Part 13 of my documentary, “Mucky Secrets”, about the marine life of the Lembeh Strait in Indonesia.

After a quick look at the panther grouper, Cromileptes altivelis, also known as the humpback grouper or barramundi cod, I explore demersal fishes, those that live on or near the seabed. Of these, benthic fishes actually rest on the sea floor.

The whitemargin stargazer, Uranoscopus sulphureus, spends most of its time buried in the substrate, with only its upper, or dorsal, surface exposed, where its eyes and mouth are located. Like frogfishes, stargazers are ambush predators. They have a worm-like lure that extends from the upturned mouth to attract fish that pass overhead. Stargazers are also equipped with poisonous spines at the rear of the operculum, the gill cover. The papillae fringing the mouth help stop sand from falling in when the fish is buried.

The leopard flounder, Bothus pantherinus, has adapted to life on the bottom with a superb camouflage. Such lefteye flounders are symmetrical and swim upright like other fishes when young. As they develop, the eye on the right side migrates to the left, thus enabling them to lie flat on the bottom. Their eye stalks can be retracted for protection, but enhance their view when extended.

Flatheads also have excellent camouflage and a stealthy, low profile, but unlike flounders, they are dorsally compressed and remain symmetrical. They are also ambush predators, and often hide by burying much of their body in the substrate. Flatheads are related to scorpionfishes and have short, venomous spines on top of their head.

We meet a Japanese flathead (Inegocia japonica), a black-banded flathead (Rogadius patriciae), and finally a pair of spiny flatheads (Onigocia spinosa) at Retak Larry, a classic, dark sand muck diving site named after the late Lembeh pioneer, Larry Smith.

Part 12 of my documentary, “Mucky Secrets”, about the marine life of the Lembeh Strait in Indonesia.

In this video I look at fishes in the order Tetraodontiformes. First of all we encounter a very young boxfish, possibly a longhorn cowfish, Lactoria cornuta. Along with toxic skin, the boxfish’s main defence is a very hard carapace of bony plates. The juvenile’s coloration helps it remain unnoticed while the body hardens.

Next is a juvenile thornback cowfish, Lactoria fornasini, sheltering in Halimeda algae. Juvenile boxfishes and pufferfishes often tuck their tail to one side when it is not needed for swimming.

Next we meet a juvenile starry puffer, Arothron stellatus, and its dramatically different adult counterpart.

Although puffers are slow movers, the tail can give them a great turn of speed when threatened. As a further defence, puffers can inflate their bodies with water, vastly increasing their size and revealing short, sharp spines on their skin.

They are believed to be the second most poisonous vertebrate on earth, after the golden poison frog. However some predators can tolerate the toxin, and some parts of them are carefully prepared as a delicacy in Japan, Korea and China.

The juvenile guineafowl puffer, Arothron meleagris, has a black and yellow coloration that advertises its toxicity to potential predators. This is a common combination of warning colors in the animal kingdom.

More elongate puffers are found in the Lembeh Strait too. We encounter a narrow-lined puffer, Arothron manilensis, at Hairball and a shortfin puffer, Torquigener brevipinnis, at TK.

Sharpnose puffers, also known as tobies, have elongated snouts and slimmer bodies. We meet at a Valentini puffer, Canthigaster valentini, a Bennett’s sharpnose puffer, Canthigaster bennetti, and a compressed toby, Canthigaster compressa.

The birdbeak burrfish, Cyclichthys orbicularis, is a type of porcupinefish. It is covered in spines which are permanently erect, and it can inflate its body like puffers. It’s eyes contain iridescent green specks.

Conversely, the spines of the long-spine porcupinefish, Diodon holocanthus, lie flat against its body when not it is not inflated.

Finally we encounter a long-spine porcupinefish sharing its home with a small birdbeak burrfish.

Part 11 of my documentary, “Mucky Secrets”, about the marine life of the Lembeh Strait in Indonesia.

