• Photo by Rantje Allen

  • Photo by William Tan

  • Photo by Rantje Allen

  • Photo by William Tan

  • Photo by Rantje Allen

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Yearly Archives: 2025

Risso’s Dolphins Sunbathe and Play

Risso’s Dolphins thrive in the deep waters off Gorontalo’s southern shores. One day, we spotted a large, active pod. Using a drone, we watched as they sunbathed, played, and possibly mated.

Ghostly Apparitions

Risso’s Dolphins (Grampus griseus) are a distinctive species of dolphin. They are born gray but become whiter with age. The older one is, the whiter it appears. When passing under the dive boat or swimming nearby, they look like ghostly apparitions.

Their bodies also show visible scarring. Most scars come from fights with other Risso’s Dolphins, while other scars come from bites of deep-sea squid, their main diet. These features make them easy to identify.

Unlike other dolphins, Risso’s have rounded heads and no beak. They also have a crease running from the blowhole down to the upper lip. This unique feature is only visible up close or from a drone’s view.

Drone Video of Risso’s Dolphins

One day, our dive boat was heading to the second dive site when our captain spotted a pod of Risso’s Dolphins. They were sunbathing on the ocean’s surface, which is typical behavior in Gorontalo. Their distinctive white bodies confirmed their identity.

As we watched from a safe distance, one of our Indonesian guests launched his drone. Dr. Reyhan Aditya captured dramatic footage of this large pod. Some dolphins rested on the surface, while others played. One sequence even suggests mating behavior.

Risso’s Dolphins typically grow to three to four meters long and weigh between 300 and 500 kilograms. Clearly, most dolphins in this pod were adults. At other times, we have seen baby Risso’s among them. Usually, we see pods of about ten individuals, but this pod was much larger.

Worldwide Sightings

Risso’s Dolphins live in temperate and tropical oceans worldwide. They prefer deep offshore waters. Sometimes, they swim closer to land or oceanic islands when the continental shelf is narrow. This is true of Gorontalo’s southern coastline. Here, the continental wall of Sulawesi lies just a few meters from shore, plunging to four kilometers deep. This unique geography makes Gorontalo a great place for pelagic encounters.

Antoine Risso, a French naturalist, first described this species in 1812. Later, the dolphin was named in his honor.

For your chance to see unusual marine life in Gorontalo, please make your dive reservations directly with Miguel’s Diving.   

Redlined Jorunna Love Triangle

Redlined Jorunna nudibranchs made a rare appearance in Gorontalo. During the required safety stop, divers hovered over a patch of sandy rubble as they rested for three minutes. Looking at the sandy bottom, they discovered a cluster of black Long-spined sea urchins, several shy pipefish, and sea stars. Then, in the gentle surge, they noticed a moving, intertwined mass. It was three Redlined Jorunna nudibranchs engaged in group mating!

Love among Redlined Jorunna

Like other nudibranchs, this species is hermaphroditic. This means each nudibranch has both male and female reproductive organs. To fertilize the eggs, sperm must come from another individual.

It seems the three Redlined Jorunna we saw were donating sperm to each other. Nearby, divers noticed a pinkish ribbon of eggs already laid. According to scientific observers, this nudibranch species only appears in the open during mating. Otherwise, they hide in the reef.

Red lines and Fur

The scientific name for this species is Jorunna rubescens because of its reddish lines and markings. Underwater, divers can use additional light to bring out the reddish color.
Like other dorid nudibranchs, Redlined Jorunna have twin rhinophores on their heads and a bushy tuft of gills at the tail. These three parts can be pulled inside the body when the creature feels threatened.

Redlined Jorunna nudibranch
Redlined Jorunna nudibranchs

Unique to dorids, fur-like caryophyllidia cover the body of Jorunna rubescens. Tiny spine-like spicules surround these sensory tubercles. Together, they give the body of this nudibranch a velvety appearance. As a result, some observers commonly call this species the Pink Furry Nudibranch.

For additional underwater photographs of Jorunna rubescens, including close-ups of the caryophyllidia, open this link.

Life and Environment

One of the larger dorid nudibranch species, Redlined Jorunna can grow up to 15 centimeters in length. The largest of the three we saw measured about nine centimeters. Jorunna rubescens lives on the seafloor in Indo-Pacific waters, including areas of coral reef and sandy or rocky bottoms like those found we found. For your chance to see unusual marine life in Gorontalo, please make your dive reservations directly with Miguel’s Diving. 

Alligator pipefish hunts for lunch

Alligator pipefish are rarely seen, despite their size. Even more remarkable is to follow one as it searches for something to eat. Yet that happened one day in Gorontalo – and we have the video to prove it!

A Mangrove Seed or a Blade of Grass

Alligator pipefish
An Alligator pipefish in Gorontalo

The Alligator pipefish (Syngnathoides biaculeatus) has a long, slender body that mimics a blade of seagrass. Some divers could also mistake it for a floating seed of a mangrove tree. Its body is usually green or brown. This camouflage helps it blend into its habitats. These include seagrass beds, mangroves, and estuaries. Predators and divers have difficulty recognizing one, even though it can grow quite large – up to 50 centimeters in length!

Most pipefish have paddle-like tails. But not Syngnathoides biaculeatus. Its body tapers to a point. That earns it the common name “Double-Ended Pipefish.” However, most divers call it the Alligator or Crocodile pipefish. Although it lacks a true prehensile tail like seahorses, it can bend its tail to form a hook. This allows the fish to hook onto something on the sea floor and remain motionless.

One Hungry Alligator Pipefish

One day in Gorontalo, we made our safety stop in a sandy area. Suddenly, one of our dive masters waved excitedly. He pointed to something floating motionless above the sand. It was an adult Alligator pipefish, measuring about 20 centimeters. While other divers relaxed and lunched above in our dive boat, we grabbed a video camera and followed the pipefish around.

The pipefish ignored us as it slowly surveyed the area. Soon, we noticed it was actually searching for something to eat. First, it swam across the seagrass bed, then among some coral boulders, and finally among clumps of dead Turbinweed. With the noonday sun beating down, it finally spied something to eat.  

Syngnathoides biaculeatus Inhales its Food

The Alligator pipefish uses its elongated snout to suck in tiny prey. It likes to eat mysid shrimp and copepods. While on the hunt, a pipefish moves slowly through the water, probing and looking. When it spots prey, it quickly sucks it into its snout with a powerful vacuum-like motion. We caught all of this in our video.

Although we have seen this pipefish since the initial encounter, we cannot know how long it will stay. For your chance to see unusual marine life in Gorontalo, please make your dive reservations directly with Miguel’s Diving. 

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