Michigan Department Of Natural Resources
Fisheries Research Report No. 1847, 1977

Food Selection by Walleye Fry


James W. Merna


      Abstract.-Plankton samples and walleye fry were collected from two rearing ponds during the first week of life of the fry. The ponds, borrow pits created in construction of Interstate 75, are located in Roscommon County, Michigan. Fry were stocked in the ponds on May 14, 1975, while in the yolk-sac stage, and were first sampled the following day. The fry collected ranged in size from a mean of 9.17 mm in the first collection to 9. 56 mm at the end of one week.

Pond 1 contained a mixed population of zooplankton, and the fry indicated a positive selection of Bosmina, but the selection was more a function of size than species.

Pond 2 contained almost a monoculture of Daphnia, and as a result they were the dominant organism in the diet of the fry. The average size of the Daphnia in the zooplankton population was significantly larger than the size in the diet of the fry. Apparently the fry were forced to seek the smaller individuals in the population.