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0:03
(upbeat instrumental music) - [Narrator] The open ocean. A realm of vast and powerful forces.
0:13
Home to the largest animals on our planet.
0:17
(upbeat instrumental music) Far from land and thousands of meters deep, (upbeat instrumental music) its limitless blue punctuated by bursts of frenzied action. (upbeat instrumental music) But at night, the open ocean changes. (light instrumental music) Billions of animals rise from the deep.
0:46
Strange new creatures.
0:49
Animals that thrive an impenetrable dark. (upbeat instrumental music) This is the greatest migration on earth.
1:02
Now one man plans to do what no one has done before.
1:08
He will enter a strange and dangerous night time world
1:14
and attempt to film this epic movement of animals by immersing himself in it as it happens.
1:22
His aim, to unlock the secrets of the great migration. The Secrets of the Dark Side of the Ocean.
1:35
(slow serene music)
1:39
Marine biologist, and acclaimed underwater camera man, Rick Rosenthal, has spent more than 30 years filming the creatures of the open ocean.
1:50
Most of the time he films during the day, when there is enough light for his cameras.
1:58
But now he plans to film a night time phenomenon. A vast, vertical migration. Billions of deep water animals that rise from the abyss to feed in darkness on plankton, near the surface.
2:18
By rising at night, they avoid detection by daylight predators.
2:27
At dawn, they descend again to the safety of deep, dark water.
2:34
These concentrated layers of animals are so dense that military submarines can hide beneath them, undetected.
2:46
In terms of sheer numbers and bio-massive animals, it's the largest migration on earth.
2:57
- I've been lucky enough to film a lot of cool animals in natural history events in the open ocean. But there's one spectacle I've never seen. And that's the vertical migration of animals from the deep up to the surface at night.
3:14
Several years ago, I was diving way off Costa Rica. And when I jumped in the water, I was treated to an underwater ballet by Mobula rays. There were also dozens of species of juvenile fish. Many we'd never seen before. Including baby sail fish. So this really fired me up to do more work in the dark.
3:39
So what I'd like to do is go out in the open ocean at night. Jump in the water with a camera, and film this great vertical migration.
3:51
- [Narrator] It's a huge challenge.
3:55
The vertical migration only occurs in the open ocean. And only in certain areas.
4:03
So Rick must draw heavily on three decades of experience. By day, subtle signs in the ocean will lead him to places where life congregates.
4:15
These are the areas that are most likely to be active by night.
4:22
(light serene music) His search starts in the tropical Pacific. (light serene music)
4:34
With veteran captain, Dennis Bishop aboard the MV Cocoa, standing 100 meters off,
4:42
Rick searches for signs of marine life.
4:46
(light serene music)
4:51
- I'm looking for birds that might be swooping low over the water, I'm looking for a distant blow from a dolphin or a whale, And I'm looking for fish that are cutting through the water or breaking the surface. (loud splashes) (light serene music)
5:12
These signs in the sea are so important for us to find anything out there. It's just too expansive, too big. (light serene music)
5:29
- [Narrator] Rick is searching here because he saw a blow of spray from a whale.
5:35
The whale might have moved on. But a tell tale smooth patch suggests that something large is hidden below.
5:48
At first, he sees nothing.
5:52
A two kilometer column of water. Lifeless and empty. (slow serene music) Until vague shadows emerge. (high-pitched screeches)
6:13
Pilot whales.
6:15
They feed on deep water squid, which form an essential part of the nightly migration. (high-pitched screeches) If there are whales on the surface, there may be life far below, waiting to rise up at night. (light serene music)
6:39
Then another shape in the blue.
6:43
An oceanic white tip shark.
6:51
- [Rick] When I'm in the water and I see these shadows, it's not about being frightened or anything, you're pumped up. You're, you're excited.
7:02
- [Narrator] The shark is a surface feeder, and an opportunist.
7:08
The whales offer the chance of an easy meal. (light playful music)
7:16
- [Rick] When I see sharks and whales get close to one another, I go into a hunting mode. Because something's going to happen here. (high-pitched whale screeches) (light playful music)
7:40
It looks like the shark is trying to frighten the whales into defecating before they dive.
7:48
- [Narrator] During the day, there's often very little food in the open ocean.
7:54
The shark has developed a way to steal a meal from the whales.
8:00
- [Rick] A red plume is a sign that the whales have been eating squid.
8:06
I can see the shark picking off bits of squid in the feces trail.
