Deep Sea Fish

Deep Sea Fish

The deep sea environment is characterized by darkness and low temperatures, because sunlight is unable to penetrate beyond the surface layers of the ocean. In addition the weight of the water above, means that very high pressure exist in the abyss. The depth at which sunlight begins to fade is about 200m (656ft.). This is where a zone known as the mesopelagic begins. Beneath, at a depth of 1,000m (3,280ft.) another zone begins, called the bathypelagic. Below this, at a depth of 4,000m (13,123ft.), the true abyss begins, otherwise known as the abyssopelagic. In places where there are additional deep sea trenches, a fourth term, hadopelagic, is used.

Angler Fish

With no sunlight in the deep sea there is very little energy available in the form of warmth, except in places where there happens to be volcanic activity, so that water is heated by escaping lava or by hydrothermal vents. The result is that life forms tend to concentrate in places where the energy allows for a food chain to exist. In other regions, organisms are few and far between, which is one reason why deep sea fish are not well studied. In some cases, they are only known from one or two specimens encountered by chance. Living without light and with few other fish around has its problems. Finding food is a tricky business, so deep sea fish have evolved ways to attract prey, to save them having to search in vain. They posses bioluminescence, which means they can produce light. They use the light to attract or lure prey animals that come to investigate. When the prey gets close enough they quickly grab it. This is generally done with a large gulping mouth, so that the prey gets trapped inside, or with fearsome teeth, so that the prey is speared and cannot escape.

Deep sea anglerfish (order Lophiiformes) are well known. They use light- producing lures on the ends of fishing rod- like filaments growing from their heads. They have large, upward- turned mouths able to gulp prey as soon as it comes near enough. Another familiar deep sea species is the pelican gulper eel (Eurypharynx pelecanoides). Its scientific name alludes to its massive, pelican- like gape, which enables it to capture prey before it has a chance to swim away. Common prey fish are the lantern fish (family Myctophidae).