The Channel Clinging Crab (Mithrax spinosissimus)

Channel Clinging Crab (Mithrax spinosissimus)

by B. N. Sullivan

We were on a night dive in the Turks and Caicos Islands when we came across this crab.  It is a Channel Clinging Crab (Mithrax spinosissimus), the largest species of Caribbean reef crab.

How big is he?  We estimated that this crab's carapace measured about 15 cm (6 inches) across.  If you could measure across its spread-legged footprint, however, it would easily be over to 30 cm (12 inches).

We were scanning around with our lights across a sandy area off the coast of West Caicos, when we saw this crab gallumphing along, hunting for his dinner.  I had been shooting macro photos earlier that day, but for some reason I did the night dive with a wide angle (15mm) lens on my camera.  As it turned out, that lens allowed me to get these wide angle close-up shots of this crab.

We located this crab out on the sand flat, at a depth of about 15 meters (50 feet).  I maneuvered around in the dark to position myself to intercept its path. I settled on the sand just a meter or so in front of the critter, while Jerry shone a small beam of light on it from above so that I could set up the shot.  I waited, and when the big crab was right in front of me, I snapped the shutter release.  The result is the first photo on this page.  By chance, I managed to capture him just as he began to raise one of those claws in defense!

Of course, as soon as the camera's strobe blasted the poor crab with bright light, he decided to leave in a hurry.  He 'turned on a dime' and retreated quickly, but not before I was able to capture an image of the posterior of his carapace and those wonderful, bristly, spidery walking legs!

Channel Clinging Crab (Mithrax spinosissimus), posterior view

We know this species by the common name Channel Clinging Crab, but it turns out that it has several other common names, including Reef Spider Crab, and Spiny Spider Crab, among others.  The crab's scientific name is Mithrax spinosissimus, and that designation stays the same, independent of the common name, which varies from place to place.  This crab belongs to the Majidae family and is a 'true crab' (as opposed to, say, a hermit crab).

Majidae tend to have long slender legs -- just like this example -- which is why the common names of many species in this family include the word 'spider'.  Majids also tend to have little hairs or bristle-like structures on their carapaces.  Bits of material -- algae, sponge, and so on -- attach to those hairs and act as part of the crab's camouflage.

Note that the walking legs of this species also are rather hairy, and are covered with 'stuff' while the business end of the crab -- those impressive claws -- are smooth.

Like so many reef creatures, this species forages mainly at night.  During the day, they hunker in the reefs, under ledges, and in cavelets.  Because of their size, they can't wiggle into small cervices like so many smaller species can do.  Still, they can be difficult to spot during the day, since their decorated carapaces blend so well with their surroundings.

These crabs inhabit a range from the sub-tropical western Atlantic to the Caribbean. They can be found in reef areas along the coasts of southern Florida, through the Bahamas and the Turks and Caicos Islands, and throughout much of the Caribbean.

Happy Holidays from The Right Blue!

Christmas Tree worm (Spirobranchus giganteus) and Pillar Coral (Dendrogyra cylindrus), with polyps extended

by B. N. Sullivan

We chose this image for our holiday post because we thought it looked festive. We hope you agree.

The photo, taken during a night dive off  Providenciales in the Turks and Caicos Islands, shows a stand of Pillar Coral (Dendrogyra cylindrus) with its polyps extended for feeding.  Nestled cozily in the coral is a kind of Polychaete worm called the Christmas Tree worm (Spirobranchus giganteus).  The worm burrows into coral and secretes a calcareous tube in which it lives.  Only its pair of feathery 'Christmas Tree' shaped crowns are visible outside its tube. The feathery tentacles on the crowns trap tiny tidbits of food, and also are used for respiration.

The Christmas Tree worm can retract its crowns into its tube for protection.  When the crowns retract, a structure called the operculum closes snugly over the tube like a lid or a little trap door.  Christmas Tree worms come in lots of colors: red, orange, yellow, blue, and white. We also have seen a version that is striped!

We hope all of our readers are enjoying the holiday season, and we wish you all a very happy, healthy, and prosperous New Year.

