POPULATION ASSESSMENT OF CHINOOK SALMON IN
SOUTHEASTERN LAKE MICHIGAN

by

Jason S. Lucas
School of Science and Natural Resources
Lake Superior State University
Sault Ste. Marie, MI 49783



ABSTRACT. A common complaint of fishermen is, "Why aren't there any quality salmon in the
lake?" I wanted to demonstrate that there are quality salmon in Lake Michigan, specifically
Chinook salmon (Oncorhynus tshawytscha). To a fisheries manager, the quality of a fish
population can be assessed by the relative weight (condition) of each fish in the population. In this
study, the condition of the chinook salmon in southeastern Lake Michigan was determined at
various locations and as a ftinction of diet and age. In addition, the relationship between length
and weight was investigated to ascertain the effects of location, diet, and age. This study was
conducted in the Michigan boundary waters off South Haven, Saugatuck, St. Joseph, and Holland
while noting nearshore and offshore capture locations.
	The chinook salmon data (1ength, weight, scales, and stomachs) were collected &om
charter boat captains. The stomachs were frozen until the end of the summer, when they were
preserved in a 10% formalin solution. The stomach contents were then weighed and prey species
were identified. The prey species included alewife (Alosa pseudohareiigtis), smelt (Osmerus
mordax), zooplankton, and invertebrates. The scales were used to age the fish and the prominent
age class ofthe population was 2 year olds.
	The overall condition of the sample population was 91.3%, where > 100% is ideal.
However, the Holland population had the highest condition at 124.3%. Using Tukey's Method,
there was no significant difference (p<.05) in condition between nearshore and offshore samples.
The 3 year old age class of chinook salmon had the highest condition at 98.16%. A linear
regression between length and weight of the sample population had a significant relationship
(r =.895); however, Saugatuck was significantly higher (r =.915). Again there was no significant
difference (p<.05) between nearshore and offshore L/W relationships. Once more, the 3 year old
age class had the highest r-value at .953. In summary, location played a major role in determining
the condition of the chinook salmon population. However, the effect of diet on population
condition and length-weight relationships could not be statistically determined due to the uneven
distribution ofprey species in the diet. Overall, from a fisheries management perspective, yes there
are quality salmon in the lake.


Selected References

Koffier, C.C and W.A. Hubert. 1993. Statistics for stock assessment. pages 140-150. Inland
Fisheries Management in North America. American Fisheries Society. Bethesda,
	Maryland.

Rybici,	R.W. and D.F. Clapp. I 996. Diet of Chinook Salmon in Eastern Lake Michigan.
Department of Natural Resources. Fisheries Research Report 2027.