Embryonic and larval development of the Pacific cod Gadus macrocephalus from Taui Bay, northern Sea of Okhotsk

Abstract

Experimental data on the embryogenesis and early post-embryonic development of the Pacific cod Gadus macrocephalus Tilesius that breed in Taui Bay are considered. Fertilized eggs at stage II have a diameter of 1.000–1.250 mm, and a mean of 1.103 ± 0.003 mm. Numerous teardrop-shaped inclusions in the plasma of the blastodisc and in blastomeres presumably prevent cod eggs from freezing at low temperatures during incubation in vivo. Embryogenesis of cod in vitro at the temperatures of 2.2 and 5.2°C lasts for 490 and 768 hours, respectively. Newly hatched cod prelarvae have a body length of 4.28–5.10 mm, a mean of 4.34 ± 0.03 mm; they switch to mixed and exogenous nutrition by 6 and 10 days, after reaching a mean length of 4.97 and 5.18 mm, respectively.