0:00:04 > 0:00:10The power of the sun drives the seasons, transforming our planet.
0:00:11 > 0:00:16Vast movements of ocean and air currents bring dramatic change
0:00:16 > 0:00:18throughout the year.
0:00:22 > 0:00:26And in a few special places, these seasonal changes
0:00:26 > 0:00:30create some of the greatest wildlife spectacles on earth.
0:00:35 > 0:00:38The seas along the Pacific coast of North America
0:00:38 > 0:00:41can be some of the richest on the planet.
0:00:45 > 0:00:50These coastal waters create the perfect conditions
0:00:50 > 0:00:53for the greatest explosion of life on Earth.
0:00:53 > 0:00:58It's driven by some of the tiniest creatures.
0:00:58 > 0:01:02As their numbers multiply, they feed vast shoals of fish,
0:01:02 > 0:01:06which in turn provide food for ever larger hunters.
0:01:10 > 0:01:15Billions of lives will be shaped by this immense bloom.
0:01:19 > 0:01:21And the mightiest hunter of them all
0:01:21 > 0:01:26has devised a remarkable way to harvest this great feast.
0:02:02 > 0:02:05It's January.
0:02:05 > 0:02:10Both land and sea are locked in the depths of winter.
0:02:15 > 0:02:19The seas along the coast of Alaska and British Columbia
0:02:19 > 0:02:23can become the richest on Earth.
0:02:23 > 0:02:25But for the moment,
0:02:25 > 0:02:26they lie dormant.
0:02:28 > 0:02:33The time of great feasting is many months away,
0:02:33 > 0:02:37and a number of magical changes must first take place.
0:02:40 > 0:02:44The most crucial change will be driven by the sun.
0:02:46 > 0:02:48But now it is weak,
0:02:48 > 0:02:51and offers little to those trapped here for winter.
0:02:58 > 0:03:01This coastline, a maze of islands
0:03:01 > 0:03:07and inlets carved by glaciers, will also shape this great event.
0:03:09 > 0:03:13For now, it remains shrouded in cold.
0:03:13 > 0:03:16Only the toughest can survive.
0:03:19 > 0:03:23Steller sea lions huddle together to share warmth.
0:03:25 > 0:03:28It's 15 degrees below zero.
0:03:36 > 0:03:39They have little choice but to suffer this,
0:03:39 > 0:03:42the coldest Alaskan winter on record.
0:03:52 > 0:03:57The shoals of fish they depend on spend winter in the deepest water.
0:04:01 > 0:04:04For now, the fishing is hard.
0:04:08 > 0:04:12It's an unforgiving place to raise a family.
0:04:15 > 0:04:19Conditions are so severe that mothers must suckle their young
0:04:19 > 0:04:21for up to three years.
0:04:24 > 0:04:26SEAL BARKS
0:04:31 > 0:04:36For this pregnant sea lion, the risks are even greater.
0:04:38 > 0:04:42The seas must come to life in good time for the arrival of her pup,
0:04:42 > 0:04:45and at this stage, the odds don't look good.
0:04:52 > 0:04:58For now, all she can do is wait for the sun to bring change.
0:05:07 > 0:05:10These seas have the potential to be so rich
0:05:10 > 0:05:12at the height of the great feast
0:05:12 > 0:05:16that they will attract animals from across the vast Pacific.
0:05:19 > 0:05:23And 3,000 miles away, in the waters of Hawaii,
0:05:23 > 0:05:28another mother is about to embark on an epic journey.
0:05:36 > 0:05:40This humpback whale has already given birth.
0:05:46 > 0:05:50Her calf is just a few weeks old.
0:05:52 > 0:05:55He stays close to his mum.
0:06:08 > 0:06:13The difference between Hawaii and Alaska could hardly be greater.
0:06:20 > 0:06:22These are calm,
0:06:22 > 0:06:28warm waters with few predators, an ideal nursery for the youngster.
0:06:30 > 0:06:35The calf is now drinking 400 litres of milk every day,
0:06:35 > 0:06:40building up strength for the long voyage he'll soon have to undertake.
0:06:48 > 0:06:53More than 5,000 humpbacks come to Hawaii each year.
