• Photo by Rantje Allen

  • Photo by William Tan

  • Photo by Rantje Allen

  • Photo by William Tan

  • Photo by Rantje Allen

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Category Archives: Marine Life

Blacktip Shark Mating in Gorontalo

Blacktip shark mating is a rarely witnessed event. But that is just what happened one dive day in Gorontalo.

The Tell-tale Fin

blacktip shark drawing
The Blacktip Reef shark

The Blacktip Reef shark is the most common shark sighted in Indo-Pacific waters. Its scientific name is Carcharhinus melanopterus. Divers can easily identify this shark by its distinctive, black-tipped dorsal fin. Additionally, its anal fin is also black tipped. It can grow to a maximum length of less than two meters. Actually, another shark also has a narrow tip of black on its dorsal fin. However, this other shark has a pale anal fin. It also can grow to over two and a half meters in length. This oceanic blacktip shark is named Carcharhinus limbatus.

The Blacktip reef shark prefers shallow waters close to shore. Divers should look over reef ledges and flat sandy areas. Two dives sites in Gorontalo often have this shark patrolling sandy flats. That is where we witnessed a rare event.

Blacktip Shark Mating

One fine dive day Miguel’s Diving staff and guests watched two Blacktip reef sharks mating. Two guests had their GoPros ready and we created a combined video. Please watch it on our YouTube site.

You may notice that the male bit the female behind her gills. The love bite does not leave a deep wound. It should heal completely within a month or so. Also, notice that there is much thrashing about. At the end of the video, the sharks end up turning up-side-down and falling into a trance.

Tonic Immobility in Sharks

Some species of sharks become motionless and generally unaware of their surroundings when turned up-side-down. This is called tonic immobility. Once up-side-down, the shark will quickly become catatonic. This strange state can last up to fifteen minutes, as long as the shark remains undisturbed. The shark will eventually snap out of its trance and resume normal activities.

Sharks susceptible to tonic immobility include Whitetip and Blacktip reef sharks, as well as Lemon, Silky, Sandbar and Tiger sharks.

Notice in the video that that ecstatic pair of Blacktip sharks flip up-side-down and become catatonic. They fall together down the reef slope to a deep sand flat below.

For your chance to witness rare marine events in Gorontalo, please book your dive trip with us.

Juvenile Trevally Accompany Jellyfish

Juvenile trevally escorts jellyfish in Olele Bay, Gorontalo.

Travel Buddies

juvenile trevally pusing jellyfish
A juvenile Blue trevally pushes a jellyfish away from shore

Several times, Miguel’s Diving staff have observed juvenile trevally travelling with large jellyfish. Oftentimes, the young fish hide inside the bell of the jellyfish. They are safe there from predators and from the bushy, oral arms of the jellyfish. Usually, these large jellyfish travel the open oceans. Sometimes currents or winds will bring one of them close to Gorontalo’s reefs. The jellyfish will die if it gets caught on coral or drifts onto a beach. At those times, the fish seems to push the jellyfish away from danger and towards the open sea.

Thysanostoma species

We have only seen juvenile trevally accompanying large Thysanostoma jellies. Jellyfish of the Thysanostoma genus live in warm waters from the central Indo-Pacific to Japan. The Latin word thysanura means “bristle tails.” This name refers to the large, bushy oral arms that hang from the jellyfish’s central bell. They are active swimmers, using a pumping motion of the bell for propulsion.

Juvenile Trevally

Pilotfish (Naucrates ductor) are famous for accompanying large pelagic marine life. However, the juvenile trevally found in Gorontalo with Thysanostoma jellies are different. In 2009, we found a juvenile Blue trevally (Carangoides ferdau) darting in and out of a jellfish’s bell. The fish was so active that it is blurred in all its photographs. Its pattern, though, is disctinctive.

Longfin juvenile trevally
A sub adult Longfin trevally accompanies a jellyfish

Recently in 2017, we saw a fish grown too large to hide inside the bell of its travel buddy. This fish was not actually a juvenile trevally but a sub-adult. This stage of life for ocean swimming trevally species is rarely documented. Mr. Rudie Kuiter suggests that the one we observed was a young Longfin trevally (Carangoides armatus).

For your chance to see marine life interaction in Gorontalo, please contact with us for a dive package booking.

