The M74 syndrome is a reproduction disorder of

salmon Salmon () is the common name for several list of commercially important fish species, commercially important species of euryhaline ray-finned fish from the family (biology), family Salmonidae, which are native to tributary, tributaries of the ...

(''Salmo salar'') feeding in the

Baltic Sea The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden and the North and Central European Plain. The sea stretches from 53°N to 66°N latitude and from ...

. M74 manifests as offspring mortality during the yolk-sac fry phase. Before dying, the yolk-sac fry display typical symptoms.

Thiamine Thiamine, also known as thiamin and vitamin B1, is a vitamin, an essential micronutrient, that cannot be made in the body. It is found in food and commercially synthesized to be a dietary supplement or medication. Phosphorylated forms of thi ...

(vitamin B1) deficiency in eggs is the immediate cause of M74 mortality. The deficiency can be prevented by thiamine treatments. For the first time Bulgarian research team opines that with M74 syndrome are affected also male gametes and worsened parameters of the spermiogram. The use of Bulgarian semen protective media 49282, 49283 and 49397 for trout sperm fertility improving was proposed. The thiamine deficiency syndrome M74 is related to the fat and thiamine content of prey fish. The diet of Baltic salmon leads to thiamine deficiency in eggs and consequently to the mortality of yolk-sac fry: The main prey species of the Baltic salmon are

sprat Sprat is the common name applied to a group of forage fish belonging to the genus ''Sprattus'' in the family Clupeidae. The term also is applied to a number of other small sprat-like forage fish (''Clupeoides'', ''Clupeonella'', '' Corica'', ' ...

(''Sprattus sprattus'') and

herring Herring are forage fish, mostly belonging to the family of Clupeidae. Herring often move in large schools around fishing banks and near the coast, found particularly in shallow, temperate waters of the North Pacific and North Atlantic Oceans, i ...

(''Clupea harengus membras''). Average fat content is greater in sprat than in herring. The fat content is highest and the thiamine concentration is lowest in the youngest sprat. The need for thiamine depends on the amount of fat in the diet. Thiamine deficiency in eggs results from an unbalanced diet abundant in fatty prey fish, such as young sprat, from which the supply of thiamine is insufficient in proportion to the supply of energy and unsaturated

fatty acids In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, f ...

for salmon. Relationships between fish stock changes in the Baltic Sea and the M74 syndrome: The M74 syndrome is connected to a weak

Atlantic cod The Atlantic cod (''Gadus morhua'') is a benthopelagic fish of the family Gadidae, widely consumed by humans. It is also commercially known as cod or codling.Baltic Sea The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden and the North and Central European Plain. The sea stretches from 53°N to 66°N latitude and from ...

. Since the collapse, heavy fishing mortality as well as predation on cod eggs by sprat and food competition between sprat and young-of-the-year cod has inhibited cod recovery. Coincidentally with the decline in the cod stock since 1982, and following the consequent reduction in predation pressure, the sprat stock increased rapidly, and salmon therefore had more food. Salmon grew faster, resulting also in a high CF.

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External links

Briefly: Plentiful fatty sprat as prey for salmon leads to reproduction disorder
{{salmon Syndromes in fish