Adaptations of Deep Sea Fish

Adaptations of Deep Sea Fish

Deep sea fish are pretty bizarre looking, perhaps even scary to the human eye. Living in total darkness, under crushing pressures, and in frigid temperatures – these fish are built to survive in one of the world’s less friendly environments. Although the ocean itself is quite deep with different creatures living among its different layers – certain adaptations are found again and again beneath the epipelagic zone.

Deep Sea Fish Live Without Light

The epipelagic layer is the top most layer of the ocean and extends about 200 meters down. Light can’t penetrate the ocean much farther than this which means the bottom 10,000 meters of the sea exist in total darkness. That is, except for the light created by deep sea creatures themselves. Some deep sea animals are able to create light through a chemical reaction called bioluminescence.

Since some light does exist due to bioluminescence, many deep sea fish have evolved large well-developed eyes in order to see what light they can. According to the book Ken Schultz’s Field Guide to Saltwater Fish by Ken Schultz, deep sea fish may or may not have eyes at all. Those that do, however, have eyes relatively larger than any other animal with a backbone. This helps them to see and catch prey as well as avoid predators. Those creatures that have bioluminescence can lure in prey or use their light to find mates.

How Deep Sea Fish Find Food

Many deep sea fish however are blind or cannot rely on light too often. Thus these creatures rely on other senses including smell, touch, and taste in order to understand their surroundings. According to Dr. J. P. Shukla’s book “Fish and Fisheries” deep sea fish often have well developed lateral lines – a sense organ that can detect movement and vibrations in the water – as well as long fins that can do the same.

Food is scarce in the deep. Since sunlight does not reach the depths of the ocean, there are no plants except those that fall from above. Deep sea fish must be prepared to eat what they find and thus are often equipped with large mouths, huge jaws, and expandable stomachs that can stretch for large prey. Many deep sea fish are known for their large and ferocious looking teeth which can help catch and hook prey. According to Shukla, deep sea fish are primarily predators or scavengers. Bodies falling from above though tend to stay well preserved given the chilly temperatures of the deep.

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Deep Sea Fish Withstand Crushing Pressures

The water pressure in the deep ocean is extreme. According to NOAA’s National Weather Service on its “Layers of the Ocean” page, the pressure at 4000 meters is over 5850 pounds per square inch. Deep sea fish however are well adapted to these crushing pressures. According to the organization, on their page “The Deep Sea”, these fish often have soft and flabby flesh and bones that can’t collapse under all that pressure. Deep sea fish also don’t have excess body cavities, for example most do not have a swim bladder.

Protecting Deep Sea Fish

Deep sea fish are well adapted to their environments, but they have not yet learned how to avoid their greatest predator – man. The book “High seas bottom trawl fisheries and their impacts on the Biodiversity of Vulnerable Eco-systems” by Matthew Gianni, notes that deep sea fish are “highly vulnerable to overfishing” especially since so little is known about them (p. 50). Avoiding stocks that are overfished is a great way to promote conservation of one of the world’s least understood environments.

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