The sheltered conditions make the Lembeh Strait a successful nursery, and juvenile fishes can be seen everywhere. First we encounted the bright orange and white coloration of a young spotted parrotfish, Cetoscarus ocellatus. Previously, all specimens bearing this pattern were thought to be of a species commonly known as the bicolor parrotfish (Cetoscarus bicolor), but those are now deemed to be local to the Red Sea. In later life it undergoes a dramatic change in coloration.

Sweetlips are another family that change dramatically during their life cycle. We meet a juvenile painted sweetlips, Diagramma pictum, which bears bold stripes, and an adult which exhibits spots.

The juvenile harlequin sweetlips, Plectorhinchus chaetodonoides, mimics toxic flatworms and sea slugs, and the movement is confusing for predators. As it matures, the movement slows down and the pattern starts to change. It’s coloration as an adult is entirely different from that of the young.

Juvenile yellowblotch razorfish, Iniistius aneitensis, a type of wrasse, are here too. This fish will dive head-first into the sand to sleep or if it is alarmed. The slim, bony head is optimized for this purpose. It prepares an area of sand in advance by loosening it to make it easier to dive into, and it is able to move significant distances under the sand before re-emerging. We see a white variation with two false eyespots on its dorsal fin.

Juvenile filesfishes are a common sight in the Lembeh Strait too. Their retractable dorsal spine deters predators. The name filefish comes from the rough skin. It is said that dried filefish skin was once used like sandpaper to finish wooden boats. In Australia they are known as leatherjackets. We encounter both juvenile and adult strapweed filefishes, Pseudomonacanthus macrurus.

Part 10 of my documentary, “Mucky Secrets”, about the marine life of the Lembeh Strait in Indonesia.

Frogfishes of the family Antennariidae, are a type of anglerfish in the order Lophiiformes. They are rare at most dive destinations but common in the Lembeh Strait.

Frogfishes such as the painted frogfish, Antennarius pictus, are highly camouflaged to resemble sponges or rocks covered in algae. They have an amazing ability to adapt their skin color and texture to blend in with their surroundings, and numerous color variations of the same species can be found.

Rather than blending into the surroundings, the warty frogfish, Antennarius maculatus, mimics toxic sea slugs to deter predators.

Although frogfishes can swim, they usually walk around on their pectoral fins which have evolved into arm-like limbs complete with an elbow-like joint.

Frogfishes are generally ambush predators, and have a very clever hunting technique. Their first dorsal spine, the illicium, ends in a fleshy lure known as an esca, which resembles a variety of marine creatures depending on the species. The frogfish waves the illicium like a fishing rod to attract prey. The appearance of the esca is useful in distinguishing between species. If the illicium and esca are removed, the frogfish can grow a replacement.

The illicium is not always deployed, and opportunistic frogfishes will snatch what food they can. They will often just lie in wait, their upturned mouths ready to devour unsuspecting bypassers.

We meet a giant frogfish, Antennarius commerson, taking up a more elevated position on a tube sponge, from which to ambush prey.

A warty frogfish appears nervous as it finds itself in the path of a highly venomous flower urchin, Toxopneustes pileolus, before the urchin finally changed course.

The striated frogfish, Antennarius striatus, is a real star amongst Lembeh critters, and high on most divers’ list of favorites. Many examples in the area bear long skin filaments and are known amongst the dive community as “hairy frogfish”. They are usually found on the open sand amongst algae. The esca resembles a polychaete worm. A black phase of the striated frogfish, without significant skin appendages, is encountered. Its possible that the filaments may be seasonally shed.

Finally we encounter a tiny juvenile painted frogfish, just a few millimeters in length.

Part 9 of my documentary, “Mucky Secrets”, about the marine life of the Lembeh Strait in Indonesia.

In this video I study dragonets including the amazing mandarinfish. Dragonets are benthic animals, meaning that they live on the seabed. They thrive in the muck of Lembeh. Dragonets are well-adapted to benthic life. They are well camouflaged and at night they bury their bodies. The eyes and gills are placed high so only they remain above the sand.

The fingered dragonet, Dactylopus dactylopus, is found in the Lembeh Strait. The first ray of each pelvic fin is effectively a limb or “finger” that the dragonet uses to walk along the seabed and dig for food. The male has warpaint-like facial markings and has long filamented rays on its dorsal fin that it holds forward when walking. The female has a bright orange upper lip.

