Seminatural propagation and rearing of roach (Rutilus rutilus caspicus)

A research experiment was conducted to provide a protocol for seminatural propagation and rearing of Roach up to release size. The attempt was made to combat the declining trend in the population size and catch of the fish in the Caspian Sea. The optimum temperature for spawning brood-stocks lasts from middle March to late April when the ambient temperature range is 12-17°C. During the four months research period, brood stocks were caught in the estuary of the Gorganrood in Golestan Province, north east Iran. The stocks were released into 2 hectare earthen ponds enriched with manure and fertilizers. Artificial spawning grounds made of pine branches were placed in the ponds. Ponds were stocked with 700 female breeders with an average weight of 150 grams and around 350 male breeders weighing 100 grams on average. Spawning and fertilization of eggs occurred in the ponds of which an estimated 80-90% eyed that were observed from the fifth day onwards. The starting of hatching was observed in the 6th day and yolk sac absorption was observed in day 4 to 6. The lame were fed on natural zooplankton and artificial food. Assessment of 146 fries for ingested food indicated that the fries fed on Rotifer (Rotatoria sp. and Daphnia sp.) in the ponds. The length-weight relationship was not significantly different among the ponds and also specific growth rates (SGR) did not show any difference in the fries. The relative gut length in the fries were smaller than I (RLG<l) and fries with an average weight of 0.5 to 1 gram were released into their natural habitat

Effect of different dietary levels of plant protein on growth indexes of white Leg shrimp

The influence of different dietary levels of plant protein (30, 50 and 70%) on growth indices of White Leg Shrimp (Litopenaeus vannamei) fed with an original 38 percent protein was assessed and compared with that of the commercial shrimp diet. The average weight gain at the end of the culture period in treatment 1 (30% plant protein and 70% animal protein), was 5.89 plus or minus 0.06 grams, for treatment 2 (50% plant protein and 50% animal protein), was 6.22 plus or minus 0.25 grams, for treatment 3 (70% plant protein and 30% animal protein), was 6.19 plus or minus 0.24 grams and for the control treatment (20% plant protein and 80% animal protein), was 6.42 plus or minus 0.40 grams. Our study of the influence of experimental and control diets on growth indices including growth rate (GR), food conversion ratio (FCR), protein efficiency ratio (PER), specific growth rate (SGR), and average daily gain (ADG), demonstrated that the indices were better in the control compared to the treatments. No significant difference was found among the treatments and between the treatments and the control for the indices (P>0.05). The percent of net protein utilization (NPU) in treatment 1 was significantly more than other treatments (P<0.05). We also found that the application of diets containing 50% plant protein (with 20% soybean meal) and 70% plant protein (with 41.72% soybean meal) can decrease diet costs. Cost of one kilogram of pellet in treatments 1, 2, 3 were 83.3%, 68.3% and 53.3% lower than the control diet respectively. Decrease of cost in treatment 2 and 3, in comparison to control in terms of lowering shrimp production cost is very important