Aging scales of walleye, yellow perch, and northern pike: James C. Schneider.

3. Males usually grow slower than females,
and males (especially) may quit growing
after they reach sexual maturity.
4. Because of points 1-3, age estimated from
scales tends to be less than true age. Reliability
of scale aging; often declines after age 4.
5. High variation in growth is characteristic of
all three species. Even within the same
population, some individuals may grow very
quickly and others very slowly.
6. All three species may exhibit spring and fall
spurts of growth. This is more common in
shallow southern, Michigan lakes that
become too warmn for optimal growth in
midsummer and in waters where forage
abundance is cyclic. This seasonal pattern. is
often evident in the second and third years
and sometimes in the first and fourth years.
A summer check may be formed which can
appear as a true annulus on some (but
usually not all) scales.
7. Scales of stocked fingerling walleye may
show changes in growth (and checks) caused
by changes in diet while in rearing ponds,
the stress of stocking, and stocking into
food-rich waters. It is helpful to take scale
samples from a few fish right at stocking,
and later that first year, to establish a firstyear scale pattern. for stocked walleye
specific to each water body and year.
8. Because of all of the above,, there is much
variation in scale patterns among populations.
9. The first annulus may not be clearly visible
or consistently located. However, this
problem is usually less severe in yellow
perch, walleye, and northern. pike than in
bluegill Lepomis miacrochirus and species

Recommended Procedures
1. Make an extra effort to collect scale samples
from small fish,, even ones which are
obviously youngr-of-year or yearlings.
These help the scale reader establish the
likely location of the first annulus and may
give clear evidence of whether or not this
population is prone to checking. This
knowledge can then aid interpretation of
adult scales. Samples of small fish also
provide length-at-age data.
2. Clean,, soften, and flatten scales if necessary.
Scales may be cleaned by soaking in water
and rubbing on paper towel. Make goodquality impressions on plastic (six or so
scales per fish). Edges and lateral fields
should be clearly visible.
3. Arrange scale samples by increasing fish
length. Start with the smallest.
4. Plan to go through all scale samples twice:
the first time to obtain a "feel" for the
pattern for this population and the second
time to assign an age. Difficult scales may
require a third examination.
5. On the first run through the envelopes:
a. Examine several scales per fish to
develop a feel for the pattern of this fish,
to make sure that scales from other fish
have not been mixed in, and to find
scales with clear and representative
patterns.
b. Establish the appearance and approximate
location of the first annulus from small
and clearly readable scales. It is helpful
to mark the distance from the focus to

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