Shark Geek: A Window into Shark Ecology in the Southern California Bight

Shark Geek: A Window into Shark Ecology in the Southern California Bight


(letters beeping) (gentle music) – Good evening everybody,
my name is Harry Helling, I’m the executive director here at the Birch Aquarium at Scripps. I’d like to welcome you this evening. It is my great pleasure to introduce our speaker this evening, Dr. Dovi Kacev. Dovi is an assistant teaching professor in Marine Biology, Research
Division here at Scripps. His research interests are
in the field of ecology, marine biology, and with a special focus of understanding the ecology
of migratory shark species. His research is focused on
using molecular techniques used to analyze mako and
thresher shark populations and migration patterns in the
Southern California Bight. He hopes to incorporate these findings in the future fishery management
plans for those species, to ensure a viable pelagic
shark population, of course. And then, more recently, as
a post-doctorate scholar here with NOAA’s Southwest Fisheries Center, Dovi’s work has turned to the application of next-generation genetic sequencing to identify the early
life stages of fishes and to answer questions
of fishery science. At Scripps, most of Dovi’s time is spent teaching marine biology in
the ecology labs and courses, but he’s also going (clears
throat) to, excuse me, continue doing his field work and involving undergraduate students through research-based
active learning experiences. Dovi grew up traveling between
San Diego and South Africa where animals in the ocean
quickly became his passion. He holds a PhD in Ecology
from a joint program offered by San Diego State
University and UC Davis, and he holds a BS in Marine
Biology and Economics from UCLA. Please join me in welcoming Dovi for his talk entitled “Shark Geek: “A Window Into Shark Movement
in Southern California.” (audience applauds) – So, thank you everyone for being here. I’m gonna pretend you’re here for me, not because sharks are cool. It’s weird that when I give
talks about larval fish, we don’t get 400 people. (audience laughs) But it’s really great to
see so many people here. I wasn’t nervous about the crowd until I just ran into my
junior high science teacher (audience laughs) who’s one of the people
that set me down this track, and now I really have to do a good job otherwise I might not
make it to high school. (audience laughs) I’m here to talk about sharks. I’ve really been interested
in sharks since I was a kid, I just never grew out of it. And to be able to be here and to share some of this
information of what I’ve learned and what other people
have learned about sharks is just really a pleasure and it’s fun, so thank you all for being
here and for this opportunity. And this is especially exciting for me because I know this
“Perspectives on Ocean Science” is linked to Professor Jeff Graham who was one of my research
mentors and heroes. And so to be able to be here
and presenting under his name is really exciting. When he retired from Scripps, I actually stole this
sign from his office, this shark crossing sign. So now that I’m back at SIO
it’s fun that I get to now hang this up back in an office at Scripps, so I’m pretty excited about that. So here in this picture, this was on a research
cruise back in the mid 2000s, and here we have myself and Jeff Graham. I remember him, I think he was telling me, “Stop trying to save all the sharks. “We need their data, it’s okay.” (audience laughs) But again, it’s really fun to be here and to be a part of this, so thank you. As I mentioned before, I’m an assisting teaching
professor here at SIO, which is a new position for
me and a new position for SIO. So really my job is to be
one of the driving forces behind the undergraduate
Marine Bio program at UCSD, and that’s really exciting
for several reasons. One is that’s my office view. (audience laughs) Rivaled only by the view
here at the aquarium, which makes me jealous still. It’s also really amazing
because I get to have the coolest colleagues in the world. I mean, the research
that’s coming out of SIO is really incredible. I have colleagues that are discovering new species of fish, of shrimp, people that are going out and looking at the effect of climate change. It’s one of the first places where climate change was documented. And I get to be a part of that. And not just do I get to
be part of that community, I get to help translate that information to a really amazing crop
of undergraduate students. And one of the fun things about teaching undergraduate students is also one of the fun things
about being here today, is talking scientists among
scientists is really easy to get jaded about what’s cool, right? But when you work with the students and you teach them something
that you take for granted ’cause you know it really well, and then you see how excited
they are to learn it, it really reenergizes my love for science. And I get the opportunity
to teach this year, this is my first year here, so this is my second quarter at UCSD, but I taught last quarter an
Introduction to Marine Biology, which is a fun class to teach. It was about 200 students in the lecture, so smaller than this one. And, unlike them, you guys
actually all want to be here, which is fun.