0:06:59 > 0:07:04The males, lured here in the hope of mating, compete among themselves
0:07:04 > 0:07:07with great shows of strength.
0:07:26 > 0:07:30But none of these whales can actually feed here.
0:07:32 > 0:07:37For these tropical waters are comparatively lifeless.
0:07:41 > 0:07:47The ocean's greatest riches are only to be found in colder seas.
0:07:47 > 0:07:52So, all these whales must return to the North Pacific to feed.
0:07:57 > 0:08:02The playful calf suckles from his mother every day.
0:08:04 > 0:08:06But she hasn't had anything to eat
0:08:06 > 0:08:10since she left Alaska over four months ago,
0:08:10 > 0:08:13and she won't feed again until she returns.
0:08:21 > 0:08:28Like the pregnant sea lion, this mother has to get her timing right.
0:08:28 > 0:08:30She must arrive in Alaska
0:08:30 > 0:08:34for the moment when the seas are at their richest, full of fish.
0:08:38 > 0:08:42Their journey north will take three months.
0:09:07 > 0:09:12Back in Alaska, the seas are starting to awaken.
0:09:15 > 0:09:21It's March, and as the sun gathers strength, winter loosens its grip.
0:09:29 > 0:09:33For the sea lions, things are beginning to look up.
0:09:36 > 0:09:40The sun is drawing life from the depths.
0:09:50 > 0:09:54With each passing day, the sun warms the water for longer,
0:09:54 > 0:09:58penetrating deep into the mineral-rich waters.
0:10:00 > 0:10:04Fertilising nutrients of phosphorous and nitrogen
0:10:04 > 0:10:08fuel a miraculous change that is just beginning.
0:10:12 > 0:10:16Empty seas start to come to life.
0:10:21 > 0:10:26As we enter an enhanced view of this microscopic world,
0:10:26 > 0:10:30we see the beginnings of a magical transformation.
0:10:32 > 0:10:36Phytoplankton - tiny floating plants - emerge.
0:10:43 > 0:10:47Each is scarcely bigger that a speck of dust.
0:10:47 > 0:10:53But together, these plankton will bloom in such immense numbers
0:10:53 > 0:10:55that they transform lifeless seas.
0:10:59 > 0:11:03And whether that happens this year is yet to be determined.
0:11:12 > 0:11:14All creatures here,
0:11:14 > 0:11:17from the sea lions to the migrating whales,
0:11:17 > 0:11:21ultimately depend on these miniature plants.
0:11:25 > 0:11:30For one creature that relies directly on the plankton,
0:11:30 > 0:11:32this is the moment to emerge.
0:11:35 > 0:11:39Pacific herring have spent the winter
0:11:39 > 0:11:41in the depths of the fjords,
0:11:41 > 0:11:45but they now rise up and head for the shallow coast.
0:11:45 > 0:11:48Stimulated by the sun and the warming water,
0:11:48 > 0:11:51they gather in their hundreds of millions.
0:11:54 > 0:11:57But they're not drawn here to feed.
0:12:00 > 0:12:04They're following an irresistible urge to breed.
0:12:09 > 0:12:12Groups of males sweep through the shallows
0:12:12 > 0:12:17and release their sperm in vast milky clouds.
0:12:22 > 0:12:26The females follow, covering the seabed with eggs.
0:12:31 > 0:12:34Such a concentration of fish
0:12:34 > 0:12:37is just what the sea lions have been waiting for.
0:13:06 > 0:13:08The herring won't be here for long,
0:13:08 > 0:13:13the sea lions must make the most of the fishing while it lasts.
0:13:18 > 0:13:23Other predators gather, also hungry after the lean winter.
0:13:28 > 0:13:35This short-lived bounty is a magnet for millions of migrating birds.
0:13:56 > 0:14:01This is just the first, brief course in the great feast.
0:14:01 > 0:14:06The herring spawning will be over in a matter of days,
0:14:06 > 0:14:10and the shoals of fish will then scatter along the coast.
0:14:14 > 0:14:18The herring have spawned on an astonishing scale.
0:14:21 > 0:14:26They turn hundreds of miles of coastline white with spawn.
0:14:28 > 0:14:34In this bay alone, they have laid 800 billion eggs.
