Sea urchin mortality at the Johnson Atoll

Harilaos Lessios LESSIOSH at
Thu Mar 7 16:14:05 EST 2002

Lindsey Hays, the refuge manager at the Johnson Atoll, reports widespread
mortality of Echinothrix (and maybe Diadema as well) all around the Atoll.
It seems that most of the sea urchins got sick and died rapidly.   He is
making efforts to collect samples, so that  the pathogens and the hosts can
be identified.

This may turn out to be a localized phenomenon, but this is what we
initially thought about the Diadema mortality in the Caribbean as well.
Just in case it spreads, it would be very useful for people in other areas
in the Pacific (particularly Hawaii and the Marshall Islands) to be ready
for it.  Surveys to determine population density of Echinothrix and Diadema
done now in unaffected areas can provide data that will become extremely

It would also be a good idea to know ahead of time what to do if the
mortality should  appear elsewhere.  It is all common sense, but when things
are happening in a hurry, it is good to have a list.  If you notice sick or
dying sea urchins anywhere in the central Pacific:

1.Note  the date of the observation, and also note the date that populations
were last seen to be healthy.

2.  Collect specimens.  Some should be kept in 95% ethanol, some in 5%
formaldehyde, some frozen and (if possible) some should be cooled down on
ice for fast shipment to a microbiologist.

3.  If there are still healthy-looking animals around, collect some of these
too, so that their bacterial fauna can be compared with that of the sick

4.  If you have the time and the inclination, mark areas where the mortality
is occurring and areas where it does not seam to have reached yet.  Then
monitor these areas by counting numbers of healthy, sick and dead animals.

5.  Keep looking, even after the time that it seems that all the Echinothrix
is dead.  You may notice new ones emerging after a while (it happened with
Diadema antillarum).

6.  Don't expect the tests to stay around for very long.  They break down to
unrecognizable ossicles in a matter of days (parrot fish may help).

I hope that none of this will be necessary, because whatever is killing the
sea urchins at the Johnson Atoll will remain there.  Lindsay Hayes did a
great job of contacting people as soon as he realized that something was
amiss.  I wanted to spread the world around more widely in case things get

Haris Lessios

H.A. Lessios
Smithsonian Tropical Research Institute
Balboa, Panama

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