[Hunble]

I will vote for "polymorphism, like eye color in humans", since the difference is rather minor.

Question: Can electrical impulse patterns be learned, like a language? In addition to basic prey location, it is well known that these electrical pulse patterns are also used for communication.

[AntiGuv]

I will vote for "polymorphism, like eye color in humans", since the difference is rather minor.

Except, of course, that humans of different eye color do not automatically refuse to mate with one another, which makes the fish difference rather major by comparison.

[bobdsmith]

Of course if green eyed humans and brown eyed humans formed seperate populations and didn't interbreed, then they could be considered seperate species.

If in this case you have two distinct populations each with their own features then the case for them being seperate species is stronger.