Translation Series No.1211

7.3. Losses in the recruitment phase
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We designate here as the recruitment phase the period of life
from the emigration from the rivers to the beginning of exploitation.
This period comprises on an average slightly less than 1.5 years, since
the salmon enter the exploited phase only in the fall of the second year
in the Sea.
7.3.1. The natural enemies
We have a number of papers that treat the enemies of the salmon
fry and of the parr. • here are only a few investigations of the losses in
smolt- White -(1936) found in the river Màrgaree (Nova Scotia) that king-
fisher (Megaceryle) and mergansers (Mergus) had eaten daily more than 40
fish (salmon, sea trbut, sticklebacks). The mergansers alone consumed
390,000 smolts of salmon and sea trout. Huntsmann (1941) could show with
the aid of tagging that the number of. emigrating smolt could : be more than
doubled when kingfishers and mergansers were controlled. Elpson (1962) even
obtained a five-fold increase in the nùmber of migrating smolt.through the
control of kingfisbers and mergansers.
In the Betio Sea similar investigations have been carried out
hitherto by Lindroth (1955a). In the Indalsâlv the mergansers had eaten
preponderantly the Parr of salmon and sea trout. One hundred adult and one
hundred and tWenty-five juvenile mergansers -consumed from June until Sep-
tember 350,000 parr. The annual production of smolt in the Indalsâlv is
around 3504000. These investigations show that the losses of smolt alone
through Mergansers and kingfisheré can amount to 50 to 80 per cent. , •