Helen FieldsScience Writer

The other day I was at the grocery store, and I had tuna on my list. It’s easy, it keeps more or less forever, it fits in cans, I can put it on salads. But then when I was actually standing in front of the canned fish, I was hit by this sudden wave of guilt at using giant, long-lived fish at the top of the food chain for cheap protein. I’ve heard many talks in which people who understand the oceans say we really ought to be eating bait fish. (And I’ve been buying tuna all along, so I don’t know why the guilt chose last Saturday to set in.) I looked at the other cans on the shelf.

Which brings me to today’s lunch:

I haven’t quite been able to figure out the full environmental implications of this choice. Fish are confusing. If you look up “tuna” on the Monterey Bay Aquarium’s Seafood Watch website, there are six different kinds of tuna, and whether or not you should buy them depends on how they’re caught. If you look up sardines, they give you two options, actual sardines and atlantic herring – but it seems that what I have is actually a little Atlantic fish called a “brisling” or “sprat,” which the Monterey Bay Aquarium doesn’t cover. (Read about sprat here.)

But I do understand food webs, and sardines are way lower down than tuna are. It’s like eating grain-eating chickens instead of man-eating tigers – it’s a more efficient use of resources. Fortunately, they taste pretty good. I polled my Facebook friends, and the consensus was that they should be on toast. A former choir director also suggested a large whisky and soda. I haven’t added that particular flourish yet, but I can’t imagine a large whisky and soda would make anything worse.