Questions for literature

The fish :

Why do you think that Elizabeth Bishon call the fish him , not it or her ?
Why do you think that Elizabeth Bishon let the fish go ?
                                                             
How he was  speckled  ?
(He was speckled with barnacles,
fine rosettes of lime,
and infested
with tiny white sea-lice)

What symbolised rainbow in text or in general ?