Aquaculture looks to green dawn

Feed stocks
Image caption Not a science fiction movie, but the lab that breeds food for growing fish

Here's a thing you might not know about aquaculture.

The amount of food it's producing is increasing faster than anything else - meat, cereals, vegetable, whatever - and it has been that way since the 1970s.

This is one of the top line findings from a new report on the industry, Blue Frontiers, co-produced by the WorldFish Center and Conservation International.

Whether news of its rapid growth produces warm feelings ("lots more lovely fish to eat!") or alarm ("lots more horrible environmental damage!") might depend on what you already know about the business.

Certainly its environmental issues have been well documented - soil salinsation by shrimp ponds, vast extraction of wild anchovies to feed farmed salmon, disease, and so on.

But equally certain is the fact that it's here to stay, now producing about as much fish and shellfish as comes from the wild - and, you might argue, just as well, given the depletion of the oceans' stocks.

Its growth is one of the reasons why fish consumption per person reached an all-time high last year, according to UN Food and Agriculture Organization statistics.

Like many big industries, aquaculture is really many small ones.

Different species are farmed using different methods in different places; and each combination may have a different environmental footprint.

That's what Blue Frontiers is about.

It's a detailed breakdown - perhaps the first - of which impacts are caused where by which type of aquaculture; and also an overview of how farming in water compares with farming on land.

Image copyright Other
Image caption The world according to fish; aquaculture production centres on Asia, and China especially

Here's something else you might not have known; herbivorous fish are much more efficient with the plant material they eat than are herbivorous farm animals.

"The production of 1kg of finfish protein requires less than 13.5 kg of grain, compared to 61.1kg of grain for beef protein and 38kg for pork protein," the authors conclude.

Given the pressure that's put on land by growing grains to feed cattle - and the health benefits that eating more fish and less meat would bring in many societies - that presumably qualifies as good news.

There are serious environmental impacts, such as greenhouse gas emissions, eutrophication of water, and (for species such as salmon) the need for wild fish to feed the farmed ones.

The report documents these, and compares them across different types of product.

Carp - a favourite in what's by far the world's biggest aquaculture producer, China - emerges with an environmental footprint that's pretty big, leading to a number of serious impacts.

Salmon, however, emerges as relatively benign, except in its hunger for wild fish.

(Critics would point out that the report doesn't cover diseases such as sealice infestation; the industry would point out that progressively less wild fish is being used per salmon produced, as companies become cleverer with diets and using waste from fisheries.)

And some shellfish farming proves to have positive environmental impacts, reducing eutrophication of water.

So what's the point?

Well, if aquaculture is here to stay - and it is - then clearly it's an advantage to governments to know the environmental implications of the licences they grant, and to be aware of benign options that their industries could pursue.

Given the growing consumer interest in sustainable fish, good information is vital if people are to select on the basis of what's benign and what's harmful - and if they're to pressure the industry to clean itself up.

Plus, the capacity to compare impacts of the same industry in different countries should help operators to establish best practice across the board.

Habitually, aquaculture is compared with fishing, in terms of environmental impacts, taste and nutrition.

But maybe that's the wrong way of doing things. Maybe a comparison with agriculture is now more constructive.

After all, it's all farming; it all needs land and water and chemical inputs, and it all produces food.