A Review of Early Mortality Syndrome (EMS) in Great Lakes Salmonids: Relationship with Thiamine Deficiency

摘要

Early mortality syndrome or EMS that affectssalmonids in the Great Lakes exhibits mant of the sameclinical signs as Cayuga syndrome, that affects Atlanticsalmon (Salmo salar) in the New York Finger Lakes andthe M74 syndrome that affects Atlantic salmon from theBaltic Sea. These similarities may reflect their sharedcharacteristics of associated low thiamineconcentrations in eggs and therapeutic responsivenessto exogenous thiamine treatment. When egg thiaminelevels fall below a species-specific threshold clinicalsigns include loss of equilibrium, depression ofrespiration and reduced heart rate. Although feedingstudies with thiamine deficient diets have yet toconfirm a thiamine cause-effect relationship, EMS-likesymptoms can be induced with thiamine antagonists.Patterns of temporal variability of EMS among GreatLakes' salmonids over the last 3 decades have beensimilar. In coho salmon (Oncorhynchus kisutch), EMS wasnegatively correlated with alewife (Alosapseudoharengus) abundance in Lake Michigan. Wehypothesize that this may reflect quantitative orqualitative changes in the alewives eaten becausedespite their fluctuating abundance they have remainedthe preferred diet item. The limited data available forother salmonids suggest similar trends.