Remediation of Cayuga syndrome in landlocked Atlantic salmon Salmo salar using egg and sac-fry bath treatments of thiamine-hydrochloride

A lethal thiamine deficiency, termed Cayuga Syndrome (CS), affects larval l andlocked Atlantic salmon Salmo salar in several of New York's Finger Lakes . This syndrome has been linked to a maternal diet of alewife Alosa pseudoh arengus that have high thiaminase concentrations within them and were not e ndemic to the Finger Lakes. We evaluated thiamine bath treatments at a rang e of concentrations for remediation of the syndrome (CS) by treating eggs d uring water-hardening or sac-fry at the onset of CS when clinical signs suc h as yolk sac and cerebral edema, vascular and mandibular abnormalities, an d in particular when abnormal swimming, lethargy and yolk sac oppacities, f irst became evident. Concentrations of thiamine in sac-fry from both treatm ents were elevated by a single 1-h exposure of eggs or sac-fry in a thaimin e bath. Thiamine concentrations of at least 1,000 mg/L during water hardeni ng, or 10,000 mg/L if treated as moribund sac-fry, were necessary to almost eliminate syndrome-related mortality. When post-treatment total thiamine t issue concentrations (i.e., the sum of thiamine pyrophosphate, thiamine mon o-phosphate and free thiamine) approached or exceeded a threshold of 0.8 nm ol/g sac-fry in the sac-fry, mortality due to CS was significantly reduced, Earlier treatment at the egg hardening stage may provide a greater likelih ood of avoiding long term effects of the deficiency.