13 Answers

Very hard to tell.They lie about it worse than women.

Fish, like women, don't like to discuss their age.  Do you mind?  Just eat it.

country bumpkin

tee-hee

By examination of the fish's scales. They are like tree rings and grow seasonally.

Why not just ask their highly inteligent after all their in school consistently..

Be there at it's birth.

 by the eyes and fins/tail.

poop.

weight.

Put it into a pint of beer and see if it can take its ale.

Give the Oroliths (spelling?) to scientists

Count the number of candles on the cake.

Peek under their gills whilst no-one is looking.

Check its ID, especially if it is attempting to purchase alcohol or cigarettes.

Doo loves these answers.  Fish won't tell you their age because they simply don't count years the way we do.  They might be able to tell you some things like how many times they dive to the big rock  or how many friends mysteriously bit on a piece of food, thrashed and fought something unseen, and then ended up out of the water-never to be seen again!!!  Sharks will tell you that some time ago they remember more seals and sea lions to chose from or how many license plates are lodged in their stomachs...but this really doesn't answer the age question.  

I count their teeth and divide by three.