A Lake Superior State University study on Atlantic salmon conducted by researchers in the LSSU Aquatic Research Laboratory has shed some light on why the fish are not reproducing naturally in the Great Lakes.

The study, which took place in the LSSU lab on the St. Marys River, where LSSU raises Atlantic salmon for annual release, found that Atlantic salmon have difficulty reproducing when the amount of vitamin B1 is low in their eggs.

This deficiency leads to a disease called Early Mortality Syndrome, or EMS.

The findings, conducted by Marshall Werner, Ph.D., associate professor of chemistry, Roger Greil, laboratory manager, and Benjamin Rook, a student from Holt, will be published in June in the Journal of Great Lakes Research.

"EMS is a potential problem for all salmon in the Great Lakes," said Dr. Werner. "This disease appears to be due to the presence of certain bait fish such as alewives, smelt, and gizzard shad in the Great Lakes. These types of fish contain an enzyme called thiaminase, which breaks down vitamin B1, or thiamine."

Dr. Werner and his colleagues at the LSSU lab have been investigating the EMS in the Atlantic salmon that are stocked in the St. Mary's River every year.

They have observed that when the levels of thiamine are low in the eggs of spawning females, the resulting juvenile salmon have high death rates.

"Presumably, the levels of thiamine in eggs are low because the salmon have been feeding on diets that consist mainly of alewives and other thiaminase-containing fish," Dr. Werner said. "Because these fish contain high levels of thiaminase, the female cannot put enough thiamine in her eggs and her young do not survive."

The researchers also conclude that a new rapid method for measuring thiamine in fish eggs may help fishery managers make decisions concerning salmon stocking in the Great Lakes.