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Dear Group:
Here's our situation.
We are attempting to measure adult Atlantic salmon scales
(however,
the problem we are experiencing has been encountered with other
species). We want to obtain radius (line) and distance to individual
circuli (points along the line). We are using an Olympus BX60 compound
scope with a COHU video camera and a Flashpoint 128 (4MB) framegrabber.
To get the complete scale image onto the screen we are using objective
1.25 with additional magnification of between 1 and 2.
The problem is with the life history of Atlantic salmon.
Individual
circuli are laid down in conjunction with an individual's growth.
Atlantic salmon grow slower in the freshwater environment (first 2 years
of life) than in the marine environment (second two years of life).
When the entire scale is displayed on the screen, the marine circuli are
clear, but the freshwater circuli are indistinguishable (due to the
small spacing between adjacent circuli). If we are measuring just the
freshwater zone, we would usually use objective 4, mag 1-2. This gives
us the clarity needed to identify individual circuli. We would like to
measure the entire scale using a single transect line
We are looking into purchasing a high resolution digital
camera. At first glance,
it appears as if the needed resolution will be there. There will be
some draw
backs though such as cost, the need to work with saved images, and
increased
CPU power/ processing time (the image files can be quite large. Before
we
proceed we want to investigate any and all possibilities available. A
few months
ago we posted to the Optimas (image analysis software) User's List. We
received
a few good ideas and are looking in to them. They include tiling images
together,
appending data from two separate images, using a digital microfiche
reader, and using
a 35 mm slide scanner.
Any help, guidance, and/or suggestions will be greatly appreciated. I
will post a summary
of responses sent directly to me.
Thank you in advance.
--
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Ruth Haas-Castro, Research Fishery Biologist
NMFS/NEFSC
166 Water Street
Woods Hole, MA 02543 USA
voice: 508-495-2302 fax: 508-495-2393
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