St. John Virgin Islands Marine Life
St. John USVI Marine Life
The Fascinating Sea Creatures of the Virgin Islands
Snorkelers exploring the underwater wonderland awaiting just off the St. John coast will be treated to a vast new world of under sea delights. On these pages, we present interesting sea creatures that you may encounter on your snorkeling expeditions.
This anemone pictured here is called an Orange Ball Corallmorph (Pseudocorynactis caribbeorum) They are usually found in depths of about 20 -80 feet and have one -two inch-long tentacles. They inhabit coral reefs and sandy areas close to the reef. They quickly retract their tentacles if disturbed.
Barracudas can usually be found near the surface. Look for juveniles in mangrove forests, estuaries and shallow sheltered inner reef areas. Adults can grow to be as much as four to six feet long.
The most important thing to remember here is that despite the barracudas ugly and fearsome appearance unprovoked attacks on humans are extremely rare. They will often follow you around the reef opening and closing their mouth to display their big sharp teeth, but not to worry, they are just curious and don’t intend to attack you.
Barracudas often can be found hanging around under boats as this one is:
St. John Life Blog Entry: Barracuda
What Conchs Eat and Who Eats Conchs
Conchs are vegetarians. They graze the seagrass beds of the Caribbean and its vicinity. Sticking out their claw-like operculum and digging it into the sand in front of them, they make use of their strong muscular foot, which is attached to the operculum, and pull the rest of their body forward. In this manner they can pass through over 400 feet of seagrass in a single night, the time when conchs most frequently move about.
Conchs do not eat seagrass. They scrape off the covering of algae that adhere to the blades of grass. The seagrass remains unscathed. To accomplish this the conch uses an organ in its mouth called a radula, which according to Webster’s New Collegiate Dictionary, is “a horny band or ribbon … that bears minute teeth on its dorsal surface and tears up food and draws it into the mouth.
Conchs, in turn, are eaten by several species of predators. First and foremost are human beings. Humans get conchs out of their shells by using tools such as hammers and knives or stoves or freezers. Humans have developed quite a taste for this Caribbean mollusk and every year they consume millions of pounds of conch meat.
The spotted eagle ray is another predator that enjoys a conch dinner. These big, beautiful rays can often be seen gliding over the seagrass beds. (A good place to see spotted eagle rays is Rendezvous Bay on the south coast of the island.) Spotted eagle rays, which can have wingspans of over six feet and weigh more than 500 pounds, can break open a large queen conch shell with one crunch of their powerful jaws.
Interestingly, marine biologists have yet to find pieces of shells in the stomachs of those rays unfortunate enough to be the subject of such an experiment. This indicates that spotted eagle rays can somehow separate the shell from the conch meat and dispose of it.
The seemingly innocuous starfish is another conch predator and has developed a unique way of feasting on conch. Because the conch’s operculum does not completely close off the entrance to the conch’s shell, the starfish can insert one of its arms in the opening, preventing the conch from slipping further back. Then the starfish does an amazing thing; it forces its own stomach out of its body, sticks it inside the conch and digests the conch right inside its own shell.
Divers and snorkelers will often pick up a conch shell only to find it inhabited by a hermit crab. Hermit crabs live in the shells of mollusks that, for some reason or other, have left their homes. The hermit crab will force the conch out of its shell by turning it upside down so that it can’t get away. It then inserts its powerful claws into the shell opening and pulls the conch out. The hermit crab then devours the unprotected animal, and takes over the shell.
The octopus is another animal that dines on conch. It can extract a conch from its shell by using its suction cup-like arms. Evidence of this can often be observed by snorkelers who may notice piles of empty conch shells surrounding an octopus’s den.
Young, very small conch, called rollers, are vulnerable to even more predators, such as sharks and turtles that will eat them, shell and all. Even tinier conch can fall prey to lobsters and triggerfish that will work at crushing or grinding away the conch’s shell, little by little, until they can finally get to the meat inside.
The conch is a truly a tasty dish, so tasty that it is disappearing quickly. Between 1970 and 1980 it is estimated that the conch population decreased by 90% and the decline continues. Human beings may have to curtail their appetite for these creatures, as well as show a greater respect for the seagrass environments that supports them, so that future generations of people, starfish, spotted eagle rays, hermit crabs, sharks, lobsters and triggerfish will have the opportunity to enjoy a hearty conch meal every now and then.
