Five year trends in the egg-thiamine status of Atlantic salmon from the St. Marys River, Michigan

Early mortality syndrome (EMS) is the term used to describe the mortality in early life stages of salmonids due to thiamine deficiency within the Great Lakes basin. Since 1985, Lake Superior State University (LSSU) has raised Atlantic salmon Salmo salar for stocking in the St. Marys River region near Sault Ste. Marie, Michigan. In 2000, the Atlantic salmon raised at LSSU experienced 99% mortality due to EMS related symptoms. In order to better understand and document the incidence of EMS in the St. Marys River population of Atlantic salmon, egg-thiamine content has been measured in this population since 2003. Egg-thiamine levels were measured using a rapid reversed-phase solid-phase extraction (RP-SPE) method of thiamine analysis. This paper presents the egg-thiamine data for this population of Atlantic salmon for the years 2003-2007. Over this five-year period, the egg-thiamine content of eggs from 2005 saw a significant increase. This one year shift may have larger ecological implications related to changes in the diet of this population of Atlantic salmon.