0:00:07 > 0:00:09The waters around the UK hide treasures
0:00:09 > 0:00:11and surprises we rarely get to see.
0:00:13 > 0:00:18Powered by Arctic currents to the north, and the Gulf Stream to the south,
0:00:18 > 0:00:23our island occupies a unique position in the Atlantic ocean.
0:00:26 > 0:00:28'I'm explorer Paul Rose.
0:00:28 > 0:00:32'I was base commander of the British Antarctic survey for ten years...'
0:00:32 > 0:00:34Right, let's go diving!
0:00:34 > 0:00:38'..And I've scuba dived all around the world.'
0:00:38 > 0:00:42Just look at that. It's so easy to take this kind of thing granted.
0:00:44 > 0:00:51But now I've come home, to lead a team of specialists to uncover the secrets beneath our seas.
0:00:52 > 0:00:53Divers up.
0:00:53 > 0:00:57Joining me is marine biologist Tooni Mahto.
0:00:57 > 0:01:03Her underwater expertise will reveal the unexpected riches of British marine life.
0:01:05 > 0:01:07I'm glad I've got my gloves on!
0:01:07 > 0:01:10Journalist and underwater archaeologist Frank Pope
0:01:10 > 0:01:14will examine the bigger picture of our relationship with the sea,
0:01:14 > 0:01:17and explore our maritime history.
0:01:17 > 0:01:20Ships like this can generate awesome power with the wind.
0:01:23 > 0:01:25This series will take us on a journey right around
0:01:25 > 0:01:30our British seas, to uncover the most startling underwater wonders.
0:01:34 > 0:01:38This time we're exploring the sea off Britain's eastern shores.
0:01:38 > 0:01:41To the east, we've got one of the youngest seas on the planet.
0:01:41 > 0:01:45It was only formed 10,000 years ago at the end of the last Ice Age.
0:01:45 > 0:01:49But that doesn't stop these shallow waters from being truly remarkable.
0:01:51 > 0:01:54Beneath our waves is a world of secrets.
0:02:04 > 0:02:07Our journey starts in the Farne Islands,
0:02:07 > 0:02:09on the rocky shores of Northumberland.
0:02:12 > 0:02:16It's here in these cold, harsh waters we'll be studying
0:02:16 > 0:02:18our most powerful native marine mammal,
0:02:18 > 0:02:21the grey seal.
0:02:21 > 0:02:24This group of islands is home to the largest population
0:02:24 > 0:02:25of grey seals in England.
0:02:25 > 0:02:29There's probably over 1,000 of them on the islands right now,
0:02:29 > 0:02:30and they're thriving.
0:02:30 > 0:02:34We're going to try and find out what makes the grey seal
0:02:34 > 0:02:37such a powerful and successful predator.
0:02:37 > 0:02:43'The Farne Islands have been a national nature reserve since 1993.'
0:02:43 > 0:02:46We should see some seals. There's stacks of them here.
0:02:46 > 0:02:49'But the local population of these tough, adaptable animals
0:02:49 > 0:02:53'has suffered a long history of human exploitation.'
0:02:53 > 0:02:55Something like 100 years ago
0:02:55 > 0:03:01there were about 500 seals here, and now there's over 150,000 of them.
0:03:01 > 0:03:05One of the reasons they're doing so well is that we used to hunt them.
0:03:05 > 0:03:09They were hunted for their blubber, their fat, which was used for oil.
0:03:09 > 0:03:13- Yeah...- Their skins were fairly useful as well,
0:03:13 > 0:03:15and people used to eat them.
0:03:15 > 0:03:16But now that's stopped,
0:03:16 > 0:03:20the culls have stopped, and the numbers are increasing.
0:03:20 > 0:03:22Actually they were the first mammal
0:03:22 > 0:03:24to have been given full protection in the UK.
0:03:24 > 0:03:28I mean, in 1914 they decided to protect the grey seal,
0:03:28 > 0:03:32and that was following all the slaughter that happened
0:03:32 > 0:03:33in the 19th century.
0:03:33 > 0:03:36But the end of hunting alone isn't enough to explain
0:03:36 > 0:03:39the dramatic success of the grey seal.
0:03:41 > 0:03:45We're going to head out to the islands and figure out
0:03:45 > 0:03:48why the grey seals have bounced back so strongly,
0:03:48 > 0:03:50and why they've been such a success story.
0:03:52 > 0:04:00Grey seals have to eat five kilos of fish a day to survive the cold temperatures of the North Sea.
0:04:00 > 0:04:02Fish stocks in these waters are in decline
0:04:02 > 0:04:05but these seals are still finding enough to eat.
0:04:05 > 0:04:09The key to that is their amazing ability to dive.
0:04:12 > 0:04:16I'm planning an experiment to find out how they do it
0:04:16 > 0:04:18with Dave Thompson, a marine biologist
0:04:18 > 0:04:22from the Sea Mammal Research Unit at St Andrews University.
0:04:26 > 0:04:29As mammals, seals can't breathe under water
0:04:29 > 0:04:34but they've evolved to maximise their use of oxygen.
0:04:34 > 0:04:38One of the ways they do it is by something called
0:04:38 > 0:04:40the mammalian dive reflex,
0:04:40 > 0:04:44a reflex shared by many mammals, even humans.
0:04:44 > 0:04:48'It's a survival mechanism that conserves oxygen
0:04:48 > 0:04:50'by slowing your heart rate.
0:04:50 > 0:04:54'It's triggered when your face is immersed in cold water.'
0:04:54 > 0:04:58Right. I'm going to test this mammalian dive reflex here.
0:04:58 > 0:05:02What you need is a bucket and some nicely cold water.
0:05:02 > 0:05:07- Dave, have you got the heart monitor, mate? And we'll get set up here.- Yes.
0:05:07 > 0:05:09How are we going to hold that on? Oh, duck tape, great!
0:05:09 > 0:05:12Yeah, OK. Putting it on's going to be all right...
0:05:12 > 0:05:14Yeah, I've got my suit on, you see.
0:05:14 > 0:05:18OK. Normally you'd try and get it down below your pecks.
0:05:18 > 0:05:21That's all right.
0:05:21 > 0:05:25You should be able to read that now on your machine.
0:05:25 > 0:05:27Have you got me there?
0:05:27 > 0:05:30OK, we're getting a heart rate of about 81 beats a minute.
0:05:30 > 0:05:31OK. Right, shall we give it a go?
0:05:31 > 0:05:33Yeah, let's give it a go.
0:05:45 > 0:05:46'Sensing the cold water,
0:05:46 > 0:05:52'nerves in the face instruct the brain to slow down the heart.'
0:05:52 > 0:05:57An immediate drop. It's dropped from 85 to 74, 73...
0:05:57 > 0:06:03'Just as in seals, the reflex saves oxygen by slowing the metabolism
0:06:03 > 0:06:07'and diverting blood to the vital organs.'
0:06:07 > 0:06:0965, 64.
0:06:09 > 0:06:12So it's already dropped 20-odd beats per minute.
0:06:14 > 0:06:15- Did it go down?- Yeah, it did.
0:06:15 > 0:06:18It dropped from mid-80s down to about 56.
0:06:18 > 0:06:21- Wow, just in that... - Over that period of time.
0:06:21 > 0:06:25Rapid decline at the beginning and then a gradual decline after that.
0:06:25 > 0:06:27So it proves the point - you get cold water...
0:06:27 > 0:06:32So we still have that, within us, that mammalian dive reflex.
0:06:32 > 0:06:35- It's a reflex. It's nothing you're consciously doing.- No, for sure.
0:06:35 > 0:06:40Dave's been studying the same reflex in grey seals
0:06:40 > 0:06:43to find out how their physiology is adapted for life under water.
0:06:47 > 0:06:51To see how much more effective grey seals are than humans at diving,
0:06:51 > 0:06:54we've enlisted the help of an expert.
