[Coral-List] reply Canthigaster rostrata masive death

[Kristof Ketch]

I had made the following post on a reef.org forum about Roatan, 
Honduras. I'll try to dig up the report I had written for my class to 
forward to Frank.

Observations of Canthigaster rostrata (sharpnose puffer)
Submitted by Kristof on Wed, 01/28/2009 - 18:27.
I just recently got back from a week intensive class at the University 
of Minnesota that went down to Anthony's Key Resort in Honduras, and I 
once I noticed the event I decided to do a small project looking at the 
density of the sharpnose puffers since it is a recent event that nobody 
quite understands.
On Jan 6th at 10am, I counted 104 sharpnose puffer individuals in 30m2 
by doing a 15m belt transect, and Jennifer (one of the coordinators 
there) confirmed 98 individuals by counting behind me. The transect was 
at 40 ft at the Fish Den dive site.
On Jan 7th at 3pm,  Jennifer, the center's resident scientist, counted 
91 individuals using the same technique at 40 ft at Barry's Reef dive 
site.
There density seemed to remain fairly similar in all the other dives we 
did ranging from a wreck dive at 120 ft to snorkeling in the shallows, 
but those two transects were the only two counts we took.
We didn't see many dead sharpnose puffers, but we did occasionally see a 
few on the sea floor during our dives. They weren't dieing off by the 
hundreds or thousands, at least not yet.
I'm hoping that either Jennifer or anybody else continues to monitor the 
population, health, and behavior during this event.
I also took some observations and noticed that most of them were located 
on a little patch of reef and I saw many of them fighting to defend 
their territory. Many of the ones with territory also occured in pairs. 
In general, those that had territory looked healthy, and most of the 
lone free swimmers looked starved, sickly, and some were diseased with 
white spots covering their body. Jennifer had said that they normally 
ate inverts, but during the dives I saw them picking at everything 
including algae, sponges, corals, and sea fans (although I couldn't tell 
if they were eating little creatures off of them or were trying to eat 
the item itself). Wouldn't surprise me if they are trying to eat 
anything because their high population density has probably caused them 
to eat most of their normal food source.
I don't know much about it, but my thoughts on the event are similar to 
Dr. John Ogdon. I think that there was recent spawning event that 
doesn't normally occur or else the majority of the larvae somehow 
survived a normal spawning event, and now there is an over abundance of 
the population that will disperse in area and die off until they reach 
their environments carrying capacity.
~Kristof

Also in that forum discussion, was this post:
Population Explosion of Sharpnose Puffers - an explanation
Submitted by Christy on Wed, 12/31/2008 - 11:08.
Hello all.
This phenomenon was recently noted by several researchers and scientists 
on the Coral Reef Listserve. The most likely explanation for the 
explosion was posted by Dr. John Ogdon -- "My guess is that sharpnose 
puffers have the same type of recruitment as Bill Gladfelter and I 
observed for balloonfish (Diodon holocanthus) many years ago in St. 
Croix. The larvae are pelagic for a long larval life, up to a year. 
During this interval; they slowly gather into huge schools of many 
thousands of individuals (about 3cm long) which then recruit en mass to 
whatever coastal region is favorable within the time frame of 
development. The area then becomes completely flooded with recruits 
which gradually disperse and are preyed upon. You could call this a sort 
of 17-year locust type of recruitment."
You can view the entire thread of Coral Listserv posts on this topic 
here --
 
http://coral.aoml.noaa.gov/pipermail/coral-list/2008-December/038308.html
-- Christy Pattengill-Semmens
REEF Director of Science