From http://marxfood.com/a-guide-to-fish-terminology/:

> Whole/In The Round: Whole fish or fish “in the round” are being sold completely intact, exactly as they were caught.

>Drawn/Gutted: Drawn fish are whole fish that have been gutted

>Headed & Gutted: Headed & gutted fish have had their viscera (guts) and head removed.

I'm native speaker who has never heard this particular jargon :-)