0:06:54 > 0:06:57Emma Farrell's trained herself to dive to over
0:06:57 > 0:07:0240 metres holding her breath, in a sport known as freediving.
0:07:02 > 0:07:06So what sort of depths can seals dive to compared to humans?
0:07:06 > 0:07:11OK, as a seal biologist, I'm going to say the seals win by a long way.
0:07:11 > 0:07:14In the North Sea, they're going down to about 100-120 metres.
0:07:14 > 0:07:16We've had some off the west coast going deeper.
0:07:16 > 0:07:20How long are they under water? How long can seals hold their breath?
0:07:20 > 0:07:23Grey seals can hold their breath for up to 40 minutes,
0:07:23 > 0:07:25probably 45 minutes.
0:07:25 > 0:07:30- Free divers, Emma?- The record is 11 and a half minutes, which is completely phenomenal.
0:07:30 > 0:07:33Only a few years ago, the record was six and a half, seven minutes
0:07:33 > 0:07:38and people thought, "No way will anyone reach ten," and now it's eleven and a half.
0:07:40 > 0:07:44We're going to measure Emma's heart rate while she dives,
0:07:44 > 0:07:47and compare it with that of grey seals.
0:07:47 > 0:07:54The sea here is 20 metres deep, and she'll be diving to the bottom on a single breath.
0:07:56 > 0:08:00Free diving always carries a risk, even for the experts,
0:08:00 > 0:08:03so we have safety divers standing by.
0:08:03 > 0:08:06You can just see
0:08:06 > 0:08:10the outline of Emma way up there on the surface.
0:08:10 > 0:08:13It's quite an experience watching actually.
0:08:15 > 0:08:19She just looks really, really relaxed. She's just laying there,
0:08:19 > 0:08:21not using any energy whatsoever.
0:08:27 > 0:08:29Here she comes.
0:08:32 > 0:08:35You can see her pinching her nose.
0:08:35 > 0:08:39That's so that she can equalise the spaces in her head.
0:08:39 > 0:08:43You know, the ears and sinuses would be incredibly painful here.
0:08:48 > 0:08:50She's holding her breath for a long time.
0:08:50 > 0:08:55There's no way I could hold my breath for that length of time.
0:08:57 > 0:08:59There she goes. Bye, Emma!
0:09:16 > 0:09:19- We'll go and download this and see what's on it.- Thanks.
0:09:19 > 0:09:24This is the data from the heart rate monitor that we put on you before you went diving.
0:09:24 > 0:09:27You've got a gradual reduction in heart rate,
0:09:27 > 0:09:32from what was quite a high level before you went in, down to...
0:09:32 > 0:09:37it's dropped you about 20 beats a minute, maybe, 15-20 beats a minute.
0:09:37 > 0:09:39You can see where you came to the surface.
0:09:39 > 0:09:43But gradually your heart rate was getting slower and slower
0:09:43 > 0:09:47- and slower, where that mammalian reflex must have kicked in quite clearly.- Yeah.
0:09:47 > 0:09:52And it looks like the longer I'm in the water, the more it's becoming affected, so...
0:09:52 > 0:09:54Starts to really kick in, yeah.
0:09:54 > 0:09:57'Dave's done exactly the same experiment on grey seals.'
0:09:57 > 0:10:02These are heart rate traces from a couple of grey seals.
0:10:02 > 0:10:06As soon as his face goes in the water, his heart rate drops and it drops like a stone...
0:10:06 > 0:10:11So this is 120 beats a minute?
0:10:11 > 0:10:15Yes, at the surface, they're like a racehorse, breathing incredibly hard.
0:10:15 > 0:10:19- Then very quickly down to five or ten or whatever that is.- Yeah.
0:10:19 > 0:10:23This one averaged about 15 beats a minute during the dive.
0:10:23 > 0:10:27- Wow, look at that. - It's amazing, absolutely amazing.
0:10:29 > 0:10:35Emma's trained herself to hold her breath for over four and a half minutes.
0:10:35 > 0:10:42Seals can go ten times longer and it's not just because their heart rate slows down more than hers.
0:10:42 > 0:10:48They have twice as much blood as we do, and many more of the red blood cells that carry oxygen.
0:10:48 > 0:10:53This means they can store far more oxygen in their bodies than we can.
0:10:53 > 0:10:59With no sinus cavities, they don't suffer from changes in pressure like humans.
0:10:59 > 0:11:02And they can dive to over 120 metres to catch their prey.
0:11:05 > 0:11:08They swim in a highly energy efficient way.
0:11:08 > 0:11:14'Even a top competitive free diver can learn a lot from the grey seal.'
0:11:14 > 0:11:15That's what it's all about.
0:11:15 > 0:11:20Just look at the smooth efficient way that she's moving.
0:11:20 > 0:11:23Moving just as the seals do.
0:11:23 > 0:11:26'The ability to dive so efficiently on a single breath
0:11:26 > 0:11:29'is the key to their success as a top predator.'
0:11:38 > 0:11:42Emma has trained for years to dive deeper and far longer than I could
0:11:42 > 0:11:48even dream of but today even Emma has been outdone by the grey seals,
0:11:48 > 0:11:54because they have evolved to become one of the most powerful diving mammals on our shores.
0:11:54 > 0:12:00There's more to their success as predators than diving prowess.
0:12:00 > 0:12:04They also have to become expert hunters.
0:12:04 > 0:12:10Later on, Frank and Tooni will be diving with some young seals to see how they do it.
0:12:18 > 0:12:22The whole of our eastern seaboard is flanked by the North Sea.
0:12:22 > 0:12:27These are the shallowest waters around our shores, averaging less than 100 metres deep.
0:12:30 > 0:12:36But these waters have provided us with some of our most valuable resources.
0:12:36 > 0:12:40The east coast has played vital role in our industrial history, not least
0:12:40 > 0:12:44because it's here that we first discovered offshore oil and gas.
0:12:44 > 0:12:51For over 30 years they have kept us self-sufficient in energy but today, they're starting to run out.
0:12:53 > 0:13:01However, it does look like there's another resource that might see the North Sea come to our rescue again.
0:13:01 > 0:13:02Wind.
0:13:07 > 0:13:11I'm on board the Pelican at the start of the annual Tall Ships Race.
0:13:11 > 0:13:14This leg is an eastward dash to Holland.
0:13:14 > 0:13:19Ships like this can generate awesome power with the wind.
0:13:19 > 0:13:23And out here you can really see why they've been so successful.
0:13:23 > 0:13:26The winds here are twice as strong as the global average.
0:13:26 > 0:13:31Stand by to set the main topsail!
0:13:31 > 0:13:34Haul away the sheet!
0:13:34 > 0:13:38It's a magnificent sight, and a striking example
0:13:38 > 0:13:39of the power of the wind.
0:13:46 > 0:13:51With a full spread of sail up, the Pelican can generate 1,000 horsepower.
0:13:51 > 0:13:55That's three times more than the engines can produce.
0:13:55 > 0:14:00It's clean, there's no diesel fumes, there's no carbon footprint, nothing.
0:14:00 > 0:14:04There's just the silent beauty of the wind.
0:14:09 > 0:14:13Because of our position on the edge of the Atlantic,
0:14:13 > 0:14:17the one thing we're not short of in the North Sea is wind.
0:14:17 > 0:14:22Basically, you get wind because as the sun warms the air
0:14:22 > 0:14:26at the equator it rises, and cool air blows in to take its place.
0:14:26 > 0:14:29Now that means you get cool air coming in
0:14:29 > 0:14:34from the north at low altitude, and then recirculating back up
0:14:34 > 0:14:36when it's warm at high altitude.
0:14:36 > 0:14:40Now that's the simple picture. Actually what happens is much more complex, because the earth
0:14:40 > 0:14:45is spinning, and the land and the sea warm and cool at different rates,
0:14:45 > 0:14:48and that creates all sorts of local variations in the strength
0:14:48 > 0:14:51and the direction of the wind that we actually see.