Bearded Scorpionfish: A Name That Suits

Bearded Scorpionfish (Scorpaenopsis, barbatus), Red Sea

by B. N. Sullivan

Meet the Bearded Scorpionfish (Scorpaenopsis barbatus).  Both the common and scientific names of this fish refer to the frilly, fleshy flaps of skin protruding from its chin.  (The Latin name "barbatus" translates to "bearded.")

Like others in its family, Scorpaenidae, the Bearded Scorpionfish is an ambush predator.  Its strategy is to lie in wait for its prey to come swimming past at close range, and then to spring forth with its mouth wide open to engulf its meal in one big gulp.  In order to do this successfully, it helps to be as inconspicuous as possible.  It helps to be camouflaged.

The scorpionfish usually rests on algae-covered rocks, or among corals and marine plants.  The frills on this guy's chinny-chin-chin are a part of its disguise, helping it to blend in with its usual surroundings.

Despite its elaborate camouflage, the individual in these photos was easy to spot since it was out in the open, resting on a patch of sand.  Hoping I could get a close-up photo of its head, I lay down on the sand, too, and inched toward the fish.  To my delight, my subject did not flinch or flee after the first shot, so -- still on my belly --  I was able to move around carefully and face him to take a head-on shot of his impressive 'beard' at close range.

Bearded Scorpionfish (Scorpaenopsis, barbatus), Red Sea

Basking Sea Turtles in Hawaii

Green Sea Turtle (Chelonia mydas), basking at Puako, Hawaii

by B. N. Sullivan

Imagine that you are in Hawaii, walking along near the edge of the ocean.  You come upon a sight like that in the photo at the top of this page -- a sea turtle lying on the sand or on the rocks.  You may notice that its carapace is dry, indicating that it has been out of the water for awhile. You may feel alarmed, wondering if it is stranded.  You think: Maybe a wave washed it ashore and it doesn't know how to get back into the ocean. Or perhaps it crawled out of the water intending to nest, but got stuck.

If it is a Green Sea Turtle (Chelonia mydas),  chances are very high that it has come ashore intentionally, it is not distressed or stranded, and it is not about to lay its eggs.  It is engaging in a behavior called "basking" -- another term for sun-bathing.

So far as anyone knows, only green sea turtles engage in this behavior, although no one is certain why they do it, or why they are the only sea turtle species who like to bask.  One proposed explanation for basking has to do with temperature regulation, since other kinds of reptiles are known to do this.  Another hypothesis is that basking ashore allows the turtles to rest for relatively long periods of time (hours) without risking predation, e.g., by sharks.

Regardless of the reason, Green Sea Turtles do come ashore regularly in many locations in the main, human-populated, Hawaiian islands, none of which are known to be nesting areas for this species.  They come ashore to bask in the sun.

So, if you come upon a turtle on the beach or rocks near a shoreline in Hawaii, what should you do?  You can watch them for awhile if you like -- just don't get close enough to disturb them.  You can photograph them, but please don't use a flash.  Don't try to move them or "help" them back into the ocean.  They need no assistance: when they are ready to go back to sea, they will do so unaided.  So don't block their path to the water, either!

Here are a couple more photos of basking turtles.  The first shows one turtle already basking while a second is preparing to "haul out."  The final photo shows a turtle who apparently has decided she has worked on her tan enough for the day, and is returning to the water.

Green Sea Turtles near the water's edge in Hawaii

A Green Sea Turtle returning to the ocean after basking

All of the basking sea turtles on this page were photographed at Puako, on the west coast of the Big Island of Hawaii.

For more information about this behavior of sea turtles in Hawaii, see:

Whittow, G.C., & Balazs, G.H. (1982). Basking behavior of the Hawaiian green turtle. Pacific Science, 36(2), 129-139 -  (11-page PDF)

Scarlet Hermit Crab from the Cayman Islands

Scarlet Hermit Crab (Paguristes cadenati), Cayman Islands

by B. N. Sullivan

Many small crustaceans look quite similar to one another, but it's hard to misidentify this little hermit crab.  A denizen of reefs in the Caribbean Sea, the brilliant coloring of the Scarlet Hermit Crab (Paguristes cadenati) sets it apart from other hermit crab species of that region.

