15 August, 1999
Aloha from UH- Manoa.
This is my last day in the lab. I will try to perfect
my technique in preparing the otoliths for examination
under the microscope so that I can look for the
incremental growth rings.
Dr. Radtke told me that we will actually be removing
the otoliths while we are in the lab at Thule and we
won't have to try to do this in the cold. while we
are at the lakes we will be mapping where we take the
fish, some physical parameters of the water, and take
measurements of the we catch in a specific size class
fish and keeping those that we will look at in the
to prepare the slides I use a resin compound that will
melt on a hot plate and then solidify again at room
temperature. It can be reheated any number of times
so that I can get the otolith completely covered by
the resin and oriented parallel to the surface. This
way the growth rings can be counted easily. The resin
is appears similar to the resin used on surf boards
for glassing. It is clear and is easily as it is
worked and reworked. when the otolith is set in the
resin, it is ground on a flat glass plate with very
fine sand paper (500-600 grit)so that the otolith is
exposed flush to the surface yet held by the resin
around it. this is tricky as you don't want to shave
it so far down that you damage the outer edge for
counting rings, yet you want to easily see the rings
with no resin distorting the view. Then the otolith
is polished with a felt wheel coated with an aluminum
grit solution. One I dropped and the tiny otolith
fell out of the resin mold. The other two, according
to my teacher, Dave Schafer, Dr. Radtke's post
doctoral student, were excellent.
After this preparation the otoliths are viewed with a
light microscope. The microscope has a video camera
hooked up to it that feeds the image into a computer.
The National Health Institute, NIH, makes a freeware
program that anyone can down load that takes the image
and allows it to be enhanced. This way you can count
the magnified image from the computer screen which is
This work will be done on the Greenland otoliths when
the research team returns to Hawaii. I will get to
parcticpate in doing some of this lab work and will
report our finding to you at that time.
Aloha again to my fellow travelers. Paul, Heather, and
Hans have been writing and asking for more pictures.
We have been experiencing some incompatability
problems and the bugs are being worked out. If you
return to my July Alaska journals you will now find
pictures. Please let me know if there is something
you would like to see and I will attempt to get a
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