Tunafish. It's a favorite of human beings and cats alike. I mean, it's a real convenience food - it comes out of a can. The only thing you have to do to it is open it into a bowl (draining off the water first), put in some mayonnaise and mash it up. The result can be spread between two slices of bread with either a leaf of lettuce, a little butter, maybe some pickle relish and served as part of a healthy and delicious lunch (or you can put a tunafish sandwich or two into a baggie and save it for lunchtime). Cats, being none too particular, will eat tunafish without any special preparation; all you need to do is open a can and set it in front of them. Many cats will even lick out the can once the tunafish is out of it. Tunafish is the one thing that cats are dreaming of when they're chowing down on the kibble that their owners typically set in front of them. About the only thing a tunafish doesn't do well is smell like a bouquet of peonies. No, it smells like tunafish, and the longer it smells like tunafish the worse it smells - except to pussycats, who would eat it even if it had been fermenting in the sun for a week.
I've had tuna in many different forms. I've had tunafish on rye (yum). I've had tuna melts on rye, on the presumption that warm tunafish always tastes better with a little melted cheddar cheese on it. I've had tuna salad, which in most restaurants is a whole lot of lettuce, some tomato and maybe a few bits of fish hiding underneath it all on the plate. I've eaten tuna sushi, which presumes that Americans can be suckered into eating a raw piece of fish on a finger of rice if you make it expensive enough (this is also the French theory of cooking that created steak tartar). And I've had tuna steak, which is premium eating with very little fat and cholesterol.
Tuna steaks are tasty for the same reason that swordfish, shark and marlin are. These are gamefish. They are not small; in fact, the full-grown bluefin tuna is often over one thousand pounds, making it one of the biggest fish in the ocean. It is also a voracious eater. It has to be; it spends a lot of time and energy just swimming from one end of the ocean to the other. As a result, it is a very lean and muscular fish (despite its almost oval shape), which is not something you would imagine looking at a six-ounce can of it on a store shelf.
Tuna come in many varieties - about 50 in all. The ones we see on store shelves are yellowfin and skipjack, but there are other varieties. Bluefin is a favorite - so much so that it is at risk of overfishing. Then there is the albacore, which is the premium white tuna you see in a can. I am told there is also a variety called emocore; it swims mostly in the darker corners of the ocean and wonders why its life always sucks.
Tuna is just about a perfect source of protein for both man and feline, but there are some caveats. First of all, in the process of eating other fish, tuna tend to collect a whole lot of mercury; in fact, pregnant women are warned not to eat tuna, and even us mere mortals are warned to not make a habit out of eating albacore. Second, there was a time when tuna were fished in these large purse-seine nets that trawled up just about everything in the water - tuna, other fish, and dolphins, which are intelligent mammals that die in the nets and are discarded by fishermen afterwards. Lately, a lot of the major canners have been touting their tuna as "dolphin safe", so some of the furor has died down. Now, it's the tuna themselves that are in danger of being overfished, so a lot of well-meaning organizations have tried to get the fishing industry to adopt protocols that avoid the wholesale slaughter of tuna. It only makes sense; we have to think about what future generations of pussycats are going to eat if there aren't any tuna.