It was filmed recently in Monterey Canyon in California's Monterey Bay by the remotely operated submersible vehicle Doc Ricketts.
"We've been diving out here in the Monterey Canyon regularly for 25 years, and we've seen three," MBARI Senior Scientist Bruce Robison told the Santa Cruz Sentinel.
Robison also narrates the video, and describes the unusual appearance of the fish:
Anglers have a remarkable apparatus on their heads: a fishing pole, with a luminous lure at the tip, which they use to attract their prey. In the darkness of deep water, they flash the light to attract prey and draw them near the angler's mouth. When a fish or a squid swims up, it is quickly inhaled by the angler's huge mouth and trapped by its long, sharp teeth.
It's a hunting technique familiar to anyone who's seen the film "Finding Nemo." But as scary as the fish may appear, it's not very big. This one is just about 3.5 inches long.
The video was recorded at a depth of more than 1,900 feet and shows a female with a broken tooth. Males are smaller, and don't have the "fishing pole" attachment.
"Males are ill-equipped for feeding, and their sole responsibility appears to be to find a female and mate with her as soon as possible," Robison says in the video.
When he finds one, "the male bites into the body of the female, their tissues fuse. The male's body degenerates until it's a lump of tissue surrounding testicles," Robison told KSBW, the local NBC affiliate. The female will then carry the male around for the rest of her life, and collect more along the way.
He told the station he's seen 11 males attached to a single female.
"The deep sea is filled with surprises and wonderful creatures," Robison says in the video. "Humans have only just begun to explore this vast realm, and we can only imagine what discoveries are yet to be made."