The old fisherman's proverb popularized by Star Wars I: The Phantom Menace has a history of uses in literal contexts (fishing), however after the release of Phantom Menace the metaphorical use of the expression to mean there's always someone/something more powerful has exploded in popularity.
However, Phantom Menace cannot be credited with starting this (not to mention, the use in the movie is pretty literal). I have found a metaphorical use of the expression in the political science magazine The New Republic in 1981:
[…] become victims of this ineluctable logic than ordinary innocent people are. There is always a bigger fish swimming behind, and the higher the official, the more certainly he will be devoured.
What I'm curious about is how far back metaphorical uses of this expression can be traced. Is there any recorded use of it prior to the 1980s?
Best Answer
A Google Books search for "always a bigger fish" yields two relevant matches, albeit with quite different connotations.
From "Where Ignorance Is Bliss," a letter to the editor of The Spectator, dated October 29, 1929 [combined snippets]:
Here, the expression—although used figuratively—takes the perspective of a fisherman trying to catch a fish, and the general sense of the expression is optimistic: if you don't catch a fish here, you'll have a chance to catch an even bigger one at the next point along the river where you cast your line.
And from an unidentified article in The Fisherman, volume 6 (1955) [combined snippets]:
Here the expression is literally about fish and makes the familiar observation that even a large fish is subject to being eaten by a larger fish.
Earlier than either of the two preceding instances is this instance that a Hathi Trust search turns up, from "British Sea Anglers' Society: Seventeenth Annual Dinner," in The Fishing Gazette (March 12, 1910):
In this context, the expression, again used literally, indicates essentially that "there are more and better from where the current catch came from."
Of the two senses of the expression the one used literally in the 1955 Fisherman article seems to capture the idea of smaller fish being pursued by bigger fish in an endless pattern of larger and larger prey and predators.
Of course, the image of a very small fish being chased by a slightly larger fish, which is being chased by a slightly larger one, and so on, is a standard visual representation that seems to have been around for many years. Steven Pulimood, "Dreams of a Distant Wildness: Pieter Breughel," in the [New York City] Columbia [University] Spectator (October 3, 2001) reproduces a photo of a painting by Pieter Breughel the Elder called Big Fish Eat Little Fish (1556) that shows a monstrous fish being cut up by two fishermen and disgorging somewhat smaller fish that are themselves shown with fish in their mouth. The caption reads as follows:
Whether the saying "Big fish eat little fish" was a proverb in Breughel's day or not, the observation has been a familiar one for centuries—and it is only one step beyond the commonsense figurative wisdom of that saying to note that, however big a fish may be, there is always a bigger one somewhere.