(audience laughs) I taught a Marine Bio-Laboratory. Right now I’m teaching Biostatistics, which, again, maybe that would
be a another program here. We’ll see what kind of
crowd we draw for that one. I get to work with grad students teaching a thesis writing class. And I’ll be teaching a marine mammal class which I think will be a big
hit next quarter as well. And I also get to take classes, so I’m actually sitting in
on a communicating science to the public class being taught
here at Birch this quarter. I will say I’ve only been to one lecture, so if I don’t do a good
job, it’s not their fault. It’s still mine. But it’s fun, and I’m really happy to be here to talk about sharks, ’cause there’s a couple things. Sharks are cool, I think they’re cool. The other cool thing about
lecturing about sharks is that everybody really
knows about sharks. They’re in the press,
they’re on “Shark Week,” so people know about sharks. Sometimes they’re correct, not always. But I just wanna give you a quick outline on the direction of the
talk so we don’t get lost, like my colleagues and I
down in Baja, California, while doing some of this research. I’m gonna start by giving you
kind of a brief introduction to sharks and shark biology. This is not necessarily my research, but things that we know about them that I think are interesting. Then I’ll turn and talk about
their distribution movement here in the Southern California Bight, which I’ll define. And then I’ll talk a little about the effects of human impact
on those shark populations given that they live in these habitats adjacent to where we live. And then talk a little
bit about shark mating. But we’ll start with an
introduction to shark biology ’cause I think people are interested. I have to start by talking about ecology. I’m actually an ecologist. It’s depending on who I talk to, an ecologist, a marine
biologist, or whatever might be. But I’m an ecologist, so I study sharks. We study the biology of the animal. But we also have to study the
environment in which they live and how the animal interacts
with that environment. It’s not just the environment but it’s the other
organisms that live there, what are the things that
those animals might eat, what are the things that might eat them, how does that affect the way they interact with their environment. And of course, we as human beings are a major part of that environment. Every time we go into the ocean we have an impact on the ocean. And, perfectly frank,
any time we do anything, whether it’s on land or in the ocean, we do have an impact on the ocean. And of course we are one of
the top predators in the ocean, so we have to consider that as well. And kind of in food chain or ecology 101, who here’s ever heard of a food chain? I can’t see most of you, but I’ll just take for granted that some of you have your hand up. So there are things that produce energy, these primary producers they
producer energy from the sun. Things that eat those,
other things eat that, and so on and so forth as
you move up this chain. But in reality this is not
how the ecosystem works. It’s way more complex than that. Things eat each other. Sometimes if you’re
young you eat one thing, and you get older, you eat something else. Or your predator might be
your prey and everything else. So it gets a little bit complex. Trying to understand all of
these relationships is not easy and it requires really kind of, there’s been advances in technology that have allowed us to study
some of these interactions much better that we could
understand them before. So does this seem more appropriate? Does this make sense? All right, still a little too simple. If we look at an ocean food web, it might look something more like this. (audience laughs) And add to the top of it
that we actually can’t, unless you’re Jules Jaffe
who’s giving the next talk, we don’t actually get to
see into these things. He’s developed all sorts of cool oceanographic instrumentation that allows us to see these things. But we don’t get to see them. So this is all happening, it’s
complex, and it’s invisible. That’s our starting point. And then we say, okay, let’s
try and figure this out. And it’s really exciting. So, again, the complexity is important. These are not independent. It’s not like, oh, I study the ocean, so that’s all I’m gonna focus on. There’s birds and there’s people and there’s other things that connect the oceans to the land, so it’s all one big ecosystem. Again, humans being a major part of that. And where do sharks now fit in? I know you guys are here to
hear about sharks, not ecology, so I’ll get there. Where do sharks fit into this? I mean, who here has a sense of sharks? Everyone thinks they’re top predators. Who here thinks sharks are top predators, that’s what makes them awesome? A couple of you. Who thinks that they’re primary producers and photosynthesize their food? (audience laughs)
No, okay, good. So where do sharks fit into this food web? The truth is they’re everywhere. Sharks are incredibly diverse, and if I say the word shark I’m not really doing them justice because they’re so different
and they’re so diverse, and I’ll talk about that in a second. How many different sharks are there? And I would guess, when I do
this exercise in class rooms and things like this, people kind of get a sense
that there’s probably more species than they know by heart. There’s actually more
than I know by heart, and they all look
different from one another. So, how many different sharks are there? Generally, the answers I
get when I ask this question are somewhere between 10 and 50 or 60 or whatever it might be. But in reality, there’s
more than 500 species. More than 500 species, and that’s growing. Every year we describe
roughly one or two new species that we discovered that either they were cryptic, so they looked similar to something else, we didn’t know they were different, or they just had never been seen before. So this list is growing. I certainly don’t know all 500 by heart. And if you look at
them, they’re different. Ranging from these really
colossal whale sharks to these really tiny,
this is a pocket shark, so this is one of those
newly discovered species that was just described this past year. It was discovered in the Gulf Mexico. That’s a full-grown adult shark, and you can see a scale to a person. So these are very different. Some sharks have hammers on their heads, some have these really long crazy tails. They are bizarre and they are
neat and they are interesting, and we don’t know much about them, and we’re doing our best
to learn about them. But if I were to ask you about a shark, most people just have one vision, and that vision generally
is the white shark. And white sharks are really
neat and cool and interesting, and they’re important for the ecosystem, but they’re certainly not
the only thing out there despite what “Shark Week” might tell you. (audience laughs) Things that I think makes
them really interesting. So, reproduction, reproduction in sharks. So if I were to ask people, do mammals give live birth or lay eggs? Do people know the answer to that? (audience murmurs)
Live birth. With a couple of exceptions in monotremes, but we don’t need to talk about those. They give live birth. How about birds, lay
eggs or give live birth? (audience murmurs)
Lay eggs. What about sharks? – [Audience] Both. – Not just both, but both, and then some. Some lay eggs. And the Birch Aquarium, if you ever get a chance to
come here during the day, they have really cool
exhibits with the shark eggs and sometimes you can actually
see the little baby sharks swimming inside those
