Seeing Green: The Octopus’s Garden

Opinion by Holly Moeller
March 3, 2011, 12:24 a.m.

Seeing Green: The Octopus’s GardenIt took me 24 years to find an abalone shell. Granted, I’d spent the first 23 years of my life living on a coastline where abalone don’t —  but I’d faithfully combed West Coast beaches at every opportunity to no avail until, last weekend, a crescent of mother of pearl finally caught my eye.

I pulled aside some rocks, and there it was: four inches long with a freckling of barnacles and delicate arch of pores — the perfect red abalone shell.

Although any long-term California resident who’s really looked knows abalone shells aren’t impossible to find, they are quite rare these days. In the late 1900s, abalone — once so common that it was considered a “trash fish” eaten only by the poor — fell victim to the combined pressures of overfishing and Withering disease (a bacterial infection that starves the mollusk to an untimely end). Today, the sole abalone fishery in California is recreational, with each license limited to only 24 red abalone each year. The few restaurants that still serve abalone — at a premium — acquire their portions from Mexico or, increasingly, from local abalone farmers.

Today, with only 22 percent of US fisheries sustainably managed and at least 14 percent of global fisheries collapsed, piscivores increasingly turn to the products of aquaculture — the captive rearing of fish, shellfish, crustaceans and even algae. Abalone farming — in which juveniles are reared in shallow-water pens on a diet of fast-growing kelp in tidally flushed waters — is touted as one of the most sustainable examples of the expanding industry. It is also a labor of love: it can take half a decade for abalone to reach harvestable size. (Before it died, the owner of my shell would have been a scanty mouthful.)

Mariculture — as practiced by abalone farmers, for example — harnesses the natural ocean system by placing enclosures adjacent to or just off the shoreline. Such farming strategies use seawater to flush out waste products and provide clean water for captive animals. Other examples include shrimp ponds in Southeast Asia (sadly, known for their role in mangrove habitat destruction), salmon farms in the Pacific Northwest and tuna “ranches” off the coast of Mexico (which produce “laxfish,” as the Japanese call the LAX airport-marked meat).

Aquaculture has intuitive appeal: it seems like an ideal way to conserve wild populations while shrinking humanity’s marine “footprint” by concentrating biomass production in a small area. Yet modern aquaculture, as it is currently practiced, is hardly a viable substitute for sustainably managed fisheries.

Most fish farms bear eerie (but unsurprising) resemblances to high-density terrestrial livestock operations. Farmed fish require huge inputs of food and regular doses of antibiotics and hormones, and they produce high concentrations of waste products. Many farm-reared species are predatory in the wild and require high-protein diets in captivity; even ecological herbivores, like tilapia, grow faster on fishmeal and oil. So fish farms can actually intensify pressure on wild fisheries while converting anchovies into bluefin. Densely packed pens are incubators of disease; farmed salmon are believed to spread sea lice to migratory wild populations as they swim by.

Farm denizens can also have direct effects on their wild cousins if and when they escape their watery corrals. As much as terrestrial livestock are the products of hundreds of years of domestication, so too are aquaculture species chosen — and bred — for domestic viability. These species are transported to farms around the world, where their escape means introduction of a non-native species. Atlantic salmon reared in British Columbia are the postcard example: in the last 15 years, one million have escaped into the Pacific Ocean. Today, an Alaskan recreational fishing permit comes with strict quotas for native salmon — but you’re welcome to as many Atlantics as you can hook.

Even when farms rear local species, escapees can dilute the wild gene pool by introducing maladaptive traits acquired over years in captivity. Such “outbreeding depression” disrupts the balance between the native population and the environment it has adapted to.

And farmed replacements for wild catches don’t necessarily protect at-risk fisheries. Bluefin ranches, for example, rear ocean-caught juvenile fish, removing a subset from wild populations. And the reintroduction of abalone to commercial markets, where today a pound of meat can sell for a whopping $58, has whetted the appetites of poachers.  Just last month, two San Francisco men were arrested after their third illegal harvest of wild red abalone.

Still, there are plenty of ways to make aquaculture sustainable: using closed circulation systems that prevent contamination of local waters, choosing native herbivorous fish and exercising patience instead of boosting natural growth rates with wild fish biomass. Like the creation of the abalone shell I’m holding, though, these methods take time and a sense of the delicate balance between organisms and nature.

Today, aquaculture produces 45 million tons of food each year (compare to: 100 million tons extracted annually from the ocean). It’s a growing business sector and a critical protein source — something we cannot ignore as we look for ways to feed a burgeoning human population. So it’s important that we learn to do it right — right away.


Do you know where your seafood comes from? Send your thoughts and comments to Holly at [email protected].

Holly is a Ph.D. student in Ecology and Evolution, with interests that range from marine microbes to trees and mushrooms to the future of human life on this swiftly tilting planet. She's been writing "Seeing Green" since 2007, and still hasn't run out of environmental issues to cover, so to stay sane she goes for long runs, communes with redwood trees and does yoga (badly).

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