AmericaMarine biologists on an expedition in Monterey Bay, California, encountered an extremely rare deep-sea fish called the high-fin arowana (Bathophilus flemingi).
High-fin arowana on the seabed of Monterey Bay. Image: MBARI
For three decades, a team of experts at the Monterey Bay Aquarium Research Institute (MBARI) have probed the deep bottom of the bay using a remote-controlled vehicle (ROV), finding many interesting creatures, including several species dragon fish. However, the highfin arowana is the most reclusive species. The fish in the video was discovered at a depth of 300 meters. This is the rarest of all arowanas. Previously, scientists had only observed a few living individuals.
“High-fin arowanas are very interesting animals, in part because of their color,” said Bruce Robison, a scientist at MBARI who led the study. The iridescent scales with copper tones of the highfin arowana are different from any other fish living in the deep sea. The pigment that makes up their shiny bronze skin can be a form of camouflage. This tone absorbs blue light reaching the deep sea, making arowanas almost invisible in their habitat.
The camouflage above is very suitable for high-fin arowanas, which are ambush predators. They float in the dark, waiting for small fish and crustaceans to swim past. However, the prey does not swim by randomly, but is often attracted to the arowana by the bioluminescent fiber protruding from their chin. Arowanas use that part to trick their prey into coming closer by mistaking the bright spot for food. When the prey gets close enough, the arowana will use its wide jaws full of sharp teeth to grab them.
Arowanas use bioluminescence not only to catch prey, but also to avoid being eaten. According to Robison, many carnivores hunt by looking up, trying to detect the outline or shadow of their prey against the light of the water above. To blend in with the background, the arowana has a series of glowing organs along its flanks. These organs correspond to the color and intensity of the light above, causing the outline of the fish to be blurred.
When Robison and his team discovered the fish, they were on a week-long expedition aboard the Western Flyer research vessel, conducting numerous experiments and observations in a relatively short time. However, they did not expect to see the highfin arowana during the trip.
An Khang (According to Live Science)
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