Well one issue with sardines is over-fishing. After the collapse of the Portuguese sardine population they are rebuilding, but still very few sardine fisheries are certified as sustainable (though admittedly the certification process leaves much to be desired).I recommend sardines, not just any old tinned fish.
Sardines are forage fish - caught from the wild, not farmed. A lot of the fish in the supermarket these days is farmed, which is problematic in all sorts of ways, just like industrial chicken or beef production. The lower down the food chain a fish is, the more likely it is to be healthy. The smaller it is, the more likely it is to be wild and caught in open water. Sardines satisfy both categories. They contain a good amount of protein, all the electrolyte minerals (calcium, sodium, potassium, magnesium, phosphorus) plus some iron, zinc and manganese, plus B vitamins, and the whole suite of essential amino acids.
And besides all that, tinned sardines are available even in small corner shops, and are one of the cheapest fish to buy anywhere, because they are plentiful in the sea. I do not understand why anyone chooses any other type of fish.
And for tax, here are some chickens choosing to go to town on my pumpkin.