Same or different?

by B. N. Sullivan

This image reminds me of those puzzles: Which one is not like the others?

At first glance, all the fishes in the photo look alike.  They're similarly shaped, their bodies are white with lines, and they all have yellow fins and black trim, including a black bar over the eye.  But if you look more carefully you will notice that there actually are two species of Butterflyfishes swimming together.

The two fishes in the foreground of the photo -- the ones with the black spots near the trailing edge of their dorsal fins and the diagonal lines on their bodies -- are Threadfin Butterflyfish (Chaetodon auriga).

The larger fish in the upper part of the photo is a Lined Butterflyfish (Chaetodon lineolatus).  Note that it has a broad black arc on its back, instead of a spot, and the lines on its body are vertical rather than diagonal.  (And yes, that's another Lined Butterflyfish behind the two Threadfins.)

Both of these are Indo-Pacific species, and they are widely distributed.  We have seen them -- usually in pairs -- in many locations from the Red Sea all the way to Hawaii.  The ones here were photographed in Honaunau Bay, Hawaii.

Earlier we posted close-up images of each of these species.  If you take a look at those earlier photos of the Threadfin Butterflyfish and the Lined Butterflyfish, you will be better able to appreciate the differences in their markings.

So, if you see a pretty Butterflyfish -- white, with lines on its body, and with yellow and black trim -- now you know which details to look for that will distinguish the Threadfin Butterflyfish from the Lined Butterflyfish.


  1. Too bad people of this world that are different couldn't get along as well as some breeds of fish.

  2. They are so beautiful! Love to see sea creatures living together so peacefuly.

  3. The diversity among the fishes kind of puts the hobby of birdwatching to shame, doesn't it?

  4. @ damontucker - Yes, that would be so nice.

    @ antigoni - We love to see this as well.

    @ lavendarbay - Actually, I think birdwatching and fish-watching (by humans) are quite similar - they're just performed in a different medium, so to speak. One difference, though, is that fish-watching divers usually pay as much attention to critters in other phyla as they do to the fish, whereas most birders (the ones I know) focus mainly on birds.

    TRhe commonality among all of those: we're all nature lovers. :-D


  5. I have really missed your underwater shots. I'm hoping I'll be able to visit more often. :-)

  6. I would never be able to notice that if that title wasn't there. The intricicies of patterns.


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Bobbie & Jerry