The South Pacific's richest store of life is found in the silent underwater world of the pelagic and lagoon fishes. It's estimated that half the fish remaining on our globe are swimming in this great ocean. The Pacific reefs provide a habitat for over 4,000 fish species, five to 10 times the diversity of temperate oceans.
Coral pinnacles on the lagoon floor provide a safe haven for angelfish, butterfly fish, damselfish, groupers, soldierfish, surgeonfish, triggerfish, trumpet fish, and countless more. These fish seldom venture more than a few meters away from the protective coral, but larger fish such as barracuda, jackfish, parrot fish, pike, stingrays, and small sharks range across lagoon waters that are seldom deeper than 30 meters. The external side of the reef is also home to many of the above, but the open ocean is reserved for bonito, mahi-mahi, swordfish, tuna, wrasses, and the larger sharks. Passes between ocean and lagoon can be crowded with fish in transit, offering a favorite hunting ground for predators.
In the open sea the food chain begins with phytoplankton, which flourish wherever ocean upswellings bring nutrients such as nitrates and phosphates to the surface. In the western Pacific this occurs near the equator, where massive currents draw water away toward Japan and Australia. Large schools of fast-moving tuna ply these waters feeding on smaller fish, which consume tiny phytoplankton drifting near the sunlit surface. The phytoplankton also exist in tropical lagoons where mangrove leaves, sea grasses, and other plant material are consumed by far more varied populations of reef fish, mollusks, and crustaceans.
It's believed that most Pacific marine organisms evolved in the triangular area bounded by New Guinea, the Philippines, and the Malay Peninsula. This "Cradle of Indo-Pacific Marinelife" includes a wide variety of habitats and has remained stable through several geological ages. From this cradle the rest of the Pacific was colonized.
While most people use the terms dolphin and porpoise interchangeably, a porpoise lacks the dolphin's beak (although many dolphins are also beakless). There are 62 species of dolphins, and only six species of porpoises. Dolphins leap from the water and many legends tell of their saving humans, especially children, from drowning (the most famous concerns Telemachus, son of Odysseus). Dolphins often try to race in front of ferries and large ships. The commercialization of dolphins in aquariums or enclosures for the amusement of humans is a questionable activity.
Whales generally visit the tropical South Pacific between July and October. Humpbacks arrive in Tonga about this time to give birth in the warm waters off Vava'u. Whales are also commonly seen in the Cook Islands. As the weather grows warmer they return to the summer feeding areas around Antarctica. Since 1900 the number of humpback whales in the South Pacific has declined from 15,000 to less than 1,000. Sadly, Japanese whalers continue to hunt the animals in Antarctica for "scientific purposes," and endangered fin and humpback whales are hidden among the 400 minke whale kills reported each year. Whale meat is openly available at Tokyo restaurants. Conservationists have demonstrated how a living whale can generate over a million dollars in tourism revenue during its lifetime, and Australia, the Cook Islands, Fiji, French Polynesia, New Zealand, Niue, Papua New Guinea, Samoa, Tonga, and Vanuatu have all declared their exclusive economic zones marine mammal sanctuaries.
The coconut crab (Birgus latro) is a crustacean with a hard skeleton on the outside and no bones inside. The animal must periodically shed its skeleton as it grows: Young crabs change shells two or three times a year, while an old crab does so every other year. At these times, the crab is extremely vulnerable and it usually buries itself in the ground until a new shell grows, which can take a month.
The slow-growing crabs mature when they're five years old and can live as long as 40 years, at which time they might weigh four kilograms. The crabs rest in protected holes in the ground, under rocks, or in hollow trees in plantations and forests. Their diet includes fruits, rotting leaves, small animals, and occasionally other coconut crabs, but they're best known for their ability to open coconuts with their strong front claws.
Although coconut crabs live on land, their eggs hatch in the sea. The crabs mate during the rainy season and the female lays her eggs two or three weeks later. The mother carries the eggs around under her belly on land for over a month. When they are ready to hatch, she enters the sea during the evening at high tide and the eggs hatch immediately upon release. The larval crabs float in the water for a number of weeks, before settling in shallow water where the larvae change into tiny crabs. The babies hide in abandoned mollusk shells on the beach until they're large enough to move inland.
Six of the seven species of sea turtles are present in the Pacific (the flatback, green, hawksbill, leatherback, loggerhead, and olive ridley turtles). These magnificent creatures are sometimes erroneously referred to as "tortoises," which are land turtles. All species of sea turtles now face extinction due to ruthless hunting, egg harvesting, beach destruction, and pollution. Sea turtles come ashore from November to February to lay their eggs on the beach from which they themselves originally hatched, but female turtles don't commence this activity until they are 30 years old. Thus a drop in numbers today has irreversible consequences a generation later, and it's estimated that breeding green, hawksbill, and leatherback females already number in the low hundreds. Turtles are often choked by floating plastic bags they mistake for food, or they drown in fishing nets.
Sea urchins (living pincushions) are common in tropical waters. The black variety is the most dangerous: their long, sharp quills can go right through a snorkeler's fins. Even the small ones, which you can easily pick up in your hand, can pinch you if you're careless. They're found on rocky shores and reefs, never on clear, sandy beaches where the surf rolls in.
Most sea urchins are not poisonous, though quill punctures are painful and can become infected if not treated. The pain is caused by an injected protein, which you can eliminate by holding the injured area in a pail of very hot water for about 15 minutes. This will coagulate the protein, eliminating the pain for good. If you can't heat water, soak the area in vinegar or urine for a quarter hour. Remove the quills if possible, but being made of calcium, they'll decompose in a couple of weeks anyway—not much of a consolation as you limp along in the meantime. In some places sea urchins are considered a delicacy: The orange or yellow urchin gonads are delicious with lemon and salt.
Although jellyfish, stonefish, crown-of-thorns starfish, cone shells, eels, and poisonous sea snakes are dangerous, injuries resulting from any of these are rare. Gently apply mentholated spirit, alcohol, or urine (but not water, kerosene, or gasoline) to areas stung by jellyfish. Inoffensive sea cucumbers (bêche-de-mer) punctuate the lagoon shallows. Stonefish also rest on the bottom and are hard to see due to camouflaging; if you happen to step on one, its dorsal fins inject a painful poison, which burns like fire in the blood. Fortunately, stonefish are not common.
It's worth knowing that the venom produced by most marine animals is destroyed by heat, so your first move should be to soak the injured part in very hot water for 30 minutes. (Also hold an opposite foot or hand in the same water to prevent scalding due to numbness.) Other authorities claim the best first aid is to squeeze blood from a sea cucumber scraped raw on coral directly onto the wound. If a hospital or clinic is nearby, go there immediately.
Never pick up a live cone shell; some varieties have a deadly stinger dart coming out from the pointed end. The tiny blue-ring octopus is only five centimeters long but packs a poison that can kill a human. Eels hide in reef crevices by day; most are harmful only if you inadvertently poke your hand or foot in at them. Of course, never tempt fate by approaching them (fun-loving divemasters sometimes feed the big ones by hand and stroke their backs).