This was a question posed by ebonibarbie. It was such a brilliant question I decided to dedicate a Text post to it instead of answering via ask.
So this is Chris and why he is so closely connected with fish.
Chris especially in Series 1 is often linked with fish. In his episode in Series 1 we see Chris feeding his fish pills. Later on in his episode all he has to his name is a bag of clothes and a fish given to him by Angie.
When it comes to symbolism often times fish are connected with good luck, fertility, prophecy, knowledge, and wisdom. I feel as if none of these work for Chris and the use of fish for Chris is actually a more straightforward parallel.
Fish are usually the first pet that most children have. It is usually the test pet to make sure a child is ready for something more substantial. Meaning most of the time gold fish do not live long and they are delicate. Often times flushed down the toilet and forgotten. Fish are essentially the neglected childhood pet. Much like Chris was the neglected child forgotten after tragedy tore apart his family. His brother Peter died of a brain condition (hereditary) soon after his father left, re-married, and began to have his own family. His Mom also seems to neglect Chris most of the time and eventually left him. The favorite son passed away and his parents instead of cherishing the fact that they had Chris they pushed him away. Essentially making him that neglected pet. That you are responsible for yet do not feel that emotional attachment to take care of them that well.
Fish are often used in a phrase explaining opportunity. “There are plenty fish in the sea.” Chris is a character that lives life pretty hard and fast. Seizing opportunities and never saying “no.” He goes in expecting that those who love him will stay and those who don’t won’t. So this could be a bonus explanation or another option depending on how you want to look at it.
The main way I see the use of fish and Chris is that it ties Chris’s childhood with what a fish is to a child. That neglected first pet.