This has to do with the symbolic meaning attached to fish (note: for the reunion dinner, every dish has a symbolic meaning). There are two phrases relevant to fish in Chinese. The first, "有头有尾," translates to: there is a head (beginning) and a tail (end). The second, “年年有余,” translates to: may you have surplus every year. Because "fish" and "surplus" in Chinese have the same pronunciation, a whole fish with its head and tail has always been used in the reunion dinner to symbolize prosperity in the coming new year.