Vision is an important cue in larval survival to capture prey. Therefore, we examined the development of the retina structure in the Chinese sturgeon (Acipenser sinensis), the density of single cones, the ganglion cells and the nuclei of the outer nuclear layer of newly hatched larvae, covering different developmental stages ranging from hatching (13.3-13.6 mm TL) to 180 days post-hatching (dph) (290.7-301.6 mm TL). At hatching, larvae exhibited an undifferentiated retina. The retina at 3 dph (16.0-16.9 mm TL) had single cones (SC) at high density. The rods appeared at 9 dph (24.8-25.5 mm TL), and it is assumed that at this time the visual system was developed completely. However, the larvae showed apparent retinomotor responses not before 25 dph (42.7-44.1 mm TL). The density of single cones (SC) and ganglion cells (G) decreased with proceeding development, while the density of the rods (R) gradually increased. The ratio of nuclei of the outer nuclear layer to ganglion cells (ON/G) per 100 µm increased during development, and so did the ratio of nuclei of the outer nuclear layer to single cones (ON/SC). The investigation showed that the structure of the retina changes rapidly from 9 to 17 dph, and many become fully functional at 25 dph when retinomotor responses occur. This is the transitional period of the ontogenetic development of the visual system. These changes in the retina of the Chinese sturgeon are adaptive to their feeding requirements, and co-inciding with the ecological shift from surface (pelagic) to benthic feeding habitats.

Ten females of Kaluga sturgeon (Huso dauricus; 73.8 ± 6.49 kg, total length 204.5 ± 12.8 cm) matured for the first time after a full life-cycle in captivity. Absolute gonad biomass was 8.4 ± 1.3 kg per female and relative fecundity 11.2 ± 1.6%, at maturation stage IV. These fish were induced to spawn by injection of hormone LHRH-A2 at a dosage of 10 lg kg )1 . Male Kaluga was injected one time at 5 lg kg )1 and milt was stripped 16 h after injection of LHRH-A2. Water temperature was about 16 ± 1°C during the induction period. Fertile eggs were obtained 36.8 ± 2.6 h after first injection; they were fertilized by semi-dry method. Fertilization rate was 80.7 ± 3.8%. Fertilized eggs were incubated McDonald jars (hatching rate 85.2 ± 9.8%). There was a strong correlation between body weight (x) and time (y) needed from hormone injection to obtaining fertile oocytes (y = )0.8231x + 98.838 R 2 = 0.8428; P < 0.01). The cultured males ripened as early as at age 5 while females were 8-years old at first maturity.