8:13
(high-pitched whale screeches)
8:19
These oceanic white tip sharks are considered top predators. But when they feed in this manner, their reputation is certainly suspect.
8:33
- [Narrator] The whales dive.
8:37
They can reach depths of 600 meters, far deeper than Rick or the shark can follow.
8:47
Their diving ability allows the whales to feed on deep sea squid all day. Most other predators must wait for night and the vertical migration.
9:02
The shark swims on.
9:06
All animals here are nomads. Constantly in search of food or a mate.
9:16
For now, Rick is alone again in the blue.
9:22
But the fact the whales were here suggests the area has potential.
9:28
Rick decides to stay and see what happens next.
9:44
And after awhile, Rick finds another promising sign.
9:51
Where two currents meet, the nutrients from both become concentrated.
9:57
A line of fertile water in the otherwise featureless ocean.
10:06
- [Rick] That current line is another indicator that we're in the right area. So you're in one, stay with it. It's like a highway.
10:16
- [Narrator] Phytoplankton flourish here. Microscopic plants that need both sunlight and the nutrients in the currents.
10:25
They are the foundation of the food chain here in the open ocean. And a feast for a school of surface dwelling anchovies.
10:37
But the anchovies have a problem.
10:40
The bright light makes them an easy target for predators. (fast-paced suspenseful music) It's not long before a school of Skipjack tuna arrives.
10:51
And a feeding frenzy begins. (fast-paced upbeat music)
11:25
By the time a Silky shark appears, just minutes later, only a handful of anchovies remains.
11:34
The shark picks off the crippled fish, which the tuna have left behind. (slow serene music)
11:45
But the plankton the anchovies were feeding on, remain.
11:50
Food for more cautious creatures that only come to the surface in the dark.
12:00
- [Rick] I think we're really close now. There's lots of plankton and bait fish in the water. And we're drifting over a deep underwater canyon.
12:10
- [Narrator] Searching by day has paid off. This spot attracts life, thanks to currents and sea floor geography.
12:18
It's time for Rick and Dennis to refine their search still further. - Dennis, I'm seeing them thrash through flotsam and animals under it. I think we're in a good spot, what do you got? - [Dennis] Yeah I can see it a little farther than you, it goes all along the edge out there. I see, oh wait, oh there's a log over there. - [Rick] Okay, we're gonna go for it. - [Dennis] There, you're good. - [Rick] Camera, I've got the camera, very good.
12:46
Got your gear.
12:49
- [Narrator] Dennis has spotted a log in the distance.
12:53
- Good, okay, alright let's get her going. Let's get her going.
12:57
- [Narrator] This kind of flotsam can act like a tiny, mobile reef. Creating shelter for many species of fish. If life gathers here by day, there's every chance Rick will be in the thick of the action at night.
13:14
- We get close to it, I'll get in and I'll swim over to it. - Okay, very good. (boat engine roars)
13:27
- [Narrator] A pod of spotted dolphins heads in the same direction. Another encouraging sign. (upbeat music)
13:50
Rick gets in a few hundred meters from the log.
13:56
It looks to him like the dolphins are feeding here. (high-pitched dolphin squeaks) He's right.
14:05
These open jawed postures are a warning to back off.
14:11
But Rick is not alone in following the dolphins. Yellowfin tuna often hunt together with dolphins. And they appear soon after. (light serene music)
14:28
(high-pitched dolphin squeaks)
14:34
No one knows quite why the activity spreads so wide around pieces of flotsam.
14:41
Perhaps it's simply that the log cannot shelter them all. (light serene music)
14:54
Finally, Rick reaches the center of the action.
14:59
But the frenzy is all around him. Stretching further than he can see.
15:07
- [Rick] The dolphins are buzzing and rocketing around the log. Chasing the small fish out into the open water. (light suspenseful music)
15:22
- [Narrator] Some species spend their entire lives here.
15:28
How they find something as small as a single log in thousands of kilometers of open ocean is a mystery. (light suspenseful music)
15:41
But predators and prey are both here in abundance. (light suspenseful music)
15:50
A black tip shark. A sign that Rick needs to be careful.
15:59
- [Rick] It's one thing to be a small fish hiding under the log. But if you're a cameraman, you're exposed. You're fair game. There's just too many animals coming in here and joining this feeding frenzy.
16:13
- [Narrator] A sail fish. Almost three meters long and capable of incredible speed. (light serene music)
16:25
Its skin normally bright silver turns black when it's hunting.