0:14:51 > 0:14:54Out here, we get a lot of south-westerly winds,
0:14:54 > 0:14:57and that's been powering ships here for centuries.
0:14:57 > 0:15:03And the wind might just be about to come to good use again.
0:15:03 > 0:15:08No-one knows quite how much longer we'll be able to keep getting oil and gas out of the North Sea.
0:15:08 > 0:15:13It's getting a little bit less every year and somehow we've got to make up that shortfall.
0:15:13 > 0:15:18Wind farms like this one at Scroby Sands on the Norfolk coast could be the answer.
0:15:19 > 0:15:23Scroby Sands, just two miles east of Great Yarmouth,
0:15:23 > 0:15:26was the first offshore wind farm to get planning permission in Britain.
0:15:26 > 0:15:30It produces enough electricity to power 40,000 homes.
0:15:30 > 0:15:37The electricity from Scroby Sands comes ashore here in three cables, at 33,000 volts.
0:15:37 > 0:15:40It comes all the way up the beach, under the promenade,
0:15:40 > 0:15:44past Deb's Diner, then round the corner under three kilometres of streets
0:15:44 > 0:15:51until it gets to here, the substation, where it feeds into the local network.
0:15:51 > 0:15:56To meet our power needs and cut carbon emissions, the government's
0:15:56 > 0:16:00earmarked an area of seabed big enough for 10,000 turbines.
0:16:00 > 0:16:05It's the most ambitious plan for offshore wind power in the world.
0:16:08 > 0:16:12But if we are going to build this number of wind farms, I think we
0:16:12 > 0:16:16need to know what effect these are going to have on our marine life.
0:16:18 > 0:16:22With only 30 turbines, Scroby Sands is a small wind farm compared
0:16:22 > 0:16:27to the ones planned in the waters off Kent and the Thames estuary.
0:16:27 > 0:16:30Although building wind farms is very disruptive to marine life,
0:16:30 > 0:16:35some scientists argue once they're in place, they could be good for it.
0:16:35 > 0:16:39You can see sort of classic zonation there.
0:16:39 > 0:16:44Right at the top of that level there, that's where high tide is. We're at low tide now.
0:16:44 > 0:16:48And that's a whole layer of barnacles and limpets growing on the metal there.
0:16:48 > 0:16:54And as you get further down, there's some seaweed just where the water level is now.
0:16:54 > 0:17:00Right down at the bottom of this steel shaft is a layer of boulders that have been put there
0:17:00 > 0:17:07specifically to make sure the water currents dragging past the bottom don't scour the metal.
0:17:07 > 0:17:12They are to protect the metal itself, and it's the bottom - it's these boulders
0:17:12 > 0:17:14right at the bottom - that act like an artificial reef.
0:17:14 > 0:17:17So they create extra habitat for marine wildlife.
0:17:19 > 0:17:23Diving this industrial installation is going to be a tough technical challenge.
0:17:23 > 0:17:28Dive supervisor Richard Bull has his concerns.
0:17:28 > 0:17:30We've got vicious tides here.
0:17:30 > 0:17:32We haven't got very long slack water.
0:17:32 > 0:17:35If that tide takes off, you're going with it.
0:17:35 > 0:17:40If ever there was a graphic demonstration of, "time and tide wait for no man," this is it.
0:17:40 > 0:17:44- I can see you're looking forward to it after that. Fantastic.- Can't wait.
0:17:44 > 0:17:48It's not just the current we have to contend with.
0:17:48 > 0:17:54The sea on this part of the east coast is infamous among divers for having terrible visibility.
0:17:54 > 0:17:58I'm going to go right down to the base of this wind turbine
0:17:58 > 0:18:04behind us to take a look at just what exactly is happening to the marine life down there.
0:18:22 > 0:18:25As you come down the post you can see
0:18:25 > 0:18:29plenty of barnacles, mussels...
0:18:31 > 0:18:33..and a sort of band of seaweed.
0:18:35 > 0:18:38As I feared, the water is thick with sediment.
0:18:39 > 0:18:43It's so bad I can't even see where the camera is.
0:18:43 > 0:18:44Ah, there you are.
0:18:47 > 0:18:49This is one of the support structures
0:18:49 > 0:18:53holding the actual main shaft of the turbine, which is over there.
0:18:53 > 0:18:58It is literally covered with life that wouldn't normally be here
0:18:58 > 0:19:03if it wasn't for these huge, man-made things in the sea.
0:19:03 > 0:19:10So these are all filter feeders jutting out into the water column, picking up plankton as it comes.
0:19:12 > 0:19:16So what these turbines have done is create a whole other food chain
0:19:16 > 0:19:19in an area where it wouldn't normally exist.
0:19:19 > 0:19:27'At the base of the turbine, there are piles of rocks placed there to protect it from erosion.'
0:19:27 > 0:19:32What it's also done is create a habitat for a wide diversity of marine life.
0:19:32 > 0:19:35Underneath here there are plenty of anemones.
0:19:35 > 0:19:38There are crabs in the small nooks and crannies, lobsters.
0:19:38 > 0:19:44There are even reports of octopus here as well.
0:19:44 > 0:19:48These are incredibly pretty dahlia anemones.
0:19:48 > 0:19:53This is exactly the kind of thing that you wouldn't normally find
0:19:53 > 0:19:59in this environment were it not for these artificial, hard surfaces
0:19:59 > 0:20:02that they can attach onto.
0:20:06 > 0:20:09'The tide has started to turn and we have to get out
0:20:09 > 0:20:11'to avoid being swept away.'
0:20:14 > 0:20:20For me, the major positive of wind farms, aside from the fact that they're supplying renewable energy,
0:20:20 > 0:20:26is the fact that you don't get any fishing trawlers going through here, so essentially it acts almost like
0:20:26 > 0:20:34a marine reserve, a place where fish larvae can come, they can grow, and it acts like a refuge for them.
0:20:34 > 0:20:38Hopefully that will have a sort of spill over effect so seeding other
0:20:38 > 0:20:44fishing grounds around the North Sea with more fish, helping to create a really productive environment.
0:20:56 > 0:20:59100 miles north of Great Yarmouth is Flamborough Head.
0:20:59 > 0:21:05Here, warm water from the southern North Sea collides with cooler water from the North
0:21:05 > 0:21:09to bring a wealth of nutrients to the surface,
0:21:09 > 0:21:13providing food for a wonderful variety of marine life.
0:21:13 > 0:21:19I'm here to explore a phenomenon I've never fully understood.
0:21:19 > 0:21:22There's a blooming great shoal of fish down here. How cool is that?
0:21:22 > 0:21:27'This shoal of fish is made up of whiting, pouting and bib.
0:21:27 > 0:21:33'They've come together around this wreck of an old steamer, attracted by the density of food.'
0:21:33 > 0:21:37And a shoal is a very relaxed group of fish.
0:21:37 > 0:21:41It's where feeding and breeding occurs.
0:21:41 > 0:21:46'But a shoal is transformed into a school if it detects the presence of a predator.'
0:21:46 > 0:21:49As I start swimming towards them,
0:21:49 > 0:21:55they'll get themselves more organised and you'll see they'll quickly turn into a school.
0:21:55 > 0:21:59That's happening - they're starting to school now.
0:22:00 > 0:22:02When they're in that school...
0:22:04 > 0:22:08..they're much safer because if I really was a predator
0:22:08 > 0:22:11I'd have too many targets.
0:22:12 > 0:22:20Once they reach a safe distance, the fish will stop schooling and go back to being a loose feeding group.
0:22:20 > 0:22:25This is a force of nature that is actually a work of art.
