Sd. Bryan et al., THE INFLUENCE OF CHANGING WATER LEVELS AND TEMPERATURES ON THE FOOD-HABITS OF WALLEYE IN LAKE OAHE, SOUTH-DAKOTA, Journal of freshwater ecology, 10(1), 1995, pp. 1-10
Fluctuating water levels and water temperatures in recent years have h
ad an influenced the food habits of walleye (Stizostedion vitreum) in
Lake Oahe, South Dakota. We collected walleye from the upper, middle,
and lower regions of the reservoir in 1993 and, using the relative imp
ortance (RI) index, compared walleye food habits in 1993 with those fr
om a similar study of Lake Oahe conducted in 1991. Rainbow smelt (Osme
rus mordax) had higher RI values than other prey in all regions of the
reservoir throughout 1993. In 1991, rainbow smelt dominated the diet
of walleye only in the lower portion of the reservoir. Ephemeridae and
chironomidae were the only macroinvertebrates found in the walleye di
et; however, neither constituted a large portion of the diet in either
year. Seasonal importance did, however, vary slightly among sites as
diets became more diverse in the upper reaches of the reservoir. The p
redominance of rainbow smelt in the diet of walleye throughout the res
ervoir in 1993 was probably due to cooler water temperatures and incre
ased reservoir volume. Cooler water temperatures in 1993 allowed rainb
ow smelt to occupy areas where water temperatures exceeded their upper
thermal limit in 1991.