If you just ask for “fish and chips” what fish would you expect to get?
Where I am it’s flake (gummy shark). It’s something different in Sydney (hoki). Cod in most parts of the UK, I suppose.
**Not ** shark (as in Melbourne). There was an article in the SMH on this very issue a few weeks ago. Apparently Sydney people won’t each shark - supposedly too many folk memories of fatal attacks at the beaches.
Snapper, most likely. If we’re really lucky, it would be hoki.
Hoki is the cheap stuff!
I love fish and chips but fish tastes like fish to me, well except for tuna and salmon.
I tend to like hoki, sorry! 
(But terakihi, of course, is divine.)
Either cod or haddock, round here. Haddock being more traditional, locally, and the preferred choice of the more discerning.
I like Hoki too! It is cheaper then snapper though.
This, I didn’t know/realise (I’m food blind, I reckon!)
Ordinary pieces of fish in a Sydney fish ‘n’ chips place are usually New Zealand hoki, South African hake or basa which is Vietnamese Catfish. All are super cheap. The basa is really interesting for people who want to increase the amount of fish they eat but aren’t great fish lovers. It has a really mild fish odour and taste and any flavourings go well with it. They must catch thousands of tons of it because fillets are always in plentiful supply and very cheap.
Cod is endangered in the Atlantic now, so I think a lot of UK fish and chip shops are now using hake. Don’t know if they’re still calling it cod or not as I rarely eat in them.
The poor sad fish is orange roughy. Almost tasteless (as in fish taste) it WAS the premium “flash” fish to serve in resturants, it turns out that they live a lot longer then we knew and therefore have a breeding cycle that is a lot slower then we knew. Poor bastards are being fished out.
Bye bye orange roughy, it was nice eating you.
Cod, haddock, plaice, skate, in order of popularity
Cod: Highly processed, probably fish-eyes, entrails etc pureed and spat out into little uniform blocks, fried to within an inch of its life. Dont think about it. Just eat it.
It’s haddock here. There’s a local place that has fish and chips on the menu. They give you a couple of pieces of breaded fish, applesacue and a small bag of lays potato chips. 
Applesauce and a bag of chips? Why would anyone want applesauce with fish?
In Buffalo, NY, you would need to ask for “fish fry.” On menus, the fish is most often listed as scrod (young cod or haddock) if they bother to specify.
Walleye is also popular, and I think viewed as the authentic local fish. Could there possibly be a less appetizing name for a fish?
For your fish fry, you will get:
Choice of beer-battered fish or broiled fish (for the healthy, I suppose)
Choice of french fries or potato salad
Choice of macaroni salad or coleslaw
Some places will include french fries AND potato salad AND macaroni salad AND coleslaw. Good thing they include the healthy broiled fish option!
Up here in WA you generally have a choice between cod or halibut, and often salmon.
The best fish’n’chips I’ve had are at Ye Olde King’s Head in Santa Monica. Their cod is firm and flaky, and their batter is the best.
Here in Northern California, it’s usually cod, sometimes haddock.
At my local I have the choice of cod or halibut. The halibut is good, but I usually go for the cod.
Here in the desert you get whatever they’re willing to truck in several hundred miles from either the Pacific or the Gulf and you generally can only get it at fast food places like Long John Silver’s and Popeye’s. I think it’s probably cod. Now, the last time I tried making it, I used catfish as it was several dollars cheaper than the other types of fish I could get. I didn’t really care for it, but other people loved it.