Sardines or "Pilchards" are a small fish related to the Herring. They're oily, extremely good for you, and apparently stimulate the brain- and my god, do I need that this morning. In this country, we used to have masses of the critters down in Cornwall, but the stocks petered out in the late nineteenth century.
Have a look at the paintings by the Newlyn School artists (such as Stanhope Alexander Forbes), which often depict Cornish fishermen of that period. Nowadays, we're more used to imported sardines packed in olive oil in small tins. Back in the 1920's, gourmets thought that oil improved the sardines, so we had the interesting (and slightly bizarre) concept of vintage sardines. Oscar Wilde's son, Vyvyan Holland, who was a connoisseur of this sort of thing, even had an exclusive dining society where they met expressly to sample the different "vintages". Well, the sad news is that this was a total fantasy, but I like the idea of grown men putting on dinner jackets to eat sardines out of the tin.
Here's a simple recipe for "Grilled Sardines stuffed with Onions and Capers". I've taken it from Anton Mosimann. Generally, I'm not that keen on the "celebrity chef" culture, but I think Anton Mosimann (one of the first celeb chefs in this country) was (is!) rather good. And some of his food is simpler than you might imagine.
Chop up an onion and sweat it in olive oil for a few minutes. Take the cooked onion off the heat and mix it with some chopped parsley, three tablespoons of chopped capers, a strip of finely chopped lemon peel, salt and pepper, and a pinch of cayenne. Get hold (or catch) some fresh sardines, and make sure they are scaled and gutted (but keep the head and tails on). Stuff the sardines with the onion and capers mixture, and sprinkle some of the mixture on top of the sardines. Season the fish with lemon juice, salt and pepper. Shove them under a hot grill for about five minutes.