manta rays are the first fish to recognise themselves in a mirror
why can't I translate " the fish IS SEEING the mirror"?
You can both are meaning possible
Is it just coincidence that the Hebrew word "מראה" sounds a lot like the English word "mirror", or is there some linguistic connection between them?
Well מראה comes from the root .ר.א.ה, meaning to see. I believe it is a noun form of the הפעיל word לְהַרְאוֹת, to show (that is, to cause one to see). I doubt it has any connection to the English word, but if it helps you remember...
Why does she say "hadage roeh" instead of "hadag roeh"? Is the extra schwa necessary?
This caught my ear also. It's not actually an extra schwa. It's the ר sound coming from the back of the throat.