نوع مقاله : مقاله پژوهشی
نویسندگان
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
In order to study the growth rate of stellate sturgeon, three earthen ponds with 2 hectares area were selected randomly two ponds were treated with 16 tons organic fertilizer and 40 kg Daphnia. The total culture period considered 35 days. The physical and chemical parameters of and also the density of zooplanktons and benthos were measured during the rearing period. Apart from these factors the gastrosomatic index (GSI), daily growth rate and the condition factor of the fingerlings were also determined in order to assess the output of each pond. On the basis of the statistical analysis conducted, no significant difference was observed in the physical factors of the water in the three ponds but for nitrite values were significant.
The major productivity of zooplanktons and benthic organisms were Daphnia (D. magna and D.pulex), cyclops and nauplii of cyclops.
The minimum and maximum biomass of zooplanktons and benthic organisms m the ponds treated with fertilizer and live-food were estimated 0.018 and 38.63 g/m3; 00 to 2.1 g/m2, respectively. No significant difference was observed in the productivity of the ponds. On the basis of the abundance of prey in the studied pond, D. magna and D. pulex were the primary prey (FP>50), cyclops and nauplii cyclops were secondary prey (10<FP <50) and Tubificidae and Chironomidae were the occasional preys (FP=0). The results or GSI observations indicated a decrease in daily growth rate and condition factor with an increase in weight and length or the fingerlings, but this difference was not significant, The analysis of gut contents of the 120 fingerlings in the ponds treated with animal fertilizer and live-food indicated that 30 of the fingerlings were reared under good rearing conditions.
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