Hagfish are eel like animals (Class Agnatha, Vertebrata) found in cold seas at depths above 4000 feet. They lie buried in burrows where the sea bottom is soft. They grow up to 32 inches. Their skin is without scales, smooth and soft. The color ranges from pink to dark blue. They have no true fins. Their tail is paddle like. The head portion has no eyes. The mouth is a slit like sucking opening surrounded by six sensory barbells. There is only a single nostril. Hagfish are scavenging animals.
The hagfish use their rasping tongue, which has horny teeth and bore their way through the bodies of dead fish or crippled fish and feed on the inner contents. They penetrate through mouth or gills or anus. Hagfish are a great nuisance to fishermen as they attack the fish caught on lines or in nets.
The hagfish are also called slime eels (there is no relationship between the two groups), because of their rich secretion of mucus or slime. On both sides of their body there are a number of slime glands, the size of a pea, which secrete a special type of slime. The slime consists of strong thread like fibers, similar to spider silk. The fibers are about 5 inches long and are released in coils by the slime glands. The fibers get uncoiled quickly to their full length. They provide strength to the slime mass.
When provoked, the hagfish release the slime in a thick concentrated form. As soon as the slime comes into contact with seawater, it swells into a thick gel. It forms a protective cocoon around the body of the hagfish.
The hagfish escape attack from predators by their slimy cocoon. The slime is capable of suffocating the predators when extended to them. But the hagfish do not get suffocated. They free themselves from the slimy cocoon by tying themselves in an overhand knot. The knot quickly passes from head to tail wiping the slime away.
Catching hagfish is a tough job. Researchers use punctured steel drums loaded with fish bait . The drums are lowered into the sea where hagfish are found. The hagfish enter the drum through pores feed on the bait and remain trapped unable to get out of the pores because of their swollen tummies. The drum is hauled and the hagfish are transferred to washing machines with large amounts of enzymatic detergents and run on a continuous rinse cycle to wash the slime off their bodies. They are then preserved in alcohol or formalin solution.
Hagfish are eaten in Japan and Korea.