how can one know

[gunfish]

Sorry if this is a stupid question, but how can someone tell the sex of the fish? I always wanted to know.

[leebca]

Not stupid at all!

Some marine fishes are distinguished by different markings or size variations that indicate the gender. However, this is not all that common amongst the marine hobby fishes. A fish of a mated pair or in courtship sometimes gives away its gender through behavior.

The definitive means of determining gender on hobby marine fishes include operations (on the living or deceased fish) and blood tests. I''ve performed the operation a few times. The fish must be cut open and the fish inspected for sexual organs to verify the gender. Alternatively, there are some very expensive blood tests that can be performed, which are not done that often.