0:14:44 > 0:14:46The herrings' spawning is so timed
0:14:46 > 0:14:49that when the next generation hatch in a few weeks,
0:14:49 > 0:14:52they'll be able to feed on the growing plankton.
0:15:01 > 0:15:06And this year, the herring appear to have timed it just right.
0:15:08 > 0:15:11The minute plant plankton,
0:15:11 > 0:15:15the driving force behind the seas' transformation,
0:15:15 > 0:15:17are starting to bloom.
0:15:17 > 0:15:21Great swathes of sea grow green with life.
0:15:28 > 0:15:32The humpbacks are still out in the middle of the Pacific.
0:15:35 > 0:15:39They've missed the first taste of the great feast.
0:15:41 > 0:15:43At just eight weeks old,
0:15:43 > 0:15:48the young calf must cross the biggest ocean in the world.
0:15:59 > 0:16:03His mother will only swim as fast as her young calf,
0:16:05 > 0:16:08as he tires, she supports him from beneath.
0:16:31 > 0:16:36She's been living off her fat reserves for the last six months,
0:16:36 > 0:16:39and has lost a third of her body weight.
0:16:43 > 0:16:46She's close to starving.
0:16:55 > 0:16:59It will be a further two months before mother and son
0:16:59 > 0:17:02reach their feeding grounds in the North Pacific.
0:17:08 > 0:17:11It's May, early summer in Alaska,
0:17:11 > 0:17:15and the days are getting ever longer.
0:17:17 > 0:17:21The sun continues to fuel the growth of microscopic plants
0:17:21 > 0:17:24that make up the plankton bloom.
0:17:30 > 0:17:33They're joined by a growing community
0:17:33 > 0:17:38of tiny animals - zooplankton.
0:17:43 > 0:17:47These are the first creatures to feed on the bloom.
0:17:56 > 0:17:59Over the coming months they will multiply,
0:17:59 > 0:18:02crowding the surface waters in their trillions.
0:18:02 > 0:18:07The next stage of the great feast is underway.
0:18:21 > 0:18:25All life here depends on this plankton bloom.
0:18:30 > 0:18:33The herring feed on it directly.
0:18:33 > 0:18:37The greater the bloom, the more abundant the shoals.
0:18:43 > 0:18:49And the fish themselves become food for the larger hunters.
0:18:53 > 0:18:57But the shoals of herring are now spread far and wide,
0:18:57 > 0:19:02and once again for the sea lions, the fishing is tough.
0:19:03 > 0:19:06They must venture further to find food.
0:19:09 > 0:19:12But open water is a risky place to fish.
0:19:17 > 0:19:22This male sea lion hunts alone.
0:19:22 > 0:19:27He's three metres long and a ton in weight.
0:19:27 > 0:19:30Few would dare tackle HIM.
0:19:48 > 0:19:50The smaller females travel as a group.
0:19:50 > 0:19:54Keeping a watchful eye in all directions.
0:19:57 > 0:20:02They know that killers lurk in the depths.
0:20:04 > 0:20:10The surface is a dangerous place to linger, especially if you're alone.
0:20:35 > 0:20:40Orca - killer whales.
0:20:42 > 0:20:47The sea lion is wounded, but the killers keep their distance.
0:20:50 > 0:20:55His powerful jaws are still a threat to the hungry orca.
0:20:58 > 0:21:01He struggles towards the safety of land.
0:21:11 > 0:21:14But his injuries are slowing him down.
0:21:39 > 0:21:43Blow-by-blow, they wear him down.
0:21:55 > 0:21:59It's a carefully coordinated attack.
0:22:05 > 0:22:08One killer distracts his attention,
0:22:08 > 0:22:10while another hits his soft underside.
0:22:33 > 0:22:37The richest seas on earth can be treacherous.
0:22:43 > 0:22:45Orca attacks, although savage,
0:22:45 > 0:22:50have little impact on the fate of most sea lions.
0:22:56 > 0:22:59Their survival depends more on the tiny plankton
0:22:59 > 0:23:04that sustains the great shoals of fish on which they feed.
0:23:12 > 0:23:15It's now late May.
0:23:15 > 0:23:19The sunlight lasts for 17 hours a day.
