expired Woolworths Mackerel in Oil/Tomato Sauce - 425g Can (~275g Drained) - New Line - $1.55
For those that eat murdered animals, it's probably now the cheapest option of canned protein per kg (for human consumption…or otherwise?) in Australian supermarkets and almost certainly the cheapest canned form of Omega 3.
If you compare its drained weight with the cheapest fresh meats in Australia (probably chicken derivatives) and assume cooking meat causes a 25 - 33% loss of water weight the price still ain't too shabby at $5.64/kg. Most canned fish isn't as impressively cheap once you look at the drained weight (except maybe no name sardines, and now mackerel). Considering you can get chicken breast at a local supermarket for $5.99/kg (Greener Grocer, Maroubra) and a dollar more per kg at supermarkets it's hard to compete with at the moment from the perspective of palatability.
The mackerel is a product of Thailand but the species isn't listed. Larger, predatory mackerel are known to harbour significant levels of methylmercury but the species and origin isn't listed on any of these cans. Generally, mackerel around SE Asia would be of the smaller variety and contain less mercury, but some regions are known to be contaminated (though mostly shorelines probably). It probably contains less mercury than Skipjack tuna but whether it's as low as levels in canned salmon and sardines is anyone's guess.
Much like the cheap'n'nasty no name sardines they're not anything special but are less fishy than budget sardines. You can now get the fancy-pants Brisling Sardines at Aldi (110g cans) for $1.10 I think.