Translation Series No.1211

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furnish the energy fer the spawning migration and the maturing of the oo-
cyte e appear thus to proceed hand in hand.
D. R. Idler and B. Bitners have determined the energy consump-
tion of Oncorhynchus nerka during the migration from the river mouth to
thé spawning ground. They did find that a female of 2.2 kg weight requires
on an average 1.1 kcal/kg/km. The Baltic Sea salmon have to travel distances
of 700 to 1300 km from the southern Baltic Sea to their spawning grounds.
Although the travel in the Baltic Sea . certainly requires the expenditure
of less energy than in the rivers, we shall take the value of Idler and
Bitners as basis. Here it has to be taken into account that the salmon have
fat deposits not on4r in the fillets, but also in the mesentheries of the
intestines, which contain one-third to one-half as much fat as the fillet.
A aalmon of about 70 cm length has a live weight of about 3 kg and therefore
30û0
requires about(3kcal for 1000 km. Since oils, liver oils and the like have
a content Of about 900 kcal per 100 g substance (J. R. Geigy 1953), about
350 g fat will be required for 3000 kcal. This amount corresponds to a fat
content of about 12 per cent in the fillet (110 g intestinal fat, 220 g
fillet fat; fillet weight = 60 per cent of the live weight). To overcome
a migration distande - of 1000 km a fat content in the fillet of about 12
per cent is required.
The analysis of the age of the ascending salmon can undoubtedly
show best at what age the salmon emiàrate from the Baltic Sea in order to
spawn. To be sure, an unambiguous material should contain results from the
P. 275]
most important spawning rivers. For this I have three series of meaaure-
ments that have kindly put at my disposal by B. Carlin. In one case these
concern beach-dragnet catches of 715 salmon, which were caught between June
12 and September'2, 1959 in the Ingermanâlven. The second series concerns