Reproduction, embryonic and early post-embryonic development of saffron cod Eleginus gracilis (Gadidae) from the Tauyskaya Guba Bay (northern Okhotsk Sea)

• Published in: Izvestiya TINRO
• Main Authors: Ravil R. Yusupov, Marina V. Rakitina
• Format: Article in Journal/Newspaper
• Language: Russian
• Published: Transactions of the Pacific Research Institute of Fisheries and Oceanography 2017
• Subjects: тихоокеанская навага; размножение; эмбриональное развитие; предличинка; личинка; Aquaculture. Fisheries. Angling; SH1-691; Ochre; Okhotsk; Tauyskaya Guba; okhotsk sea
• Online Access: https://doi.org/10.26428/1606-9919-2017-189-52-66; https://doaj.org/article/ce7bb8a8f46540caacd7da14f4122ace

New information on reproductive biology, embryonic and early post-embryonic development of saffron cod Eleginus gracilis Tilesius is presented on the base of long-term observations in the Tauyskaya Guba Bay, northern Okhotsk Sea. The species begins to spawn in this area at the age of 2 years, with the body length of 14 cm, and reaches mass maturity (when at least 50 % of fish in the age group are matured) at the age of 3 years. All fish are matured at the age of 5 year and elder. Males prevail in the first three age groups, but females dominate in elder groups. The mature fish enter to the spawning grounds in the Tauyskaya Guba Bay in December. The spawning occurs in January-March under the water temperature of -1.5оC. The saffron cod females spawn 7.2-172.0 thousand eggs, depending on their size, weight, and age (on average 56,600 eggs or 334 eggs per 1 g of body weight). Relative fecundity of the females increases until the age of 7 years, elder females have slightly lower but stable fecundity. The eggs at the beginning of the second stage of development have the diameter of 1.00-1.58 mm, on average 1.410 ± 0.005 mm, and are distinguished by almost transparent shell and colorless yolk, with the ochre colored plasmodisc. The animal pole (were plasmodisc is formed) is in the upper position. A micropyle on the outer shell is clearly visible as a small bulge with diameter slit surrounded by two concentric beads (this structure remains during entire embryogenesis and can be considered as a taxonomic sign of the species rank). Under the incubation temperature of 2.8оC, the eggs reach the stage of two blastomeres in 11-12 h. At the first stages of partition, numerous small fat-like inclusions are visible in the blastomeres. The second and third cycles of the zygote division with forming of 4 and 8 blastomers pass in the age interval 14-18 h. The interphase between divisions increases from 3 h between the first and second divisions to 5 h between further divisions. The eggs reach the early stage III (large cell ...