Английский язык: Сборник текстов и упражнений. Дьякова Н.П. - 95 стр.

ence in dynamics of the development of the osmoregulatory function. Hypoosmo-
regulatory ability of try was assessed by dynamics of blood plasma sodium con-
centration, 24 and 48h after their transfer from fresh water to sea-water (30‰)
and by fry survival in water of 40‰ salinity. Hatchery fry reared a significant dis-
tance from the sea (at the Malkinsky Salmon Hatchery) did not show a Hypoos-
moregulatory ability until the end of May. And only by the end of June did these
fish reach a size of 4–5g that approximately corresponds to attainment of smolt
status (Zaporozhec and Zaporozhec, 1993). However the final testing in water
with salinity of 40‰ did not reveal a reliable ability to maintain homeostasis.
That indicates that these fish were not completely ready for transition to the salt-
water environment and likely would lead to their mortality in an early sea life.
     In contrast to the Malkinsky Hatchery results, chum salmon fry reared near the
east of coast of Kamchatka – at a fish hatchery located on the Paratunka River –
showed physiological readiness for migration to the sea environment in February at
a size of 0,5–0,8g and maintained this ability until late June (at a weight of 6g). The
survival test in water with salinity of 40‰ has confirmed good osmoregulation of
young already by the beginning of April. At this time the wild fry of the chum
salmon from the Paratunka River (size of 0,4–0,7g) also demonstrated good os-
moregulatory function in water with salinity of 40‰.
     Certainly, it is possible to assume that chum salmon artificially reared at the
Malkinsky Salmon Hatchery fully smolted during their migration to sea. In such a
case it would be most probable that adults will return their migration to sea. In
such a case it would be most probable that adults will return only to those places
where a smoltification and imprinting were completed (Hasler and Sholz, 1983),
i.e., in mid- and lower mainstem areas located downstream from the hatchery.


               Statement of Pacific Salmon Stocks on Kamchatka

    Kamchatka is one region in Russia where mass natural reproduction of five
Pacific salmon species (pink, chum, sockeye, chinook and coho salmon) occurs.
Artificial reproduction in Kamchatka is not of a comparable scale and is primarily
used in some cases when spawning grounds have been destroyed or endangered.
Total area of spawning grounds on Kamchatka is about
    245 million m2 , about 60% of, which is located in western Kamchatka rivers
with the remaining 40% in eastern Kamchatka.
    The most abundant salmon species in the Russian Far East is pink salmon. Pink
salmon spawning grounds comprise about 175 million m2. In western Kamchatka
the abundance of odd-year pink salmon is extremely low and odd-year pink fishe-
ries have been prohibited since 1989. Total pink spawners escapement in 1997 was
than one million. Even-year pinks have dominant abundance in western Kamchatka
rivers, with the number of spawners in 1998 totaling 42 million and total catch con-
sisting of 112364 tons. In eastern Kamchatka dominant pinks are of the odd-year
class. Total harvest of pink salmon in 1997 was 83 750 tons in this region, with
spawning escapement of about 22,5 million. In comparison total 1998 pink harvest
                                          95