eggs, which is awesome. And then some give live birth. And then some actually have eggs that hatch within the mother
and then they’re born alive. We call that ovoviviparous,
it’s a very big word. So that’s really neat, but it’s not just neat because it’s cool and it’s not just neat because it’s crazy. It’s neat because sharks
actually represent a really interesting lineage
on the vertebrate tree of life. They split from all other
vertebrates very early on. So by studying things like
reproduction in sharks we can actually learn about
reproduction in all vertebrates. So studying sharks is
not just about sharks and it’s not just about the ecosystem in which those animals live. It’s actually about understanding the entire kind of
vertebrate tree of life. So that’s all those organisms
that have backbones, like most of us. (audience laughs) I’m glad some people
caught up on that. (laughs) Again, where do sharks live? That’s a question that’s kind of a seminal question in ecology. Where do these things live? And if I were to say,
where does a shark live? I’ve already told you,
there’s 500 different species, or more than 500 different species, so where do these things live? And the answer is in
the ocean, everywhere. You go in the intertidal, and when the tide’s high
you have the leopard sharks and things coming in. You go into the open ocean and there’s things like
mako sharks and blue sharks. And you go down into deep water and there’s sleeper sharks
and all these things that we never get to see. But they’re everywhere, and
they are important parts of all of these ecosystems. And, again, to state
that one studies sharks kind of implies that we know all of this. And the truth is most
everyone knows none of this, including those of us that study. Like, if you asked me
about deep sea sharks, I don’t know that much
about them, you know why? Because nobody does, ’cause we don’t get to see them very often and they’re hard to study. But again, it’s this diversity that really makes them interesting to me. That’s what keeps it
exciting to study sharks. Not just because they’re cool predators. It’s because there’s still
so much we don’t know and so much that we need to know if we’re going to be able to manage them and understand the larger ecosystems. All right, let’s talk a little
bit about what sharks eat. Again, we’ve kind of
alluded to this before, but sharks, major top predators. Yes, sometimes. So, again, things like
tiger sharks, white sharks, they’re eating marine mammals,
they’re eating turtles, they’re eating large fish. They are apex top predators, and that’s obviously very interesting and that’s the main thing
most people think of when you think of sharks. But there are also meso predators. A meso predator means you’re a predator, but you’re eating lower
on that food chain. So if things like these leopard
sharks and nurse sharks, they’re eating snails,
they’re eating small fish, they’re eating squid. They’re not out there hunting mammals, they’re not something that
we have to worry about. Some are scavengers, so they’re looking for areas where, let’s say a big whale dies in the sea and sinks to the bottom, and then things like sleeper sharks will come and feed on that dead carcass. Even if the carcass is floating, you have things like white sharks actually that will act as scavengers. So they’re an important
part of the ecosystem, much like a hyena in
the savannas of Africa. Then there’s some that are filter feeders. Some of the biggest sharks are
eating the smallest things. So megamouth sharks, whale
sharks, basking sharks. So there’s a basking up to
and a megamouth down below. These are huge fish, these
things are 40-feet long. And they’re feeding on krill. And they’re doing that
by opening their mouth and swimming through
these schools of krill and filtering those over their
gills, which is really neat. And then there’s some that
I can’t really describe in any other way other
than calling them weirdos. (audience laughs) The one that we have on top
here is a cookiecutter shark. Cookiecutter sharks are
called cookiecutter sharks ’cause they feed, they’re
about this big, they’re small, but they feed on dolphins and
huge tunas and other fish. But what they do is they have, their mouths are kind of like a melon ball or an ice cream scoop, and they go and they bite a chunk off and leave a little circle that looks like you just
took a cookie cutter to it. And they don’t kill those animals, they just take a bite and
swim on their merry way. (audience laughs) There have been a couple people swimming between Hawaiian islands that have been bit by cookiecutter sharks, which is interesting. Then the one down at the bottom there is a Greenland shark. That’s the longest-living
vertebrate that we know of. And if you look closely, I know it’s hard ’cause
the screen’s small, but on the eye of that
animal there’s a parasite. And that parasite is a
bioluminescent copepod. These things live in
deep water or under ice. They can’t see, likely, because that parasite
might make them blind, but it glows in the dark. And other things will come
to check out and think, “Maybe that’s something I can eat.” And as those things try
to eat that copepod, the Greenland shark then eats them. It’s a trap. So, lots of crazy cool things. So what I’m hoping to impress you is that when you start thinking about sharks, that we kind of broaden
our minds and remember that this is a diverse group. And if I add in the rays, there’s at least 600 species of ray, which is the shark’s closest relative. So they’re really diverse,
they’re really interesting, and I hope we get the chance
to talk more about it. I’ll be here after this
talk if you wanna go crazy. When I titled this talk “Shark
Geek,” I really meant it. I think of nothing better
than hanging around and talking about sharks with people. All right, so. Despite the fact that they’re
all over the food web, they are all predators. There’s a couple of instances of sharks that can feed on sea grass, but primarily they’re predators whether their prey is small or big. And the question is, are predators important to the ecosystem? And time and time again
studies have been done to find out that they are. Not just for the sake of
these species themselves, but they have this huge impact on the other species in those food webs and they alter the behavior, they alter the nature of the food web. And if you remove the predators,
it changes everything, and we can’t predict what
that change might look like. So whether or not you
love sharks like I do, or whether you’re morbidly
interested in them, you should care about them, because they are critically
important to our ocean habitats. Also, the question is, do
we have to care about them? Are they in trouble? Are sharks populations stable? And again, lots of studies
have looked into this. I know that I don’t wanna
get into data too much in this talk, but I do wanna point out
that what we have here, that panel there on your right is each one of the little graphs is a different species of shark. On that X axis, which is the
horizontal, you have time. On the Y axis, which is the vertical axis, you have the population size. And what you should see in
every single one of these is the population is decreasing. That decrease in population is what could be potentially troubling because, again, it’s not just
for the sharks themselves, it’s for their ecosystem effects. Why might they be decreasing? Well, there’s lots of reasons. We’re destroying their habitat. These are lemon sharks in
an island called Bimini that rely on the mangroves. We remove the mangroves to
