The big Blue ocean stories from down under episode 2 free documentary Nature

Goat Island in the Hauraki Gulf, and the reefs are alive with fish. Like nowhere else around mainland New Zealand. Tens of thousands of fish school just metres from the shore. Only 90 kilometres north of Auckland. This is such a special piece of our big blue backyard. That in 1975, Goat Island became New Zealand's first marine reserve. Snapper, crayfish and many other species may be fully protected from us while they remain in the reserve. But life here is full of jeopardy. Human laws don't prevent ocean-going marauders like dolphins calling in for a feed. The aerial assaults of shags and kingfishers. Or the vanguard of predators that lie in wait beyond the boundaries of the reserve. Even those which never leave the safety of the reef as adults face a massive hurdle at the beginning of their lives. Scattered as tiny eggs on the ocean currents, they must somehow find their way back. Guided by the unique sounds of their birthplace. The Goat Island Marine Reserve consists of five kilometres of coastline. From the mudstone platforms of Ōkākari Point. To the rocky cliffs of Cape Rodney. And extends 800 metres out to sea. In the middle of the reserve lies Goat Island itself. Named for goats released as food for shipwrecked sailors around the turn of last century. On the seaward side, spectacular caves are carved out by the waves. Below the surface, they provide shelter for numerous fish. The rocky platforms extend 300 metres out to sea. In a series of stepped reefs towards the sandy bottom. Before the reserve was established, this coastline was mostly barren rock. Decimated by overfishing in the 1950s and 60s. Today, the only word for it is lush. Dense kelp forests now cover much of the reserve. In turn, huge schools of silver drummer have returned to feed on the kelp. Along with other algae eaters like this parori. Grey and blue maumau have also returned in massive numbers. But snapper are probably Goat Island's most famous residents. Outside the reserve, snapper are shy, retiring fish. Rarely seen by divers. Inside the reserve, they are everywhere. They're huge and they appear to feel safe. Some grow so big and distinctive they have names. This is the legendary monkey face. Only the oldest fish turn dark grey and develop this domed forehead. No one knows if monkey face is male or female. Or how old he or she is. Left alone, snapper can outlive most humans. This magnificent fish was probably able to outsmart the spearfishers of the 1960s. And was already living here when Goat Island became a marine reserve nearly 40 years ago. On the reef, fish this big have few natural enemies. But the same can't be said for the schools of small baitfish. These bottlenose dolphins are some of a population of 450 that travel between Northland and Tauranga. Pods frequently visit to raid the reserve's fish stocks. Each adult dolphin needs to eat up to 15 kilos of fish a day. The sheltered reserve is also a perfect training ground where young dolphins learn the pod's fishing techniques. By mimicking the adults. Bottlenose dolphins are highly social and intelligent creatures. It's recently been discovered they even have names for each other. One dolphin will call to a specific individual with a unique whistle. And only that dolphin will respond by echoing the signature call. For now, this pod seems content to play in the safety of the marine reserve. From above, nothing escapes the attention of a colony of pied shags. That occupy prime real estate overlooking Goat Island Bay. It's now March, the end of summer. But the yellow patch beside the eyes shows this pair is just getting ready to breed. Pairs usually stay together for life and often rebuild nests from previous years. But hutukawa twigs are the building material of choice. And this male seems to have found a good source. His nest has a front door. He always arrives by the same branch. The female takes care of construction. While her mate slips out the back door to gather more material. Pied shags breed all year round. So some of the colony's residents already have chicks. While others are just getting started. Below the waves, another cycle of life also starts afresh. Sea urchins, or kina, spawn from November to March. On the seafloor, a female releases around 80 million eggs into the water. While males broadcast their sperm from a high vantage point. The clouds of kina spawn meet in the current and the eggs are fertilised. They then drift and develop for 10 weeks. Most will be eaten by predators. But enough settle to continue the species. Autumn is also the time for another of the reserve's residents to begin its breeding cycle. Crayfish were once among the most overfished species in these waters. But along with snapper, they recovered the quickest. Flourishing in the first 10 years. There are now thousands of these massive crays of breeding age. They may be 10 years old and weigh more than 6 kilograms each. For most of the year, they pack tightly into crevices and caves for mutual protection. Venturing outside during daylight hours could mean death by snapper. This looks like a crayfish made a fatal mistake. But the owner of this shell or carapace is safe inside her cave. In order to grow, crayfish must molt regularly. While their new shells harden, they stay well hidden. The females always molt in autumn just before they breed. Soon, they'll