Karol Rzepkowski, managing director of Johnson Sustainable Seafoods

Natural cod stocks in the North Sea have reached an all-time low and a ban is now on the cards. Karol Rzepkowski, managing director of Johnson Sustainable Seafoods, is pioneering an organic sustainable cod farm in the Shetlands. He talks to Emily Manson

Do you think there should be a complete ban on North Sea cod fishing?

I'm not a marine biologist, but all the evidence seems to indicate that there should be a ban - even if it's temporary. But we should be looking at sustainable farming regardless of whether there's a ban. If we hadn't developed from hunting to cattle farming where would we be?

Why has it taken so long for something to be done about stock depletion?

I think when politics gets involved things inevitably grind to a standstill. But it shouldn't cloud the judgement that ensuring the survival of wild cod is a primary concern. The social aspect of fishermen's livelihoods is obviously also an issue, but it's not all doom and gloom - 80% of our site staff are ex-fishermen.

Is cod a difficult species to rear in a farmed environment?

The initial challenge was the production of juvenile cod, as we had to re-create the whole food chain, but once we got that cracked the cod actually lends itself to aquaculture better than salmon as it's a non-migratory, chilled-out fish which is happy plodding about.

How high is the risk of an outbreak of disease on a fish farm?

We haven't had a major outbreak, as we vaccinate our fish individually at the hatchery. It's like children: it's more important to prevent disease rather than wait to treat them after they become ill. We also monitor the health, wellbeing and quality of life of the fish.

How do you ensure it tastes good?

When we set out we just wanted to do it right. We are doing something new and unique, but we are also idealists and want to provide a future for sustainable rearing. We don't use colorants, dyes or pesticides and try to give the fish a good quality of life. We hoped that by producing happy fish we would also produce tasty fish, and it seems to have worked.

Is there a demand for farmed cod in the hospitality sector?

Very much. Since we started producing it we've been inundated with enquiries, as we are producing the world's first organic sustainable cod. Chefs can put it on menus in good conscience, and it's also parasite- and worm-free as it is fed from our own feed; the supply and price are guaranteed; and it's low on food miles, too.

How much more expensive is farmed cod compared with North Sea cod?

It's currently about 30-60% more expensive than supermarket cod, but if you compare it with wild, fresh North Sea cod, then there's barely any difference - which is quite crazy, given that we have to grow and feed our cod for three years.