Age and Growth of Brown Bullheads (Ameiurus nebulosus)
from Kinross Lake.

Richard H. Trojanowski
School of Science and Natural Resources
Lake Superior State University
Sault Ste. Marie, Michigan 49783 USA


Abstract: Seventy-three brown bullheads (Ameiurus nebulosus) were collected from
Kinross Lake located in Kinross MI., during the fourth week of September in 1995.
Because fish that were collected appeared stunted, an age and growth study was
conducted to better understand this population. Fish were caught using two fyke nets set
in two different areas of the lake. Removal was conducted in order to thin the large
population of bullheads that occupied the lake. The bullheads were individually measured,
weighed and a pectoral fin spine was removed for aging. Age was determined by reading
the patterns of slow and fast growth visible in a cross-section of the spine viewed with
magnification. Back-calculation of overall length at the end of each growth period was
determined using the Dahl-Lea method. Back-calculations reveal that the average length
at the end of year 1 was 44.4 mm., 104.0 mm. at the end of year 2, 159.6 mm. at the end
of year 3, and 21 1.8 mm. at the end of year 4. As a result of this study and comparisons
with other age and growth studies pertaining to brown bullheads, it appears that the
population is stunted. Thinning may result in larger fish if stunting is occurring because of
limited resources, however, if the population is stunted due to the short growing season
the thinning may have little effect on the size ofthe brown bullheads. A comparison
involving two lakes of similar resource compositions but located in different climatic
conditions would help to differentiate between the two possible causes ofthe stunted
bullhead population.


Selected References

Marzolf, R.C. 1955. Use of pectoral spines and vertebrae for determining age and rate of
growth of the channel catfish. Journal of Wi1dlife Management 19(2):243-249.

Keast,	A. 1985 . Growh responses of the brown bullhead (Ameiurus nebulosus) to
temperature. Canadian Journal of Zoology 63:1510-1515.