C. coloratus was first described from a single specimen collected off the coast of Panama during an expedition in 1891 aboard the U.S. Fish Commission steamer Albatross. 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 from MBARI, Moss Landing Marine Laboratories, and the Monterey Bay National Marine Sanctuary 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. Although C. coloratus had been dredged from deep-sea environments in other ocean basins, it had never been seen in the north Pacific. After the cruise, the researchers recruited ichthyologists from California Academy of Sciences and elsewhere to help them identify the fish.
Then, in 2010, MBARI 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 research team noticed that not all of the fish were red or rose-colored, as they had previously been described in the scientific literature. Instead, some of the fish were blue.
After comparing the sizes of the fish in ROV videos, 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. coloratusdeploying 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” Lundsten and his colleagues 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 MBARI's ROV observations, researchers 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).
Via Dr. Stefan Gruenwald