Once again I greet you with a crazy contraction—it’s not fission or fiction, it’s a fish mission—I could probably have gotten away with fishmish. Words set their own rules—I recently discovered that the Hindi word for ‘titillation’ is gudagudaana—beat that!

I spent the week on some farms off the Mediterranean coast of Spain—they like to organize their cages in double rows, with about two hundred thousand bass or bream in each, although that varies—lower numbers for bigger fish.

Ringo’s unmistakable vocals on one of the Beatles silliest tunes.

Since 2013, farmed fish have outpaced wild capture, when you consider the data for direct human consumption—fishing still brings in many species that humans don’t eat, or eat sparingly, and those animals are converted to meal and oil, used to feed land animals and also cultivated fish.

There’s a lot of discussion about that issue, and concern that by converting small fish into food for other species we’re harming the marine environment by upsetting the balance of predators and prey.

In many parts of the world, the discharge of nitrogen and phosphorus into the coastal waters is a serious problem—this excess of nutrients leads to abnormal plant growth, and of course plants in the sea tend to be microscopic since they have to float near the surface where they can use energy from the sun.

Excessive phytoplankton growth turns the water green, sucks the oxygen out of the deeper layers, and can cause widespread mortality of fish and shellfish—going green isn’t always a good thing.

But the Mediterranean is an exception in this respect—the surface water layer is very poor in nutrients, so there isn’t much plankton available to grow fish—which is why the water is so transparent. This happens for various reasons—the main one is that the deeper water is colder and more salty and doesn’t mix with the water above it, so the nutrients in the lower layer don’t get to the surface.

Since there’s little plant biomass available to drive the food chain, there are less fish. Large parts of the ocean are like that—the equivalent of marine deserts. And if you’re a dolphin or a shark preparing to make a long journey you must weigh the consequences of your decision, since you may well find yourself in a desert region where the options of going forward or returning home are equally dangerous—for some reason, humans don’t think of fish starving to death but it happens all the time.

So you’re living in a place where food is scarce and every day is a challenge. And then suddenly there’s a twin row of twenty cages, let’s say four million fish—at an average weight of six or seven ounces, or two hundred grams, that’s eight hundred thousand kilos, a little less than two million pounds.

On a good farm, ten to twenty percent of the feed is uneaten, and in the Med, where natural food is not plentiful, that’s a heck of a subsidy. So it’s no surprise that below the cages, the water is teeming with fish—grey mullet, bass, bream, you name it—a recent study in Turkey found about forty different species in residence.

WordPress levies a premium charge to upload video, but you can watch the movie here.

When you’re on the water at a Mediterranean fish farm, it’s almost certain you’ll see dolphins at some point. They’re curious about the boat, the people, the activity, and they generally enjoy a bit of an exhibition, jumping around the cages. What you don’t see are the big boys—even when you dive, the tuna, and swordfish, and rays tend to move away.

But on this occasion, a small robotic submarine was at hand, and the fish thoroughly investigated it. One ray even tried to take a bite out of the little guy.

The sea below the cages, down to about one hundred and fifty feet, is a feast for the big predators. In the movie you see a large bluefin tuna swimming idly past the nets, and you’ll also notice that the most aggressive ray has a gaping wound on its ventral side, perhaps inflicted by a shark—the sea is a dangerous place.

But the most interesting part of all this is that fishing is forbidden within farm limits, which turns these Mediterranean fish farms into marine protected areas—with a twist, because the uneaten feed draws wild fish, and these provide ample food for top predators—MPAs on steroids.

This is particularly important for endangered species like bluefin tuna, which find a safe habitat and plentiful nourishment under the cages.

Quite a lot of research has been published on the relevance of fish farms to wild species, but almost all of it appears in aquaculture journals, desperate to make the case for positive effects on the environment.

All over the Med, farms like these play a key role in wildlife conservation and provide a core ecosystem service.

The sad part is the farmers don’t get a cent for the valuable service they provide.

They don’t even get recognition.

The India Road, Atmos Fear, Clear Eyes, and Folk Tales For Future Dreamers. QR links for smartphones and tablets.

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