The environment in deep water is a very challenging place to live. The fish that live there have many special adaptations to deal with these challenges.
Taking the Pressure
Fish in the ocean experience pressure that increases as they go deeper. The pressure is from the water that surrounds them and presses on them from all sides. To get a sense of what this pressure is like, imagine a giant hand squeezing you. As the pressure increases, it is as if the hand is squeezing you harder.
- Above the surface, the air around us pushes on our body. The pressure is measured as 1 atmosphere.
- Below the surface, for every 10 metres down, the pressure of the water increases by 1 atmosphere.
- So, deep-sea fish living at 1000 metres are under 100 times more pressure than we are at the surface!
- Deep-sea fish have soft and flabby skin and bones to help them deal with the pressure of the water.
What Do Deep-Sea Fish Eat?
- Deep-sea fish feast on smaller fish, smaller creatures, or dead organisms that fall from above.
- Food is hard to find deep in the ocean, so deep-sea fish do not eat every day like we do. In fact, they can go a couple of weeks, or more, without finding food.
- Many deep-sea fish species are predators that do not actively hunt for food. Hunting takes too much energy, which they can’t afford because they don’t eat often.
- Once a deep-sea fish has eaten, it takes a long time to digest its meal. This makes its food supply last longer.
How Do Deep-Sea Fish See?
Fish near the ocean surface have normal eyes. Fish eyes get larger with depth so that they can gather increasingly feeble light. At lightless depths, fish often have small eyes, presumably to sense bioluminescence. Of course, some fish at deep depths have normal eyes because they migrate up and down in the water column, thereby entering lighted areas.
Because very little sunlight, if any, penetrates into the depths of the ocean, many deep-sea fish have organs that glow in the dark. In other words, they are bioluminescent. They use this light to locate each other and to lure prey.
Q: What else lives down in the deep?
A: Apart from fish, the deep sea is also home to many different creatures, such as squids, crustaceans and marine worms.
See a squid of the Teuthowenia pellucida species.