These little crabs (about an inch long) inhabit old gastropod shells, and for some unknown reason, the shells they choose as their portable houses usually are pretty cruddy looking.  The one in the photo on this page is covered with a layer of coralline algae so thick that it almost looked like a stone, rather than a seashell.

Like many hermit crab species, these little guys are difficult to find during daylight hours.  At dusk they emerge from their hiding places in the reef and go about foraging for their food.  We spotted this individual during a night dive at Little Cayman island.

Most often, divers see only the crab's red legs and pale eyestalks poking out of the aperture of the shell in which they live.  This individual was cruising along across some coral, so we got to see a bit of the pretty speckled markings on its back, too.

The Scarlet Hermit Crab is a member of the Diogenidae family.  Comprised of more than 400 known species, the Diogenidae are the second-largest family of marine hermit crabs.

Hunting Together: A Bar Jack and a Southern Stingray

A Bar Jack and a Southern Stingray hunting together

by B. N. Sullivan

We spotted this pair of hunters in the Caribbean.  The dark colored fish in the photo is a Bar Jack (Caranx ruber). This fish makes its living as an opportunistic feeder.  In this instance, it is swimming a little above and behind a Southern Stingray (Dasyatis americana) hoping to snag a free lunch.

The stingray finds its food by rummaging in the sand, looking for little creatures to eat -- worms, small clams, tiny crabs, and such. To locate its prey, it fans away the top layer the sand by fluttering the wing-like tips of its body disc.

The crafty Bar Jack follows closely, letting the stingray do the excavating.  If the stingray uncovers something that looks tasty to the Bar Jack, the jack will snatch it in a lightning strike, then resume its position keeping watch over the stingray's shoulder, as it were.

We've seen Bar Jacks throughout the Caribbean.  In addition to pairing with hunting stingrays, we've also seen them following goatfish -- another species that digs around in the sand and rubble for food. 

By the way, the Bar Jack doesn't always look so dark. When it's not feeding, it is a handsome silvery blue color, with a black bar running along its back from its dorsal fin down to the lower lobe of its tail fin like a racing stripe.

A Queen Conch snail, giving us the eye

Eyes and proboscis of a Queen Conch (Strombus gigas)

by B. N. Sullivan

Conch shells, like all seashells, are created by secretions from the mantle of the snail that lives inside. This happens gradually, over the snail's lifetime.  Most people have seen empty Conch shells, yet few have seen the snails that are the natural inhabitants of those large, heavy shells.  Fewer still realize that those critters have wonderful stalked eyes.

All of the snails in the family Strombidae, to which Conchs belong, have these stalked eyes.  If you come across a live Conch shell while diving, you can see the snail's eyes for yourself if you are patient.  If you pick up the shell and turn it over, the animal inside will retract into the shell almost immediately.  Set the shell down with the glossy aperture exposed and just wait.  Eventually -- say, in five or ten minutes -- the snail will extend its eyes to look around.  If you are lucky, you also may get to see its proboscis (tubular mouth), as in the photo above.

The snail in an upended Conch shell has the ability to right itself, but to do so takes quite a bit of effort on the part of the critter.  So, if you do handle one or set it aperture side up to try and catch a glimpse of the eyes, please do return it to its natural aperture-down position before you leave it.  The photo below shows the snail's eye peeking out of the shell as it moves along the sand in its normal position.

The creature in the photos on this page is a Queen Conch (Strombus gigas), a species common to the Caribbean. I photographed this one during a night dive off the north coast of Cayman Brac.

An eye peeks out as a Queen Conch snail crawls along the sand

The Spiny Puffer's Message: You can't touch this!

Spiny Balloonfish (Diodon holocanthus)

by B. N. Sullivan

You can't touch this... and you definitely can't swallow it!

That is the message that fishes in the Spiny Puffer family attempt to transmit to potential predators.  While other creatures defend themselves from predators by fleeing, or hiding, or with camouflage, members of this family (Diodontidae) inflate themselves.  In addition, evolution has armed these guys with another feature: rigid spines all over their bodies that are erected when the fish inflates.

The Spiny Puffer's spines actually are like specialized scales. When the puffer is not inflated, most of the spines lie more or less flat against the skin, but when the skin stretches during inflation, the spines go upright.