0:22:31 > 0:22:34That was a great dive. It's a beautiful thing to see
0:22:34 > 0:22:38thousands of fish in a relaxed shoal suddenly turn into a very organised school.
0:22:38 > 0:22:40I can understand why they do it, but how?!
0:22:43 > 0:22:49I went to see marine biologist Jens Krause to try and find out.
0:22:49 > 0:22:55Jens has devised a pioneering experiment to figure out how fish swim in schools.
0:22:55 > 0:22:59He's created a remote controlled imposter - Robofish.
0:23:02 > 0:23:06- So here we have Robofish. The whole set-up.- So this is it!
0:23:06 > 0:23:09- The fish is actually over here. - Oh, yeah. That looks great.
0:23:09 > 0:23:12'By moving the robotic fish around the tank, Jens can observe
0:23:12 > 0:23:18'how a school of live fish respond to the movement of an individual.'
0:23:18 > 0:23:20In a moment I'll put some live fish in.
0:23:20 > 0:23:24Then we can watch the interaction and then you can release them.
0:23:24 > 0:23:28- Yes, please.- You can pull the gate. - OK, let's have a go.
0:23:28 > 0:23:35The tank is a neutral environment where the fish have no reason to move in any particular direction.
0:23:35 > 0:23:37I put in the fish so they're joining the Robofish now.
0:23:37 > 0:23:40Let's give it a go. You tell me what to do and I'll do it.
0:23:40 > 0:23:43OK, I'll give you a countdown and you pull the gate.
0:23:43 > 0:23:45Okey-doke, I'm ready.
0:23:45 > 0:23:48Three, two, one...
0:23:48 > 0:23:50go.
0:23:50 > 0:23:54- The gate's open. - OK, so the Robofish is coming out.
0:23:54 > 0:23:57- The live fish are following.- Oh, yeah, look! They're making the turn.
0:23:57 > 0:23:59They've made that turn, right over here.
0:23:59 > 0:24:04Look at that - a lot of them have followed him even back into the trap!
0:24:04 > 0:24:06- That's right. - Kind of led them back home.
0:24:06 > 0:24:10Jens' experiment has shown how a group of fish will tend to copy
0:24:10 > 0:24:14the movements of whichever fish moves the most decisively.
0:24:14 > 0:24:17In this case Robofish.
0:24:17 > 0:24:21You can really see that this is local information transmission,
0:24:21 > 0:24:23like a Mexican wave in a football stadium -
0:24:23 > 0:24:26people are responding to their near neighbours.
0:24:26 > 0:24:28They are getting up and the next one is getting up
0:24:28 > 0:24:31and the wave travels through the stadium. The same thing happens here.
0:24:31 > 0:24:36The closest fish copies the Robofish and the information is transmitted to the other individuals.
0:24:36 > 0:24:41The other fish copy Robofish because they perceive its decisive movement
0:24:41 > 0:24:43as being a response to a threat.
0:24:43 > 0:24:46Jens has been working with sticklebacks to develop his theory
0:24:46 > 0:24:51but the way they react is the same in many other species.
0:24:51 > 0:24:55There are a number of different sensory organs that are involved in this.
0:24:55 > 0:25:02There is first of all vision. Eyes are laterally positioned so fish have near round vision.
0:25:02 > 0:25:05Some species have a small sort of blind spot at the back.
0:25:05 > 0:25:06But they can see very far back.
0:25:06 > 0:25:10But as you get closer, they can also feel you.
0:25:10 > 0:25:11How do they do that?
0:25:11 > 0:25:14This is usually done with a lateral line.
0:25:14 > 0:25:19This is an organ that forms a canal alongside the body of the fish,
0:25:19 > 0:25:22and inside are tiny sensors that are pressure sensitive.
0:25:22 > 0:25:27The lateral line enables fish to detect exactly how close
0:25:27 > 0:25:31they are to their neighbours and maintain their position.
0:25:31 > 0:25:34When one fish moves to avoid a predator, the movement
0:25:34 > 0:25:37is copied by its neighbours and ripples through the school.
0:25:37 > 0:25:45This is one of the major advantages of schooling behaviour, that the fish on the outside of the school
0:25:45 > 0:25:52work like an array of independent sensors and each individual will have its own information
0:25:52 > 0:25:55about what's going on in the environment and can then alarm
0:25:55 > 0:25:58other group members nearby and then the information
0:25:58 > 0:26:01will spread from them to others and inform the entire group.
0:26:03 > 0:26:06Individually these fish might have small brains
0:26:06 > 0:26:10but they've evolved to share their collective intelligence.
0:26:10 > 0:26:14I'm never going to look at a school of fish in the same way again.
0:26:17 > 0:26:21Back on the Farne Islands, we're looking at how grey seals
0:26:21 > 0:26:25recovered so well after being hunted almost to extinction.
0:26:26 > 0:26:32I've seen how grey seals' physiology has evolved to make them formidable divers.
0:26:32 > 0:26:38Tooni and Frank are off to observe how the young grey seals learn to become accomplished hunters.
0:26:38 > 0:26:42Although grey seals spend most of their time at sea,
0:26:42 > 0:26:45it's at places like the Farne Islands where they come ashore,
0:26:45 > 0:26:48for breeding, pupping and rearing their young.
0:26:48 > 0:26:53It's here that we can actually watch them both on the land and in the water,
0:26:53 > 0:26:57how they interact with each other and, crucially, how they learn to hunt.
0:27:02 > 0:27:04FRANK POPE: We're heading to the outer Farne Islands.
0:27:04 > 0:27:09Grey seals spend two thirds of their life at sea.
0:27:09 > 0:27:13With their thick blubber and short flippers, they're clumsy on land.
0:27:13 > 0:27:17Out of the water, they're vulnerable and easily spooked.
0:27:17 > 0:27:22We're getting in the boat to go and have a closer look at the seals' haul out site.
0:27:22 > 0:27:27We don't want to approach them on land because we don't want to disturb them too much.
0:27:31 > 0:27:35This group is mainly juveniles and females.
0:27:35 > 0:27:38Most of the adult males are out at sea, hunting.
0:27:38 > 0:27:44They just look like slugs on the surface, and you see them in the water, and they're beautiful.
0:27:44 > 0:27:46The females up there will be quite heavily pregnant,
0:27:46 > 0:27:54which obviously is another reason why they'll be sensitive to any kind of disturbance.
0:27:54 > 0:27:59When grey seal pups are born. They're fed on a fat-rich milk to build up their strength
0:27:59 > 0:28:01and help them put on weight quickly.
0:28:01 > 0:28:05The mother gives them a very good start in life, then she heads off.
0:28:05 > 0:28:09After three weeks, the pups are left to pretty much fend for themselves.
0:28:10 > 0:28:13This is a much shorter period with their mothers
0:28:13 > 0:28:15than most large mammals have.
0:28:15 > 0:28:21So how do young grey seals master the hunting techniques they'll need to survive?
0:28:21 > 0:28:23There's no point just seeing a seal on a rock.
0:28:23 > 0:28:26You need to see a seal in the water.
0:28:28 > 0:28:31Grey seals learn the skills they need through play,
0:28:31 > 0:28:34like land-based carnivores such as fox or leopard cubs.
0:28:36 > 0:28:40The Farne Islands are a great place for us to observe them.
0:28:40 > 0:28:45With the rocky shores and seabed, the water is exceptionally clear.
0:28:45 > 0:28:51This spot's perfect for the seals because they've got shallow rocks that they can haul out onto
0:28:51 > 0:28:57and rest and digest, but also for the juveniles to learn to play in this very shallow, calm bay.
0:28:57 > 0:29:01It's absolutely ideal for them to pick up the skills they'll need
0:29:01 > 0:29:03for living their life further out to sea.
0:29:17 > 0:29:20'At first, they seem to be avoiding us.'
0:29:23 > 0:29:25Where are they?
0:29:28 > 0:29:30Ah, here they all are!