Schooling Bigeye Scad in Gorontalo

Bigeye scad can form large schools in quiet inshore areas of Gorontalo.

Thousands in Synchronized Motion

For several weeks in October 2016 a large school of Bigeye scad called Olele Bay home. Actually, this is a typical pattern for this fish. Since they hunt for food mostly at night, they gather in large schools during the day. During daylight hours they do not travel much. This was certainly true of the scad found in Olele.

With undetectable communication, the fish school moved and changed directions all at once. Their movements and direction showed astounding synchronization. Watch for yourself in the video below. At one point, they swam into the sunlight. Notice how the sunbeams danced around the school of fish.

Bigeye Scad

The scientific name of this oceanic fish is Selar crumenophthalmus. It is found in tropical regions worldwide, including equatorial Gorontalo. The local name of the fish in Gorontalo language is “oci.” It is a fast reproducing species and plays an important part in the local diet. One fish is the right size for one person. Other common names in English include Purse-eye or Goggle-eyed scad.

Bigeye scad schooling
Schooling Bigeye scad

The Bigeye scad is considered pelagic since it is associated with the open ocean rather than the reef. In Gorontalo, ocean depths plunge several kilometers just off the beach. That is why pelagic species including whale sharks swim right over the coral slopes of Gorontalo.

Inshore or Offshore

When they are swimming close to shore, Bigeye scad eat small shrimps, invertebrates and forams. When they are in open ocean conditions, these scad will eat zooplankton and fish larvae. Perhaps you notice them eating in the video. Clearly, they were plucking planktonic morsels from the water.
For your chance to see a school of Bigeye scad, please contact with us for a dive package booking.

Seahorses Rocking and Rolling in the Deep

Seahorses are favorites of many divers. Gorontalo waters host several different species. Pygmy seahorses are so cute, but many divers love ones that are big enough to see.

The Common Hippocampus kuda

Hippocampus kuda is the most predictable seahorse for divers to see. Its English name varies considerably. Some call it the Common seahorse. Others call it Estuary seahorse. It lives in shallow waters of mangrove swamps, estuaries and bays. Colors are generally dull, mainly blacks and browns. A yellow colored Common seahorse will be female.

female seahorse
A female seahorse lies quietly on the sea floor

Their dull pattern makes them look like debris lying on the ocean floor. This way they wait for small crabs or shrimp to come by. These seahorses suck in their prey whole through their long mouth. They do not have any teeth.

Rocking and Rolling

The Common seahorse is usually solitary. Sometimes, two of them will be lying still on the sand bottom near to one another. One day we saw several of them rocking and rolling in the deep. Watch Sami Lindross’s great video.

Pregnant Males

seahorse video
Watch the video!

Seahorses are most famous for their unusual biology. Males are the ones to give birth not the females. A mature male will develop a brood pouch on his belly. The female inserts her eggs into this pouch for the male to fertilize. The male’s pouch has placental fluid which surrounds the embedded eggs. This fluid provides oxygen, nutrients and waste disposal for the developing eggs. Moreover, the fluid becomes saltier. That way the babies are already adapted to salt water when they hatch. Pregnancy lasts 20 to 28 days. Then the male goes into labor, releasing the baby seahorses from his pouch.

Seahorses in Gorontalo

The Common seahorse is found at several dive sites in Gorontalo. However, finding them will often require a skilled dive guide. Even after they are found, they can easily drift away. For poor swimmers, seahorses can disappear quickly when they feel disturbed or threatened. For your chance to sight a seahorse in Gorontalo, please book your dive trip with us.

Scuba Diver Ocean Planet Magazine Features Gorontalo Whale Sharks

Scuba Diver Ocean Planet magazine recently featured the whale sharks of Gorontalo.

Scuba Diver Ocean Planet Magazine Featured Destination

Scuba Diver Ocean Planet Magazine photo spread
Double page magazine photo spread

Gorontalo’s new whale shark reserve at Botubarani Village became a featured destination in Scuba Diver Ocean Planet magazine. “Gorontalo Botubarani” encompasses four pages. This includes a dramatic double page photo of a whale shark swimming above a diver. In the foreground of that photo lies some of Gorontalo’s beautiful coral. Noteably, Mr. Arief Yudo Wibowo took this and other photos for the feature. He is the managing editor of Scuba Diver Ocean Planet magazine.

