Fishing the deep sea has great potential, but scientists warn that we should understand these ecosystems before we start fishing. (Photo: <a href=http://www.shutterstock.com/pic-358062173/stock-photo-sun-sea-underwater-ocean-blue-background-with-fish.html
 "blank=_">Shutterstock</a>).
Fishing the deep sea has great potential, but scientists warn that we should understand these ecosystems before we start fishing. (Photo: Shutterstock).

Scientists: Deep-sea fish can solve world food shortages

There is a lot of food hiding in the deep ocean and it could help feed the entire world. But we must take care not to overfish, marine scientists warn.

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How to feed the world is one of the most pressing global problems that we face right now and in the future as the world’s population continues to grow.

But some scientists think they may have found a solution, deep below the sea.

In a new article, marine scientists examine the potential of seafood in the mesopelagic zone, which is the part of the ocean that is between 200 to 1,000 meters deep. The article was recently published in the journal Frontiers in Marine Science.

"There is a huge potential in the mesopelagic zone. It suggests that there is a resource so great that it alone could feed the entire world population," says lead author, Professor Michael St. John, from the Danish Technical University.

10 billion tons of fish in the mesopelagic zone
The sea is divided into five zones based on depth. A huge amount of fish that can be used to feed the earth's soaring population live in the mesopelagic zone (200 to 1000 meters deep) (Illustration: NOAA)
The sea is divided into five zones based on depth. A huge amount of fish that can be used to feed the earth's soaring population live in the mesopelagic zone (200 to 1000 meters deep) (Illustration: NOAA)

Enormous amounts of fish are believed to live in the so-called mesopelagic zone. Recent observations indicate about 10 billion metric tonnes of biomass is hiding down there. This is considerably larger than the previous estimate of about 1 billion tonnes in the 1980s.

Some of these deep-sea fish are suitable for human consumption, but right now most of it end up in fishmeal--feed for fish farming and farm animals.

"We could produce tremendous amounts of food with fish meal. If we imagine that we can fish 5 billion tonnes without further depleting fish stocks--that corresponds to a food output of 1.25 billion tons," says St. John.

Read More: More fish found deeper in the ocean.

Scientists warn against overfishing

However, it is still too early to sit back and rely on deep-sea fish to solve the world’s food problems.

"The figure can so far only be described as a guess. I personally believe that the 10 billion is a conservative estimate--a minimum number. But we need many more studies before we can say anything definitive," says St. John, who stresses that the potential is so great that urgent research is needed.

Most fishing takes place in the top layer of the ocean, where we know most about the ecosystem.

But according to St. John the fishing industry is already waking up to what is hiding in the mesopelagic zone and it is important to learn from our past experience with overfishing. We should make sure we understand the ecosystem somewhat before we start fishing there, he says.

"We’ve seen so many examples of overfishing that has destroyed stocks and ecosystems in the oceans. Take for example cod, which began to be fished in the mid 00s. We fished without taking into account that [cod] become sexually mature at a late age, which reduced the population considerably. We must make sure not to repeat these kinds of mistakes,” says St John.

"We need to start researching immediately so we [know how to proceed]. Because there are many things that can go wrong when we have such a large biomass," he says.

Read More: Top four ocean threats according to marine scientists.

Concerns about climate and biodiversity

With such a large biomass, a lot can go wrong. Fish play an important role in the marine ecosystem as feed for the predators. So overfishing would destroy more than just the stock of mesopelagic zone fish.

These deepsea fish also take up large quantities of CO2 through their participation in the so-called biological pump. Every day fish migrate up to the surface and move carbon from the sea surface down to the deep ocean.

So St. John suggests that fisheries hold back until we understand the role of deep-sea fish in these systems.

Associate Professor Peter Grønkjær, from Aarhus University's Institute of Bioscience agrees.

"The potential of this is huge, but we must be careful. We must have complete control over how we handle this biomass. If it’s as big as it seems, it has an enormous impact on the Earth's climate and ecosystem--so one must tread very carefully," he says.

Read More: How climate change changed the face of marine science.


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Read the Danish version of this story on Videnskab.dk
 

Translated by: Catherine Jex

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