Dış Kaynaklı Proje Süreçleri Yönetim Sistemi
The aim of this study was to identify the effects of reduced daylight over shaded ponds on growth during adult rearing of Russian sturgeon (Acipenser gueldenstaedtii). Growth performance was determined as weight gain, condition factor, specific growth rate, and feed conversion ratio using 7+ years old sturgeons. The mean initial weight of fish held in the non-shaded pond was 3850 g (±780) and in shaded ponds was about 3550 g (±660). The culture period lasted for 1 year (25 September 2007–24 September 2008). For individual monitoring fish were externally marked with T-Bar Anchor tags. The experimental groups were fed commercial extruded diet (protein content 49–50%, lipid content of 15%), prepared by the Sibal Blacksea Company. The final mean weight of fish held in the non-shaded pond was found to be 6710 g (±1670) and reached in shaded ponds about 6404 g (±1291). The maximum and minimum individual condition factors were 1.0 and 0.4 in both groups in the 4th period (March–May). The minimum specific growth rates (SGR) were 0.07 (non-shaded pond) and 0.06 (shaded ponds). These values were observed between January and March (cold water conditions) while the maximum SGR was (0.3) between September and November. The best feed conversion ratio (FCR) was obtained in the shaded ponds with 1.3–1.5 during September–November and March–May, respectively. The mean FCR was around 2.5 in both test groups. During the entire experiment on average light intensity was 70% reduced in the shaded ponds compared to the open pond. The growth performance between the two groups did not differ significantly (P > 0.05). However in the non-shaded ponds, the colour of the fish was darker when exposed directly to sunlight.