These creatures are completely adapted to survive at this deep in the sea.
They can attract prey using the glowing part of their heads, which emits a strong light (strong, considering that at this deep in the ocean there is close to 0 sunlight reaching the environment), and lure smaller fishes to the anglerfish. When the fish is hunting, he remains still as he waits for his prey to come.
The process of locating a mate is initiated by the female, who is usually much larger than the male. The female angler fish execrates chemical that attracts males, and once the male founds her, he will bite her skin and will slowly merge with her until they become one, providing semen when she is ready to procreate.