ABSTRACT
Tentative indications of possible pollution-associated disease conditions in marine fish and shellfish began to appear in the scientific literature in the 1960’s and early 1970’s. In the late 1970’s and throughout the 1980’s, evidence for an association of numerous disease conditions in marine fish and shellfish with degraded habitats increased dramatically. The evidence, though substantial, for an association of polluted habitats and fish and shellfish diseases, should still be considered as largely “circumstantial” or “inferential,” since direct cause and effect relationships have not been demonstrated to the satisfaction of all observers. Most disease conditions considered are traceable to tissue damage and metabolic disturbances induced by toxic chemicals, or to increased infection pressure from expanded populations of facultative pathogens, combined with suppression of internal and external defense mechanisms of stressed animals. Abundance of year classes of commercial fish and shellfish can be influenced, sometimes drastically, by environmental events before and after spawning or during larval development.
