ingredients vs. food

You can categorize tins of fish on a spectrum ranging from "ingredient" to "food". An ingredient is something that needs further processing before you eat it; food is ready to go. Tinned fish... is both! When I meet a new tin of fish, I consider where it sits on the ingredient-to-food spectrum and let that inform how I treat it.

Vacuum-packed bags, like Patagonia Provisions' salmon fillets, are mostly ingredients. You could heat and eat, but you'll be happier if you do something more with it. But many otsumami---savory Japanese drinking snacks---are vacuum packed bags that are fully cooked, ready-to-eat foods.

Water-packed tins and brine-packed tins are almost always ingredients: tuna, mackerel, and sardines in water need some other treatment, even if it's just mixing with mayo or putting on a complex sandwich. (Cockles in brine are a notable exception.)

Oil-packed tins can be both. Sardines in oil are food, ready to go. But they're also ingredients, for spaghetti con sarde, a rice and sardine nabe, or battered and fried. Anchovies in oil could be simply put on bread (with butter and parsley!) or skewered on a Gilda, or they could be turned into a salsa verde or a pasta puttanesca. Mackerel in oil tends to the ingredient end of the spectrum, though Patagonia's offerings are tenderer than most. Mussels in escabeche demand no further processing: just grab some potato chips; oysters want only for sardines and hot sauce.

Sauce-packed tins are food, but they often benefit from being heated or having their sauces reduced. (To safely preserve the fish, the tin can't have any air in it---a watery sauce helps push out all of the air.) Fish in tomato sauce, squid in ink---put the whole, closed tin in hot water for five minutes and you're ready to go.

I try to keep a variety of tins in my "tinned fish tidepool": some that I can eat directly when I need something quick, and some that will make an appearance in a more involved recipe.