The orange-black dragonet, Dactylopus kuiteri, is very similar. We encounter an adult and juvenile in close proximity, feeding on the seabed.

The Morrison’s dragonet, Synchiropus morrisoni, shuffles around the seabed without the aid of the separated fin rays.

A similar species of dragonet, the mandarinfish, Synchiropus splendidus, stays well hidden amongst shallow hard corals during the day. At dusk the males eagerly seek out female mates. During the hunt they hold their first dorsal fin aloft as an advertisement to the females and a warning to competing males.

When a mate has been found, the female rests on the larger male’s pectoral fin and the couple rise up together from the reef. At the peak of their ascent they simultaneously release sperm and eggs and then make a dash for cover as the spawn drifts away in the current.

This frenzy of sexual activity typically lasts some thirty minutes until nightfall. If fertilized, the eggs will hatch about a day later and the tiny larvae will drift for a further week or two before settling onto the bottom to begin their benthic life.

Part 8 of my documentary, “Mucky Secrets”, about the marine life of the Lembeh Strait in Indonesia.

This episode features some of the unusual fish found in the Lembeh Strait. First we encounter a pair of short dragonfish, Eurypegasus draconis, a type of seamoth. Seamoths are monogamous and bond closely with their mate.

We then meet the oriental flying gurnard. The juvenile oriental flying gurnard deters predators by appearing as large as it can. The false eyespots on its pectoral fins make it appear like a much larger fish from above.

The starry blenny, Salarias ramosus, is a type of combtooth blenny, of which there are some 400 species. By far the largest combtooth blenny is the hairtail blenny, Xiphasia setifer, also known as a snake blenny. It burrows its body into the sand, much like a snake eel.

Gobies represent the world’s largest fish family, and one of the most varied. The yellow pygmy goby, Lubricogobius exiguus, traditionally seeks refuge in natural shelters such as empty shells. Here we meet a pair living in a discarded bottle.

Finally we encounter a toothy goby, Pleurosicya mossambica, a type of ghost goby, living on a sea pen, Pteroeides sp.. The sea pen receives neither benefit nor harm from the relationship, but provides the goby with shelter and a good spot to feed on plankton passing by in the current.

Part 7 of my documentary, “Mucky Secrets”, about the marine life of the Lembeh Strait in Indonesia.

In this episode I take a look at members of the order Syngnathiformes, ray-finned fishes with long tubular snouts and elongate bodies.

The spotted seahorse, Hippocampus kuda, also known as the common seahorse, adapts its skin color to blend in to its environment. It has small hairs which gather algae and other matter to increase the camouflage. It feeds on small crustaceans, and its eyes can move independently to maximize its field of vision. It anchors itself to the seabed using its prehensile tail. The male seahorse incubates eggs then fetuses in a brood pouch on its belly until they are ready to hatch.

The tiny pygmy seahorse, Hippocampus bargibanti, is perfectly camouflaged amongst the branches of gorgonian seafans. Pygmy seahorses are so small and well camouflaged that they were only discovered in 1969 in a sea fan that had been collected by staff of an aquarium.

Pipefishes (Syngnathinae) are closely related to seahorses. They share the same long snout and toothless mouth, but have a straight body with ridges running along it. The ornate pipefish, Halicampus macrorhynchus, is well camouflaged to match its environment. The short-tailed pipefish, Trachyrhamphus bicoarctatus, resembles a gorgonian sea whip, and we see a translucent gorgonian shrimp, Manipontonia psamathe, standing on its back.

The banded pipefish, Dunckerocampus dactyliophorus, is a type of flagtail pipefish. The large, colorful tail fin makes it a faster and more agile swimmer than most other pipefishes and is used in courtship and territorial displays. Like seahorses, it is the male that incubates the young. Females compete to deposit their eggs in compartments under its abdomen. Scientists have suggested that the process of sexual selection continues after copulation. The males tend to fertilise and nurture the eggs of attractive females, while the eggs of less attractive females may be neglected or even digested by the male as he prepares for future pregnancies.

