M74 syndrome in Baltic salmon The incidence of M74 is monitored in salmon feeding in the Baltic Sea to ensure sustainable exploitation of Baltic salmon stocks. What is M74?
M74 syndrome is a reproduction disorder of Baltic salmon (Salmo salar). It leads to death in yolk-sac fry. Before dying, the yolk-sac fry display typical symptoms. Parent fish may also show a loss of equilibrium.
Topical
The incidence and frequency of the reproductive disorder of Baltic salmon, the M74 syndrome, is annually monitored in yolk-sac fry. In spring 2007, salmon eggs from the rivers Simojoki, Tornionjoki, Kemijoki, and Kymijoki were in female-specific experimental incubations.
The mean yolk-sac fry mortality of salmon from the River Simojoki was 26%, i.e., significantly higher than it was over the period 2003–2005. In 2007, nearly one third of the salmon offspring groups from the River Simojoki displayed M74 symptoms, and 16% of the offspring groups died entirely because of the syndrome.
The offspring mortality rate of the salmon from the River Tornionjoki was at the same level as it was during the previous four years. One of the offspring groups died entirely.
Salmon from the River Kemijoki underwent M74-monitoring for the second time, and the mean yolk-sac fry mortality was 40%, the same as in the previous year.
While no M74 cases were detected in the salmon from the River Kymijoki in 2006, one quarter of the offspring groups displayed M74 symptoms in 2007. Of the River Kymijoki salmon offspring groups 10% died, and the mean yolk-sac fry mortality exceeded 20%.
Report in January 2008: The M74 syndrome of Baltic salmon: the monitoring results from Finnish rivers up until 2007. (Abstract in English) (pdf)
The deaths of newly-hatched fry due to M74 syndrome have decreased the natural reproduction of Baltic salmon significantly since the early 1990s. During the period 2003-2005, the situation was good, with the fry death rate in Bothnian Bay rivers being less than 5%, as low as before the 1990s. However, mortality seems to be on the increase again. In 2005, all fry died in a few offspring groups of the Simojoki and Kymijoki salmon. The causes of M74 are still unknown, but its occurrence is clearly connected with low thiamine (vitamin B1) content of eggs.
Aims and lines of research
The aim of the research is to clarify the causes and mechanisms behind the M74 syndrome. The M74 research covers the ecology and feed of Baltic salmon and the role of organohalogens in the syndrome. The incidence of M74 is monitored annually by experimental incubations of eggs from those salmon stocks that are able to reproduce in the wild. These are salmon ascending the Tornionjoki, Simojoki (the Bothnian Bay) and Kymijoki (the Gulf of Finland) rivers. Salmon from the Tenojoki river (the Arctic Ocean) have been monitored as a comparison.
The incidence of M74, in terms of frequency and severity, is being monitored in salmon ascending different rivers
- to find out mean yolk-sac fry mortality and the proportions of females producing offspring suffering from M74 by means of experimental incubation and biochemical analysis and by studying physiological changes;
- to produce information for evaluating of the state of salmon stocks and fisheries management;
- to develop methods for predicting the incidence and severity of M74;
- to find the causes of temporal variation and river and female-specific variation in the strength of M74 for developing ways of mitigating the effects of the reproduction disorder and for the sustainable exploitation of salmon stocks
International cooperation
The project has included cooperation in M74 studies with researchers from countries around the Baltic Sea and with researchers from North America studying a similar syndrome called Early Mortality Syndrome (EMS), or more recently also known as thiamine deficiency complex (TDC).
Scientist in charge of project
Pekka Vuorinen
Finnish Game and Fisheries Research Institute
P.O. Box 2
FI-00791 Helsinki
Finland
Street address:Viikinkaari 4
Phone +358 205 751 277
Gsm +358 40 732 7357
Fax +358 205 751 201
e-mail: firstname.lastname@rktl.fi
Other scientists: Marja Keinänen, Erkki Ikonen
 Text version
|