16:31
And these are perfect hunting conditions. (light suspenseful music)
16:43
Predators will travel hundreds of kilometers for a feast like this.
16:51
It's not long before Rick is surrounded by ocean giants.
16:59
They use their huge sails to herd the fish into a group. (light suspenseful music)
17:09
Then they take turns to lunge through the bait bowl to feed.
17:15
(light suspenseful music)
17:24
Within an hour, almost no bait fish remain at the surface.
17:33
As evening approaches, the predators dive to meet the rising migration of deep sea creatures.
17:41
Rick can dive without scuba gear to 20 meters or more.
17:46
But the vertical migration is probably still hundreds of meters down. For now, he must wait.
17:55
Finding a similar aggregation of predators and prey in the dark, will be tough.
18:02
Most of the open ocean will be as empty at night as it is during the day.
18:09
But Rick is convinced the predators he has seen are proof that the migration could happen right here.
18:18
They circle the area, waiting for the dark.
18:25
The depth sounder registers a dense mass beneath them, moving slowly towards the surface.
18:31
The mass covers an area the size of a small city. And it's made of entirely of living things.
18:43
Soon the most challenging part of Rick's mission will begin. Filming at night, here in the open ocean.
18:55
(light serene music) This baby Leatherback turtle feeds on small gelatinous animals. Creatures that should arrive in the first wave of the night migration. (light serene music) And very soon, they do.
19:15
A salp, the night's first arrival. And the turtle's favorite food.
19:24
(light ominous music)
19:31
Night filming is challenging and dangerous. A single mistake could be fatal.
19:39
As the boat drifts with the wind and currents, it's easy for a diver to get separated.
19:47
Lights will help keep Rick oriented when he's under the water. - Then I'll put the LED, well wherever. - [Narrator] Rick is also interested in trying out a set of lights that night fishermen use as lures. - We can make a whole string of 'em. Let's go with two first.
20:06
I'm just gonna leave it long later so we don't have to cut it. - [Narrator] Many deep sea creatures are bioluminescent. They literally glow in the dark. The theory is that from a distance, predators will see the lure lights as a potential meal.
20:25
It's a clear moonlit night. Conditions on the surface are perfect. (light serene music)
20:41
He hides in the dark, below the boat, with the lure lights 10 meters below him, and waits.
20:55
- [Rick] When you first jump in the water in the dark, it's a bit unnerving. You're not sure what you're jumping into. And you just see darkness, black. (light ominous music)
21:09
(high-pitched dolphin screech) (light ominous music)
21:34
- [Narrator] Strange creatures emerge from the deep.
21:40
The ocean is transformed.
21:47
A string-like siphonophore.
21:52
Its tentacles glowing in the dark, like Rick's lure lights to draw in its prey.
22:01
Some siphonophores reach an astonishing 40 meters in length.
22:07
Rick keeps a safe distance.
22:13
- [Rick] There's a lot of stinging organisms in the water tonight.
22:19
And these siphonophores really pack a wallop. (light ominous music)
22:31
- [Narrator] A pyrosome. Bioluminescent. As are so many creatures of the deep.
22:38
(light playful music) The light serves different purposes in different species.
22:45
They can lure prey, distract predators, or attract a mate. (light ominous music) A larger pyrosome acts as a refuge for a tiny sergestid shrimp.
23:01
Out in the open, it would be an easy meal for predators. (light ominous music)
23:14
A juvenile mantis shrimp.
23:18
Its eyes are among the most complex in the animal kingdom.
23:22
They need to be. Without stingers or shelter, young mantis shrimps are extremely vulnerable. (light ominous music)
23:35
These are remarkable encounters. But Rick has seen fewer animals and far less diversity than he expected.
23:46
- [Rick] I was expecting the water would be full of animals by now.
23:51
I'm either doing something wrong, or I'm in the wrong spot.
23:58
- [Narrator] Dennis can still see the dense layer of life on the depth sounder. But it has stopped rising. It's 50 meters down. And going nowhere.
24:10
Why?
24:13
It's clear that Rick needs to learn more before he tries again.
24:24
Several days later, and in search of answers, Rick travels to the Monterey Bay Aquarium Research Institute in Central California.
24:36
Rick joins the team on their research vessel, the Rachel Carson.
24:41
The institute develops sophisticated technologies for studying the deep ocean.
24:47
It's at the cutting edge of research on the vertical migration. - [Rick] I'm hoping that the MBARI scientists will give me some of the answers that I need to successfully film the vertical migration.
