During a family walk we saw a baby swan isolated f...

During a family walk we saw a baby swan isolated from the group.
Thinking he was stuck I tried to help him.
An adult swan attacked us and the baby.
I picked it up and found it had hooks on its neck / throat.
He couldn't lift his head.
I went home with him and cut the thread.
The 2 ties were still in his neck.
I called various vets without much success, the flora and fauna are not taken care of in their homes.
So I got the phone number of Maisons-Alfort Alfortville the school veterinary clinic and I went.
There when we arrive we fill out a document and we leave the animal.
I do not understand why it is necessary to indicate our coordinates telephone and address and that in parallel they do not give the follow-up of the animal but that in addition they say to us "think of making a donation".
In addition I would like since I have the opportunity to push a little cry against the fishermen who leave their damaged equipment and their "place" with rubbish that may harm terrestrial animals.