To be a “big fish” is to be an important person. It is often accompanied with the unspoken assumption that everyone else around that person is less important. Such people are often referred to as “small fry.” The important person is measured in relation to others within a specifically-defined area such as a company, artistic genre or locale.
The exact origin of the term is unknown, but it is thought to come from America. Being a “big fish in a small pond” was first written in the Galveston News in June 1881. The origin may come from a pond having an abnormally large fish in it, though this pond, if relating to fishing, could just as easily have been a river or lake; "the pond" is also a euphemism for the Atlantic Ocean separating Britain and America. The term has come to denote a person who is far superior to his or her contemporaries and colleagues; in this case, it is a mark of respect.
It can also be employed to denote a lack of ambition. The theory goes that the big fish in the small pond is unwilling to apply for a better position or move to a bigger town. It also implies that the person is comfortable or even happier to be the big fish than to become unimportant.
In sporting terms, a big fish is a talented player who plays for a relatively poor team. Usually, the big fish will move to one of the bigger clubs in order to better himself, but this is not always the case. One such player, Steve Bull, spent his entire career at his hometown club, Wolverhampton Wanderers, even though it played mostly in the second tier of English soccer.
“Big Fish” is the title of a book by Daniel Wallace and its film adaptation directed by Tim Burton. The story covers myth and legend, imagination and reality. In it, the central character Edward Bloom recounts his life as a series of tall and improbable tales crossing the southern states of America in the latter half of the 20th century. Bloom is the big fish, who left the pond, but felt the need to exaggerate his own life in order to remain important, even when he did not need to.