build golf courses and hotels, they can’t live there anymore. Pollution and toxins. We’re putting all sorts
of chemicals and debris into the ocean, including lost fishing gear
and plastics and other things, which have effects on these animals. We eat their prey. So things like mako sharks
that might eat tuna, when Atlantic tuna populations crash, what are the mako sharks gonna eat? Their prey might disappear. But by and large the biggest impact we’re having on shark
populations is overfishing. We fish them, they are slow to grow, they are slow to reproduce,
they don’t rebound very quickly, and we can have really major
impacts on their populations. But it’s not all doom and gloom. Shark fishing can happen sustainably. And by and large in the US we have kind of amazing sustainable
shark fisheries. And when populations
seem to be in trouble, we have mechanisms that allow
us to stop fishing them, or to take action when we need to. So I don’t wanna commentate
humans are terrible people, or, we’re the only people,
but we’re terrible animals. (audience laughs) But in reality, we have the ability to manage
these populations well. But in order to do that we need to understand these populations and we have to learn about them. We need to learn their biology, we need to learn their ecology, we need to learn where they
live and when they live there and how they’re interacting
with their environment. And, just as a plug, because I was told that I should do this, I’m also gonna throw in here ’cause I’m in the process of writing a children’s book on sharks, and the idea is I teach
the alphabet to the sharks and then science to their parents. Well, the kids already
will get the science, but also the parents, and it’s called “ABChondrichthyes” which is the group that
includes sharks, rays, and other cartilaginous organisms. And so I just wanna give you an example of what this book looks like because hopefully I’ll be
able to make progress on it. I’ll just give you a couple of them. This is an angel shark for A. A is for angel shark. Their bodies dorso-ventrally compressed. When you see their feeding speed, you will be quite impressed. If you don’t know what
dorso-ventrally compressed is, that’s the whole purpose, I want you to look it up after this talk. (audience laughs) B is for bull sharks that
can swim in lakes and rivers. They maintain neutral buoyancy
with oil in their livers. That’s how sharks actually can maintain their space in the water and why they don’t sink to the bottom, is they have lots of oil in their liver. Anyway, since we’re at the aquarium and I think it’s a fun thing, I wanted to at least talk about that before I jump into actually marine biology and studying sharks. I’ll start quickly by talking about, so this is a video of a great hammerhead from work I did in the Bahamas. I’m mostly showing it because I think it’s what
you guys all want to see, cool videos of sharks. (audience laughs) And it is fun. The most fun part of my job is when I get to go out in the field and do fun stuff like this, and you really get to interact with these really neat animals. This is in the Bahamas. We’re trying to put a
tag on the back of it in shallow water. It turns out to be a lot harder because they swim much faster
than we give them credit and they can actually spin in
circles and swim really well. But putting the tags on is one way that we’re able to understand
where these animals live, which I’ll discuss in a second. But, in reality, much to the chagrin of most incoming marine biologist students who is with whom I’m
interacting most of the time, marine biology is science, so we spend a lot of the
time in the laboratory. This is one of my undergraduate techs doing some of the genetics work for me. I make him wear the wizard coat because it makes him feel important. (audience laughs) And then coding. I never thought that I would
have to learn computer code until I realized that I can
collect all the data I want, but if I can’t understand
what that data means, it’s useless, right? So I spend more of my time
coding than doing anything else. And to be perfectly honest,
it makes me really happy, ’cause I figured out how to do it, and that’s the reason why I
decided to teach bio stats, is because if I can do
it, I know anyone can. (audience laughs) And it’s been really fun
to teach this to students. I’ll move forward to
kind of the main players that I’ll be talking about today, although one of them will be the focus. So here’s our cast. We have these pelagics. Pelagic means open ocean sharks that live offshore San Diego. So the first one, we have the blue shark. We then have the shortfin mako shark. A common threshen shark which has a, a common thresher, excuse me, that has the long tail,
which is really neat. And focusing on an area that we refer to as the Southern California Bight. The Bight is like a large embayment that runs from Point Conception
north of Santa Barbara down to Punta Eugenia in Baja, California, which is a really neat
biodiverse, interesting region because it’s protected
from the California Current which runs down the West
Coast of the United States. So that actually allows for this really neat
interesting habitats to exist. And so it turns out there’s a lot to learn about the area that we live in. This is where we live, and it’s a really important
biodiverse habitat. And I’m mostly gonna focus
on thresher sharks today because I wanna be able to tell a story without getting lost in jumping
and forth across species. First, I wanna talk a little bit about the tools that
we use to study sharks. So one is tagging. We go out onto the ocean. I know, George Lucas, that’s
my ocean at the top there. You’ll see my animation. We go out, we catch the shark, we put a tag on its back, and then the shark goes and swims around and we go on our merry way. Some of the tags, it’s just, when they come to the surface
and they happen to get caught, we learn where that animal moved to. Some of them we actually
follow it around on the boat with a hydrophone, which
I’ll talk a little bit. So a hydrophone is an
underwater microphone. The tag makes a beeping sound, I sit on the front of the boat, and just literally drive
a few hundreds meters behind the animal so we don’t scare it, but we actually follow in its footsteps so that we can track where it’s been. More recently we’ve been
using these satellite tags, which are really neat ’cause
you can put this on the animal, it then goes on its merry way, and I can come back and don’t
have to spend 70 hours at sea. But when it comes to the surface, it transmits data from where it’s been and it sends that signal
back to my computer, and I can learn about
where that animal was even though I wasn’t there to see it. And it’s almost becoming an old hat now ’cause, again, every “Shark
Week” episode has tags, but tagging technology is
improving every single year and it really has allowed us to learn a lot more than we ever knew before. I also use genetics. So, if you look at these
two mako sharks right here, they might look the same, but they’re from different areas. So they have certain
signals within their genes that can tell you where
that animal was from. And if anyone wants to talk
about that in more detail, I’m happy to, but I’m not gonna do it now. But if you go out and
sample a bunch of sharks, you can compare their DNA. And by looking at their
DNA you can either say this piece of meat or fin
that I got in the market I know where it came from
or what species it was. Or, if you see a bunch of sharks that live in two different areas, you can say, do their DNA look the same, or do they look different? And if they look different, that’s a pretty good sign that they’re not interbreeding