0:29:30 > 0:29:34'Their curiosity soon gets the better of them.'
0:29:36 > 0:29:40These young seals aren't here to catch fish.
0:29:40 > 0:29:45They do that much further out at sea. They're just here to play.
0:29:45 > 0:29:50This is the perfect spot for them. It's very shallow, very calm here at the moment.
0:29:50 > 0:29:56It's an ideal location for them to really learn how to hunt, to interact with each other,
0:29:56 > 0:29:59to get those skills they'll need to survive.
0:30:03 > 0:30:08'These seals are all juveniles. They can already feed themselves,
0:30:08 > 0:30:11'but will continue to perfect their hunting skills
0:30:11 > 0:30:16'in this underwater playground until they become sexually mature around the age of six.'
0:30:18 > 0:30:21They learn through play exactly as toddlers do.
0:30:21 > 0:30:23It's through this that they develop
0:30:23 > 0:30:27their motor ability, their muscle tone and actually learn
0:30:27 > 0:30:32how to forage and feed in the underwater environment.
0:30:32 > 0:30:36'They also learn to master their whole range of senses,
0:30:36 > 0:30:40'which include incredibly precise pressure sensors in their whiskers.'
0:30:43 > 0:30:46These whiskers, they're not just decoration.
0:30:46 > 0:30:50They're as important for the seal as their eyesight.
0:30:50 > 0:30:56They use them to probe the water and sense the vibrations around them.
0:30:56 > 0:31:02They can determine the direction in which a fish is swimming up to 50 metres away.
0:31:11 > 0:31:17These complex and adaptable animals may also learn by copying the behaviour of others.
0:31:19 > 0:31:21Look at that.
0:31:21 > 0:31:23Is he copying me?
0:31:23 > 0:31:27When I cross my arms, the seal crosses his flippers.
0:31:27 > 0:31:31We know the seals mimic each other to learn.
0:31:31 > 0:31:34It looks like this one has gone a step further.
0:31:42 > 0:31:48They're so puppy-like. It's hard not to think of it as very puppy-like behaviour.
0:31:50 > 0:31:53I'm glad I've got my gloves on because those claws...
0:31:53 > 0:31:56But that certainly wasn't aggressive.
0:31:56 > 0:32:00Well, this is a very playful gesture but it's very important to remember
0:32:00 > 0:32:08that these are wild animals, and this seal's bite is in fact more powerful than a pit bull's.
0:32:13 > 0:32:17Grey seals are solitary foragers, exploring the sea on their own,
0:32:17 > 0:32:23often up to 100 kilometres offshore until they find a good place to fish.
0:32:23 > 0:32:26As they grow up, these young seals will have to discover
0:32:26 > 0:32:29their own hunting grounds if they're to survive.
0:32:47 > 0:32:54When the one really inquisitive one comes up and actually jiggles with Frank's fins
0:32:54 > 0:32:57or mimics him by lying in the seaweed, that's the point at which you
0:32:57 > 0:33:04really begin to understand that they're truly learning about their environment by playing in that bay.
0:33:04 > 0:33:07And hopefully that will help them
0:33:07 > 0:33:11exist in the sea when they have to forage for food for the rest of their lives.
0:33:11 > 0:33:17We'll be coming back to the Farne Islands to see how grey seals have benefited from their
0:33:17 > 0:33:21hunting prowess and come to dominate their neighbours, the harbour seals.
0:33:24 > 0:33:28For centuries, the shallow and productive waters to our east have provided us with fish
0:33:28 > 0:33:34for our tables and supported a huge industry on our east coast.
0:33:34 > 0:33:38But over the past 30 years, that industry has suffered.
0:33:38 > 0:33:44Fish stocks in the North Sea collapsed in the 1970s and '80s, decimating our fishing fleet
0:33:44 > 0:33:48and leaving harbours up and down the east coast struggling to survive.
0:33:48 > 0:33:52But one North Sea fishing town has found a new lease of life.
0:33:52 > 0:33:55FAIRGROUND MUSIC
0:34:03 > 0:34:08Bridlington, on the coast of East Yorkshire, has a long and proud fishing tradition.
0:34:15 > 0:34:19Bridlington used to be one of the busiest harbours on our east coast,
0:34:19 > 0:34:22with trawlers landing hundreds of tons of cod and haddock every year.
0:34:22 > 0:34:28But in the 1980s, this fishery collapsed when stocks of these lucrative white fish became scarce
0:34:28 > 0:34:32and limits were placed on the total amount that fishermen were allowed to catch.
0:34:32 > 0:34:35The town's ancient fishing tradition seemed to be at an end,
0:34:35 > 0:34:40until fishermen realised there was a different catch right under their noses.
0:34:44 > 0:34:49Last year they caught 350 tons of lobster.
0:34:49 > 0:34:54But even under that intensive fishing pressure, numbers of lobsters are still going up.
0:34:54 > 0:35:01Today in Bridlington, the entire fishing fleet of 40 boats has turned from catching white fish to lobsters.
0:35:01 > 0:35:05But are lobsters going to go the same way the cod did?
0:35:11 > 0:35:13Determined not to let that happen,
0:35:13 > 0:35:18the Bridlington fishermen have launched a scheme to protect them.
0:35:18 > 0:35:23I want to find out what effect this scheme is having on the lobster population.
0:35:23 > 0:35:28I particularly love lobsters because I think they are the most curious,
0:35:28 > 0:35:34archaic, alien creatures that we have around the British coastline.
0:35:34 > 0:35:37I just think they're immensely likeable, actually,
0:35:37 > 0:35:40rather bizarrely, in their strangeness.
0:35:46 > 0:35:49It's like being born every time, isn't it?
0:36:04 > 0:36:09There have been lobsters on the planet for at least 100 million years.
0:36:09 > 0:36:12Individuals can live for up to a century.
0:36:16 > 0:36:20They have eight legs for walking and two more that are adapted as pincers.
0:36:23 > 0:36:31These wonderful pincers on the ends of his claws are different
0:36:31 > 0:36:34on either side of his body.
0:36:34 > 0:36:37This larger right one is for crushing.
0:36:37 > 0:36:39So anything he finds on the sea floor
0:36:39 > 0:36:46can literally be squished into oblivion, ready for eating.
0:36:46 > 0:36:52The left pincer is for cutting, so it's more serrated and much finer.
0:36:52 > 0:36:55But that means he's perfectly equipped
0:36:55 > 0:37:00for taking on any bits and bobs he finds on the sea floor,
0:37:00 > 0:37:04which is why they make such fantastic scavengers.
0:37:04 > 0:37:09It's like they're just wielding these two massive boxing gloves
0:37:09 > 0:37:13that are completely oversized and out of proportion
0:37:13 > 0:37:15to the rest of the lobster.
0:37:15 > 0:37:19Some scientists believe the recent rise in water temperature in the North Sea
0:37:19 > 0:37:22has helped lobsters to thrive here.
0:37:22 > 0:37:25The decline in cod stocks could also be helping them
0:37:25 > 0:37:28as the cod would have eaten lobster larvae.
0:37:28 > 0:37:32Now this male is sexually mature.
0:37:32 > 0:37:36Lobsters have a slightly strange way of assessing
0:37:36 > 0:37:39if another lobster is also sexually mature.
0:37:39 > 0:37:44Basically, they pee in each others' faces
0:37:44 > 0:37:48with a special gland that comes out from underneath here.
0:37:48 > 0:37:51From the pheromones in that substance,
0:37:51 > 0:37:57they can assess if the mate they find is prime for mating or not.
0:37:59 > 0:38:03Each of the boats operating out of Bridlington
0:38:03 > 0:38:05puts down over 400 lobster pots.
0:38:09 > 0:38:14The way these cages work the lobsters enter through these funnels
0:38:14 > 0:38:19that get narrower and narrower, so once they get inside,
0:38:19 > 0:38:22they can't turn round and exit through the same way.
