Surprisingly, some forms of aquaculture can actually benefit to the health of the ocean. Shellfish farms, for example, can help to filter and clean the sea water in sensitive estuaries and coastal areas.
Saving the Small Fry!
Paradoxically, farming large predatory fish like salmon has led to the depletion of many smaller fish species, commonly known as forage fish. The smaller fish are used as fish meal for the larger species, and since it takes about three pounds of fish-meal to produce one pound of farmed fish, pescetarians would remove far less biomass from the ocean by eating the little fish directly. They would also provide themselves a significant health benefit by avoiding the concentrated pollutants from smaller prey that accumulate in the bodies of predatory fish.
Be a Sardinista
Sardines and other small fish are also caught without the destructive bottom-trawling methods that destroy the sea-floor habitat. Humble sardines, even the canned variety (when rinsed with lemon juice to remove the taste of the low quality olive oil) are a sustainable and sumptuous choice. Consider adding them to a saffron-threaded tomato sauce, seething with onions, capers, minced herbs, olives, green garlic, and lemon.
Gills Gone Wild!
In most cases consuming non-predatory responsibly-farmed fish (catfish, trout, etc.) will be the most sustainable choice. Avoiding most tuna and farmed salmon is a good idea. In the United States the most-consumed predatory fish, farmed salmon, can now legally be genetically modified. But even unmodified, most farmed salmon today has already been transformed into a different creature than its untrammeled version in the wild. There, a salmon is in constant motion, a wild and indefatigable creature making a devout passage of regeneration through its engagement with the world. This is why precisely where and when a wild Salmon is pulled from the sea on its migratory life-cycle is so important to its fat-content and flavor. The best spot, if you love the rich oily delight of “salmon candy” the way native people traditionally smoke it, would be to catch that wild salmon right at the mouth of a river as it returns homeward after a long voracious forage at sea, well feasted and ready to make a rigorous passage back up the river of its birth so it can spawn and die.
Farmed salmon, on the other hand, live on a suburban diet of man-made protein supplements and spend their lives lounging around their rocking sea cribs like a bunch of surf-potatoes. This is why wild salmon can have twice as much omega-3 fatty acids, and half the fat of the farmed variety.