There is a steadyly growing demand for fish in the world. In statistical terms in 2011 each inhabitant of our planet would have eaten nearly 19 kilograms of fish a year,  according to Data of the United Nation's Food and Agricultural Organization FAO.

That's three times as much per person than it was in 1950.

Today there are circa three times more pepole on earth than were in those days.

"Global supply of fish has grown by a factor of eight since 1950", Christophe Béné (International Center forTropical Agriculture) writes in an article.

He also points out:

• Fishery, fish-farming, fish-processing and trading is the basis of livelihood for more than 10 % of the world population. 90 % of these people live in developing countries.

• As a major source of animal protein dish is twice as important as pultry and three times larger than cattle.

• And fish does even have many advantages over the meat from meadow, perch or stable. Fish has less fat, more protein per biomass and a lot of healthy features for human child devolopment and adult health, contains important micronutrients, Vitamins and minerals, Christophe Béné states.

Christoph Béné writes.

That means: Don't capture more fish than is regrowing. Plan and coordinate fishery thoroughly.

I will focus on this.

Aquaculture (breeding fish in cages in open sea, lakes ponds or arificial bassins) is the fastest growing sector in food production (I have learned  this, when I prepared a radio documentary (in German) on modern aquaculture.).

"You need to feed about one kilogram of food to fishes to obtain one kilogram of fish biomass, for pultry the relation is two to one and pork for example a farmer needs three kilogramms of food for one kilogram of meat, Werner Kloas told me. This professor of zoology is head of the aquaculture department at the Leibniz-Institute of Freshwater Ecology and Inland Fisheries in Berlin, Germany. And cattle does even need much more food.

 According to FAO livestock production occupies 3/4 of all agricultural land, including crop for animal feed and pasture land. It consumed 8 % of global human water use, mainly for the irrigation of feed crops, FAO states. 

But there is not only use of land and water  on the list of problems.

Producing animal feed does also mean emission of CO2 from shipment of meat, tractors on the field, trucks and huge ships needed to transport the feed from the fields to somewhere else on the planet where cattle, pigs, chickens await it.

• Ponds, lakes, rivers, creeks may be over-fertilized by fishes' excretions,
• drugs for treatment and prophylaxis of infection may get into the water circle,
• natural habitats are destroyed to build auaculture facilities. And -

About one fourth of the fish caught in the oceans anually is caught for fishmeal production. Fishmeal has become rare and prices have grown on the world market.

Aquaculturist have been looking for alternatives since years. They have bred new varieties of fish, which need less fishmeal in their food. And some fish, whose predecessors were predators, are vegetarians today. But some do not grow well enough without animal protein in their food.

In Switzerland scientists have developed a protein meal made from the maggots of black soldier flies. The flies are harmless for human health.

Remnants from food processing are are the maggots' food.

When grown big enough they are killed by cold and then processed into protein meal and oil.

The remnants of their skin contain chitosan, which can be used as a ressource for chemical or polymer industry.

And the fish tasted well, the scientists learned from feeding experiments and human degusation tests.

But in the EU currently food made from insect meal only may be used for pet feed and not for livestock. This is due to the BSE-scandal and hygienic desaster in cattle feeding back in the 1990s.

But scientist hope they can convince the resonsible persons and gremia in EU, how  insectmeal can be produced without any risk for consumers' health.

In Ghana soldier flies' maggots' meal currently is tested as feed for aquacultures in Ghanaian-British and Ghanaian-Swiss research collaborations.

Food is not the only challenge.

Of course fish need it. And of course they leave their excretions in it, where else should they do? Sounds like: Give them a lot of fresh water. But

E.g., in Berlin, Germany, at the Leibniz-Institute for Freshwater Ecology and Inland Fisheries Werner Kloas and his team have optimised a so called aquaponics system.

They keep fish in bassins in a greenhouse and the fish water is - roughly said - used to fertilize vegetables. They are grown in the same greenhouse.

Fish and veggies grow very well well.

The system needs very low amounts of fresh water replacement. Plants' evaporation water is recycled into the system.

A photovoltaic plant provides the electricity for the Berlin fish-greenhouse.

Licenses are available via  Agrathaer GmbH in Müncheberg, Germany.

Fish and plants like warmth. In Berlin during cold seasons the water needs to be heated. Therefore the researchers use waste heat from cogeneration plants or biogas plants.

But in permanently warm regions no heating is needed.

Currently in Central Europe these aquaponic systems are mainly an issue for avantgarde restaurants. They get fish and veggies on their guests' plates without any effort or energy for transportation.

Owners of a  fish greenhouse in Berlin have started production for sale. Fish there is still growing, but plant produce are ready for sale. The operators offer weekly delivery of herbs and vegetabels to 300 customers an o subsciption basis. When fish will have grown sufficiently, they also want to offer offer 30 metric tonnes of tilapia per year.

Consultants and manfacturers, e. g., in the Netherlands, UK, US, Canada or Australia offer complete facilities for home or commercial production. Schools in the US are operating aquaponic facilities. A benedictine-nun in a Florida-based monastery has started aquaponic production of fish and vegetables last year. She wants to show others how to do it. For her, it is a way of fighting hunger in the world.