The Black Durgon Round Up

    Over the last ten days, we've experienced difficult conditions.  For several days, here in Kona, it rained terrifically.  Following the rain, the surf came up.  At long last, the sun is out and the surf  looks small enough to permit easy, clean and enjoyable snorkeling.
    

Black Durgons All Lit Up.  Kahaluu September 2012

   All this is presented as an excuse for not writing a blog recently.  In fact, we weren't even taking many pictures.  It was just yesterday that we downloaded from the Canon D10 and found some documentation for a curious behavior.

     On an overcast day a week or so ago, Sandra and I swam out from the pier to the area in front of  Hulihee's Palace.  The water was cold and just moderately cloudy.  Swimming along we encountered the fish ball, an aggregation of hundreds of Big Eye Scad.  You will recall the blog from last November where we discussed the fish ball.  This large aggregation still gives Sandra the creeps.

    Thus it was this day.  We saw the school of scads, Sandra surfaced and said, "They give me the creeps."  But then she noticed something extremely

Black Durgons Herding Big Eye Scad Fish Ball.

unusual.  There were in excess of  a dozen black durgons, positioned at intervals along the fish ball, actively herding the scad. We watched for several minutes, during which time the tremendously outnumbered durgons moved the fish ball at least ten yards towards the pier.

    Of course, we were no where near the pier and the reef seems pretty homogeneous out there.  It was obvious, though, that there had to be some reason that the durgons were expending such time and energy to move the scads.  Neither species eat other fish.  Triggerfish eat a variety of invertebrates, from coral to the odd sea urchin.  Scad are reported to eat plankton at night.

      Individual triggerfish are known to protect their nest, but I have not heard of a breeding group engaged in organized nest protecting behavior.  Jack Randall in Shore Fishes of Hawaii notes that Black Durgons may form aggregations at the time of breeding.  It seemed to Sandra and me that the durgons believed that the scad were a danger to a communal nest site.  To quote Confucius, "Those who eat plankton at night are not above dining on caviar by day." 
 

Short Nose Wrasse, Kailua Kona

   Suffice it to say, this was a difficult picture to take.  The water was cloudy, the day overcast.  Durgons are black, scads are gray.  On the other hand, the behavior was totally remarkable, so I hope you will accept the picture for what it is.  To be fair, I'm leaving you with a picture of the tiny Shortnose Wrasse that we captured on the way in from the Great Durgon Round Up.  Keep snapping and sooner or later you will get one in focus.

jeff