is arctic char bad to use for fish stock? I know salmon is too fatty, so would I be correct in assuming char is as well?

Interesting, pierino. Think it's just because americans are so skittish? In London it was relatively cheap and I even find it pretty regularly in South Africa (though I'm wary, having once bought some that went ammonia on me...).

I'm also a big fan of skate. Unfortunately (depending on which coast you live on) it can be hard to find in fish markets. When I'm traveling and I see skate wing on a menu it's almost a sure thing that I'll order it.

I find that skate works really well for a stock. It's all cartilage instead of bone, so I get a nicely gelling stock from it without too strong a flavor. And skate is generally a really cheap item.

I would imagine the flavor from the char would be quite overpowering in whatever recipe you might be using, unless it involved salmon or char ...

Shrimp heads and lobster heads have a fair amount of fat too, but you can make delicious stock from them. I've never experienced the bitter effect. The good thing about fish stocks is that you can make them fairly quickly as compared to meat and poultry stock. An hour of simmering is all you need.

If I remember correctly to my stock making days in culinary school, we only ever used white, non oily fish in our stocks. If you're concerned about waste, whenever we had scraps after fileting a char, we'd usually scrape the bones and make the flesh bits into a sort of tartare with a little stilton, walnuts, chives, and chervil.

yeah I wouldn't use the flesh anyway, but sometimes greasy fish can make the stock taste bitter... so Im worried about that. I know char isn't quite as fatty as salmon but i've never used it for stock.

If you are working from a whole fish using the bones, head and tail couldn't hurt. Using the flesh in stock seems like a waste anyway. Just take off the fillets.