carry their eggs under their tails and won't be able to shed their armour. Crayfish often share their caves with these shy nocturnal fish called big eyes. For years, divers believed that crayfish made noises when approached. But scientists discovered that the noise was produced by the big eyes. All fish respond to sound and most have internal ears. But only a few can vocalise. Big eyes produce this distinctive sound by vibrating their swim bladders, the air-filled sacs that keep them afloat. These sounds may be a way to help the school stay together. Communication in the dolphin pod is much more sophisticated. They're not just keeping in touch with each other, they're hatching plans. The complexities of their highly developed language are still a mystery. But it's not hard to guess what they're discussing. The hunt is on. The peace of an autumn afternoon at the Goat Island Marine Reserve is shattered by the arrival of a pod of bottlenose dolphins. Tail slapping is an effective way to attract attention. It can be heard all over the bay and may very well mean, I've found fish. Bottlenose dolphins feed mostly on small school fish and squid. This rich marine reserve is a perfect place to teach youngsters the pod's various hunting strategies. One technique is to corral the fish before charging into the school. Some dolphins achieve this by swimming around the fish in tight circles, while others herd their quarry toward the beach, trapping them in shallow water. As the dolphins feed, scraps drift down to the snapper waiting below. Snapper will eat almost anything, whether it's dolphin leftovers or the supposedly inedible puffer fish. Many species of puffer fish contain a deadly toxin in their organs, but it seems large snapper might be immune to it. These big fish have formidable jaws, lined with teeth strong enough to crush muscles, break limpets off rocks, and even pierce crayfish's armour. But luckily for this one, it seems monkey face has already eaten. It's mid-afternoon, yet all over the shallow reef, the usually nocturnal crayfish cruise the seafloor, risking attack from predators. They are all males. Most of the year they jam into caves together, but autumn signals the time to fight. Big males go head-to-head to win the best cave, which will attract the most females. Some disputes can be settled with displays of size and strength, but equally matched males have to fight it out. When the victor courts a female like this, they'll spend hours face-to-face, gently stroking each other's antennae. Eventually, the male transfers a package of sperm to the underside of his mate, which she'll use to fertilise up to half a million eggs. This dedicated mother will carry her developing eggs under her tail for the next five months, constantly watched by hungry predators. The bottom-dwelling blue cod are also voracious consumers of just about anything they can sink their teeth into. When a cod attacks, the crayfish momentarily cease fighting and use their armoured antennae to fend off the invader. This cod is persistent, but it nets nothing more than a leg, which the crayfish can regrow when it next molts. On the seafloor nearby, another persistent predator is on the prowl. An 11-armed starfish stalks its relative, the kina. Like their cousins, kina have hydraulically operated tube feet between their rows of spines. They pump water into these tubes, which makes them expand and able to move. They may be relatives, but starfish are voracious predators of kina. When the starfish gets close enough to attack, this kina activates its novel escape tactic. Kina feed mainly on kelp. Each one chews through about two grams a day. They catch drifting fragments with their suckers and move them foot over foot towards their mouths. This is the sound of their munching teeth amplified by their shells, which are natural underwater loudspeakers. Kina have five razor-sharp teeth buried in their underside that make short work of the tough kelp. As the teeth grow continually, chips flake off the cutting edges, which makes them self-sharpening. A herd of munching kina can be a thousand times louder than the ambient sounds of the reef and may be heard kilometres out at sea. The lush fish life of the reef attracts many predators. Fast hunters like kingfish and bronze whaler sharks often make forays into the reserve or close to its boundaries. There's also danger from above. Kookaburras are large kingfishers that were introduced to nearby Kauau Island in the 1860s. They're now frequently seen on the mainland around Goat Island. Our own native kingfisher is not as big and brash as its Australian cousin, but it's quite partial to a fish meal. At Goat Island, they're often perched in trees above the tidal platforms. Small fish are frequently left stranded in rock pools by the receding tide. Sitting ducks for the kingfisher. In the bay, the bottlenose dolphins have also enjoyed a great day's fishing. Now, it's time to do what dolphins do every day. Strengthen the bonds of their pod through play. As the sun sets over the Goat Island Marine Reserve, the dolphin invaders finally head back out to sea. Life on the reef returns to normal. For many fish, dawn and dusk are the busiest feeding times of the day. As a stingray lazes on the seafloor, goatfish forage for prey in the sand recently disturbed by the ray. Goatfish have two barbels on their chin, which are sensitive whiskers tipped with taste