Black Durgon Color changes at Kahalu'u

   The Black Durgon, Melichthys niger, is now apparently known as the Black Triggerfish.  Is nothing sacred? 
    I have been a fan of the Black Durgon for as long as I have been watching fish in Kona.  Not only does it sport a dramatic color pattern, but around the Kona coast it is plentiful.  Virtually where ever you go you are surrounded by these black beauties with their shiny blue linings.

Black Durgon, Melichthys niger, Blue Stripe Pattern

    Recently, I have seen and photographed two interesting color patterns displayed by Black Durgons.  Although our hero, John Hoover, mentions them in The Ultimate Guide, they are not pictured there.  John Randall, in Shore Fishes of Hawaii, shows a pair with both blue stripes and a bit of orange cheek blush.  At any rate, I thought it would be useful for us to publish them in the blog, making them part of the internet image collection.    
    At the outset, I would like to point out that both of these unusual color patterns were photographed at Kahalu'u.  In my site descriptions, I say some negative things about K Bay.  Here, I would like to say that in the summer when the sea is calm and the current is minimal (and the number of competing snorkelers is relatively low) Kahalu'u is a wonderful place to find something special to capture on your SD card.

Black Durgon, orange cheek pattern

    The first pattern I would like to show you is a black fish in which every alternate scale line has become a luminous royal blue. Randall's picture shows lighter blue lines, so the extent of this color change is obviously variable.   As with the next pattern,  Hoover speculates that the fish may adopt this pattern when agitated.  This individual was not involved in a group activity.  He held this pattern for at least fifteen seconds, but  reverted to plain black when approached for a close up.   To the best of my recollection, this is the only time I have seen this pattern
    I spotted two fish with the second color pattern just yesterday.  Here you see two individuals with luminous orange cheek patches.  This pattern is a bit more common; I'm sure I have seen this before.  However, I've not seen such vivid orange patches.  And I've never been close enough or quick enough to photograph the orange cheeked wonder.

Black Triggerfish, Kahalu'u September 2012

    As you can see, these two durgons are clearly involved in a group activity.  Are they breeding, dining or doing something else less anthropomorphic?  (I personally have trouble ascribing human emotions to fish. Especially when I'm eating grilled ahi.)   The presence of an argus grouper or two suggests that food may be the "agitating" stimulus.  Here is a picture taken just seconds later in which the orange cheek is all but gone.

Mixed Feeding Group, Kahalu'u

    Before leaving the enticing waters of K Bay, I wanted to share one more picture taken just a couple of days ago.  Here you see a variety of fishes in an "agitated" state.  None of them are durgons and no one is sporting an orange cheek.  (But the Orangeband Surgeon is doing his best to emulate the agitated durgons!)  I count eight species here and I assume they are drawn to a source of food. 
   Perhaps you remember times gone by when virtually every day someone would bring a bag of frozen peas, stand in the Kahalu'u shallows and attract a huge number of fish.  Back then there were legions of Milletseed Butterflies, platoons of Scribbled Filefish and swarms of Ring Tailed Surgeons.  It was quite a show.  Of course, I can't say what reduced the numbers of these fish, but my suspicion has always run heavily towards the frozen peas.  It is surely better that we do not feed the fish and find these mixed feeding groups dining upon Mother Nature's bounty.

jeff