Assessment of the fertilization requirements of the chinese carp fry, silver carp (hypophthalmichthys molitrix); big head (aristichthys nobilis); and grass carp (ctenopharyngodon idellus), during the nursing phase [electronic resource].

Includes references.

Two different manure application regimes were applied in two groups of ponds for nursing of post yolksac Chinese carp fry, big head (Aristichthys nobilis) silver carp (Hypophthalmichthys molitrix) and grass carp (Ctenopharyngodon idelIus) Five days before stocking the ponds with fry, basic manure application was done using pure chicken manure at the ratio of 0.5 kg/m³ of water for ponds of the first group and 0.25 kg/m³ of water for ponds of the second group to stimulate the development of the natural food. The ponds were stocked at a stocking density of 20 , 10 and 5 fry/m³ for the three species, respectively. After stocking, the manure application amounts were 0.2 kg/m³ and 0.1 kg/m³ of water every day for the first and second group, respectively. Peanut cake was administered for feeding at a ratio of 3 g/1000 fry per day. The duration of the nursing period was 12 days. During the experimental run, growth of fry of the three species in all pondS was monitored and the density of plankton/liter and the organic matter contents were estimated every other day. Upon termination of the try nursing period, average final weight of the try and survival rate were estimated. The initial dominant species of phytoplankton emerging initially after fertilization had intimate relation to the amount of manure. Some species of green algae Chlorophyta such as Scenedesmus, Padiastrum and Ankistrodesmus sp. and some species of blue green algae Cyanophyta such as Oscillatoria and Anabaena sp. developed vigorously when a larger quantity of manure was applied in the first group of ponds. While with less manure in the second group of ponds, many of the diatoms of class Bac/7/ariophyta were found dominant such as Navicula and Cycotalla sp. When low manure application rate was adopted the surviving number of big head and silver carp was low (70.2 and 75.1 %, respectively) and that of grass carp was high (87.5%). When high manure was applied survival rate of big head and silver carp increased significantly (89.3 and 82.7%, respectively) while that of grass carp significantly decreased (72.4%). Also, growth performance of big head and silver carp fry was poor and that of grass carp was high under low fertilization conditions compared to the high fertilization regime. Fry of big head, silver carp and grass carp reached 67.1,105.1 and 65.9 times of their initial body weight, respectively. On the contrary, fry of big head and silver carp grew better and gained significantly larger mean body weight/fry (by 82.6 and 162 times of the initial body weight, respectively) under high manure application conditions. While grass carp fry did not grow as large as the other two species and gained smaller mean body weight/fry (by 55.1 times of the initial body weight). It could be concluded, from the present study, that nursing of big head and silver carp fry requires more fertile water than that required for grass carp fry. Subsequently, monoculture system is preferable for the fry during the nursing stage.

Summary in Arabic.

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