0:23:22 > 0:23:24But the bloom will need more than just sun
0:23:24 > 0:23:28if it's to reach its full extent.
0:23:38 > 0:23:40Nutrients held in these waters
0:23:40 > 0:23:44are continuously used up as the bloom increases.
0:23:46 > 0:23:51If they're exhausted too early, the plankton will die
0:23:51 > 0:23:53and the food chain will collapse.
0:23:53 > 0:23:56The effects will be felt by all.
0:24:02 > 0:24:05Meanwhile, on the sea lion colony,
0:24:05 > 0:24:09new life is now arriving.
0:24:09 > 0:24:12After a year carrying her pup,
0:24:12 > 0:24:15this mother can at last give birth.
0:24:33 > 0:24:37The pup is utterly dependent on his mum.
0:24:38 > 0:24:41As he makes sense of his new world,
0:24:41 > 0:24:45she encourages him to take his first feed of milk.
0:24:50 > 0:24:54The mother has waited until early summer to have her baby.
0:24:54 > 0:24:58Such a small pup would never survive the winter.
0:25:01 > 0:25:05Along this coast, thousands of pups are born within a matter of weeks.
0:25:05 > 0:25:10Timed to coincide with the better conditions that may lie ahead.
0:25:31 > 0:25:35The migrating humpbacks are still weeks away from Alaska
0:25:35 > 0:25:36and their first meal.
0:25:42 > 0:25:47In these turbulent seas, mother and calf must stay close.
0:25:59 > 0:26:02A huge Pacific storm is brewing
0:26:02 > 0:26:06and heading straight for the coast of British Columbia.
0:26:25 > 0:26:30Directly in its path lies the sea lion nursery.
0:26:32 > 0:26:35The pups are now at the mercy of the elements.
0:26:44 > 0:26:47The mothers must get their young to the safety of higher ground,
0:26:47 > 0:26:50if they can find it.
0:27:02 > 0:27:05In desperation, a mother tries to drag her pup
0:27:05 > 0:27:08away from the gathering tempest.
0:27:35 > 0:27:40A pup swept into the water is unlikely to be seen again.
0:28:15 > 0:28:19As the seas begin to subside, many have survived.
0:28:23 > 0:28:26But others have not.
0:28:48 > 0:28:52There's nothing this mother could have done to save her pup.
0:29:13 > 0:29:18These mighty storms, though devastating for some,
0:29:18 > 0:29:21bring fresh life to the great feast.
0:29:23 > 0:29:25When these storms hit the coast,
0:29:25 > 0:29:29they stir up vital nutrients into the surface waters,
0:29:29 > 0:29:32nutrients that feed the plankton.
0:29:33 > 0:29:38Replenished seas combine with the lengthening days,
0:29:38 > 0:29:40to create a plankton explosion.
0:29:43 > 0:29:46And this has come just in time
0:29:46 > 0:29:50for those at the end of an incredible journey.
0:30:06 > 0:30:08The humpbacks have arrived.
0:30:18 > 0:30:22After 3,000 miles, mother and calf
0:30:22 > 0:30:25have finally made it to the coast of Alaska.
0:30:33 > 0:30:37They join other whales that have also made the long voyage.
0:30:37 > 0:30:42But their journey isn't over, for they have yet to feed.
0:30:47 > 0:30:50They're heading for a particular stretch of coast
0:30:50 > 0:30:53deep in the network of channels,
0:30:53 > 0:30:56where they know they can find the great shoals of herring.
0:30:59 > 0:31:02It's to these ancestral feeding grounds
0:31:02 > 0:31:05that the mother now guides her new calf.
0:31:11 > 0:31:15The unique geography of this coastline
0:31:15 > 0:31:18holds the final secret to this great event.
0:31:22 > 0:31:25Glaciers have carved a landscape
0:31:25 > 0:31:29of deep fjords and islands over tens of thousands of years.
0:31:37 > 0:31:40This patchwork creates a labyrinth
0:31:40 > 0:31:44through which powerful ocean and tidal currents flow,
0:31:44 > 0:31:49bringing up the raw ingredients needed for the bloom.
0:31:49 > 0:31:53It's as if an endless supply of fertiliser
0:31:53 > 0:31:55is being added to the water.
