With a bulbous body and spiky scales, a shaggy lure dangling from its head, and foot-like fins that it uses to walk along the seafloor, the deep-sea anglerfish Chaunacops coloratus has been filmed for the first time by researchers from the Monterey Bay Aquarium Research Institute (MBARI).

The anglerfish was first described from a single specimen collected off the coast of Panama in 1891. However, for over 100 years, marine researchers collected deep-sea fish using trawl nets and dredges, so this anglerfish was never seen alive.

That changed in 2002, when researchers used the remotely operated vehicle (ROV) Tiburon to explore Davidson Seamount – an extinct volcano off the coast of Central California. When the researchers first spotted this fish on video from the ROV, they weren’t exactly sure what kind of fish it was.

Then, in 2010, the researchers observed six more of these unique fish during ROV dives at Taney Seamounts, another set of extinct volcanoes off the California coast. This time, the scientists noted that the red fish were larger and more mature, while the blue fish were younger and smaller. From these observations, they inferred that this fish likely begins its life in a transparent larval form, turns blue as a juvenile, and turns red at adulthood.

One of the remarkable traits of all anglerfish is their ability to attract prey using parts of their bodies that function as lures. During one ROV dive, the researchers observed C. coloratus deploying a shaggy, mop-like lure, called an esca, which it dangled from the end of a modified fin near the top of its head. After an unsuccessful attempt at attracting prey, the anglerfish then stowed its fishing gear away in a special cavity located between its eyes.

In addition to witnessing the anglerfish using its ‘fishing lure’ the team also watched C. coloratus move across the seafloor in a manner akin to walking. This behavior is common among C. coloratus’ shallow-water relatives, the frogfish, but had not been observed in C. coloratus. Scientists speculate that ‘walking’ is more energy efficient than swimming short distances, and that it also disturbs the surrounding seawater less, reducing the chances of startling nearby prey.

As a result of the observations, the team also learned that C. coloratus can live as deep as 3,300 meters (11,000 feet) below the ocean’s surface. Previous trawl-net collections suggested that the fish lived only at depths of 1,250 to 1,789 meters (4,100 to 5,900 feet). Given the great depths these fish inhabit, it is no surprise that they had never before been seen alive.

“When you find something as rare as this little fish, it is important to clearly document what you can, and then make the information available so that other current and future researchers have access to the samples and information derived from the samples,” said Dr Lonny Lundsten, a researcher with MBARI and lead author of a paper describing the observations in the journal Deep Sea Research Part I: Oceanographic Research Papers.

“I’m curious about the world, and have a desire to make a contribution to our understanding of it, even if it’s just adding a little more information about a little fish that most people will never see. In the end, you hope to inspire other people to do the same, especially kids,” he said.

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Bibliographic information: Lonny Lundsten et al. 2012. Morphological, molecular, and in situ behavioral observations of the rare deep-sea anglerfish Chaunacops coloratus (Garman, 1899), order Lophiiformes, in the eastern North Pacific. Deep Sea Research Part I: Oceanographic Research Papers, volume 68, 46–53; doi: 10.1016/j.dsr.2012.05.012