Is fish feed a red herring in debate on aquacultured fish?

One of the oft repeated indictments of aquacultured fish is that the feeds utilized to grow out the carnivorous species use a lot of other marine species as the source of fish meal and oils.  I acknowledge the goal of reducing the baitfish component of fish feeds is a good one, I believe the issue is overstated in the context of favoring wild capture seafood to aquacultured fish.

I personally feel we need to curtail the consumption of wild species in favor of sustainable aquacultured seafood.  Yet, many who take the opposing view and urge the consumption of wild capture fish at the same time criticize the harvest of bait fish for fish meal and oils for aquacultured fish. So let's take a closer look at the issue.

The most common fish used in fish meals are sardines, anchovies, mackerels and herrings. These "forage" species are some of the links between plankton and the upper level predators.  These species are obviously near the base of the food pyramid in the seas.  These species also recover their populations fairly quickly and have been put forth as an alternative source of table food by some commentators (although many of these species make very poor table fare).

These forage fish are represent 40% of all wild harvest fisheries.  So if these fish were left in the sea what would be the net gain to the other 60% of the wild capture fisheries that so many urge us to eat?  The issue comes down to efficiencies: are the bait fish better utilized in the sea or as feeds?  I think the answer is feeds- preferably fish feeds not poultry and hog feeds.

Aquacultured fish have pretty impressive conversion ratios of feeds, typically approaching 1:1.  This is because farmed fish are raised in a controlled environment to yield the most finished fish per economic input.  Wild fish on the other hand spend a lot of time searching for food, fighting disease and stress, and reproducing.  This makes the amount of forage species necessary to grow out a wild fish three to ten times greater than growing out the same species in farmed environment.  Add in the forage fish consumed by the unwanted by-catch of wild capture fisheries, and the efficiencies are even less.  By some estimates aquacultured fish are fifty times more efficient utilizers of forage fish than wild fisheries.

This issue is not nearly as simple as many make it out to be.  The issue also has relatively less relevance if the principals of Cultural Sustainability are adhered to, especially the limitations on the consumption of wild capture fish.