Clinical Pathology and Histopathology Characteristics of Net‐Stressed Striped Bass with “Red Tail”

Simulated artificial spawning of striped bass Morone saxatilis while undergoing repeated net confinements was used to study the pathogenesis of the hyperemia of the fins and ventrum frequently observed when these fish are handled. Alterations in plasma chemistry that accompanied this external manifestation included markedly reduced osmolality, sodium, and chloride and increased plasma cortisol, total CO2, and anion gap. Hemolysis was visually detectable in plasma from five of six net‐stressed fish but not in plasma from the six control fish. Blood smears of treated fish contained spherocytes and erythrocyte fragments and exhibited anisocytosis. Histologically, the caudal fins of treated fish were characterized by mononuclear vasculitis and dilated, congested vasculature occluded with organized thrombi. Splenic architecture of net‐stressed fish was indistinct and contained diffusely coalesced erythrocytes. Conclusive evidence for disseminated intravascular coagulation was not detected by activated clotting time, estimated thrombocyte count, fibrin degradation products, or histopathology.