Conch Reproduction and Development
Scientists tell us that conchs have sex in the spring and summer, and will do so as much as possible during that time.
Although to the casual observer all conchs may look alike, some conchs are male and others are female.
The male’s sex organ is called the verge. The female conch is not the only creature to appreciate the male conchs’ verge, so do the predators of the conch, such as crabs and eels, but for a different reason. If they can’t get the whole conch out of its shell, they may feast on the protruding verge. For the conch this will not be such bad news, because unlike other species, his organ can regenerate. Perhaps medical science should look into this amazing ability for application to our human species.
During sex, the male inserts his verge into the vaginal area of the female and releases sperm that will fertilize the female’s almost one half million microscopic eggs. When the eggs mature, they emerge from the female conch attached to a gelatinous string that looks like a thin fishing line. This sticky strand containing the half million eggs could be as much as 80 feet long if it were stretched out from end to end. The female conch, however, uses her claw-like foot, called an operculum, to lightly coat the egg string with sand. She then folds it back and forth forming a mass that looks like a sand sculpture the size and shape of a sea cucumber or a banana.
The mother conch then leaves the mass of eggs in a groove that she makes in the sand and goes off in search of another male, as the mating and egg-laying process will be repeated several times during the season.
Meanwhile, the hundreds of thousands of little embryos left by their mother begin to develop. In about a week they will hatch and the tiny conch larvae, called veligers, will float to the surface and join the masses of other minute sea creatures, called plankton, that drift along at the mercy of waves and currents near the ocean’s surface. During this time, the veligers will survive by eating vegetable plankton. The vast majority of the veligers will be eaten up by bigger and more aggressive animal plankton as well as other predators, such as fish, shrimp, squid and jellyfish.
After about a month, when they are about the size of a grain of sand, the veligers transform into an immature version of an adult conch and sink down to the ocean floor. Here they will need to find a suitable environment of sand and seagrass in order to survive.
At this point, the baby conch will begin to develop its shell, which will at first be soft. The operculum will also be formed at this time, allowing them to move about on the bottom. Being small and having only a soft shell for protection, these tiny creatures are extremely vulnerable. In order to survive the dangerous world in which they have found themselves, they will hide from their predators by using their operculum to dig into the ocean floor around the roots of the seagrass and then covering themselves with the loose sand. They only will come out of hiding at night when they will feed on the algae that grow on the surface of the blades of seagrass.
It will take about four years before the conch reach sexual maturity and develop their characteristic Queen conch shell with its large and beautiful pink, orange, and yellow flaring lip.
Uses of the Conch
When I first came to St. John, grocery store pickings were sparse. It was way better to go out and catch you own dinner. In those days, if you didn’t have any luck catching fish or diving lobsters, you knew you could always get conch.
They were very plentiful and easy to get then, just lying there in the seagrass on the bottom of warm, clear, shallow bays. What’s more, they move so slowly that, unlike fish or lobster, they can’t get away from you.
If the water was shallow enough, you could just reach down and pick them up. In slightly deeper water, all you would need was snorkel gear and a sack. In no time at all, you would be on your way to a delicious and healthy dinner of conch salad, conch stew, or conch in butter sauce.
It is easy to understand why conch was such an important resource to St. Johnians, beginning with the first inhabitants who arrived some 3,000 years ago. Conch meat is an excellent source of nutrition, high in protein and low in fat, not to mention its aphrodisiac qualities.
The conch’s shell is just as sought after as its meat. This was especially so in prehistoric times, when conch shells were made into useful items and tools such as cooking pots, cups, dishes, knives, scrappers, chisels and fishhooks.
The shell’s natural beauty allowed it to be fashioned into jewelry, which was used not only for personal adornment, but also as an article of trade.
The conch’s shell can also be made into a signaling device and musical instrument. By cutting a hole in the tip and blowing into it with pursed lips, a loud trumpet-like sound is produced. It is not uncommon to hear modern day yachtsmen with every sort of electronic device available to them, using a conch shell horn to call for people ashore or to signal other boats.
