I have this peppered mackerel fillets in the fridge and I'm wondering if they/re okay to eat on induction. They are just the fillets topped with litle 'balls' - yellow, orange, red and black. There is no sauce on them. (no nutrition label)

You mean Pepper "balls"? Because Fish is fine and pepper is ok also as far as I know. If it was marinated at all that could be a problem...

It's possibly smoked and yes, just pepper balls.

Any info on the packet?? I just checked a pack of plain smoked mackerel fillets in the fridge and it says 'trace' carbs -but it has 800mg of sodium per 100 grams - make sure you drink extra water!!

According to recipezar http://www.recipezaar.com/library/getentry.zsp?id=337 one teaspoon of peppercorns has 1.4 carbs less 0.6 fiber = 0.8 net carbs, so perhaps you can estimate how many teaspoonsworth of peppercorns is on your serving of fish?

I had forgotten that smoked mackerel packet - must use it up over the Easter weekend!!
As b777 said, if it is only fish with peppers on it you should be OK

do you actually eat the peper balls?

I would hope not...they would easily crack your teeth. I find it hilarious people calling them "Balls". (peppercorns)