Mortality of Starry Flounders (Platichthys stellatus) with Skin Tumors

Abstract

The incidence of skin tumors among starry flounders (Platichthys stellatus) in Bellingham Bay, Washington, varied both spatially and temporally. Incidence was 37% in the young-of-the-year inshore fish, declining to near-zero values by age II. My results indicate that tumor regression and spatial segregation of tumorous fish were not responsible for the decline, but that tumorous individuals had a high mortality rate relative to normal conspecifics. Selection against tumorous individuals was indicated by a sharp decline in tumor incidence in 1-yr-old fish at the same time as mean tumor number per fish declined and tumorous fish became significantly smaller than their normal counterparts. There were no differences in susceptibility to stress between normal and tumorous fish until age I; age I tumorous fish had a higher mortality rate under stressful conditions. The flounder skin tumors are lethal to a large proportion of each year-class, and therefore represent one of the largest known sources of repetitive, disease-induced mortality of fishes.Key words: starry flounder, skin tumor, X cell, mortality