Ain't nobody gonna swallow these babies!

Puffers are not very streamlined even when they are not inflated, so they are not fast swimmers.  Once they inflate they really are ungainly.  Their little pectoral fins will flutter, but they don't attain much in the way of forward motion.  To survive, they rely entirely on making themselves look unappealing as prey.

When a Spiny Puffer is molested or feels threatened, it opens its mouth and draws sea water into its stomach.  The stomach is capable of expanding greatly -- so greatly that the stomach and its watery contents can virtually fill the whole fish, squishing the rest of its organs up against its backbone.  Its skin is stretchy, too, which also helps it to expand like a balloon.

Both fish pictured in this post are partially inflated.   Each was pottering along in a shallow reef area when we spotted them.   In each case, Jerry shined his light on the fish so that I could approach and aim the camera for a close-up of the Puffer's cute face and interesting eyes.  But these are touchy critters, and that was enough to induce them to begin to inflate, so in each instance I snapped two frames and retreated before they freaked out.

Some divers intentionally harass or even try to grab puffers, just to see them inflate.  This is quite a mean thing to do.  Remember, inflation is a defense.  If the fish begins to inflate, that means it is alarmed.  If it puffs out to its maximum, it is really scared!  This behavior may be amusing to divers, but it really stresses the poor fish.

If you see a puffer and it begins to inflate, move away from it to let it know you are not a threat.  Don't terrorize the puffers!

Spotted  Porcupinefish (Diodon hystrix)

Both of the Spiny Puffers on this page are Caribbean species.  I photographed them on two separate night dives in the Cayman Islands.  To give you an idea of their size, each of these individuals was approximately 12-14 inches (30-35 cm) in length.

Fine perch for a sea turtle

Green Sea Turtle perched on the coral at Pulau Sipadan, Malaysia

by B. N. Sullivan

Sea turtles have a knack for finding comfy resting places on the reef.  Earlier this year I posted a photo of a turtle who had plopped down on a bed of soft corals to take her rest.  Here we have another Green Sea Turtle, perched this time on a table coral that jutted out from a steep bank.

We spotted this turtle at the outset of our dive, and as we passed by the same spot about an hour later on our way back to the boat, she was there again -- or still! -- surveying the scene.  She looked so comfy and at ease that we reckoned this must be her regular post.  We know from having observed the behavior of individual turtles in Hawaii over periods of years that each effectively "owns" a particular spot on the reef, returning to the same rocky shelf, or cavelet, or depression in the coral day after day over a long span of time.

To us, this turtle looked a bit like a sentry posted in a watchtower.  From the outcropping, she  had an unobstructed view of the entire bank -- left, right, up to the surface, and down into the gloomy depths -- a fine perch for a turtle.

The Yellowbar Angelfish (Pomacanthus maculosus)

Yellowbar Angelfish (Pomacanthus maculosus), Red Sea

by B. N. Sullivan 

If you dive near tropical reefs in the Indian Ocean or the Red Sea, you may encounter the Yellowbar Angelfish (Pomacanthus maculosus).  Often you will see them nibbling on a sponge,  or pecking at corals and algae-covered rocks.  In our experience, they don't seem to be fearful of divers, often swimming right up to have a look at us.  They are known to be territorial, so perhaps they approach divers to judge if they are friend or foe.

The adult of this species, pictured above, grows to a rather large size (for an angelfish!) -- up to about 20 in (50 cm).  The bright yellow patch on their flanks makes them easy to recognize.  Legend has it that the splash of yellow depicts a map of Africa.  That may be a bit of a stretch, but it accounts for the fact that an alternate common name for this species is Map Angelfish.  In any case, the exact shape of the blotch is unique to each fish, rather like a fingerprint.

The individual pictured above was photographed in the Red Sea, near Sharm el-Sheikh, Egypt.

Octocoral polyps - Little flowers of the sea

Open polyps on a Nephtheid soft coral

by B. N. Sullivan

Octocorals (Octocorallia) are a subclass of corals whose polyps have eight tentacles.  The name Octocoral derives from this morphological feature [in Greek, "okto" means "eight"].