with one another, even if they look the same
and we can’t tell them apart. So, again, another powerful
tool that’s relatively new that allows us to learn
more about these animals than we ever did before. So I’m gonna use that as a way
to segue into understanding the distribution in
where these animals live and where they move. So I’m gonna start, again,
focusing on the threshers here, I’m gonna start by talking
about the adult threshers. So this is work done by a
colleague of mine, Dan Cartamil, who has given this talk in years past so some of you might have
seen some of his results. But it’s still interesting
even if you’ve seen it before. So went out, tagged some of
these adult thresher sharks offshore San Diego, then got into a boat with his hydrophone and followed them around. And for those of you
who think marine biology is really glamorous, it really involves sitting
in a small boat like that for 72 hours with very little food, listening to a ping beeping sound, trying not to lose an animal in the ocean that you can’t see. It’s a really good way to
know if you like somebody, is to be on a boat for
this amount of time. (audience laughs) Luckily, I like Dan, so that’s good. But anyway, what did they find out? So these right here, these
colored plats, that’s a map. The white part there is land, and then the blue part is the ocean, and the gray part is shallow water over the continental shelf. So what I want you to see here is all the tagged animals moved. These are highly migratory, these are animals that move a lot. They all moved in different directions, which makes it hard to understand what these animals are trying to do. But the most important part
is that you don’t see them over that shallow water. They’re staying in deeper water. That’s gonna be critical once
we get to this next slide. So key here is they’re moving a lot but they’re staying in deep water. All right, a follow-up study
did something very similar. We went out and we tagged the juveniles. And these are the cutest
sharks you could ever see. They’re this long but
half of their body is tail and they have giant eyes. So if you want proof that
sharks are not scary, just look at a picture
of a baby thresher shark, I promise you. There’ll be a couple coming up. But we tagged and tracked
them in a similar way. And here are the animals that we tracked. Same way, we have the black line and everything to the
right of that line is land, then everything to the left is water, that darker gray being the
shallower continental shelf. But what you notice here is, again, these animals move a lot, but they’re spending all of
their time over the shelf. So the adults spend all of
their time off of the shelf, the juveniles are spending all
of their time over the shelf. That was an interesting finding. We can speculate all day
about why that is the case, but just in and of itself
it was interesting. And then we did, similarly, we went out and we satellite-tagged some
of these juvenile threshers ’cause maybe we just
didn’t have enough data. So we put these satellite tags and we got movement data
for longer periods of time. And low and behold, they still spent the vast
majority of their time over the continental shelf, far away from where the adults might be. And this is just a really neat
sight, so I put it up there. This is instead of looking at a map like we’re used to seeing it, this is the ocean depth. And this is really neat
’cause you’re seeing is they’re spending their time
at night in shallow water and the time during the day in deep water, which is just a really cool finding because that is true for a
lot of animals in the ocean. They’re following plankton
that are doing that same thing. The things that eat the
plankton are doing that, and therefore the things
that eat the things that eat the plankton are doing that. So tying back to that
food web I put before, it really kind of ties up together, showing that the behavior
and movement of these animals is in fact tied to the
things that they eat. Again, that’s a major part of ecology. Okay, so why are adults
and juveniles distribution different from one another? That’s something we have
to start thinking about. Well, to do this, I
had to kinda think back to work I did a few years
before in the Bahamas where the lemon sharks
have these nursery habitats inside the mangroves. And in these nursery habitats, the sharks have lots of prey, ’cause there’s lots of crabs and shrimp and small fish there, but they also have
protection from big sharks that can’t fit in those mangrove roots. And we call these areas where babies live and adults don’t live nurseries. I know, it’s really creative, right? You’ve never heard it before. So we know that these coastal
sharks have nurseries. Perhaps these pelagic
sharks have nurseries too. So to do that we had to really dig down into what defines a nursery, and there’s three things
that define a nursery. You find the juvenile sharks there more often than you find
them somewhere else. They remain in that habitat
for long periods of time. And they use that repeatedly over time. And we found evidence for
all three of those things. So it’s really neat as to say, yes, we now nurseries are
important for coastal sharks, but you know what? They’re important for
these pelagic fish too. So this habitat close to shore is a critical part of the
habitat and the life cycle of these kind of open ocean
highly-migratory sharks. Hopefully that makes you think, wait, when I go into my backyard, I also have to think about the fact that I can have these
impacts on these things that I normally think of
as living far offshore. This kind of led to our next question, and this is with a colleague of mine at the Southwest Fisheries Science, the NOAA office just right next door. This is something that you
see a lot in shark science. Is you go out and you
tag a handful of animals and you learn here’s
where this animal moved, here’s where this animal moved, here’s where this animal moved. But we don’t get to put hundreds
and hundreds of tags out ’cause it’s expensive and
it’s hard to catch the animals in the first place. So we have a hard time kind
of making bigger statements about what happens to the species, how does the population respond to things. And that’s kind of a problem, because I’m not interested
in where one animal moved, I’m interested in the behavior
and ecology of the species. So how do we deal with that? Well, it turns out, coming back
to these quantitative tools, we can in fact use these new, so we have new tag technology, we have new genetic technology, we also have new statistical technology which allows us to do
really exciting things and start asking more nuanced questions. And we wanted to know
this about the threshers, but, as you can see, we don’t
have that many animals tagged. So we can say, hey, we developed this cool statistical model, and I’m not gonna bore you
into what that looks like, but we can say that if we did
that and we know everything. But the scientist that is gonna
read the paper is gonna say, “Well, how do you know it worked? “Great, you’re telling me something, “but it’s not validated.” So we had to validate it, it
was a really long process. A project that I thought was
gonna take like three months ended up taking five years. But eventually we were able
to demonstrate that it worked, and we did that by using it on species that we had more data for, and then removing some
of the data and saying, does it still work when we have less data? And low and behold, it did. But what did we learn? Well, we learned that
