And now there are 5!

Have not been to the canal for two days and then I could only see three cygnets, which was sad, however this morning in the wind and rain I went down and to my great surprise there were five little ones. The were able to eat the bird seed I brought them. On my way home I met them again and to my horror the male had fishing line all around his head. I phoned the SSPCA and they came out. They have just phoned me to say while they were there the male managed to get the line off, so thank goodness all is now well. Why or why can fishermen not take this dangerous line home with them.