When the polyps are feeding, the feathery tentacles are spread wide to capture passing bits of nutrients.  In macro photos of Octocorals, like the one above, the open polyps look like a dense garden of little flowers.

When the coral polyps are not feeding, the tentacles retract into little balls, like an open hand closing into a fist.  To see what I mean, look at these recently posted macro photos of another soft coral with closed polyps.

The Octocoral species pictured above is a a Nephtheid soft coral.  I took the photo at Indonesia's Bunaken National Park, a lush marine preserve near the northern tip of Sulawesi Island.

Purple sea slug (Hypselodoris apolegma)

by B. N. Sullivan

Isn't this a pretty little critter?  It is  Hypselodoris apolegma, a nudibranch from the family Chromodorididae.  It doesn't have a standard common name, so we just call it the purple sea slug. This attractive nudibranch lives in the western tropical Pacific region.

H. apolegma feeds on sponges. It seems to prefer a dysideid sponge of the genus Euryspongia, but it may feed on other sponges as well.

Like many nudibranchs, the purple sea slug lays its eggs in a ribbon-like mass. The egg mass of H. apolegma is yellow.

The creature's striking coloration makes it an attractive subject for underwater macro photography.  I photographed this one off the northern coast of the Indonesia island of  Sulawesi, in the Celebes Sea.  This specimen was about 3 cm long (about an inch).

The species fact sheet for H. apolegma on the Australian Museum's authoritative Sea Slug Forum describes this creature's coloring as follows:

The background colour is a rich pinkish purple with a white border to the mantle. At the edge of the mantle the border is solid white but inside this is a region of varying width in which the white forms a reticulate pattern gradually merging in to the pinkish purple. The rhinophore stalks and the base of the gills is an intense purple, the rhinophore clubs and the gills are orange yellow.

Yep, that's our purple sea slug!

Visit the Hypselodoris apolegma species page on the Sea Slug Forum for more information and photos, including feeding records, mating, and the egg mass of this species.

Seeing stars in the Mediterranean Sea

by B. N. Sullivan

If you go diving or snorkeling in coastal areas of the Mediterranean region, you are very likely to see this Red Sea Star (Echinaster sepositus), which is the most common starfish species in that area.  Divers and snorkelers have a good chance to spot this sea star resting on the bottom along rocky coastlines.  Although there are records of Mediterranean Red Sea Stars found at depths of more than 200 meters, they are seen most often in relatively shallow water -- less than 10 meters.

Mediterranean Red Sea Stars are actually red-orange in color, rather than pure red.  As sea stars go, they are relatively large.  The one in the top photo on this page was about 20 cm (8 in) in diameter.  The individual in the photos below was even larger -- nearly 30 cm (12 in) across.

Like many common sea star species, Echinaster sepositus has five rays, or arms.  One time, however, we found a six-armed sea star that looked just like E. sepositus, except that it had an extra arm.  At first I was not certain that it was indeed the same species, so I took the time to photograph it carefully.  Someone who knows much more than we do about Echinoderms looked at the photos and assured us that the six-armed sea star was a less common, though well-known, morphological variant of E. sepositus.

The two macro photos below are of the unusual six-armed Mediterranean Red Sea Star.  In these macro photos you can see the characteristic surface of the sea star, which is uneven -- sort of dimpled.  In the first of the two photos below, you can see the tiny structures, called papullae, which protrude from the 'dimple' indentations on the sea star's surface. In the second photo below you can see the animal's tube feet protruding from grooves on the underside of each ray.

Both the tube feet and the papullae facilitate water exchange, and are involved in the animal's respiration and excretion.  The sea star 'breathes' by extracting oxygen from sea water.  It excretes some dissolved waste matter through the papullae and tube feet, too.

The tube feet also aid the sea star in locomotion.  The tube feet in each row move successively, in a wave, using hydraulic pressure from the animal's water vascular system.  This allows the critter to crawl along.  By a similar process, the tube feet also can be used to pass bits of food from the distal ends of the rays to the sea star's mouth, which is at the center of its underside.

