ca va barder pour la poiscaille!

[incandescens]

Attempts at translation:

Look on this as a comment on translating slangy speech.

One Piece : Book Nine

Luffy : (rallying his crew to attack the fishmen) Ca va barder pour la poiscaille!!!

Me : Hm.

Ca va barder: there's going to be trouble, sparks will fly (slang)
pour: for
Poiscaille: fish (slang)

Me : Hm.

Luffy : There's gonna be trouble for those fishes!
It's trouble time for those fishies!
Time to kick some fish ass!
It's gonna be a hot time in Fishtown tonight!

(and, my personal favourite)
Luffy : Time to grill some fishies!