, unfortunately are one of the groups that is worst off. These are amazing animals. A slightly flattened shark with a hedge trimmer for a nose! They use their nose, or saw, to whack fish and stun them or grub around in the mud for food. They are truly bizarre and beautiful. This really cool saw, however, means they get tangled up in nets very easily. Fishermen in the Gulf of Mexico used to kill them to get the out of their nets. And then there are the people who want the saw for a trophy. It’s surprising how many sawfish saws I have seen hanging on walls in bars, marinas, etc. When we viewed our current house the previous owner had a sawfish saw hung on one of the walls! All 5 species of sawfish are listed by the IUCN Red List as Endangered or Critically Endangered and their populations have declined around the globe. Australia is one of the remaining strongholds for many of these species, and in the US the smalltooth sawfish was the first elasmobranch included under the Endangered Species Act after their populations had declined by 95%. Recovery from such a large decline will be very long.


Dr Colin Simpfendorfer releasing a smalltooth sawfish in the Florida Everglades.

So, we need to start doing a better job conserving ray species. They need to become a priority research area. We know very little about even the basic biology of many species and under the current circumstances that isn’t good enough. We can, and should, do better. So while campaigning for better conservation and management of sharks spare a thought for the rays. They need our help too.

Gizmos and Shark Science

Written by Dr. Michelle Heupel

I love gizmos. There are so many cool machines in the world now that make life more interesting and entertaining, and in science they let us do things we couldn’t even have dreamed of in the past. In this post I want to tell you about some of the cool tools that we can use to help learn about what sharks are doing.

Shark movement:

This is my area of research and we have some of the best gizmos around. If we want to track the long-range movements of sharks the go-to gizmo is the satellite tag. This comes in two types. One that gives positions every time the shark comes to the surface and one that records data to send back to you later. Heather Marshall is using both of these tags if you’ve seen her posts. The first tag is one that you attach to the dorsal fin and has a small antenna on it. The unit has a sensor on it that tells it when it is out of the water and then it sends a signal to the satellites to say “here I am!”. Researchers use these tags on all kinds of animals, not just sharks, including turtles and marine mammals. The second satellite tag is what we call a pop-off tag. It looks like a microphone and gets attached to the back of the shark. This tag records the light level so it can tell when it is day or night, has a depth sensor to tell how deep the shark was swimming and a temperature sensor. It records data for a programmed time and then like the name suggests it pops itself off the shark, floats to the surface and sends back its data. These tags are usually programmed to record for up to a year. We can use the data from both of these tags to see how far a shark has moved and learn about their diving patterns.

Blog Photo

John Tyminksi from Mote Marine Lab releasing a blacktip shark with a pop-off satellite tag off the coast of Florida.

If you want to track a shark that lives in a relatively small space then you can use passive acoustic tracking. This is mostly what I do. We put listening stations (or receivers) in our study sites. Then we go out and catch some sharks and put a transmitter in them. The transmitters send out an ID code for the shark and can also report temperature and depth. The receivers sit and listen for a shark to swim by and record the information from its transmitter. This way I can track where my sharks are for really long periods because acoustic transmitters can last for years, some of them last as long as 10 years.

The earliest tracking of sharks was done by active acoustic tracking where you attach a transmitter and then follow the shark in the boat with a hydrophone (an underwater microphone) for as long as possible. We still do this if we want to know detailed movements of sharks. It is hard work though and most people can only last a few days before the track is terminated. This means we only get short bits of information about movements of the individuals tracked. However, this method gives really detailed information about what the sharks are doing and in that respect is better than some of the other approaches depending on your research question.


Understanding how much energy it takes for a shark to swim or how often they really eat are difficult questions to answer. People have been thinking about these things for a long time. To test the energy needs of sharks we have to put them in a tank, make them swim against a current and then measure how much oxygen they use from the water. There are some new approaches coming though that might help answer some of these questions. Chris Lowe, (California State University Long Beach – look him up!) did an interesting study where he fitted a transmitter to the tail of a shark to see how many times the tail moved. Kind of like a pedometer you can buy to count how many steps you take, except for sharks. New transmitters are coming out that can tell us about the acceleration of sharks. This tells us when they make burst speed swimming movements or other behaviours. These tags have been used to look at nurse shark mating behaviour (Nick Whitney, Mote Marine Laboratory) and to look at energy needs of great white sharks (Jayson Semmens, University of Tasmania). Other researchers are trying to build transmitters that will tell us when sharks eat. All of these tools and toys tell us a little bit more about what sharks are doing out in the wild.

Technology keeps evolving and I have no doubt we will keep seeing cool new gadgets and gizmos not only in our daily lives, but also in the daily lives of sharks. We have so much more to learn and I can’t wait to see what the next set of gizmos can tell us.

Top 10 things you didn’t know about white sharks

Written by Michelle Wcisel
1) They are picky eaters

South Africa is an area of high whale abundance, and when a whale dies, the white sharks come rushing in!  Recent research highlighted that “sharks generally exhibited an initial preference for feeding on the whale caudal peduncle and fluke, before moving to feed along the rest of the body” (Fallow et al. 2013).  Sharks will feed for hours on a dead whale carcass to the point where they “would simply bounce off the carcass and slowly sink underwater.”  Talk about gluttony!!

2) They are 
warm-blooded (kind of)
White sharks are “lamnid sharks” which have a unique system called a ‘counter current heat exchange,’keeping their body warmer than the outside conditions by +/- 10-15 C°. So if a white shark is in 9 C° water, its body temperature will be +/- 19-24 C° and so on.  The generator of all this heat comes from the long muscles running down the length of their bodies, which charge a core of ‘white muscle’ ready for quick bursts of energy even in cold environments, which is why they are the apex predator of our temperate seas. Researchers call this, “heterothermy”.

3) They can 
heal themselves
Many white sharks have been shown to heal themselves for minor wounds, but there has never been such a severe case as ‘Prop’ – a Gansbaai shark that was nearly split in half by a boat propeller.  In 9 months, this shark’s wounds were entirely healed (see the video: ).

4) They like it 

White sharks have never been filmed mating, but we have a good indication that there are no roses and poetry involved!  We have seen several female white sharks with bite wounds along the gill areas (above!)

5) They don’t have passports

Gansbaai white sharks have been documented in Mozambique, near Marion Island, Madagascar, even western Australia!

6) Where they 
give birth

You don’t know this about white sharks because NO ONE knows this about white sharks.  White sharks around 1.0-1.7m are considered young of the year and are seldom documented along the South Africa coastline.  Internationally, YOY white sharks are regularly found within the southern California bite in summer time.

7) They save lives

Problem: Hospital acquired infections kill 99,000 people/year.  Solution: Shark skin?  Fine, this isn’t white shark specific, but it turns out that shark skin’s unique design makes it almost impossible for living organisms to attach and grow on its surface (which is why you never see a shark covered in algae – for example!). Biomimicry engineers have developed shark skin surfaces to implement in hospitals, cutting bacteria growth by over 80%!

8) They have blue eyes

No “black dead eyes of a killer” here!  They actually have beautiful baby blues.

9) They 
like calamari

White shark stomach contents off of KZN found cephalopod beaks in 24 white sharks.  Of the 24, small 2.5m sharks had “mesopelagic and oceanic prey with few coastal taxa.

10) They can get massive!

Check out this well over 5.0m female next to a 4.5m cage….ay caramba!