buds. They taste the seafloor, looking for small worms and crustaceans. Like goats, they'll eat anything. As night takes hold, the reef life changes. Many of the familiar fishes from the day seek shelter in caves or crevices, as the night predators begin to patrol. The goatfish puts on red pyjamas. This color makes it harder to see in the darkness. Some predatory fish, like this snapper, sleep by night. But new dangers lurk on the reef. A hungry conger eel has spent the day in a cave. By night, it roams the reef, looking for any vulnerable creatures to pick off. Finally, the big eyes, named for their massive, light-sensitive eyes, leave their caves to hunt small creatures floating in the plankton. As they hunt, they call to each other, possibly to keep the school together. Nighttime is also when their neighbors venture out to feed. Crayfish leave their caves on the rocky reef and make long foraging trips up to 100 meters to seek shellfish which live on the sandy seafloor. They gather up this prey to take back to their caves to eat. Cockleshells around cave entrances are a dead giveaway that crayfish have been feeding. Crayfish arms are powerful enough to prise open their victims to devour their flesh. As the sun rises over the Goat Island Marine Reserve, red moki leave their caves to graze amongst the hard pink algae that encrusts the rocks. These moki are hunting for small creatures living in the algae. They suck them in and expel the waste out through their gill slits. In the branches overlooking the bay, the shag families are also waking up. On average, they have three chicks, not all of which will survive to adulthood. One parent always stays with the chicks while the other goes off to fish. They swap shifts at least three times a day. Shags don't plunge dive from a height. Instead, they duck dive. Once underwater, they're remarkable swimmers, methodically checking the reef for small fish. They can hold their breath for three and a half minutes, feeding to depths of around 10 meters. Unlike other seabirds, they have very little waterproofing oil in their feathers. Being waterlogged helps them stay under, but there is a downside. When the water gets cold in winter, shags are susceptible to hypothermia, and waterlogged wings don't fly well. At the end of a dive, the birds often spread their wings to dry and perhaps absorb some warmth from the sun. Then it's home to feed the waiting chicks. Each adult needs to catch 500 grams of fish for itself, but their fast-growing chicks will each gobble up to 800 grams of the marine reserve's inhabitants every day. Small fish are constantly under attack. To survive, they need some sort of protection. Very young trevally often keep company with big snapper. This smart one rides the bow wave by the snapper's head, out of reach from any potential predator, but always keeping on the safe side of the snapper's powerful jaws. As they grow a little bigger, groups of trevally set up mobile cleaner stations on the reef. Fish with parasites come to have them removed, and the trevally get an easy meal. This large porori is a gentle vegetarian, so the little fish are in no danger. A giant blue moki is a more dangerous proposition. Only the biggest of these fish come to Goat Island. They spawn a long way south from here. To swim north against the prevailing currents, moki have to grow very big and strong. This fish, with its worn and tattered fins, may be more than 30 years old, and it knows there's a strict etiquette to these cleaning stations. Even if you accidentally suck one in, never swallow the mouth that cleans you. In the shallow water, the wave action noticeably picks up. With the female crayfish carrying precious eggs beneath their tails, just weeks away from spawning, a major storm surge could threaten this critical stage of their reproductive cycle. The Goat Island Marine Reserve bears the full brunt of a storm rolling in from the Pacific Ocean. The pied shags have no choice but to ride out the storm in their nests, while massive swells pound the beach and the shallow reef. When the storm abates, the damage is obvious. Huge piles of kelp have washed up. It's a feast for many birds that come to feed on small crustaceans caught in the kelp, and on insects attracted to it. Below the surface, extensive patches of rock have been stripped. But the storm may not be the only culprit here. The innocent-looking kina can be a force of destruction. They usually feed on small fragments of kelp. But if their numbers aren't kept in check, they will attack the holdfasts, the root-like structures that anchor the kelp. An out-of-control colony of kina can destroy a whole kelp forest. The relationship between kelp, the kina, and their predators is complex. But scientists studying this reserve for more than 30 years have measured a big decline in kina numbers as their predators re-establish themselves. Kina have no brain, and yet they display cunning in attempts to camouflage themselves by arranging small pebbles and shells on their backs. However, crayfish see through the disguise and are responsible for nearly half of all kina predation. Despite their defences, goat island kina have many foes. So their population is kept in balance, which means the kelp forests and all their numerous inhabitants can flourish here in the reserve. It's now spring, and the countdown begins for a significant annual event for some of the residents of