0:31:58 > 0:32:04In other seas, the plankton would be subsiding by now.
0:32:04 > 0:32:07But here, the seas are repeatedly invigorated,
0:32:07 > 0:32:12which fuels the plankton bloom time and again throughout the summer.
0:32:17 > 0:32:20And with the sun at its most powerful,
0:32:20 > 0:32:26all these elements combine to create a plankton bloom of great intensity.
0:32:30 > 0:32:34In July, the ocean is alive.
0:32:37 > 0:32:41This floating community of plants and animals
0:32:41 > 0:32:43is the basis for all life here
0:32:43 > 0:32:47and a bloom of this intensity signals the start
0:32:47 > 0:32:50of a truly great feast.
0:32:54 > 0:32:57Where this rich soup hits the seabed,
0:32:57 > 0:33:00life carpets every available surface.
0:33:12 > 0:33:17The feasting begins with millions of tiny mouths.
0:33:22 > 0:33:29Barnacles sift morsels of plankton brought in on the currents.
0:33:29 > 0:33:33Many of these creatures started their lives as part of the plankton
0:33:33 > 0:33:38before reaching adulthood and settling on the sea floor.
0:33:44 > 0:33:47These animals are giants.
0:33:47 > 0:33:49They filter the plankton-rich water,
0:33:49 > 0:33:53growing larger here than anywhere else in the world.
0:34:03 > 0:34:06Jellyfish gather, forming great swarms.
0:34:15 > 0:34:17They too eat the plankton,
0:34:17 > 0:34:22rising to the surface where it is at its most abundant.
0:34:33 > 0:34:34By late summer,
0:34:34 > 0:34:39the plankton bloom is so vast it radiates across the North Pacific.
0:34:43 > 0:34:48Blooms like these provide Earth with over half of its oxygen.
0:34:50 > 0:34:54This bloom eclipses even the Amazon rainforest
0:34:54 > 0:34:56in sheer abundance of plant life.
0:35:02 > 0:35:04And it is most intense
0:35:04 > 0:35:08where the ocean streams through the maze of coastal waterways.
0:35:15 > 0:35:18The shoals of herring are now at their most plentiful.
0:35:26 > 0:35:29After feeding through the summer months,
0:35:29 > 0:35:31the fish themselves are a good catch.
0:35:31 > 0:35:35The main target for predators now gathering here.
0:35:50 > 0:35:52After enduring the bitter winter,
0:35:52 > 0:35:55the sea lions can enjoy the bounty they've been waiting for.
0:36:11 > 0:36:16Hunting together, they drive the herring to the surface.
0:36:30 > 0:36:36Then, with mesmerising grace, they pick off fish one by one.
0:37:04 > 0:37:10For a few short weeks, they'll have their share of the great feast.
0:37:16 > 0:37:20Others arrive to feed in the coastal waterways.
0:37:26 > 0:37:29Pacific white-sided dolphins.
0:37:34 > 0:37:38They dart in and snatch fish as they go.
0:37:43 > 0:37:48The tidal currents now sweep herring up to the surface.
0:37:55 > 0:38:00Here, they're within diving range of seabirds.
0:38:07 > 0:38:09Murres are the first to find the fish.
0:38:15 > 0:38:20The shoal twists and turns, trying to escape the surface dangers.
0:38:30 > 0:38:35But murres are so fast, they can even out-swim the herring.
0:38:35 > 0:38:41They head off the escape, making the shoal turn in on itself,
0:38:41 > 0:38:43creating a bait ball.
0:38:49 > 0:38:54The birds corral the herring into an ever tighter ball.
0:39:00 > 0:39:02But the commotion hasn't gone unnoticed.
0:39:05 > 0:39:10Gulls, ever the opportunists, are the next to turn up.
0:39:16 > 0:39:22They can dive no more than a metre, so the fish are still out of reach.
0:39:26 > 0:39:29The murres only attack from beneath,
0:39:29 > 0:39:31trapping the fish against the surface.
0:39:38 > 0:39:41But they push the herring within range of the gulls.
0:39:45 > 0:39:47It's a feeding frenzy.
0:40:11 > 0:40:16The table is set for the mightiest predator of them all.
0:40:25 > 0:40:29The humpbacks have reached their feeding grounds.