Research from Indonesia Whale Shark Team

The accompanying article features research from the Indonesia Whale Shark Team. Its members lived in Botubarani village while conducting their study. They lived there from April 12 to April 30, 2016. As a result, they recorded a total of 17 individual whale sharks. All were males. Worldwide, females rarely appear. Furthermore, the lengths of Botubarani whale sharks measured three to seven meters. That means all of them are juveniles. Since whale sharks are migratory, the researches expect that total to rise.

Indonesian Minister of Marine Fisheries directive 16/2013 designated the whale shark as a protected species.

Ocean Characteristics of Botubarani Village

The Scuba Diver Ocean Planet magazine article on Gorontalo explains the characteristics of Botubarani Village. It sits on the edge of deep ocean waters. Near the shoreline there is a rocky shelf. This shelf is at most four meters deep. A steep slope falls to 15 meters. Then comes a deeper inlet about 30 meters deep. Consequently, this inlet provides direct access to deep ocean water.

No net or fence blocks access to deep water. As a result, whale sharks are free to come and go. The reason they frequent this particular underwater inlet is simple. A shrimp factory is located there. For years now, workers have thrown the unused shrimp heads and skins into the water. The whale shark like these snacks! These snacks do not provide enough nutrition. So, the whale sharks still must forage for plankton and minnows on their own.

Scuba Diver Ocean Planet Magazine advert
Become a happy diver with Miguel’s Diving

Miguel’s Diving placed a half page advertisement in Scuba Diver Ocean Planet magazine. We want responsible divers to know that we follow the procedures recommended by Indonesia Whale Shark Team. That includes keeping an appropriate distance. For your chance to dive with whale sharks in Gorontalo, please contact with us.

Whale Shark Encounters in Gorontalo

Whale shark sightings have always been common in Gorontalo. But this month we are encountering these giants daily.

Sightings in Gorontalo

Since beginning operations in 2003, whale shark sightings with crew and guests have been numerous. On average, we encounter these giants twice per month. Any month will do. In other places in the world, whale sharks are seen on the surface. That is true in Gorontalo, also. However, we also see them while scuba diving. Oceans depths off dive sights here plunge to over four kilometers. No wonder divers encounter whale sharks in Gorontalo!

New Site for Whale Shark Encounters

young whale shark
A young whale shark visits our dive boat

In April 2016 a video from Gorontalo was uploaded onto social media. It was an instant hit. Seven whale sharks were seen congregating. To local fishermen, this was not news. The giant fish had been gathering in the same spot for two years. A nearby shrimp factory had been throwing its unwanted shrimp shells and heads into the ocean. The whale sharks love to eat them. This means that whale shark sightings occur daily in April at this location.

Protection Efforts

Miguel’s Diving staff, POSSI Gorontalo and government officials met together the week following the discovery. Under the direction of Gorontalo’s governor, Drs. H. Rusli Habibie, MAP, a conservation area is being established. This includes zonation.

Responsible Contact with Whale Sharks

The World Wildlife Fund (WWF) has published guidelines for whale shark encounters. This includes the call not to touch the whale shark. Certainly, no one should ride one or grab a fin. A safe distance is two meters from the whale shark’s head. Stay three meters from its tail.

Schooling whale sharks is a new phenomenon for Miguel’s Diving. We are still studying how to conduct scuba diving that is safe for guests and whale sharks alike.

Below the feeding area is a series of coral pinnacles. Divers descend and wait near the pinnacles. The depth is around 15 meters. This provides an appropriate distance for safe viewing whale shark silhouettes as they circle above. After eating some shrimp heads, they swim down to inspect the divers. Oftentimes, they swim very close.

Taking pictures or video of the whale sharks is easy to do. WWF guidelines indicate that a flash should not be used. Divers also should not chase them. The whale sharks will pass by divers waiting patiently by the pinnacles.

For your chance for a whale shark encounter, please book your dive trip with us.

Mackerel Feeding Frenzy

Mackerel feeding frenzy! Right beside the dive boat, guests of Miguel’s Diving watched schooling Big mouth mackerel feeding off Jinn Caves dive site.