0:38:22 > 0:38:27Essentially, you can get a lot of lobsters in just one pot.
0:38:50 > 0:38:52Just the weirdest things in the world.
0:38:52 > 0:38:56They've got a good catch today, I'll tell you that.
0:38:56 > 0:39:01But they are just the weirdest, most curiously wonderful creatures
0:39:01 > 0:39:04I think that you can find in these waters. I love them.
0:39:06 > 0:39:10Despite the amount of fishing going on,
0:39:10 > 0:39:12the lobster population appears to be stable.
0:39:12 > 0:39:15I'm going to join the crew of the Kimberley
0:39:15 > 0:39:18to find out how sustainable this fishery really is.
0:39:18 > 0:39:22The secret might be in the way they're catching them.
0:39:22 > 0:39:26Each lobster pot is hauled out about once a week.
0:39:26 > 0:39:28The lobsters are taken out.
0:39:28 > 0:39:30The old bait is discarded and fresh bait,
0:39:30 > 0:39:35usually some scraps of mackerel, is added.
0:39:35 > 0:39:38Today, scientist James Wood is on board the Kimberley.
0:39:40 > 0:39:45He's been monitoring the Bridlington lobster stocks for three years.
0:39:45 > 0:39:48Why are you doing this work with the lobsters?
0:39:48 > 0:39:51We're trying to determine how sustainable they are
0:39:51 > 0:39:54and whether we can gain a sustainable certification for them.
0:39:54 > 0:39:58'Like everywhere in Europe, the Bridlington fishermen
0:39:58 > 0:40:01'are only allowed by law to land mature lobsters.'
0:40:01 > 0:40:03To measure a lobster,
0:40:03 > 0:40:06you measure from the rear of the carapace,
0:40:06 > 0:40:10follow it down the mid line to the rear there,
0:40:10 > 0:40:13and we can see that individual is 106mm.
0:40:13 > 0:40:15And the minimum size is?
0:40:15 > 0:40:1787mm.
0:40:17 > 0:40:20- So anything under 87mm has to be thrown back?- Yes.
0:40:20 > 0:40:24Because the young are thrown back,
0:40:24 > 0:40:26the bait in the pots is giving them a free lunch
0:40:26 > 0:40:28every time they're caught.
0:40:28 > 0:40:32I've just been down diving, and whilst I saw an awful lot of lobsters
0:40:32 > 0:40:33wandering around the sea floor,
0:40:33 > 0:40:35there's also a lot of bait down there.
0:40:35 > 0:40:39Is that in any way helping to sustain the population?
0:40:39 > 0:40:42Yes, bait is probably having an impact
0:40:42 > 0:40:46and sustaining a higher population than would naturally occur here.
0:40:46 > 0:40:50Is that a little bit akin like almost farming free range,
0:40:50 > 0:40:53organic lobsters in this area?
0:40:53 > 0:40:56I'd prefer to think of it as a cultured stock.
0:40:56 > 0:40:58You could consider it to be like a farm.
0:40:58 > 0:41:02'The bait may be helping sustain the population,
0:41:02 > 0:41:07'but the fishermen also have another method to help preserve their livelihood.
0:41:07 > 0:41:09'Some of them have gone beyond European law
0:41:09 > 0:41:11'to give added protection to fertile females
0:41:11 > 0:41:14'carrying the tiny black eggs, known as berries.'
0:41:14 > 0:41:16A lot of berries on there.
0:41:16 > 0:41:19About that size, you're talking about 9,500 eggs.
0:41:21 > 0:41:26The number of eggs increases exponentially with size.
0:41:26 > 0:41:30'The fishermen have agreed to mark fertile females with a notch in the tail.
0:41:30 > 0:41:35'And the council has made it illegal for anyone to land them.'
0:41:35 > 0:41:38Due to a by-law that was introduced in our district in 1998,
0:41:38 > 0:41:42this individual cannot be landed now. It's illegal to land it
0:41:42 > 0:41:45and there's repercussions in the industry if you do.
0:41:45 > 0:41:48- So we have to return them immediately by law.- OK.
0:41:48 > 0:41:53The V notch will take three years to grow out.
0:41:53 > 0:41:58In that time, a fertile female could spawn hundreds
0:41:58 > 0:42:00of young lobsters to replace the ones being caught.
0:42:00 > 0:42:03With the numbers of lobsters that we've seen today
0:42:03 > 0:42:07and the care they're taking to ensure this is a sustainable fishery,
0:42:07 > 0:42:10I think they'll be fishing lobsters here for many years to come.
0:42:17 > 0:42:20Unlike the rocky shores that surround much of Britain,
0:42:20 > 0:42:24our east coast is mainly soft sediment.
0:42:26 > 0:42:29In the sea, the sands are swept by the tide
0:42:29 > 0:42:32to form an array of shifting sandbanks.
0:42:36 > 0:42:39Down in the Thames Estuary, I took to the water
0:42:39 > 0:42:40in my favourite form of transport
0:42:40 > 0:42:45to uncover an intriguing part of our country's maritime history.
0:42:45 > 0:42:49There's nothing more reassuring on a cold night at sea
0:42:49 > 0:42:53than the familiar sight of a lighthouse flashing away in the darkness,
0:42:53 > 0:42:57letting you know exactly where you are and keeping you off the rocks.
0:43:02 > 0:43:05Out here on the east coast, the real problem isn't the rocky shores,
0:43:05 > 0:43:08but it's these treacherous sandbanks.
0:43:08 > 0:43:11They're just as dangerous, but you can't build a lighthouse on them.
0:43:11 > 0:43:16So how do you stop ships from running aground when you can't see the danger?
0:43:17 > 0:43:19You anchor a light ship over it.
0:43:24 > 0:43:28A lightship is just that, a cross between a lighthouse and a ship.
0:43:28 > 0:43:32They were invented 280 years ago.
0:43:32 > 0:43:34Up until the 1980s,
0:43:34 > 0:43:39they had a crew of hardy souls on board all year round.
0:43:43 > 0:43:47These days, our light ships are all fully automated.
0:43:47 > 0:43:50They're the only ships on our seas with no-one on board.
0:43:50 > 0:43:53This is the Trinity House vessel alert.
0:43:53 > 0:43:56They're responsible for all of our lightships and buoys at sea.
0:43:56 > 0:44:00Today we're heading out to the Sunk Centre lightship.
0:44:02 > 0:44:07It's a rare opportunity to see for myself how today's lightships work.
0:44:11 > 0:44:14With Felixstowe on one side, Harwich on the other
0:44:14 > 0:44:17and Tilbury just to the south,
0:44:17 > 0:44:21this is one of the busiest shipping lanes in Britain.
0:44:24 > 0:44:27Navigating round here is really quite complicated
0:44:27 > 0:44:30cos there's these great sandbanks that run out
0:44:30 > 0:44:32pretty much north east to south west.
0:44:32 > 0:44:36It means the ships can't make a beeline for our important eastern ports.
0:44:36 > 0:44:40Many of the sandbanks lie below the surface,
0:44:40 > 0:44:44so it's vital they're clearly marked to stop ships running aground.
0:44:46 > 0:44:49Captain of the Alert is Roger Swinney.
0:44:49 > 0:44:54What fascinates me, Roger, is that in these days with all this modern technology -
0:44:54 > 0:44:58look what we're surrounded with on this ship, radar, GPS, you name it -
0:44:58 > 0:45:03that we still need lights to mark some of the most dangerous hazards at sea.
0:45:03 > 0:45:05Do we still really need the lights?
0:45:05 > 0:45:08Yes, certainly. There are dangerous banks round there.
0:45:08 > 0:45:09They're very shallow.
0:45:09 > 0:45:13You've only got to take your eye of the electronics for a little while.