25:03
- [Narrator] He joins Dr. Bruce Robeson, one of the world's experts on the deep sea environment.
25:11
The institute uses a remotely operated sub, the Ventana, to investigate ocean life at depth.
25:21
They've already made over 3,000 research dives.
25:25
This technology has enabled Dr. Robeson's team to study deep water life in unprecedented detail, both at night and by day.
25:36
The sub can go down more than a kilometer. And stay down almost indefinitely.
25:44
- [Rick] This is a window to a world I'll never see while scuba diving. I'm really interested in what's in this deep water.
25:53
- [Narrator] The science team stays safe and dry on the surface. Adjusting the Ventana's depth and position from a control suite on the mothership.
26:03
Their aim is to sink low enough to find life.
26:08
But as the sub passes the 50 meter mark, there's very little to see. (men chatter) As the Ventana sinks lower, the dark intensifies.
26:21
(light music)
26:25
At 200 meters, there's almost no light at all. And animals begin to emerge from the dark.
26:37
Then, larger animals.
26:40
A medusa, six centimeters across.
26:46
The team carefully maneuver it into a collection jar.
26:52
Previous systems use nets instead of suction. Jelly-like creatures were usually destroyed.
27:00
The new system has led to the discovery of many species new to science.
27:13
A Tiburonia jellyfish, unknown until it was captured by the research team.
27:25
This is a world of bizarre species. Many of them, like this cockatoo squid, rarely seen at the surface. (light music)
27:41
Most are jelly-like plankton feeders. Their soft bodies coping easily with the crushing pressure. (light music)
27:58
Living in near darkness, what benefit is a red body for the Bloodybelly comb jelly? (light music)
28:17
But even here in the dark, there are predators. (suspenseful music) A viper fish, half a meter long. A deadly predator of the deep, with a lifespan of 30 years or more. (suspenseful music)
28:44
A Barreleye fish.
28:47
It has a transparent head and green tubular eyes that point upwards to detect the shadow of any prey passing above. (suspenseful music)
29:02
A narrow escape.
29:08
(suspenseful music)
29:15
- Barreleye really has a set of strange eyes. I wonder what it sees. - [Narrator] Rick is intrigued. These animals were always below him as he filmed.
29:26
But why did they not come up to the surface?
29:31
Bruce explains that the trigger for the vertical migration is light.
29:38
The animals remain in dark waters during the day by only coming up to feed at night, they ensure that they are harder for predators to detect.
29:52
Dr. Robeson's research has revealed that they stay in a zone where the brightness is 1% of full daylight.
30:01
At night, this 1% light level is close to or at the surface.
30:07
And in the morning, as the sky brightens, the 1% zone gets deeper.
30:14
The animals follow the darkness back into the depths.
30:21
(loud machine work)
30:27
- [Rick] Bruce explains to me why I saw so little life on my night dive. The moon was just too bright, the animals stayed below my diving depth.
30:39
- [Narrator] Rick must try again on a darker night.
30:52
The next time Rick heads out into the tropical Pacific, it's on a night with no moon.
31:01
- [Rick] We're gonna head way off shore tonight, above those deep water canyons where we found all that life several days ago.
31:12
- [Narrator] Rick and Dennis hope that the bio hotspot they found during the day will be active again on a sufficiently dark night.
31:20
But there are no guarantees. The only way to find out is to try.
31:32
The lights on the camera and the boat seem bright in the dark. But they're far dimmer than the moon was on Rick's last dive. (light music)
31:48
These swimming crabs are a hopeful sign.
31:53
They don't dive deep, so they can only feed near the surface.
31:58
They must've gathered because they expect plenty of food to be here soon.
32:04
They're waiting for the migration to reach the surface.
32:11
A Tinafor darts through the water.
32:17
- [Rick] I've seen a real evolution in these underwater camera systems over the years. These new digital cameras capture high definition images even under very low light.
32:29
- [Narrator] More animals arrive every minute. Alien forms, most of them sightless, yet pulsing with light.
32:40
A crab larva attracted by the lights, is entangled in sticky filaments.
32:49
It struggles to escape.
32:55
And succeeds.
32:58
(light instrumental music)
33:07
But there are still far fewer animals than Rick was hoping for.
33:13
He must wait for the migration to grow denser. (light music)
33:22
- [Rick] I feel like I'm drifting in deep space looking for new life forms. I never know what's gonna come out of the dark water.
33:32
- [Narrator] Scad mackerel emerge from the shadows ready to feast on the rising plankton.
