Aqe and Growth of Bluegill in
Two Northern Michigan Lakes



Michael Bishop
School of Science and Natural Resources
Lake Superior State University
Sault Ste. Marie, MI 49783



Abstract. Aging fish is important for fisheries management.
How quickly fish grow is required for determining how fishing
affects a population.  Also, knowing the average size and size
variation of fish at different ages over several years is
important for basic comparison studies.  My purpose in this
study was to determine if fish were growing at similar rates.
Preliminary observations suggested that fishing success was
better in one lake than the other.  On September 26, 1996, 26
bluegill (Lepomis macrochirus) specimens were collected from
two adjacent lakes located in Schoolcraft Co.  Length, weight,
and scale samples were taken for each fish.  Age was determined
using scales from each fish and reading the patterns of summer
and winter growth.  The Fraser-Lee method of back-calculation
was used which determines the length of the fish at each winter
period.  Linear regression was performed on the weight versus
length data and a modified t-test found no significant difference
for the resulting slopes (p<O.05).  In addition, a Mann-Whitney
U-test indicated no significant difference between the calculated
lengths at each age for the two lakes (p<O.05).  It is concluded
that there is no difference in size distribution and growth
rates between these two lakes and further that our impressions
of a good fishing lake may be subjective.





Selected References

Neilsen, L.A., and D.L. Johnson. 1983. Fisheries Techniques.
Bethesda, MA.

Summerfelt, R.C., and G.E. Hall. 1987. Age and Growth of Fish.
Iowa State Univ. Press, Ames.