0:45:13 > 0:45:16There are so many other things, radios and faxes.
0:45:16 > 0:45:21If you fail to make a course alteration it would be easy for a ship to run aground.
0:45:21 > 0:45:27So you've always got that as a check to make sure you are where you think you are.
0:45:27 > 0:45:30Roger remembers what it was like back in the days
0:45:30 > 0:45:34when men had to live on lightships to keep the light burning.
0:45:34 > 0:45:36It took a very special breed to go out there,
0:45:36 > 0:45:40it's not like a lighthouse which is obviously pretty static,
0:45:40 > 0:45:44you're out there leaping up and down in horrendous weather.
0:45:44 > 0:45:47And you had to be able to get on with people.
0:45:47 > 0:45:49If you're cramped up on the same boat
0:45:49 > 0:45:52it's difficult to get away from each other
0:45:52 > 0:45:55so you have to put up with people's little habits
0:45:55 > 0:45:59that, after a few days, you might find quite irritating.
0:45:59 > 0:46:03The crew of seven would live on board for a month at a time.
0:46:03 > 0:46:06Now the ships are solar powered and fully automatic,
0:46:06 > 0:46:09but they still need regular maintenance.
0:46:09 > 0:46:13Bit tricky, this, we've come out here, and it's not that rough,
0:46:13 > 0:46:16but the tide is on the turn.
0:46:16 > 0:46:19So we stand a chance of just slewing round.
0:46:19 > 0:46:21Roger's busy up there getting it right.
0:46:21 > 0:46:25'Five metres off parallel. And two metres to come ahead.'
0:46:25 > 0:46:27One metre to astern.
0:46:27 > 0:46:29He's doing a good job, isn't he?
0:46:29 > 0:46:31He is. In line fore and aft.
0:46:36 > 0:46:40I've always wanted to do this. I've sailed past these things a lot
0:46:40 > 0:46:44and there's always been that thing, "I wonder what it's like on there."
0:46:44 > 0:46:47Looks like I'm going to get on. Great.
0:46:47 > 0:46:48All right, James?
0:46:48 > 0:46:52We'll get a bit closer, once we're happy she's steady we'll get across.
0:46:59 > 0:47:02OK, she's gotten away so just hold fire till she's back.
0:47:04 > 0:47:06All right.
0:47:06 > 0:47:11Half a metre to come astern, if you can. Bow's starting to open. About a metre off.
0:47:19 > 0:47:22It feels strange coming onto a completely empty ship.
0:47:22 > 0:47:24Feels a bit wrong somehow.
0:47:26 > 0:47:31James shows me inside where the crew of Sunk Centre lightship used to live.
0:47:31 > 0:47:34Through one of the watertight doors,
0:47:34 > 0:47:38just get that locked back cos it'll swing and smash us. OK.
0:47:41 > 0:47:45This would have been part of the accommodation as well.
0:47:45 > 0:47:47What would this have been?
0:47:47 > 0:47:48An old mess room,
0:47:48 > 0:47:52relaxation room, couple of sofas, maybe a little coal fire in the corner.
0:47:52 > 0:47:55- Oh, that's nice. - Yeah, little furnace.
0:47:55 > 0:47:57Something to make it a bit like home.
0:47:57 > 0:48:00Yeah, creature comforts of home, really.
0:48:02 > 0:48:05The crews would spend a month at a time on the ships.
0:48:07 > 0:48:09They did their best to keep morale up.
0:48:15 > 0:48:18Too bad it's got such an empty feel about it.
0:48:18 > 0:48:19Yeah, she does now.
0:48:19 > 0:48:22- So what was this space then?. - This is the old engine room.
0:48:25 > 0:48:29It's so strange being in a place where this many men
0:48:29 > 0:48:31spent months and years of their lives living here.
0:48:31 > 0:48:34And it would have taken a really special breed of person
0:48:34 > 0:48:37to have lived out here for all that time.
0:48:37 > 0:48:40I just would have loved to have had a go at it myself.
0:48:50 > 0:48:54The tour may be over, but we still have a job to do.
0:48:54 > 0:48:57You got me set up, I've got me torch and me gas detector.
0:48:57 > 0:48:58Gas detector there as well.
0:48:58 > 0:49:01I've got a gas detector because it's an enclosed space
0:49:01 > 0:49:04and this thing'll pick up any low oxygen readings
0:49:04 > 0:49:07due to say, anything being rusty.
0:49:07 > 0:49:09Lots of rust, eats up the oxygen.
0:49:09 > 0:49:13There's lots of batteries in here, so this picks up any gases from the batteries.
0:49:13 > 0:49:18The solar panels charge a bank of batteries during the day,
0:49:18 > 0:49:20to power the light at night.
0:49:20 > 0:49:22They need to be checked every six months.
0:49:22 > 0:49:26These are standard lead acid batteries like you might have in your car.
0:49:26 > 0:49:29- Yes, exactly the same. - But there's a lot of them.
0:49:29 > 0:49:31Yeah. A lot more of them.
0:49:31 > 0:49:34- How is it?- Dry on these two. See that, that's going off.
0:49:34 > 0:49:37- Because of that?- Coming out of that.
0:49:37 > 0:49:40Yeah, picking up the hydrogen.
0:49:40 > 0:49:43That's a signal for us to go out, we're getting too much bad gas
0:49:43 > 0:49:46from these batteries so we'll step outside for a minute.
0:49:50 > 0:49:51There you go, so they work.
0:49:51 > 0:49:54All that is is the fumes coming from the battery.
0:49:54 > 0:49:57'Once the gas has cleared,
0:49:57 > 0:50:01'we head back in to top up the batteries with distilled water.'
0:50:01 > 0:50:05- If you start pumping. - Ready?- Go on. Away you go.
0:50:07 > 0:50:10- Good system that, James. - Check another one.
0:50:10 > 0:50:13That one's quite happy. That's going off.
0:50:13 > 0:50:16- OK. - BEEPING
0:50:16 > 0:50:18That one's happy as well.
0:50:18 > 0:50:21The light is mounted on a 12-metre tower
0:50:21 > 0:50:25and it can be seen for 15-nautical miles.
0:50:26 > 0:50:29Each lightship flashes at a different frequency
0:50:29 > 0:50:32so they can all be identified by ships.
0:50:32 > 0:50:36- So that is the light, the business end? - That's the main light in there.
0:50:36 > 0:50:39- It's huge.- The optic is huge, but the bulb itself
0:50:39 > 0:50:43- is probably no bigger than that. - I see.- Couple of inches.
0:50:43 > 0:50:45This is where the light vessels come from,
0:50:45 > 0:50:49from marking the sandbanks in the Thames estuary on the east coast.
0:50:49 > 0:50:52Oh, I really like that, this was the birthplace of light vessels.
0:50:52 > 0:50:55- Neat feeling, isn't it? - Yeah, it's good.
0:50:55 > 0:50:58We've stopped making light ships now.
0:50:58 > 0:51:03In the future, the job will be done by a new generation
0:51:03 > 0:51:05of cost-effective, hi-tech marker buoys.
0:51:05 > 0:51:07I, for one, am going to miss them.
0:51:13 > 0:51:17Our expedition to understand the secret of the grey seal's success
0:51:17 > 0:51:21is coming to an end on the island of Lindisfarne.
0:51:22 > 0:51:26Over the last decade, harbour seal numbers have plummeted
0:51:26 > 0:51:27while grey seals have been going up.
0:51:27 > 0:51:31They live in the same places, they're very closely related,
0:51:31 > 0:51:36so what is it that makes grey seals so much more successful than harbour seals?
0:51:36 > 0:51:41Tooni's joining a scientist who's trying to solve this puzzle.
0:51:43 > 0:51:47There are a number of theories as to why grey seals are doing better than harbour seals.