33:40
And just moments later, a shoal of predatory squid, also rising, following their prey.
33:50
Lantern fish.
33:53
They're the most plentiful fish in the deep ocean. And well adapted to life in the dark.
34:01
Luminescent spots on their flanks help confuse predators and keep the school together.
34:13
The lantern fish's jerky movements mean the squid are never sure when to strike.
34:22
Even so, this one has caught a fish almost as big as itself. (light music)
34:37
But they're not the smartest animals here, or the strongest hunters.
34:46
The squid in their turn, are prey to larger animals. (high-pitched dolphin squeaks)
34:55
Alarmed, the squid squirt clouds of ink.
35:00
The clouds are designed to confuse predators by obscuring the squid's movements. And there's always a chance the attacker will go for the ink shape rather than the animal itself. (light music)
35:16
But dolphins hunt by sonar.
35:20
The squid's ink is no defense at all. (high-pitched dolphin squeaks) They flee.
35:30
The dolphins track them. (light music)
35:38
And eat their fill.
35:40
(high-pitched dolphin squeaks)
35:57
But for Rick, the biggest surprise is this.
36:01
A juvenile Shortbill spear fish. Just five centimeters long. - [Rick] This juvenile spear fish is such an exquisite creature. I've looked a long time to find one. And here it is in the deep sea at night.
36:18
- [Narrator] It's a close relative of the sail fish he saw earlier. If it survives to adulthood, it will be over two meters long and weigh up to 35 kilos. (light music)
36:34
- [Rick] This feels like a flashback to Costa Rica, when we first filmed baby sail fish at night.
36:41
- [Narrator] Unlike the adults, juvenile bill fish are rarely seen in daylight. While they're small, they are vulnerable so they too must hide in the dark. (light music)
37:06
With the spear fish gone, the sea seems empty once again.
37:21
- Dennis, baby spear fish. - Wow. Juvenile spear fish? - Cousin of the sail fish and marlin. About this long. - Wow. - Iridescent blue, unbelievable dorsal fin. Just rolling and feeding, little short, you know, bill. - Yeah. - I don't know if anybody's even filmed one before. I mean that thing is so beautiful.
37:43
- [Narrator] So far Rick has only seen the beginnings of the vertical migration. The majority of animals must rise half a kilometer or more. Rick suspects that these have yet to reach the surface.
37:59
He will have to dive again, later in the night.
38:07
Hours pass.
38:11
Rick and Dennis watch the Cocoa's depth sounder anxiously.
38:17
They can see the thick layer of the vertical migration rising beneath them. But is it dark enough for the migration to reach the surface?
38:29
A shark circles the boat.
38:32
The presence of these big predators tells Rick that more and more animals are reaching the surface.
38:40
The vertical migration must be nearing its peak.
38:46
It's time to get set for the next dive.
38:54
By the time Rick returns to the water, it's after midnight.
38:59
And everything has changed. (light instrumental music)
39:08
The sea is thick with plankton that wasn't here just hours before.
39:16
- [Rick] This time it's different. The water's full of tiny animals. It's like filming in a blizzard. (light music) A manta ray.
39:28
A five meter giant, feasting on the snow of microscopic creatures.
39:37
Like Rick, the manta has been waiting for this. (light instrumental music)
39:53
Rick is surrounded by animals. A living layer so dense that mariners have often mistaken it for the sea floor.
40:03
(light instrumental music)
40:12
The waters of the Pacific are bursting with life.
40:20
The greatest migration on earth. (light instrumental music)
40:29
This extraordinary event, happening every night in oceans all across the world.
40:43
Hundreds of millions of tons of animals constantly on the move, in response to changing light.
40:55
Oases of life in the sea's desert.
41:00
There to be discovered if you know where and when to look. (high-pitched dolphin squeaks)
41:13
(light instrumental music) As night ends, the migration reverses.
41:21
The deep sea creatures sink back into the dark. The mantas and dolphins drift away.
41:40
Rick is once again alone.
41:46
His extraordinary encounter is over. (light music)
41:59
A new dawn lights a vast and silent sea.
42:10
Sunlight once again nourishes the plankton that even creatures of the dark ultimately depend upon.
42:19
For Rick, there will always be new animals to film.
42:24
Always new encounters with the deep. (light music)
42:33
But now, as he travels over the seemingly limitless emptiness of the ocean,
42:40
he knows that in oceans all across the planet, the animals of the great migration are still there in the deep.
42:49
Just waiting for the dark. (light instrumental music)
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