"Let me pose you a question. Can farm-raised salmon be organic when its feed has nothing to do with its natural diet, even if the feed itself is supposedly organic, and the fish themselves are packed tightly in pens, swimming in their own filth?"

This quote by Mark Bittman is questioning the validity of farm-raised salmon being identified as organic. He is recommending that even if the feed given to the salmon is organic, it does not necessarily indicate that the salmon is natural. He also explains that the salmon are kept in pens, swimming in their own filth, which is not a natural environment for them. This quote is questioning the ethics of labeling farm-raised salmon as natural, and is suggesting that it may not be precise to do so. Bittman is implying that the conditions in which the salmon are kept are not natural, and for that reason the salmon can not be thought about natural.