0:51:47 > 0:51:50Now, both species are hard to approach on land,
0:51:50 > 0:51:53but in order to get more of an insight into their ecology,
0:51:53 > 0:51:57I need to find a place where the two species co-exist.
0:52:02 > 0:52:05I'm joining Ailsa Hall on a trip to a site near Lindisfarne
0:52:05 > 0:52:08where we should be able to find both species.
0:52:10 > 0:52:15Ailsa's been studying grey and harbour seals for over 20 years.
0:52:15 > 0:52:19In that time, grey seal numbers have reached over 150,000
0:52:19 > 0:52:24while harbour seals have fallen to less than 40,000.
0:52:25 > 0:52:29What are the main differences between the grey seals and the harbour seals?
0:52:29 > 0:52:33Well, the grey seals are a bigger mammal.
0:52:33 > 0:52:35How big do they get?
0:52:35 > 0:52:39Get up to 150 kilos for a female, 200 kilos for a male.
0:52:39 > 0:52:41Two or three times your weight.
0:52:41 > 0:52:45About your height! Whereas the harbour seal is much smaller.
0:52:45 > 0:52:49As well as being smaller, harbour seals, like this one,
0:52:49 > 0:52:54have wider eyes and shorter muzzles than the grey seal behind it.
0:52:54 > 0:52:58They might both be seals, but these are separate species
0:52:58 > 0:53:01and they can't interbreed.
0:53:01 > 0:53:03Harbour seals are also known as common seals,
0:53:03 > 0:53:06but they're far less common than greys in the North Sea.
0:53:06 > 0:53:11Why do you think the grey seals are doing so well and the harbour seals not so much?
0:53:11 > 0:53:15We've got a number of theories we've been looking at.
0:53:15 > 0:53:18One of the things we're looking at here is what they eat.
0:53:18 > 0:53:22And how the diet is the same or different between the two species.
0:53:22 > 0:53:25So, the problem is we can't watch them eating,
0:53:25 > 0:53:31but there are other ways we can see what they've been preying on.
0:53:31 > 0:53:33I have a feeling I know what's coming.
0:53:35 > 0:53:38Ailsa finds out what the seals have been eating
0:53:38 > 0:53:42by examining their excrement, known as "skats".
0:53:44 > 0:53:50Long before we get close to them, the grey seals and harbour seals scarper into the water.
0:53:50 > 0:53:54What they've left behind is easy to identify.
0:53:54 > 0:53:56Smell that.
0:53:56 > 0:53:58Do you know what, I can smell it from here?
0:53:58 > 0:54:01All right?
0:54:01 > 0:54:04We think this is probably all one skat, actually.
0:54:04 > 0:54:06- The whole of this. - There's more there.
0:54:06 > 0:54:10I think that's a separate one. This would be one, even that.
0:54:10 > 0:54:13It's just like a pooper scooper.
0:54:13 > 0:54:17Put your hand in the plastic bag. Scoop the skat together.
0:54:17 > 0:54:23Not trying to miss any parts that might have the hard parts in.
0:54:23 > 0:54:29Can you tell just from looking at these samples which species they've come from?
0:54:29 > 0:54:33Not by looking at them no, obviously this region there were more grey seals
0:54:33 > 0:54:35so these are likely to be grey seal skats.
0:54:35 > 0:54:40But the size of these, looking at them, my guess would be that's it's a grey seal male.
0:54:40 > 0:54:44Normally Ailsa would analyse the samples in the lab,
0:54:44 > 0:54:47today we're going to have a preliminary look
0:54:47 > 0:54:50to see what this grey seal has been eating.
0:54:50 > 0:54:54We're looking for otoliths - the hard ear bones of fish
0:54:54 > 0:54:56that pass through seals undigested.
0:54:58 > 0:55:01In recent years, there's been a collapse in stocks
0:55:01 > 0:55:04of the sand eels that both species prey on.
0:55:04 > 0:55:06Ailsa's research suggests grey seals
0:55:06 > 0:55:09have found a way to adapt to the change.
0:55:09 > 0:55:11We do see differences between the two species.
0:55:11 > 0:55:15The grey seals' diet seems to be dominated by the larger species,
0:55:15 > 0:55:19the larger sand eels and cod, haddock, whiting, that kind of thing
0:55:19 > 0:55:23and the harbour seals take smaller more localised prey
0:55:23 > 0:55:27because their foraging areas are much closer in shore.
0:55:27 > 0:55:30'If this theory is correct and the grey seals
0:55:30 > 0:55:33'are going further to find new sources of food,
0:55:33 > 0:55:36'we'd expect to find the bones of bigger fish species
0:55:36 > 0:55:39'like cod and haddock in their skats.
0:55:39 > 0:55:41'It's a painstaking business.'
0:55:41 > 0:55:45When you pick up the skat, you want to get all the skat.
0:55:45 > 0:55:49- Was that an otolith? - I think it might be. That looks like an otolith to me.
0:55:49 > 0:55:54We soon discover three ear bones in the skat.
0:55:54 > 0:55:58What do these bones tell you about what the seals have been feeding on?
0:55:58 > 0:56:01We know this was the skat we collected
0:56:01 > 0:56:06that we think came from a grey seal and these are relatively large otoliths,
0:56:06 > 0:56:11ear bones, possibly from a cod or a haddock, larger fish species.
0:56:11 > 0:56:13So that tells us that these animals,
0:56:13 > 0:56:17certainly the one that collected, are still preying on the larger fish.
0:56:17 > 0:56:20If they're finding prey this large,
0:56:20 > 0:56:24they must be foraging much further offshore than the harbour seals.
0:56:24 > 0:56:28Being able to go further and find different sources of food
0:56:28 > 0:56:31could be giving the grey seals their advantage.
0:56:31 > 0:56:37Where both species live side by side like here at Lindisfarne,
0:56:37 > 0:56:42the grey seals are out-hunting and out-competing their smaller neighbours.
0:56:42 > 0:56:47On the face of it, it seems the bigger more physically robust grey seal
0:56:47 > 0:56:50can adapt quicker to environmental change because it can forage
0:56:50 > 0:56:53further afield than the much smaller harbour seal.
0:57:00 > 0:57:04With its size, strength and ability to travel
0:57:04 > 0:57:07hundreds of miles across the North Sea,
0:57:07 > 0:57:10the grey seal is a formidable predator.
0:57:11 > 0:57:15With our expedition at an end, we leave the Farne Islands behind us.
0:57:15 > 0:57:18Well, for me the favourite thing was,
0:57:18 > 0:57:20aside from the obvious sheer joy of diving with them,
0:57:20 > 0:57:24which you can't deny, was just seeing how
0:57:24 > 0:57:28they are so physiologically adapted for diving.
0:57:28 > 0:57:32They're just such brilliant divers, absolutely great.
0:57:32 > 0:57:35And you see them up close and they are just such chunky,
0:57:35 > 0:57:38bulky, physically healthy animals.
0:57:38 > 0:57:41They look like the ultimate survivor in the marine environment.
0:57:41 > 0:57:46They're fantastically long-lived and sentient intelligent creatures
0:57:46 > 0:57:49and you can see it in the way that they learn to forage.
0:57:49 > 0:57:52Things that I might have taken for granted, to really study it
0:57:52 > 0:57:55over these days has been a complete pleasure. Brilliant.
0:57:55 > 0:57:57Next time on Britain's Secret Seas,
0:57:57 > 0:58:00we reveal the mysteries of the south.
0:58:00 > 0:58:05- Explore the secret life of our seahorses... - I just think they're so magical.
0:58:05 > 0:58:09Solve the puzzle of a 400-year-old shipwreck...
0:58:09 > 0:58:11This is like finding a pharaoh's tomb.
0:58:11 > 0:58:14And get up close with the fearsome conger eel.
0:58:30 > 0:58:33Subtitles by Red Bee Media Ltd
0:58:33 > 0:58:36E-mail subtitling@bbc.co.uk