The fish biscuit is the first blatant reference to Valis by Phillip K. Dick, more "Jesus fish" can be seen in Hurley's door, and branded on a tree on the Island. In addition, the word "fish" in Greek letters, overlayed, makes the "frozen donkey wheel."
The biscuit is medically active, causing changes in animals, possibly with regards to intelligence.
The biscuit contains hormones which allow the bears to adapt to the tropical environment - explaining the presence of polar bears in the south Pacific
The biscuit's appearance as a red fish is an intentional reference to a "red herring", a phrase used to describe a meaningless clue.
They are a cheap, simple food source with no mysterious properties.