Regional Names

mackerel feeding frenzy
Flashes of silver

This small mackerel is found throughout tropical Indo-West Pacific seas. Its scientific name is Rastreliger kanagurta. In the Indian Ocean it is commonly called Indian mackerel. In the western Pacific it is commonly known as Big mouth or Mouth mackerel. Sometimes Long-jawed or even Rake-gilled mackerel is its common name.

Big Mouth Mackerel feeding

This fish is easily recognized. Its feeding pattern is distinctive. It filters microscopic marine life from the water by opening wide is mouth. Then it swims quickly into those pools of plankton. Its gill rakers strain food from the water. When its mouth is open, its head looks bigger. Notice in the video how the head flashes silver during mackerel feeding time.

Notice in the video all the particles in the water near the surface. Those particles are living organisms plus some floating sticks and leaves. Surface winds and ocean currents have pushed plankton into the small cove near the dive site. This created perfect conditions for a mackerel feeding frenzy. Visibility below was nearly 30 meters.

Up the Food Chain

Big mouth mackerels feed on the smallest marine life forms. This included diatoms known as phytoplankton. They also eat microscopic animals known as zooplankton. Adults prefer macroplankton, like shrimp larvae and fish eggs.

This fish is an important part of the diet in coastal areas of the Indian Ocean. It is canned, dried-salted and smoked. It is also made into fish sauce. In Gorontalo this fish is mainly ignored. Locals prefer Yellow-fin tuna, which is available in deep waters just off the coast.

For your chance to watch Big mouth mackerel feeding, please book your dive trip with us.

Sacoglossans of Gorontalo

Sacoglossans are vegetarian sea slugs or snails. They bite into algae. Then they suck out the contents. Sometimes they are called sap-sucking sea slugs. Several species are found in Gorontalo’s diverse marine environment.

Blue-spotted bubble snail

Blue-spotted sacoglossans crawling
Blue-spotted sacoglossan

One of the sacoglossans found in Gorontalo is Oxynoe viridis. Although it looks like a simple slug, it is not. It carries a small, white shell on its back. However, the shell is rarely seen. This sea slug has twin side flaps that usually cover the shell.
Sacoglossans like this Blue-spotted bubble snail only eat algae. Typically, they feed on palm-like Caulerpa algae. This bubble snail’s green color helps camouflage it. That makes it hard for predators and divers to spot. For additional protection, this bubble snail produces a sticky, white secretion when disturbed.

If further threatened, it can break off its long tail. The tail wiggles vigorous, giving the snail time to hide. A new tail will grow in time. This bubble snail uses its long tail to hang onto algae. The one in this photo has fallen. It will climb back onto the nearest Caulerpa algae. Watch it feed in the video. Notice the algae to the left has already been munched!

Expansa sap-sucking sea slug

Another sacoglossan found in Gorontalo is Elysia expansa. Its name comes from its expanded twin side flaps. It does not have a shell. Like other sacoglossans, it is strictly vegetarian.

Expansa sacoglossans crawling
Expansa sacoglossan

It seems to prefer eating Caulerpa taxifolia. Ironically, it looks like a discarded piece of vegetation, a great disguise! Watch it rock like a leaf in the video.

Similar Sacoglossans

In Indo-Pacific waters, there are several similar looking sacoglossans. The white-spotted Elysia tormentosa was described by Kathe Rose Jensen in 1997. The Expansa sea slug has noticeably fewer hairs. The thin line that outlines the pinkish edges of the side flaps is black.

Divers never know what unusual marine life will appear. The marine diversity here is incredible. For your chance to watch Gorontalo marine life in action, please book your dive trip with us.

Gymnodoris ceylonica nudibranchs in Gorontalo

Gymnodoris ceylonica were everywhere! Pearly white nudibranchs with orange spots were crawling along the ocean floor. What was going on?

Watching a Rare Event

The dive site was Tambo’o Fish House. It is a favorite muck diving site in Gorontalo. No nudibranchs were seen the previous day. Then suddenly one day in November, there were dozens and dozens of Gymnodoris ceylonica nudibranchs. Most were about five centimeters in length.

Gymnodoris ceylonica laying eggs
Gymnodoris ceylonica laying eggs

Upon closer inspection, those Gymnodoris ceylonica nudibranchs were mating. Then they were laying eggs on various kinds of algae. A few were laying eggs on the sand. Miguel’s Diving staff had never seen this happen. So, we came back on the two following days to film this rare event. By the third day, all the nudibranchs had disappeared. Only their eggs were left.