What we in the West Indies call conch is more specifically known as the “queen conch.” Its scientific name is Strombus gigas, and it belongs to the mollusk family of animals. The queen conch can only be found in a relatively small part of the world, the islands of the West Indies, the Caribbean and Gulf coasts of tropical America from southern Mexico to northern Brazil, southern Florida and the Florida Keys, the Bahamas and Bermuda. It was unknown in the rest of the world until the voyages of Christopher Columbus in the late 15th century.
Columbus learned about conch from the Tainos whom he met in the Bahamas. He described finding conch “as big as the head of a calf” off the coast of southern Cuba. When Columbus brought back specimens of the creature to Spain, Europeans quickly became enamored with the beautiful shells. They were collected as mantelpieces and used to make jewelry and as the raw material with which to carve cameos. During the 19th century thousands of conch shells were shipped to Europe every year for use in the manufacture of fine porcelain.
Conchs, like other mollusks, can produce pearls, which can often be found in antique jewelry. Conch pearls and conch pearl jewelry are still for sale in Nassau, Bahamas. Some are reasonably priced, but individual pearls of top quality may sell for as much as $1000.00 or more.
The orange cup coral is a brightly colored orange coral with flower-like yellow tentacles that extend at night or in areas of low light.
Although the orange cup coral is a hard coral, it’s not a reef-building coral. Also, unlike other corals, the cup coral, does not depend on the symbiotic algae, which shares it’s photosynthesis-created food with the coral animal. Because of this, the cup coral can grow in dark places such as shaded walls, caves and underneath overhanging ledges.
I first noticed orange cup corals on the walls of an rocky indentation on the Tektite snorkel and again on the walls of the caves at Norman Island. Now I see them elsewhere even on the Trunk Bay Underwater Trail.
Cup corals do not seem to be a major problem here in the Virgin Islands as they seem to prefer the darker areas that other corals don’t like and I’ve not seen any great proliferation in all the years that I have been snorkeling around the Virgin Islands.
They are, however, a problem in the Gulf of Mexico where they tend to crowd out other native coral and sponge species. They especially like oil rig platforms where hundreds of thousands of colonies may be found attached a platform.
Pillar Coral is a hard coral, which are usually found on flat or slightly sloping sea floors in depths of between one and 65 feet. They can grow as large as 8 feet tall. Their polyps, which are used for trapping nutrients are usually extended during the daytime.
Flame Box Crab (Calappa flammea)
This unusual crab was photographed at Maho Bay. It’s a flame box crab that inhabits the Caribbean, Gulf of Mexico and the eastern seaboard of the United States. The flame box crab lives in sand flats and coral rubble with sandy areas. It is shy and buries itself in the sand when they see a diver approaching.
I found this crab at Hanson Bay, identification courtesy of Barb Crites
I found this crab in shallow water at Trunk Bay. Like the Puerto Rican sand crab, it buries itself in the sand and hides there.
Moray eels hide in holes in the reef during the day. They sometimes can be seen sticking their heads out of their hole, constantly opening and closing their mouths. They do this not to scare people but to pump water through their gills in order to breathe.
At night they come out of their holes and search for food on the reef.
The Peacock Flounder is, like other members of its species, a master of camouflage.
Feather duster worms are a type of tube worm. They attach themselves to the reef by a hard-shelled tube. Their colorful feathery tentacles that make them look like underwater feather dusters serve to filter nutrients from the water. When threatened they quickly retreat into their tubes.
The bearded fireworm ( Hermodice carunculata) is a slow creature, and is not considered a threat to humans unless touched by a careless swimmer. The bristles, when flared, can penetrate human skin, injecting a powerful neurotoxin and producing intense irritation and a painful burning sensation around the area of contact. The sting can also lead to nausea and dizziness. This sensation lasts up to a few hours, but a painful tingling can continue to be felt around the area of contact. In a case of accidental contact, application and removal of adhesive tape will help remove the spines; applying isopropanol to the area may help alleviate the pain…. read more
The bar jack (Caranx ruber) is commonly found swimming over and around reefs or near beaches, often seen swimming above rays. Its an efficient predator eating small fish, shrimp and squid. Although the bar jack is known to carry the fish poison, ciguatera, it is generally thought to be a considered a good-eating fish in most parts, but not in the Virgin islands, where most reported cases of the illness can be traced back to this single species.