0:40:32 > 0:40:35After six months without a bite to eat,
0:40:35 > 0:40:38the humpbacks can finally break their fast.
0:40:44 > 0:40:50The whales have learned to target these ready-made balls of fish.
0:41:07 > 0:41:10But they'll need more than just a mouthful,
0:41:10 > 0:41:14and with the feast now in full swing, this is their chance.
0:41:20 > 0:41:25To exploit the vast shoals of herring that are in deeper water,
0:41:25 > 0:41:27they rely on teamwork.
0:41:27 > 0:41:32For these whales have developed a truly remarkable way of hunting.
0:41:45 > 0:41:47WHALE SONG
0:41:50 > 0:41:56The inlets echo to the sound of a mysterious song.
0:42:04 > 0:42:06A curtain of bubbles,
0:42:06 > 0:42:12and a haunting call hold the secret to an ingenious way of fishing.
0:42:36 > 0:42:38This is bubble net feeding.
0:42:46 > 0:42:51A dozen whales work together to harvest the herring bonanza.
0:43:02 > 0:43:05Such fishing requires an extraordinary level
0:43:05 > 0:43:08of intelligence and cooperation.
0:43:11 > 0:43:15The lead whale dives first, she is the bubble blower.
0:43:18 > 0:43:21It's her job to find the fish.
0:43:23 > 0:43:26The rest follow in formation.
0:43:32 > 0:43:37Each takes exactly the same position in every lunge.
0:43:46 > 0:43:48Once she's located the fish,
0:43:48 > 0:43:53the leader blows a net of bubbles that completely encircles the shoal.
0:44:01 > 0:44:05Another whale calls to synchronise the group.
0:44:26 > 0:44:29Panicked by the eerie sound and the blinding bubbles,
0:44:29 > 0:44:32the fish won't cross this fizzing curtain.
0:45:21 > 0:45:26As few as 100 humpbacks have learnt how to feed as a team like this.
0:45:40 > 0:45:43And this is the only place on the planet
0:45:43 > 0:45:45where whales fish in this way.
0:45:56 > 0:45:59At the height of the great feast,
0:45:59 > 0:46:01these humpbacks fish around the clock,
0:46:01 > 0:46:04each eating a ton of herring a day.
0:46:10 > 0:46:15Only man has learnt to exploit the seas on a greater scale.
0:46:30 > 0:46:35As the summer ends, the feast draws to a close.
0:46:41 > 0:46:46The sun is weakening, and with it, the plankton bloom subsides.
0:46:50 > 0:46:56The microscopic plants that brought life to empty seas begin to die.
0:47:02 > 0:47:07The herring descend to spend the winter in the depths.
0:47:14 > 0:47:19Life for the sea lions will be harder once again.
0:47:22 > 0:47:26But they've fed well enough to face the dark days ahead.
0:47:41 > 0:47:45The humpback whales will soon leave these shores.
0:47:51 > 0:47:56It's astonishing to think that some of our world's mightiest creatures
0:47:56 > 0:48:00ultimately rely on some of its tiniest.
0:48:08 > 0:48:11Here along the North Pacific coast,
0:48:11 > 0:48:15the interplay between land, sea and sun
0:48:15 > 0:48:19has produced a bloom of plankton so immense,
0:48:19 > 0:48:23it has created one of nature's great events.
0:48:40 > 0:48:44To capture the spectacle of the great feast,
0:48:44 > 0:48:47the team would face many challenges,
0:48:47 > 0:48:50none greater than filming it underwater.
0:48:50 > 0:48:54It was to lead to some surprising encounters.
0:49:04 > 0:49:07The crew had three weeks in late summer
0:49:07 > 0:49:10to try to film all the underwater drama.
0:49:15 > 0:49:19They wanted to find the bait balls of herring that occur here
0:49:19 > 0:49:21in the hope of discovering exactly how
0:49:21 > 0:49:23the different predators round them up.
0:49:28 > 0:49:31Cameramen Shane Moore and David Reichert
0:49:31 > 0:49:34both have years of experience working here,
0:49:34 > 0:49:38but even they were in for a big surprise.
0:49:40 > 0:49:45The key to filming the bait balls was to first find the predators.
