Translation 2783

males begin to take an active.part in reproduction at the age of
four to six years. Gestation lasts about 11 monthS, including a
two-month delay in implantation of the fertiliZed ovum. • -
ends' in winter.
The period of intensive feedinc; begins . in late.summer and .
1Juring the breeding and moultinn periods tue seals •
continue to food, but not so intensively.
,:hey go out to the open
sea or ascend rivers in search of food, vi t ;orously• pursuin, shoals
of herring durini. their mi i;rations.
57
'line seals' principal item of diet
is various species of fishes that live in the coastal zones or in the
rivers. They eat salmon, char, and sea trout; in the open sea they
eat herring, flounder, hake, - cod, smelt, perch, etc. To a.lesser
extent . they eat small crustaceans; crabs, cephalopods, and marine
algae. Mai-hour seals are often caught in nets , hen pursuing fish,
damaging the nets and causing ldss of the catch; they are particularly
harmful to fisheries in areas of active salmon-fishing.
In some countries, such as Canada, fishermen are paid bonuses
for seals caught in their nets and killed, to compensate them for
losSes caused by these animals.
Ne.bour seals up to the age of 30 years are. encountered in
natural conditions. Cases of their survival to Le age of 14-18
ybars have been recorded in zoos.
Their natural enemies include
brown and white bears (in the Arctic parts of the seals' range),
killer whales, and sharks; among large avian predators sea-eagles
attack the pups. Still-births of pups have been observed, and births
of hairless and toothless pupu also have been recorded.
Harbour seals
in captivity are subject to such'diseaces as conjunctivitis, pneumonia,
cirrhosis of the liver, etc. fore than JO helminthic species
have been recorded in their internal ori,uns, one of them Uèorrocaecum
decipiens) also being a parasite . or cod and other fisnes.
• From some rough data it is estimated'that the western popula-
tion contains up to 100,000 harbour seals; tne annual kill ,. particularly
in Canadian waters, apparently mounts to several thousz.nds.
lossibly the :1.1ropen1 population is somewhat larher, but the extent
of the aihtu:'1 kill in 'Iceland and .1)1'itain, and jh ti
jaltic seas (in Mst and West Germany, •;weden, ..enmark, anu
nortnern and
is unknown. :ne number of harbour seals livih in -oviet coastal
waters - ilL btIL l ii.e ,ua also iJ unknown, but L ha annual kill on
these.conuts :Ippnr(:ntly doos not-exceed a A:w humlredo.
•