If you look closely at the second macro photo below, you can see that there is a little suction cup at the tip of each tube foot.  These structures help the animal stay put after it situates itself on a rock or other hard surface.  If a sea star gets overturned, it can right itself by twisting one or more of its rays so that the tube feet can grab hold of the surface and turn itself right-side up again.  (This process can take quite awhile and consumes a lot of the critter's energy, so if you pick up a sea star to look at it, be kind enough to return it to its normal position!)

The sea star lounging in an algae bed in the photo at the top of this page was photographed in the shallows of Aedipsos Bay, on the coast of the Greek island of Evia.  The two macro images below, of the six-armed Mediterranean Red Sea Star, were photographed at Cape Greco, Cyprus.

The Ornate Butterflyfish (Chaetodon ornatissimus)

by B. N. Sullivan

Fishes in the Butterflyfish family (Chaetodontidae) are among the prettiest inhabitants of tropical reefs around the world.  This species, the Ornate Butterflyfish (Chaetodon ornatissimus) is particularly nice looking, we think.

The Ornate Butterflyfish is easy to recognize, with six diagonal yellow-orange stripes on each side of its creamy body, black and yellow bars on the face (including one that covers the eye), a gray patch on its forehead, and black 'trim' around its margins.  They are said to grow to a length of 20 cm (about eight inches), although most of the adult individuals we have seen are somewhat smaller -- usually about 15 cm (six inches).

C. ornatissimus feeds exclusively on live coral polyps, so you would expect to find them in coral-rich areas. They seem to favor coral polyps of the Pocillopora and Montipora genera.  (Here in Hawaii, we frequently see them pecking on Pocillopora meandrina.)

Juveniles of this species look like cute miniatures of the adults.  The juveniles can be quite shy, hiding in corals for protection.  The juveniles live as singletons, but once they reach breeding age, they find mates and form pairs.  In fact, it is unusual to see an adult of this species not accompanied by its mate.  Also, pairs establish a home range, so once you discover a pair of C. ornatissimus, you will likely be able to find them again in the same area time after time.

'Ornates' are an Indo-Pacific species, most commonly found in the central and western Pacific, from Hawaii to Australia's Great Barrier Reef.  Sightings have been reported as well around Christmas Island in the eastern Indian Ocean, and we have seen photos of the species taken in Indonesian and Malaysian waters.  They are quite common here in Hawaii. I photographed the one pictured on this page in Honaunau Bay, on the south Kona coast of Hawaii's Big Island.

Don't feed the critters

by B. N. Sullivan

There are some dive sites where you know immediately that the fishes and other critters are used to being fed by divers and snorkelers.  How can you tell?  You can hold out your hand, like Jerry is doing in the photo above, and see if the fishes come forward.  Sometimes you don't even need to extend your hand.  At some sites, the fishes begin to converge on divers as soon as they descend from a boat.

So, is feeding the critters a bad thing or an okay thing to do?  Generally speaking, we advise against it.

For one thing, it can be disruptive to the critters in a number of ways.  Feeding an animal something that it would not naturally eat can disrupt its digestion and nutritional status.  Even if you choose to feed something the animal might normally eat, you alter its natural feeding behavior by supplying the food item.

For another thing, feeding critters encourages them to congregate in places where they might not normally stay -- like at the base of a boat mooring.  While the critters may learn that if they hang out in a particular place, they will be fed, their predators also learn this.  You may be setting up the unsuspecting recipient of your offerings for becoming a meal himself!

And then there's the diver safety issue.  If you've ever been mobbed by a swarm of fishes expecting a handout, you know what I mean. We have been followed around on many occasions by fishes that had become accustomed to being fed -- including eels and stingrays.  As annoying as being mobbed by Snappers or Butterflyfishes may be, it can be worse -- even dangerous -- if the hungry critters are large and/or toothsome and aggressively pursue divers expecting a treat.

Long-time readers of The Right Blue may recall a story we told awhile back about a particularly aggressive Napoleon Wrasse in the Red Sea.  The huge fish was accustomed to being fed boiled eggs.  The wrasse  apparently mistook the white second stage of our friend's regulator for an egg, and chomped it hard enough to detach it from the hose.

We know a dive guide who used to feed a certain large Moray eel, and then pet it.  One day he reached out to pet the eel and it snapped at him, clamping down on his finger.  At the hospital emergency room the doc said the only reason the dive guide did not lose that finger was because he was wearing a heavy class ring, which probably deflected the eel bite just enough to save the digit (although it was pretty badly mangled).

