The FR word 'jus' is widely accepted these days in 'posh' food circles — though I still put it in italics when I can.

Never 'juice' — unless it is a fruit juice or something; otherwise 'cooking juices' (but not really suitable for use on a menu).

Strictly speaking, technically, a 'jus' is not the same as a 'sauce', in culinary terms; however, in 'not-posh' EN, you might get away with that, in the simpler sense of 'something runny to accompany the other ingredients'. Though even that can be quite misleading, since often it is just three minuscule blobs decorating the plate!


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Note added at 6 heures (2017-03-25 16:11:49 GMT)
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Just to reassure Asker: although not zoologically accurate, 'shellfish' in EN and 'crustacés' in FR are both used in culinary contexts to refer to ALL types of 'seafood' — one of the problems being that there is no everyday word for the other non-crustacean type of seafood, so we can't say "seafood comprises 2 broad groups, shellfish and ????" Although technically accurate, 'crustaceans' is not commonly seen in culinary texts (certainly not on menus!)

After all, to the lay reader, even a crustacean has a 'shell', so it doesn't seem as shocking as it no doubt does to a zoologist!

The trouble with 'seafood' is that it is interpreted more or less widely by different people — if we want to be pedantic, even ordinary fish is strictly speaking 'seafood'!