these thresher sharks move depending on their length. So the longer animals are more likely to make longer migrations, and these longer
migrations might take them out of the safety of Southern California into high seas areas or down into Mexico where they’re exposed perhaps
less sustainable fisheries. They also move depending on the season. So we know that they like to be here in the late spring and early summer. We kind of knew that. But we actually were able to
demonstrate that statistically, which was important. And they do seem to differ on whether they’re male or female, and that depends on how far
they move and when they move. I just wanna pointed
out there at the bottom you have a baby thresher shark. Kyle, my colleague, not as cute. But the thresher shark,
hopefully you’ll believe. So, again, the key is
not being able to say, cool, we went out and we collected data and we made a discovery, ’cause that’s what we did at first. But then the next step was saying, cool, we made that discovery, but what does it actually mean? What can we do with that data? So this is kind of the next
step in doing that and saying, all right, we know where they live, we know where they’re moving, and now we have a better sense of what’s driving those patterns, and that’s critically important. Okay. That’s my movement and distribution. If you wanna talk more about it and you wanna talk about makos and blues, I’m happy to afterwards. But, again, these are
animals that are moving throughout Southern California
and down into Mexico. There are areas that are
heavily used by humans. We have lots of impact on the environment, so let’s see how that
might impact these animals. For those of you that don’t know, Souther California has a reputation, and that reputation is
it’s smoggy, it’s dirty. I know that it’s not
true, we love it here, we just had an amazing sunset. But on the right day, at the right moment, you might see this, especially if you go to
our neighbor to the north. We know that we have issues with plastics that we’re putting into the water. We also have chemicals
that come from industry, whether it’s agriculture or
ship building or other things, and all of those make
their way into the water. We know that. But the question is, do we see this reflected in the wildlife? Is this likely to have
an impact on the animals? And the only way to do this
is to go study the animals and say, do we see evidence
of these same pollutants inside the animal in their tissue? And there’s a couple different
ways that these can get into or accumulate in the
tissue of an organism, so this is kind of my
professor hat going back on. So there’s two ways. One is bioaccumulation, and what that means is as I’m moving and swimming
in this environment, I’m accumulating more
exposure to chemicals. And the longer I’m in that environment, the more of those chemicals
I’m going to accumulate. So the longer I’m alive,
the longer I’m there, the more chemicals I’m
gonna have in my body. The other is called biomagnification. So what this means is small things are living in the environment and they’re accumulating
toxins or chemicals. The things that eat them are
accumulating their own toxins, but when they eat it, they
also accumulate those toxins. And as you move up this kind
of food chain or food web, you’re not only accumulating
the toxins you’re exposed to but you’re accumulating the toxins that your food was exposed to. Sharks tend to live a long
time, and many of them, particularly the ones
that we’re looking here, feed relatively high on the food web. So they are potentially getting exposed to a lot of these chemicals. So I worked with a colleague that’s really good at eco-toxicology, which is a field that’s not my expertise. I am not a chemist, but
luckily Kady Lyons is. And so what did we find? So what’s really neat, and I know this is kind of a weird figure and it’s hard to see right now, so I apologize for that. But let’s just look at that
top curve for mako sharks. What we found is on the X axis here you have the the age of an animal. And on the Y axis is how many chemicals they have in their body. So it turns out the babies that have only just been born have a lot of chemicals in their bodies. And the reason for that is
’cause their mothers did. And the mothers, when they were developing
in utero or an egg, passed those chemicals on. So they’re born with a load
of chemical or toxic load, a contaminant load. As they grow and they’re feeding hopefully a little bit lower on the food web and they’re growing quickly, they actually dilute
some of the concentration of those chemicals in their body. So they lose, they’re
not really losing it, but the concentration is lower. Which is, for the record, if anyone’s worried about eating sharks because of the chemical concentration, I’m not trying to encourage
you to eat sharks, but if you do, small ones, and you can see in that kind of mid-range, tend to have the lowest concentration of things like mercury and other things. But as they get bigger, they grow slower, they’re eating bigger things, they start accumulating chemicals again. So I don’t wanna get
into this in vast detail because I know I’m gonna make an interesting topic
boring pretty quickly, but as opposed to kind of going
into the nit-picky details, what I wanna say is there
are detectable levels of a lot of these contaminants that we’re putting into the water in the tissues of these animals. So they are incorporating
these into their bodies. How that affects their
survival and their behavior, we don’t really know yet. We’re kind of getting to
that but we’re not there yet. But we can say they do
accumulate these chemicals, which is potentially a problem. So much so that this is
a study that I worked on looking at thresher sharks, looking at the microbes that live on the skin of thresher sharks. So this is a colleague of mine, he’s a microbiologist that can do all sorts of cool genetic sequencing. And he was like, hey, let’s
see if we can learn anything about the sharks by seeing the microbiome
that lives on their body. And it turns out thresher sharks have a very particular community of microbes that live on their body, different than what’s found
in the water around them. And not only that, but the
microbes that live on their body seem to have the ability
to digest heavy metals. And why is that the case? It’s because the environment
in which they live is high in heavy metals. And it turns out the
environment in which they live is the shark’s body. So that means these animals are being exposed to these chemicals, they are taking them in. Again, what that means,
we’re still working on that. We’ll see how quickly
we can get the answer. But it’s still important to
know that it’s happening. So we know where they live,
we know where they’re moving, we know that it could affect
their abilities to survive and live in this environment. I also wanna talk a little
bit about their breeding, ’cause shark breeding
is really interesting, I mentioned that before. We don’t know that much about it because we don’t get to see them mate, we don’t get to see them pup before often, especially these pelagic fish. So what can we learn about their breeding just from the data that
we are able to get? So, in the course of
studying makos and threshers, I was lucky enough to get
one pregnant mako shark that was caught by a
fisherman near Australia and one pregnant thresher shark that was caught by a fisherman
here in Southern California. And I was able to look at the pups, the babies that were in the female, and compare them
genetically to their mother. Essentially, what we’re doing