0:49:49 > 0:49:50We're looking for gulls,
0:49:50 > 0:49:53because the gulls tell us where the diving birds are
0:49:53 > 0:49:55that are pushing the herring up,
0:49:55 > 0:50:01so usually our first clue to the good action is gulls,
0:50:01 > 0:50:04distant gulls in the air.
0:50:04 > 0:50:05Lot of diving birds,
0:50:05 > 0:50:07the murres are all here, the auklets,
0:50:07 > 0:50:11they're the ones that bring it all together, so they're all here.
0:50:11 > 0:50:12So, we'll just have to watch it.
0:50:16 > 0:50:19That's something... I think that's some bait right there.
0:50:19 > 0:50:23Bait balls don't last long, so the crew had to get to this one quickly.
0:50:30 > 0:50:35But once in the water, a very careful approach is called for.
0:50:40 > 0:50:45So as not to panic the birds, David eased closer to the action.
0:50:55 > 0:50:58And with this sensitive approach,
0:50:58 > 0:51:01the birds stayed focused on the feeding frenzy,
0:51:01 > 0:51:05giving David the chance for a rather close-up view.
0:51:11 > 0:51:14But with so many predators, the fish were getting hammered,
0:51:14 > 0:51:18the bait ball was gone within minutes.
0:51:22 > 0:51:24It was an encouraging start,
0:51:24 > 0:51:27but to get the full sequence they hoped for,
0:51:27 > 0:51:30the crew would need to film more bait balls.
0:51:30 > 0:51:35And, of course, they weren't the only ones looking for herring.
0:51:41 > 0:51:44It's only in the last five or six or seven years
0:51:44 > 0:51:48that the humpback population here in this area has increased,
0:51:48 > 0:51:50which is really encouraging.
0:51:50 > 0:51:52Look, you can see one way over there.
0:51:56 > 0:51:59It was good to see the whales return,
0:51:59 > 0:52:03but it posed an intriguing safety concern for Shane.
0:52:03 > 0:52:07I think it's extremely unlikely you could get swallowed by a whale,
0:52:07 > 0:52:10but if there is a place, this is the place to do it
0:52:10 > 0:52:11because they're coming up,
0:52:11 > 0:52:14they're very motivated to get this ball of fish,
0:52:14 > 0:52:19and we're right there, and we're just a little thing to a 30 ton whale.
0:52:19 > 0:52:21The good news is I've seen whales swallow birds and other things,
0:52:21 > 0:52:25even big fish that they don't like, and they've stopped and spit it out,
0:52:25 > 0:52:27so way, way in the back of my mind
0:52:27 > 0:52:30is the outside possibility that they might swallow David.
0:52:30 > 0:52:34You didn't tell me that!
0:52:34 > 0:52:36Mindful that there were whales in the area,
0:52:36 > 0:52:38the crew turned their attention
0:52:38 > 0:52:43to filming the other stars of the great feast, Steller sea lions.
0:52:46 > 0:52:48The plan was to dive amongst the kelp
0:52:48 > 0:52:51and wait for the sea lions to come to them.
0:52:51 > 0:52:54If we go in, find a little eddy in there,
0:52:54 > 0:52:57cos the animals are just on that point there.
0:52:59 > 0:53:03This coast has some of the strongest tidal currents
0:53:03 > 0:53:07in the world, essential for fuelling the plankton bloom,
0:53:07 > 0:53:10but not so good if you're swimming against them,
0:53:10 > 0:53:12pushing a bulky camera.
0:53:17 > 0:53:19The current was getting stronger
0:53:19 > 0:53:22and the sea lions were nowhere to be seen.
0:53:26 > 0:53:30David was forced to admit that even the best laid plans
0:53:30 > 0:53:32don't always work.
0:53:32 > 0:53:34That dive was a bit of a mess.
0:53:34 > 0:53:37You know, the currents come up so fast around here
0:53:37 > 0:53:40that as soon as we got down there and got set up,
0:53:40 > 0:53:43the current was going, like, four knots
0:53:43 > 0:53:45and we were just hanging onto kelp,
0:53:45 > 0:53:48and just trying to get in to find some sort of eddy to work in,
0:53:48 > 0:53:51but we never did, and finally we just got washed down.
