Acute stress causes skin ulceration in striped bass and hybrid bass (Morone)

Exposure of striped bass (Morone saxatilis) and hybrid bass (M. saxatilis f emale X Morone chrysops male) to an acute (2-hour) confinement stress cause d skin ulceration on the fins but not on the body of all confined fish. Str iped bass displayed more severe lesions than did hybrid bass. Histologicall y, lesions had varying degrees of epithelial erosion and ulceration, which was most severe at the distal portion of the fins. Ulceration was associate d with dermal and hypodermal edema and necrosis of the remaining stromal ti ssue and tips of bone in the fin rays. No hemorrhage or thrombosis was pres ent to suggest any obvious vascular derangement. No evidence was found for either trauma or an infectious agent initiating the lesions. Injecting fish with epinephrine caused a similar response, although the degree of ulcerat ion was less severe. These findings may explain why many opportunistic skin pathogens can rapidly develop into serious infections in fish.