Duden-Oxford gives "blue trout" for "Forelle blau". Might be worth Googling it to check.

@katsushika,

Thanks for your reply, but I meant the cooking method "blau", not the type of fish... sorry if I didn't explain that clearly!

In the meantime I have found out that it is when the fish is "boiled in salt and vinegar"... but I am wondering whether poached is the better translation for this...

Any comments (anyone)?

Thanks!

Thanks Baldrick! That's what I thought.

Aunty Em, I've never seen a BLUE trout and I did understand (I live in Germany and occasionally (very) eat Forelle blau, preferring Art der Müllerin), and Duden-Oxford's "blue trout" has the prefix "Kochk.": so Duden-Oxford thinks that's what you're looking for. Pace Baldrick. Pace world.

"Poached trout" for me would be one that a poacher has caught.

Here's a recipe for "blue trout" (if a Tuvalu - wherever that is - website can be trusted):

Blue Trout
 
Trout 1 kilo or 4 portions
Vinegar 3 spoonfuls
White Wine 2 glasses
Carrots 1
Parsley a sprig
Bay Leaves 1 leaf
Peppercorns a few

Here's another recpie from the German Embassy, Washington D.C.

 
Germany Online Home: Culture & Life: Life: Recipes: Recipe Archive
 
 
Forelle Blau
Blue Trout

This recipe gets its name from the blue color the trout takes on when cooked in vinegar.

Ingredients:
4 trout, gutted and cleaned
2 quarts water
1 cup dry white wine
1/3 cup best quality vinegar
1 carrot
1 onion
1 leek
1 bay leaf
black peppercorns
clove
coriander
salt

Salt to taste
Butter 30 gr
Lemons 1
 
at http://www.germany-info.org/relaunch/culture/...

But that said, maybe for other types of fish one just says "poached".