Rats are a long-established New York subway species. Now, they’re joined by puddle-fish.

It had rained recently, and the area between the tracks was flooded. I had just given up my rat search when I saw some movement out of the corner of my eye. It wasn’t a rat, but a tiny fish swimming up and down the tracks.

I looked around excitedly for someone to share it with. Finally a subway worker came along, whom I quickly grabbed and announced, “There’s a fish!” I figured he would tell me I was imagining it, but he smiled and said: “I know. It’s been there for two weeks.”

Apparently, this is a new one: No one at the transit authority could ever remember seeing aquatic life among the tubes before, and couldn’t account for how this little fishie found its way on the 6 line at Union Square.

I had reason to take the 6 uptown yesterday, so yes, I did make a special stop at 14th Street to check this out for myself. Alas, I saw the still-standing water, but no fish. The referenced episode happened a month ago, so I’m guessing that one of the rats went fishing since then.