Prevalence of Walleye Discrete Epidermal Hyperplasia by Age-Class in Walleyes from Oneida Lake, New York

Abstract

The prevalence of visible proliferative lesions was followed on walleyes Sander vitreus at ages 3 to more than 8 years from 1997 to 2003 in Oneida Lake, New York. Walleye discrete epidermal hyperplasia, the focus of this report, is a seasonally limited skin disease caused by two closely related retroviruses, walleye epidermal hyperplasia virus type 1 and type 2. As with walleye dermal sarcoma, the in-lake transmission patterns of this disease are unknown. The percent of fish developing walleye epidermal hyperplasia lesions increased incrementally with age in this study. It is unlikely that all walleyes of a given year-class will contract discrete epidermal hyperplasia in their lifetimes because fewer than 20% of the fish age 8 and older were affected. In contrast, the prevalence of walleye dermal sarcoma, a disease we believe eventually affects almost all exposed walleyes, changes with age, decreasing after age 6, which suggests that walleyes develop resistance to that disease.