[Coral-List] crown-of-thorns starfish outbreak in American Samoa

[Douglas Fenner]

    Crown-of-thorns starfish sightings in American Samoa have been
increasing for over a year.  They are now to the point that they are eating
significant amounts of coral.  Efforts are underway to try to kill
significant numbers of them by injecting them.  Efforts have been
increasing as their numbers have been increasing, but their numbers
continue to increase.  I'm told that (independent) Samoa, which used to be
called Western Samoa and is in the same archipelago, has a similar
problem.  My guess is that the increases in those visible (and the feeding
scars) comes from more and more of them who have been in holes in the reef
all the time, coming out to feed on coral.  I'm told that their sizes have
been increasing, but of course virtually all that are seen are already
nearly a foot in diameter or more.  The increases we've seen in the last
year are unlikely to be due to continued reproduction, it is due to those
in holes coming out as they grow.  But the large numbers now present, may
well produce a large number of eggs and the next generation could be a much
larger secondary outbreak.

     Efforts to control them are an uphill battle.  The last previous
outbreak here peaked in 1978, when there were millions, and they ate around
90% of all the coral.  Over 400,000 were collected then before the money
ran out, and had no effect on their numbers.  Efforts started much earlier
this time, in hopes of controlling it before it became uncontrollable.
There was a previous outbreak that we know little about, in 1938.  In
2005-2012, coral cover increased in American Samoa, a bit of a success
story, which is now treatened.

    All this makes sense to me from what is known of crown-of-thorns
biology.


Birkeland, C.  1982.  Terrestrial runoff as a cause of outbreaks of
*Acanthaster
planci* (Echinodermata: Asteroidea).  Mar. Biol. 69: 175-185.


Birkeland, C.  1989.  The Faustian traits of the crown-of-thorns starfish.
American Scientist 77: 154-163.


Brodie, J., Fabricius, K., De'ath, G., and Okaji, K.  2005.  Are increased
nutrient inputs responsible for more outbreaks of crown-of-thorns
starfish?  An appraisal of the evidence.  Marine Pollution Bulletin 51:
266-278.


Morello et al. 2014.  Model to manage and reduce crown-of-thorns starfish
outbreaks.  Marine Ecology Progress Series 512: 167-183.

-- 
Douglas Fenner
Contractor with Ocean Associates, Inc.
PO Box 7390
Pago Pago, American Samoa 96799  USA

phone 1 684 622-7084

"belief in climate change is optional, participation is not."

belief in evolution is optional, use of antibiotics that bacteria have not
evolved resistance to is recommended.

website:  http://independent.academia.edu/DouglasFenner

blog: http://ocean.si.edu/blog/reefs-american-samoa-story-hope