Watch this amazing video, shot by Mr Yunis Amu of Miguel’s Diving. Notice the translucent body of this nudibranch. Sometimes, the yellow eggs still inside the nudibranch are visible from the outside!

The Ceylonese Nudibranch

The common name for Gymnodoris ceylonica is Ceylonese nudibranch. It was first discovered in 1858 off the coast of Sri Lanka. That island was a British Crown colony at the time marine researchers were working there. The British called their colony Ceylon, hence the name of this nudibranch.

The Life of Gymnodoris ceylonica

Ceylonese nudibranch eggs on algae
Eggs of Ceylonese nudibranch on algae

This lovely nudibranch prefers open grass beds. Plenty of algae live in that marine environment. Ceylonese nudibranchs are not vegetarian, however. They are carnivores. They eat other nudibranchs. Pictures of one eating a sea hare are available here.

Mr. Bill Rudman of Sea Slug Forum has several observations about the eggs of Gymnodoris ceylonica. Most noticeably, the eggs are not in the classic, smooth ribbon like other nudibranchs. These egg masses are almost messy in comparison. Missing are the pretty spirals that divers expect to see. Johnson & Boucher studied the eggs of this nudibranch in 1983. They discovered that the eggs are arranged in clusters of 20 to 40 eggs. Each yellow dot visible in the video and photo is actually a cluster of eggs.

Divers never know what to expect here because of the incredible variety of marine life. For your chance to watch Gorontalo marine life, please book your dive trip with us.

Sea Sapphires Mysteriously Disappear

Sea sapphires are flashy planktonic crustaceans that appear and disappear. No one knew how they did it – until now.

Suddenly Visible

In Gorontalo waters on certain days, divers are ready to descend. They notice tiny flashes of color in the water column. The flashes look like chips of iridescent blue paint. Sometimes the color is yellow. Occasionally, it is golden red. Upon closer inspection, those tiny ovals of blue are plankton floating in the water. Approach one with your finger. It will swim away and disappear. They are commonly called sea sapphires.

In the early mornings Gorontalo fishermen report seeing the ocean shimmer with these iridescent flashes. An old expression used by Japanese fishermen is tama-mizu. This means “jeweled water.”

The Life of Sea Sapphires

a male sea sapphires
A male sapphirina copepod

These brilliant and mysterious creatures are actually sapphirinid copepods. Copepods are a subclass of tiny crustaceans. They have elongated bodies and forked tails. Their scientific names reflect their jewel-like appearance.

Only male sea sapphires flash brilliant colors. They are carried by ocean currents, along with other planktonic life, to the coral walls of Gorontalo. Sea sapphires are an important part of the food chain. When we see them collecting off a dive site, we look out for whale sharks.

Female sea sapphires do not float the oceans with the free-swimming males. Instead, they congregate inside certain kinds of transparent jellys. Females have much larger eyes than males. Perhaps this allows them to scan the vast ocean for flashy boyfriends. Watch them in incredible Kaj Maney’s video.

The Arts of Reflection and Disappearance

A team of scientists from the Weizmann Institute of Science just discovered how male sea sapphires appear and disappear. Their study was published in June 2015. Males have alternating layers of hexagonal-shaped crystals. These are imbedded in their backs. Sea sapphires are only a few millimeters in length. But researchers managed to measure the distance between those reflective crystals found in sea sapphires. They used live males. The distance between crystals was only about 1/10000 mm. This measure is about the same as a wavelength of blue light. When sunlight hits male sea sapphires, only one color is reflected by the crystals. Usually, it is blue. Differences in color depend on the distance those layers of crystals are from one another. That is why some sea sapphires appear yellow or golden. This type of coloration is called structural coloration.

 tiny male sea sapphires
A tiny male sea sapphire reflects blue

Male sea sapphires swim freely in the open ocean. However, they do not swim in straight lines. They swim in spirals. Researchers also discovered how these sea sapphires disappear so quickly. As they turn, the angle of reflected light changes. When light hits them at a 45-degree angle, the reflection shifts out of the visible light range. Only ultraviolet light is reflected. Since humans cannot see ultraviolet light, male sea sapphires seem to disappear. They do this by merely turning their bodies. Although how they appear and disappear is now known, no one knows why.

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