June 14, 2014 — Down in the depths, a diver swims among cages of netting that look like underwater Towers of Pisa. Sitting inside the many 'floors' of each one are giant Japanese scallops that are keeping the delicate ecosystem in balance. The molluscs form part of an experimental aquatic farm devised by Dr Stephen Cross from the University of Victoria in British Columbia, Canada.
Aware of the pollution in the farmed fish industry, he has come up with a 'polyculture' system whereby only one species in the chain needs to be directly fed by him – as can be seen in this fascinating set of pictures from National Geographic magazine
Off the coast of Vancouver Island, he only feeds sablesfish (also known as black cod), which are native to the Pacific Ocean.
Nearby hang the baskets containing scallops, along with oysters, mussels and cockles – which feed on the fish's organic excretions.
Beyond them lie lines of sugar kelp – a brown algae used in sushi, and also as a component of bioethanol fuel.
These plants mop up the rest of the waste by converting nitrates and phosphorus into plant tissue.
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