0:53:53 > 0:53:57The team had to wait for the tide to calm down.
0:53:59 > 0:54:01And it wasn't just the currents
0:54:01 > 0:54:04that made filming sea lions underwater a bit tricky.
0:54:06 > 0:54:09What's really kinda driving us crazy here is all this plankton,
0:54:09 > 0:54:11the water's very green,
0:54:11 > 0:54:15not at all like the tropics, where it's clear and beautiful.
0:54:15 > 0:54:18It's also what feeds everything here
0:54:18 > 0:54:21and that's why we have the great amount of sea lions,
0:54:21 > 0:54:23and all the fish and invertebrates.
0:54:23 > 0:54:30On the next slack tide, it was back into the soupy water to try again.
0:54:30 > 0:54:33They'd have to settle down on the seabed
0:54:33 > 0:54:36and hope the sea lions' inquisitive nature would draw them in.
0:54:40 > 0:54:44And this year's youngsters were definitely not camera-shy.
0:54:49 > 0:54:52The sea lions were obviously comfortable
0:54:52 > 0:54:54getting up close and personal with Shane.
0:54:57 > 0:55:00Sometimes even a bit too personal.
0:55:09 > 0:55:11Even this three-metre long male
0:55:11 > 0:55:14seemed to want his share of the limelight.
0:55:18 > 0:55:23After success with the sea lions, it was time for Shane and David
0:55:23 > 0:55:26to turn their attention back to the bait balls.
0:55:30 > 0:55:34The strengthening tides were bringing more fish to the surface,
0:55:34 > 0:55:36and so, with just a few days left,
0:55:36 > 0:55:40this was their best chance to get the shots they still needed.
0:55:53 > 0:55:57The birds were gorging on herring,
0:55:57 > 0:56:00but at least one fish had a lucky escape.
0:56:00 > 0:56:03The herring, in a panic, look for a place to hide,
0:56:03 > 0:56:05and they found my camera,
0:56:05 > 0:56:07so they'd be up in my view finder,
0:56:07 > 0:56:10and of course they get in between those tubes,
0:56:10 > 0:56:14because everything is trying to eat him, the murres and the...
0:56:16 > 0:56:20There he is. OK.
0:56:20 > 0:56:22This might be the lucky one.
0:56:30 > 0:56:33Big ball of fish!
0:56:33 > 0:56:38It was the best year for bait balls that David and Shane had ever seen.
0:56:40 > 0:56:43And they discovered how each of the predators feeds.
0:56:43 > 0:56:48It's the murres that corral the bait ball against the surface,
0:56:48 > 0:56:51only ever attacking from beneath,
0:56:51 > 0:56:54while the gulls just grab what they can.
0:56:57 > 0:57:01But no-one was prepared for what happened next.
0:57:12 > 0:57:15And David was right there!
0:57:15 > 0:57:21So, what's it like to find yourself that close to a feeding humpback?
0:57:21 > 0:57:23Everything was hitting the ball,
0:57:23 > 0:57:25and I could hear the seagulls, of course,
0:57:25 > 0:57:28cos they were all around, then all of sudden it got quiet
0:57:28 > 0:57:30and they all lifted off, and I thought, "Hmmm..."
0:57:30 > 0:57:34and then sure enough, all the murres dropped out of the bottom,
0:57:34 > 0:57:36and he was right there when I got real close.
0:57:36 > 0:57:40I was like, "Oh!", and his mouth was...
0:57:48 > 0:57:50- Scary?- Yeah, it was scary.
0:57:52 > 0:57:55To capture such astonishing images,
0:57:55 > 0:58:00and for the very first time, was an unforgettable experience.
0:58:00 > 0:58:03Sitting beside that bait ball,
0:58:03 > 0:58:05and there's that moment of tension,
0:58:05 > 0:58:08and that whale just came roaring through there,
0:58:08 > 0:58:11and that's something that's gonna stay with me for ever.
0:58:17 > 0:58:21Shane and David had revealed a dramatic new way
0:58:21 > 0:58:26that humpback whales take advantage of the great feast.
0:58:36 > 0:58:39Subtitles by Red Bee Media Ltd
0:58:39 > 0:58:42E-mail subtitling@bbc.co.uk