is doing a paternity test. (audience laughs) So, who is the father? (audience laughs) And no one in this room is sitting on the edge of their seat, so we’re not gonna have
a brawl, I don’t think, but who was their father? And interestingly enough,
in both of those litters, so both in the makos and the threshers, they had more than one father. So that’s one litter of sharks, these are siblings, twins even, that have different fathers. We call this multiple
paternity, and it’s neat. It has been seen in other
organisms, including mammals, but we saw it in both of these species. And these are species that
live in the open ocean. They’re not necessarily
encountering each other at very high rates. Maybe they are, but we don’t know that. So the question then,
is this rare in sharks? Was this a bizarre
finding, or is this normal? And I put this don’t Tweet thing up there, I’m not that worried about
it, but my colleague is. This is active research happening and they asked me to do that. It’s funny because this is being recorded and it’s gonna be shown. (audience laughs) I’m not giving our secrets so
I’m not that worried about it. But the question is, is multiple
paternity rare in sharks? And the answer to that,
this is a crazy graph, I don’t want to look into it too much, but what I want to say is the X axis here is the
percentage of litters that have more than one father in them, and the Y axis is different species. So what we’re seeing is, no, this is not a crazy weird
thing we discovered, but it is in fact the rule. It seems that multiple paternity is actually really common in sharks. So having multiple fathers
in a single litter, not uncommon at all. Again, that will beg the
next question as to why. And for a long time in
a lot of the studies that have looked at this, it’s kind of been the same answer. We don’t know, but we
think it’s because females just can’t prevent males
from mating with them. It takes a lot of energy and shark mating is not that nice. It looks violent to us at the very least. It’s probably just
convenient saying, “Look, “we’ll mate with you, it’s
easier than not mating with you.” (audience laughs) Is that documented? Absolutely not. (audience laughs)
Why is this the reason? I mean, you can think about who did a lot of that research. Maybe they’re macho, I don’t know. (audience laughs) But we wanted to know,
is this likely true? So we wanted to investigate is, do females have a choice
in multiple paternity? And, again, I can’t go
into details with this yet, but our analysis that we’ve
done actually suggests that, yes, female choice is likely what might be driving multiple paternity. Not convenience, not saying, “Hey, we don’t wanna mate with you.” And the truth is female sharks
tend to be larger than males, shark mating tends to be brutal, so it’s not surprising
that if this is occurring, that it’s because there’s
a benefit for the females. And what might that benefit be
we can’t say with certainty, but it might have something
to do with the fact that the more fathers that
they’re able to mate with, the more likely that their
offspring are gonna have whatever trait might be
beneficial in the future, and we don’t know the answer to that yet. So the more mates you have, the more genetically diverse
your offspring are gonna have, and maybe that may improve
the survival of your lineage down the road. It’s not like they’re
making a conscious decision, but evolutionarily, that is what we think might be happening. So those were just some of the stories that I think are interesting, some of the things that keep me excited about the work that I get to do, and some of the reasons why I’m excited to be able to talk to you
guys about this as well. So thank you for listening. (audience applauds) – [Woman] I’ve seen many videos. First of all, thank you,
this was very interesting. Many of us have seen videos
of the shark tagging. And my question is, do you specifically go
looking for threshers or makos or whites, or you tag what you can find? (audience laughs) – That’s a good question. So the question, ’cause I have to repeat
it because I’m miked, the question is, when we go
out to try tagging the animal, can we target the species we want to tag, or do we just get lucky
and tag whatever we find? And the answer to that is it depends. In some cases, I have a colleague and he knows how that works
here on the leopard sharks. When he wants to tag a leopard shark, he knows where the leopard
sharks are aggregating, he uses the right gear to
help target those animals. And we can do that for the most part. In some cases, no, we
kind of all work together. There’s cases where NOAA used to run a juvenile shark tagging survey, which is that picture I had of myself and Dr. Jeff Graham on it, where we were targeting makos,
largely, makos and blues, but we caught other species. And if we caught them and
we had the tags available, we would tag them, because it’s an opportunity to get data on those other animals. The thing to consider is that
these tags can be expensive, and if you’ve written a
grant and you need to tag and you need to have as
many one species tagged ’cause you want to try
answer those questions, you might be reticent to put
it on a different species because you might get
your target species next. But I would say that it’s a combination of both of those things. We’re opportunistic when we can be, and we try to target
them as best as we can when we can do that. – [Woman] I am, oh, sorry. (audience laughs) I stand-up paddleboard off the coast here, and this year, a couple of months ago, it looked to me like a white breaching out near the (mumbles), and a couple of other of our friends have seen it this year. Do you know what causes that behavior? Is it common? And why they might all
of a sudden be noticed doing it this year? – So that’s a combination of questions. So people, including our question asker, have seen juvenile white sharks breaching out of the water. So why they do it, particularly juveniles, I don’t have a good answer
for that, unfortunately. We don’t know yet. Is it uncommon? No, juvenile white sharks
are known to breach. And as well as thresher sharks
are also known to breach, makos are also known to breach. So it’s not a particular
rare, uncommon behavior. We don’t see it very often because there aren’t that
many of these animals, but I will point out to the
second part of your question, as to why we might be
seeing them more often, I think that’s a two-part question. In one part, it’s
because there is evidence that white shark
populations are recovering. So they’re a protected species,
their numbers were low, and they do seem to be recovering. They don’t recover
quickly, they grow slowly, but their numbers do
seem to be increasing. That might be why we’re
seeing more of them. The other side of that coin
is that there’s more people stand-up paddleboarding,
putting up drones, just generally being in
the water than ever before, and that’s gonna lead to
more sightings as well. So I think it’s a
combination of more people with better tools to see the ocean, as well as what I hope
is a really good sign that this population is in
fact starting to increase. – [Man] My question has to
do with sharks sleeping, and can you talk a little bit
about shark sleep patterns and whether or not you
were able to determine whether or not the sharks you studied were sleeping during your surveyed route? – Right, so, the question
is sharks sleeping, do sharks sleep, can we determine that? And that, again, you guys
are asking great questions, and it sucks for me to
have to say I don’t know to a lot of them.