Remember, folks.  The creatures you see in the ocean are wild animals, not pets.  Don't give them indigestion and don't mess with the natural food chain.  Don't feed them.

About the photo:  I took this photo of Jerry (and a handful of Yellowtail Snappers) at the wreck of the Oro Verde, located off Grand Cayman's Seven Mile Beach.

Watching and being watched underwater

by B. N. Sullivan

Recreational divers are essentially underwater sightseers. Just like sightseers on land, they take in the scenery and observe 'the locals' going about their business. In this case, of course, the locals are the critters that inhabit the reef.

But make no mistake, this isn't a one-way activity. The critters watch us just as we watch them. We've mentioned this a few times in the past. Longtime readers of The Right Blue may recall the story of Brutus, the Great Barracuda, who seemed to be attracted to Jerry's black and yellow wetsuit.  Brutus took to following Jerry  around on the reef -- again and again and again!

At least we knew Brutus was there -- really, you couldn't miss him!  But sometimes creatures in the sea watch or even stalk divers while the diver is oblivious to their presence.  As an example, we once posted a photo of a sneaky shark approaching a diver from behind, while the diver -- engrossed in what he was photographing -- remained unaware of the shark.  Based on our own experiences, we think scenarios like that happen very often.

It's amazing how marine animals can seem to appear out of nowhere!  We remember many occasions when animals startled us by literally swimming right over our shoulders. The photo at right is one example of that.  I was photographing something -- I don't even remember what -- when this Gray Angelfish suddenly swooped into view from behind me.  I pressed the shutter button just in time to capture the fish, rather than whatever it was I intended to photograph!

Many animals in the sea are curious about divers.  Whales, dolphins, sharks, large jacks, eagle rays and turtles all have, on occasion, altered their course to approach us closely to look us over.  Some have paused to watch whatever it was we were doing.

Sometimes, the critters seem to be hoping we will facilitate their search for a meal.  Dig in the sand, or turn over a rock, and you are likely to attract any number of 'inspectors' watching to see if you have unearthed something they would like to eat.  Direct a beam of light onto a reef during a night dive, and you may draw the attention of nocturnal hunters.

Usually these kinds of encounters are amusing, although sometimes they can give the diver quite a start, especially at night.  We recall several instances when our hearts momentarily skipped a beat during night dives when large creatures we weren't expecting to see suddenly appeared at very close range -- like the huge Manta ray that hovered so closely above us that we could have reached up and tickled its big white belly; like the Great Barracuda that zoomed over my shoulder to snatch the little fish I was about to photograph; like the 'wolf pack' of five Gray Reef Sharks that swept past our backs so closely that we felt the turbulence, which caused us to whirl around and train our lights on them just in time to count them as they sped away down the reef.

There are several factors at work here. For one thing, a diver's visual field is reduced underwater, compared to what it would be on dry land.  Even in the clearest water, a diver cannot see ahead more than, say, 45 meters (about  150 ft.) at most, and more often, horizontal visibility underwater is considerably less.  Things near the limits of that visibility range appear as shadowy lumps rather than as well-defined objects (or critters!).

Another impediment is the diver's mask.  It's true that without the mask -- and the airspace between the glass plate and the diver's eyes -- everything would look like a blur.  But at the same time, the skirt of the mask tends to block the diver's peripheral vision -- not just side to side, but also above and below.

Finally, we don't usually hear an animal approaching us underwater. There are no sounds of footsteps, and while the exhaust bubbles from open circuit SCUBA make noise, most marine animals make no discernible sounds as they move about.

What to do?  When you are diving, we suggest that you periodically glance up, and down, and look over your shoulder to see who or what may be watching you.