Horse-eye jacks are strong-swimming predators that feed on small fishes, shrimps and other invertebrates. The horse-eye jack often swims in schools and may mix with other species of jacks notably the similar-looking crevalle jack.
The moon jellyfish is the most commonly found jellyfish in St. John waters. It feeds mostly on plankton. They can propel themselves to a limited degree, but, by and large, they drift about with the currents.
The moon jellyfish can produce a mild sting in sensitive individuals, but most divers and snorkelers do not feel anything upon contact with their tentacles.
Upside-down Jellyfish (Cassiopea frondosa)
Most jelly fish swim around with their head up and tentacles down, but the Cassiopea spends most of its time with its head down resting on the sea floor and with its tentacles extended upward, hence the name, upside-down jellyfish.
The Cassiopea can give divers a mild sting, which can be very itchy.
Mangrove Upsidedown Jellyfish (Cassiopea xamachana)
You’ll need to look carefully to see the translucent jellyfish in the above photo, but seeing it in the water is even more difficult. It has a dome shaped head and four tentacles. It’s a sea wasp. It stings hard and it’s hard to avoid. If you are unfortunate enough to get stung, pour vinegar on the the affected area and in severe cases seek medical attention.
Parrotfish swim using their pectoral fins.
The parrotfish in the photo has made a bag out of secreted mucus bubbles In which it will the spend the night.
Reef grazing fish, such as parrotfish, produce a significant amount of the sand found on our beaches. Parrotfish exist on a diet of algae, which they scrape off the surface of coral rock with their beak. They then grind this coral and algae mixture to a fine powder. The algae covering the coral are absorbed as food. The coral rock passes through their digestive tracts and is excreted in the form of sand. Snorkelers will frequently observe this process if they watch the parrotfish for a few minutes. Scientists say that for each acre of reef a ton of sand is produced by reef grazing fish every year.
Supermale Spotlight Parrotfish
A supermale parrotfish is one that began life as a female and later changed to the colorful supermale.
Ordinary male parrotfish spawn with females in groups of other males while the supermale gets to spawns with an individual female or even with several females.
Ordinary Adult Parrotfish
Southern stingrays are commonly found in St. John waters in sandy areas, sea grassbeds and around reefs.
They are usually between three and four feet long, but can grow to be as long as five and a half feet.
The southern stingray often lies on the bottom covering itself with sand by flapping its large pectoral fins. This serves to protect it from predators and from the rays of the sun. Because these stingrays can be so well camouflaged and because their sting can be so painful, it is a good idea to shuffle your feet (the sting ray shuffle) when in areas where stingrays are abundant, especially if in murky waters. In this way the stingray will be alerted and will get out of your way.
Because the sting ray’s gills are located on the underside of its body. When lying in the sand it uses the two holes near its eyes to breathe.
Mantas can leap high above the surface of the water using the strength of their powerful wings. They have short tails without the stinging spines found in the tails of many other species of rays. Their diet consists of plankton, small fish and small crustaceans.
Sea turtles are almost invariably a source of joy and excitement to the swimmers, snorkelers and divers fortunate enough to happen upon these gentle and magnificent creatures. Two species, the green turtle and the hawksbill turtle are commonly found around the Virgin Islands.
Green turtles are vegetarians and can usually be found grazing the seagrass beds in bays such as Maho, Francis, and Leinster bays.
Hawksbill Turtles Hawksbills have a distinctive hawk-like beak and are usually found around reefs where they hunt crabs, fish, and snails or use their sharp bill to scrape sponges, tube worms and encrusting organisms off rocks and coral.
The giant leatherback turtle also inhabits our waters, but is almost extinct and rarely seen. The leatherback can grow to as much as eight feet in length and weigh over 1000 pounds. Leatherbacks are so-named because, instead of having a hard shell like other sea turtles, their backs are protected by layers of leather-like plates.
Leatherbacks live in deep water and subsist on a diet of jellyfish. A major threat to the leatherback comes in the form of improperly disposed plastic bags, which the leatherback may easily mistake for a jellyfish. If consumed, the plastic bag will kill the turtle by clogging up its intestines.
Sea turtles have been in existence for about 150 million years, inhabiting the tropical and subtropical seas of the world.