(audience laughs) But the best I can really
say is I don’t know, then I can speculate a little bit. So there are different species of sharks, and some of them have to swim to breathe. We call them ram ventilators. They swim with their mouth open, that’s what forces water
that’s high in oxygen over their gills. Those animals have to be
swimming at all times. If they’re not swimming, they could drown. Does that mean they don’t get to sleep? I don’t know. Maybe they can control, like shut off parts of their
brain at different times. There are people that
are shark neurologists that would know much more
about that than I do. But as far as I know it’s
never been documented that they’re sleeping. Other species can in
fact rest on the bottom, ’cause instead of having
to swim to breathe they can pump their gills. And when they pump their gills, that forces water over them
and they breathe that way. Do those animals sleep? They certainly rest on the bottom. I can’t say for sure
whether they’re sleeping or they’re just hanging
out or what they’re doing, but they can certainly at least rest and not be swimming at all times. These pelagic fish, all
three species that I study, are ram ventilators, so they are swimming at all times. When we’re tracking them,
we don’t get a break. We are moving or we will lose them. They do not stop swimming
at any point in time. – [Man] Thank you for your presentation. You have not touched on the blue shark. I have fished around here since the 50s, and one time the blue shark (mumbles). They were everywhere. Then we had the advent of
the (mumbles) for short fish, and there are literally no blue
sharks in the Bight anymore and we see no more idol fish. So my question to you is, (man speaking indistinctly) and how soon can we expect
to see a resurgence? – Okay, so, that’s a good question. So the question is that
there were blue sharks that were very commonly sighted
off of Southern California. We don’t see them nearly
as often as we once did. There used to be dive operations based on going cage diving
with blue sharks offshore, and there’s still a couple that do it, but they’re not nearly as
profitable as they once were ’cause you don’t see as many blue sharks. So there’s a couple things. The question is, is that because the blue sharks
populations have decreased, or have they moved somewhere else? And that is a tough question to answer ’cause all we can say is how often do we see them in our surveys. That could mean that they’re not around, or it could mean that they have
changed their distribution, caused by things like their prey moving or water temperatures changing
and other things like that. Blue sharks I can say can actually have a lot of pups at once, they can have large litter sizes. So for a shark, specially
a big-bodied shark, they might actually
reproduce relatively fast. Relatively I’m talking compared to other large-bodied sharks, not compared to let’s say bony fish. A single grouper might have
a million eggs at a time. So not compared to other fish, but compared to other sharks we think they might be able to
reproduce relatively quickly. In terms of the larger-scale studies that are done by fishery
management organizations, they have not been able to demonstrate that blue shark populations
have suffered significantly. But, anecdotally, we still see people, like yourself and myself, that are seeing fewer of them. The problem is, based
on our current methods, we don’t have the ability to say whether they’re disappearing or moving or what might be happening. So that’s something that if anyone here is interested in becoming
a shark biologist, we can talk and maybe
we can figure out a way to get a better answer to that question. – [Man] Hi, Dovi. So, because baby sharks
accumulate chemicals from their mothers and because sharks give
birth in different ways, have there been any differences
in chemical exposure between sharks that are given live birth and sharks that have hatched from eggs? – You guys, are asking great questions. I don’t know the answer to that. (audience laughs) But the truth is that this is a relatively new field of
study that needs a lot more. The reproductive modes of sharks is actually a lot more complex
than what I showed here. There’s a lot more nuance to it. And the question is, do those
different reproductive modes affect the amount of chemicals
that they accumulate, particularly at birth in the young? I know that the answer to that is yes, but the answer is less satisfying because I don’t know how so. And there is some information
on the literature, and I’m not an expert on it,
so I’m not gonna pretend to be, and there’s still a lot
more that we need to know. But yeah, the different
physiology of the animal is certainly gonna have an impact on the amount of contaminants. We even see that within
these three species. The makos seem to have the highest contaminant load at birth, much more so than the
blues or the threshers. – [Woman] Thank you for
a nice presentation. I noticed that you said something about the age of the Greenland shark, and I was wondering, what is that age? You said it was the
longest-living vertebrate. And also, on your shark, the thresher, what is its average age? – So, the first part of that question, there was a study recently done. Does everyone here know you can age trees by counting the growth rings? So it turns out that’s
true for some animals too. So with sharks, you can often count bands that grow in their
vertebra to age them. And it turns out you can also
look at the lens of their eye. And so there’s a study that
came out a couple of years ago that demonstrated that
some Greenland sharks can live for close to 500 years old. That they might not even
be reproductively mature until they’re 150. And these are animals
that live in cold water, so they’re likely to have
very slow metabolisms. But that is really old. And they can also look at signatures of some of the bombs that were tested to see at what point do you
see this signal of radiocarbon and how many rings
they’re grown since then, and that also supports that
these things might be living for, again, close to 500 years. Thresher sharks don’t
live quite that long. Again, there’s varying studies
that have different answers, but my best guess based on
all the literature I’ve seen is somewhere around 50 or
something in that general range. And again, it’s a best guess, because there’s multiple studies that have slightly different answers. – [Woman] Your lecture was fantastic. My question is, do all sharks have the ampullae of Lorenzini? – That’s a good question. So, the ampullae of Lorenzini, so do all sharks have the
ampullae of Lorenzini? The ampullae of Lorenzini
is a special sensory organ that sharks have that allows, it’s a bunch of tube-filled pores largely found distributed around the head but centered around
the snout and nose area that allows them to detect
electrical conductants or electricity in the water column. And yeah, I think all
species of sharks and rays will all have ampullae of Lorenzini. Do they all have the same
sensitivity to electricity? Likely not. One of the reasons we think
hammerheads might have evolved that weird hammerhead shape is ’cause it spreads out
those ampullae of Lorenzini over a broad area, allowing them to find prey that might be hidden under the sand. So it’s a really neat
thing that they can do, and all sharks and rays seem to have at least some ability to do that. – [Woman] Well, thank you again for a wonderful presentation. (audience applauds) (gentle music)

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