Ghost pipefish, family Solenostomidae, are usually found in pairs and are very highly camouflaged. Robust ghost pipefish, Solenostomus cyanopterus, are common in the Lembeh Strait, as are ornate ghost pipefish, Solenostomus paradoxus. We encounter a female ornate ghost pipefish churning her eggs between her pelvic fins to aerate them.

Finally we encounter a school of rigid shrimpfish, Centriscus scutatus, also known as grooved razor-fish, on a night dive.

Part 6 of my documentary, “Mucky Secrets”, about the marine life of the Lembeh Strait in Indonesia.

In this episode I first take a look at the pretty Banggai cardinalfish, Pterapogon kauderni. This is an invasive species which was introduced to the Lembeh Strait in the year 2000, and now competes with anemonefish for territory. Although it appears to be thriving in the Lembeh Strait and a few other locations, the Banggai cardinalfish is nonetheless still an endangered species because of its popularity in the ornamental fish trade.

We then encounter other species of cardinalfish (Apogonidae) in the area, Moluccan cardinalfish, Ostorhinchus moluccensis, the orbiculate cardinalfish, Sphaeramia orbicularis, and the frostfin cardinalfish, Ostorhinchus hoevenii, sheltering in the spines of sea urchins.

Finally we witness a trumpetfish, Aulostomus chinensis, preying on a small group of frostfin cardinalfish. The trumpetfish’s slim profile and stealth allow it to creep up very slowly on the unsuspecting cardinalfish, before making its attack. The trumpetfish sucks in the cardinalfish in a method known as “pipette feeding”.

Part 5 of my documentary, “Mucky Secrets”, about the marine life of the Lembeh Strait in Indonesia.

In this episode we meet Lembeh’s cuddly snake eels, moray eels and ribbon eels.First up is a convict snake eel, Leiuranus versicolor, hunting in the open and diving into the sand to attack prey. It bears a similar coloration to some sea snakes, which may deter predators.

Snake eels burrow tail-first into the sand, with just the head exposed. They are ambush predators. We encounter a stargazer snake eel, Brachysomophis cirrocheilos, and a highfin snake eel, Ophichthus altipennis, being cleaned of parasites and dead skin by magnificent shrimps, Ancylomenes magnificus.

Moray eels are also common. We encounter a free-swimming snowflake moray, Echidna nebulosa, and a whitemouth moray, Gymnothorax meleagris. A palechin moray, Gymnothorax herrei, bears the scars of previous conflicts on its face.

Finally I take a look at the ribbon eel, Rhinomuraena quaesita. Juvenile ribbon eels are black with are black with a pale yellow border to the dorsal fin and lower jaw. As it grows older, the ribbon eel turns into a male, taking on a bright blue and yellow coloration. Later, the eel changes into a female. It loses the blue and takes on a completely yellow color.

Ribbon eels have greatly expanded anterior nostrils, along with protruding barbels on both jaws, apparently to help them sense passing prey.

Part 4 of my documentary, “Mucky Secrets”, about the marine life of the Lembeh Strait in Indonesia. Stingrays and sharks.

In this video we look at the two most common stingrays in the Lembeh Strait. The bluespotted stingray (Neotrygon kuhlii) and bluespotted ribbontail ray (Taeniura lymma), also known as the blue-spotted stingray, are both occasionally found. They both like to camouflage themselves by burying themselves in the sand, but the latter species prefers to seek the shelter of outcrops, and has a more circular shape and vivid coloration. Stingrays breathe through their spiracle, a hole just behind the eye.

Pelagic sharks; sharks that must keep moving to breathe, are not at all common in the Lembeh Strait. But the benthic (bottom-dwelling) brownbanded bamboo shark (Chiloscyllium punctatum), sometimes known as a catshark, is sometimes seen. Juveniles bear strong banding, possibly mimicking the coloration of some dangerous snakes and eels. These sharks can pass water over their gills while remaining still on the seabed. In adulthood the coloration fades to a more uniform gray. The shark has two sensitive barbels above the mouth that help it find prey when it hunts at night.