This is the only somewhat credible reference I was able to find:
Where's my fish?
A question asked in reference to the phrase "plenty of other fish in the sea". When searching for a significant other, one is to ask (normally to a friend suggesting that there are other fish), "Where's my fish?"
"...My boyfriend broke up with me."
"Don't worry; there are plenty of fish in the sea."
"Where's my fish?"
http://www.urbandictionary.com/define.php?term=Where's%20my%20fish%3F