Even though these large reptiles spend almost all their life in the sea, they are air breathers. They hold their breath just like we do when we dive without tanks. Fortunately for the sea turtles, they can hold their breath much longer than we can. They are excellent swimmers, possessing large flippers that can propel their streamlined bodies through the water quickly and gracefully.
Instead of teeth, sea turtles have a beak like a bird, (like a hawk in the case of the hawksbill turtle.) Sea turtles have no ears, which is probably just as well for creatures that spend their whole life diving. They can still hear, though, accomplishing this through the use of eardrums that are conveniently covered with skin. Sea turtles have a keen sense of sight while they are under the water, but are quite nearsighted when they stick their heads out of the water for their breath of air. The turtles also have an excellent sense of smell, which also functions best while they are submerged.
The female sea turtle comes ashore on secluded beaches at night to lay her eggs. She then covers the eggs up with sand and does her best to cover up any traces of her nocturnal activities. The mother turtle returns to the sea while the eggs incubate, a process that takes about eight weeks. When the eggs hatch, the baby turtles dig their way out of the sand and crawl slowly towards the sea. They are very vulnerable at this time. The tiny turtles are easy prey. Moreover they must avoid pitfalls such as getting trapped in holes in the sand, tangled up in seaweed, or having their way blocked by trash or other debris. They must reach the sea before the light of day exposes them to keen-eyed sea birds, mongooses, dogs and the baking hot tropical sun.
No one knows for certain what the hatchlings do next, but many scientists believe that the hatchlings then head out for the calm waters of the Sargasso Sea, which lies between the West Indies and the Azores in the middle of the Atlantic. Here they drift about hidden amidst the plentiful sargassum seaweed until they grow large enough to avoid most predators. The turtles then begin their long journey back to the beach where they were born. When the female reaches sexual maturity, sometime between 15 and 50 years depending on the species, she will lay her eggs on that beach.
The hawksbill, green and leatherback turtles are all listed as federally endangered species. Over-fishing and the commercial exploitation of hawksbills for tortoise shell products such as combs, hair barrettes, eyeglasses, picture frames and boxes have taken their toll on a once thriving population.
Sea turtles also face other serious problems. More and more beaches are being developed rendering them unsuitable for turtle nesting.
Development also leads to an increase in the dog population. This is a problem because dogs are adept in finding and digging up turtle eggs. Furthermore it has been shown that mongooses do not instinctively hunt turtle eggs, but begin to do so after observing dogs engaged in this activity.
The awe and fascination that we experience upon an encounter with the sea turtle was shared by the cultures that inhabited these islands before us. To the spiritually evolved Taino people of the Caribbean, the turtle symbolized the ancestral mother and was a prominent feature in their religious art. This majestic and peaceful being cannot be allowed to become extinct. We must remember that we share our environment with all of God’s creatures, and it is our responsibility to preserve and protect our unique heritage.
Sharks and rays have skeletons made of cartilage rather than bone. They have small hard scales, which gives their skin a sandpaper feel to the the touch.
While most sharks have lost their ability to pump water over through their gills and must remain in motion throughout their lives, the nurse shark is one of two species of sharks that has retained this ability and can lie at rest . The other species with this ability is the lemon shark.
Nurse sharks mostly eat marine invertebrates such as lobsters, shrimp and sea urchins. They capture their prey by their ability to create a strong suction through their small mouths and large throat cavities, which has led to their name, “nurse sharks.”
Lemon sharks get their name because many of them have a yellowish color. Like nurse sharks, they do not have to remain in motion to pass water through their gills.
Black Tip Sharks
Black tip sharks are so-named because of the black coloring on the tops of their fins.
Atlantic Tritons Trumpet
A predatory sea snail that likes to eat starfish
Flamingo Tongue Snail
The bright orange-yellow color and black designs are not part of the flamingo tongue snail’s shell, but rather a mantle tissue covering the shell.
This starfish is called a Cushion Sea Star or Asteroid. They have five arms, which can regenerate if broken off. Occasionally a new starfish can develop from a broken off arm. The mouth is on the bottom and the anus is on top. Some sea stars have the ability to stick their stomachs outside their moths and put it around their prey (often a conch) and digest it from the outside before returning their (now full) stomach to where it belongs.
Tarpon are usually found in inshore areas and feed on small fish and crustaceans. They can fill their swim with air and absorb oxygen from it enabling them to breathe air at the surface.
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