Some new results on experimental eggs incubation of walleye pollock (Theragra chalcogramma)
The eggs of walleye pollock collected in the waters of eastern Kamchatka were incubated under temperature 3.0 °С and 1.5 °С. Time of embryogenesis from fertilization to 50 % emergence of the eggs was 19 days in the first case and 23 days in the second one. Judging from the experiment and cited data, the embryonic development for the eggs from the southern part of reproduction area (at Primorye or Japan) is longer than that for the eggs from its northern part (at Kamchatka or in the Gulf of Alaska): the time difference for incubation under the same temperature is 2-4 days. Relative duration of the embryogenesis stages is defined more precise. The shortest are the stages of cleavage (I) and mature embryo (IV). The stage of germ band (II) is longer that was accepted formerly and has similar duration as the stage of immature embryo (III). Temperature influences in different ways on duration of the stages. Under the low temperature (1.5 °С), the embryo development is delayed at the stages of cleavage (for a day) and immature embryo (for 3 days). New experimental results on the time of embryogenesis and duration of its stages allow to interpret better the data of ichthyoplankton surveys for more accurate assessment of the walleye pollock spawning stock at eastern Kamchatka. The higher estimation of the stock is done by improved technique.