@Berty McJock,
I take a great brand of canned mackerel, Geisha*, lately the one with tomato chili sauce, separate the mackerel and put it in with my mashed potatoes, with a pastry cutter thingy. Salmon works, as do tinned sardines. I suppose tuna would too.
I add two whisked large eggs, mush it up. If I'm light of cooked potatoes, I add bread crumbs. Usually I add the Geisha tomato sauce or sometimes I use a spicy adobo sauce of my own. I like garlic, so some of that. No salt since there is overplenty in the tinned stuff. Yes, I add herbs - I've a battery of them and play. When the consistency is not very wet, I squish a handful and smack it into a patty and then acquaint it with a cornmeal coat. Saute in canola, distribute on rack or over paper towels, cool. Put in tin foil, freeze. Microwave and serve with condiment of your choice.
* Take the paper off the can of that brand, via soaking. The remaining can is oddly good looking, worthy of being a pencil holder for MOMA.