Humpback whales returning to Hawaii for the winter season

by B. N. Sullivan

We're at the start of Humpback whale season here in Hawaii. Every autumn, large numbers of Humpbacks (Megaptera novaeangliae) migrate from their summer feeding grounds in the north Pacific to the waters around the Hawaiian Islands, where they then spend the winter. Those of us who live in Hawaii tend to feel a bit possessive about the north Pacific stock of Humpbacks, because they are born and bred in our waters.  Over the course of their winter stay in Hawaii, the big cetaceans mate, and the females who became pregnant the year before give birth to their calves.  In spring they all migrate north again

Although we haven't yet seen this year's Humpbacks here on the Kohala Coast of the Big Island, the first whales of the season were spotted recently near Maui. That means we can expect to see them here on our coast any minute!

Earlier this month some lucky folks on an Oceanic Society whale watching boat near the Farallon Islands, 25 miles west of San Francisco, had an amazing encounter with some Humpbacks. Four friendly whales "approached the boat and for over an hour circled the boat, nearly brushing up against it, and seemed to make contact with the 45 passengers on board."

Here is the Oceanic Society's video of that exciting encounter:

If the video does not play or display properly above, click here to view it on YouTube.

A Hawksbill at Honaunau

WHAT: Hawksbill Sea Turtle (Eretmochelys imbricata) - Hawaiian name: Honu'ea

WHERE: I photographed this turtle at Honaunau Bay, on the southeastern coast of Hawaii's Big Island.

We see this species of sea turtle infrequently in Hawaii, so it's always nice to cross paths with one. Hawksbills have been known to nest on the eastern coast of the Big Island, but they are not plentiful. Seeing one on the western coast of the island always is an event worth noting.

Unlike the Hawaiian Green Sea Turtles, which are primarily vegetarians, Hawksbill turtles eat sponges and small invertebrates in addition to algae.  We  have not observed Hawksbill feeding behavior in Hawaii, but elsewhere we have seen them munching soft corals and sponges.  We once spent most of a dive watching as a Hawksbill turtle methodically devoured a tube sponge, gnawing it and pulling away hunks until there was nothing left of the sponge but a stub!

For more information about this endangered species, visit the U.S. Fish and Wildlife Service Hawksbill Sea Turtle Fact Sheet.

Allya, a captive Beluga whale that blows bubble-rings

Meet Allya, a Beluga whale (Delphinapterus leucas) who lives at an aquarium in western Japan. Like the dolphins at Orlando's Sea World, Allya has learned to blow bubble rings.

The YouTube blurb for this video notes:

Allya clearly loves interacting with her audience. She aims the bubbles at spectators as they peer in through the glass.

To learn more about this species, visit the Beluga Whale Fact Sheet on Web site of the American Cetacean Society.

If the video does not play or display properly above, click here to view it on YouTube.

Thanks to the folks at itnsource.com for this video.

Knock-knock: Who's there? A surprise from the past

by B. N. Sullivan

When I used to shoot film underwater, I made it a habit to mark a code number on the frame of each of the slides as soon as they had been developed.  The coding system I devised long ago consists of a number that corresponds to a particular entry in my dive logs -- that identifies the when and the where -- plus a letter code that indicates something about the subject.

Jerry finished scanning all of our old underwater photography slides awhile back, and as he went along, he labeled each with its original ID number and sorted the scanned images into folders according to the subject code on the slide.   I still have not finished reviewing all of the thousands of images, but every once in awhile I sit down in front of the computer and spend the next few hours sifting through those digital files.

So, there I sat earlier today, looking at images filed in the 'Sponges' folder, and I found this photo.  Looking first at the thumbnail image, it appeared to be a close-up photo of the surface of an orange sponge -- no more, no less.  Then I loaded it into the photo editor to have a closer look at the full-screen version.  Do you see what I saw?

There, peeking at the camera from an excurrent opening of the sponge is a little fish!  (I can't decide whether the fish looks surprised or merely annoyed.)

The next surprise for me came when I looked up the numerical code in my log books.  I was amazed to discover that I had taken this photo in 1990, during our first-ever dive trip to the Cayman Islands!  According to my log book notes, that roll of film was shot at a place called Angelfish Reef, Grand Cayman.

I have no idea what species of sponge that is, nor do I know the identity of the little fish. My best guess is that it is some kind of Blenny.  It's about the right size, and many fishes in that family like to hide out in small holes in the reef with only their heads visible to passers-by.  In any case, we're glad to give him a new home in our underwater menagerie here on The Right Blue.