Goat Island Marine Reserve. After five months of carrying their developing eggs under their tails, surviving storm surges and predators, female crayfish are ready to spawn. But first, they must make a journey. Each female leaves her cave in the shallows to walk several kilometres to deeper parts of the reef. They need to time their arrival to the hours just before dawn. Not all will make it. A large blue cod is eager for a crayfish meal, or at least her eggs. But the cod hesitates, because it sees something the crayfish doesn't, as she backs away from the cod. The octopus doesn't even leave a scrap of leg for the cod. A marine reserve has no fences, so many of Goat Island's inhabitants venture beyond its borders. At just five square kilometres, the reserve doesn't match the range of big fish like snapper and boarfish, which make their own decisions on where they'll forage. But they seem to return here time and time again. Monkeyface once disappeared for three years before showing up back in the reserve. As the young trevally grow up, they join schools of fish of similar size and age and leave home to feed in deeper water. In the reverse, jack mackerel are visitors to the reserve, feeding above the kelp forest before heading back out to sea. When the schools leave the safety of the shallows, they run a gauntlet of predators in the deep Hauraki Gulf. As spring turns to summer, beyond the Goat Island reserve, predatory ocean wanderers move in. Marlins swim thousands of kilometres to feed around northern New Zealand. This one rounds up a school of jack mackerel in a technique similar to the bottlenose dolphin, swimming around them to herd the fish into a tight bait ball. Then it charges, knifing the school with its pointed bill to stun and injure the fish, which it will eat at its leisure. This female crayfish has survived her dangerous journey with half a million eggs tucked safely under her tail. And her timing is just right. On the edge of the reef, she discovers dozens of her sisters, all ready to spawn before the day shift predators wake up. Just before dawn, female crayfish release their eggs in unison, entrusting them to the ocean currents. After five long months of maternal protection, millions of crayfish hatchlings float off toward the rising sun to an uncertain fate far out at sea. It's midsummer now in the Goat Island marine reserve. Up above, the warm weather is welcomed by all the resident birds and numerous sharks that venture into the Hauraki Gulf, often coming close to shore. The bronze whalers are now joined by thresher sharks. Hammerhead sharks call in. With eyes so far apart, they have almost 360-degree vision. Short-finned makos can move at deadly speeds. Mako sharks are warm-blooded, with a body temperature up to 7 degrees warmer than the surrounding water. Muscles work more efficiently when warm, which enables them to swim in bursts of up to 100 kilometres per hour. Few cold-blooded fish can match it. And these teeth are designed to make sure nothing a mako catches ever escapes. In the weeks following the crayfish spawning, the invisible cloud of larvae drifts hundreds of kilometres out to sea at the mercy of wind and currents. It's a mystery where it goes. But as it floats, the billions of eggs evolve through a number of larval stages. Magnified, it's possible to see the crayfish eggs hatch into larvae before they're released by the female. Just a few minutes after spawning, each hatchling shapeshifts into this next stage, where the eye stalks are visible. Then, foreshadowing the molting process, which will occur throughout its life, it wriggles free of its tiny exoskeleton and heads for the surface with its siblings. The young crayfish continue to morph into weird forms for the next two years, the longest larval stage of any marine creature. Many fall prey to plankton-eating fish, like this school of adult trevally picking them off at the surface. Finally, the survivors take on a form that's recognisably a miniature crayfish and swim back toward the coast. They're not alone in the plankton soup. They meet up with the larvae of many fish, including snapper and big eye. And even kilometres out at sea, they have the ability to orient themselves towards the shore. But much of our wild coastline is no place for tiny fish and crays to settle down. To find a nice, safe reef, like those around Goat Island, they listen. It's faint, but distinct. A noisy population of kelp-munching kina is a sign of a healthy reef, exactly the kind of home the young animals are looking for. No longer content to drift wherever the ocean takes them, these tiny survivors actively swim towards the kina chorus. As they draw closer to the reef, the baby big eye may be reassured to also hear their own kind. After life in the barren ocean, this marine reserve reef is an oasis of life and colour, a welcome home for thousands of little fish and crustaceans. It's the perfect place to put down roots, with numerous rocky crevices where growing crayfish can hide, lush kelp forests for food and protection from predators, and no interference from humans. Since this first marine reserve was established, 33 more have been created around New Zealand. But still, only a tiny fraction of our coast enjoys this protection. These Goat Island residents don't know how lucky they are to have settled in these five square kilometres of our spectacular big blue backyard. GoatIsland.com