14 October 2008

Filling the fish gap: Gentler trawling and new aquaculture approaches

If we don’t do something about the over fishing, stocks of wild fish will be dealt a death blow. Some fascinating new ideas are explored, in a recent article about a huge gap between global demand and sustainable supply of fish.

“On a global basis today, we have an average annual consumption of 15-16 kilos of fish per person" And as the population grows, to meet the demand, "we need to double the production of farmed fish within the next 20 years"

And what are some the things that need to be done? Among some new ideas being explored, using bubbles to fish and a simple realignment of the trawl net by 90degrees to avoid wasteful bycatch.

Take only what we need, and use what we take
We need to develop technology for more selective and gentle capture of species in the sea to enable natural growth in the stocks and only capture the quality we actually want.

Increase the efficiency of the aquaculture sector. Among others, we must stop using fish as feed for farmed fish. Fish caught at sea must be human food. Feed alternatives considered include plant oils and proteins, or convert natural gas to bio proteins.

We need to succeed in finding some new species of farmed fish and develop technology that enables a smarter and more cost-effective production of the fish species we are already farming.

One idea being developed is a bubble trawler which uses air bubbles instead of a net to surface its prey: the 3 mm long, protein-rich Calanus finmarchicus. This tiny creature contains large amounts of proteins as well as marine fats. “Capturing just one percent of this biomass would cover the requirements for the Norwegian aquaculture industry.”

Another idea is to improve trawling, “which accounts for 40 percent of the world’s total fisheries production”. As such, improvements in trawling will have widespread benefits.

One simple, but extremely effective solution to make trawling gentler and make it possible to catch fish of the correct size without damaging the small fish, is to turn the trawl net 90 degrees. This resulted in less turbulence and the meshes remain open when the trawl is stretched so that the small fish escape and the fish that are large enough are damaged to a much lesser extent. Energy consumption was also reduced.

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