Effects of all‐male,mixed‐sex and all‐female freshwater prawn in polyculture with major carps and molas in the fallow rice fields

This study was conducted to evaluate the effects of all‐male, mixed‐sex and all‐female freshwater prawn (Macrobrachium rosenbergii) in a polyculture with major carps (Catla catla and Labeo rohita) and self‐recruiting small fish molas (Amblypharyngodon mola) in the fallow rice fields of Bangladesh. There were three treatments with three replicates. All ponds were stocked with carps and molas plus either all‐male prawns (treatment MP), mixed‐sex prawns (MFP) or all‐female prawns (FP). Prawn, mola, catla and rohu were stocked 20 000, 20 000, 1750 and 750 ha^?1, respectively, in all treatments. The prawns were fed twice daily, starting at 8% body weight and gradually reduced to 3% body weight. The fish were fed in the morning with mustard oil cake and rice bran (1:2 ratios) at 3% body weight. Significantly higher production of prawns (697 kg ha^?1) was obtained in treatment MP, which yielded 34.7% and 56.2% more production than MFP and FP respectively. Significantly higher total production of 1620 kg ha^?1 and a higher benefit–cost ratio of 2.10:1 were also obtained in treatment MP. It can be concluded that an all‐male prawn culture is economically more viable than all‐female and mixed‐sex prawn cultures, along with other fish like major carps and the nutrient‐dense molas in the polyculture.     

中国黄羽鹌鹑哈德氏腺发育的增龄变化及形态组织学观察

为研究不同周龄中国黄羽鹌鹑哈德氏腺的组织学结构,采集0、1、2、3、4、5、6、10、14、18、22、26、30、34、38周龄健康中国黄羽鹌鹑的哈德氏腺,光学显微镜下观察哈德氏腺的显微组织结构,电镜下观察哈德氏腺的超微结构变化。结果显示,黄羽鹌鹑哈德氏腺位于眼眶内、眼球腹侧和后内侧,出生时就具备完整的形态,在视神经区呈喙状延伸,一端游离,另一端由腺体导管开口于第三眼睑弯窿的内角,腺体呈不规则带状,一端小,一端大,浅粉色,腺体绝对质量、长和宽随周龄逐渐增大。哈德氏腺为复管泡状腺,腺体外有结缔组织被膜,被膜延伸至腺体实质中,将腺体分为多个大小不同的小叶,小叶由腺泡和腺管组成。中国黄羽鹌鹑哈德氏腺在出生后逐渐发育,4周龄时达到成熟,5至38周龄为成熟持续期。     

Effects of including catla and tilapia in a freshwater prawn–mola polyculture in a rotational rice–fish culture systems

An on-farm trial was carried out from February to June 2006 to evaluate the growth and production performance of catla ( Catla catla ) and tilapia ( Oreochromis niloticus ) with freshwater prawn ( Macrobrachium rosenbergii ) and mola ( Amblypharyngodon mola ) in farmer's rice fields. In all treatments, 20 000 mola ha⁻¹ and 20 000 prawn ha⁻¹ were stocked. Besides, stocking included 2500 catla ha⁻¹ in treatment-I, 2500 tilapia ha⁻¹ in treatment-II and catla and tilapia at 1250 ha⁻¹ each in treatment-III . Prawns were fed in the evening with pellets at a feeding rate of 3–8% body weight (initially 8% and gradually decreased to 3%). Catla and tilapia were fed in the morning with a paste of mustard oil cake and rice bran at a feeding rate of 3% body weight. Significantly higher combined production of fish and prawn observed was 2142 kg ha⁻¹ in treatment-I. The benefit:cost ratio was found to be significantly higher in treatment-I than in treatment-II and there were no differences between treatments I and III. From the production and economic point of view, treatment-I was found to be the best proposition for the rotational rice–fish culture systems.     

Density effects of silver carp Hypophthalmichthys molitrix and catla Catla catla on the production system in all‐male freshwater prawn–finfish polyculture ponds

The effects of three different combinations of silver carp Hypophthalmichthys molitrix and catla Catla catla density on the production system in all‐male freshwater prawn–finfish polyculture ponds were evaluated in triplicate. The stocking density of silver carp and catla, respectively, were maintained at 2000 and 500 ha^?1 in treatment SC₂₀₀₀C₅₀₀, 1500 and 1000 ha^?1 in treatment SC₁₅₀₀C₁₀₀₀ and 1000 and 1500 ha^?1 in treatment SC₁₀₀₀C₁₅₀₀. Male freshwater prawn Macrobrachium rosenbergii and small fish mola Amblypharyngodon mola densities were fixed in all treatments at 12 000 and 20 000 ha^?1 respectively. Management practices were same for all treatments. Blue‐clawed male prawns were harvested twice during the 122‐day culture at 15‐day intervals before the final harvest. Plankton and macro‐benthos abundance and water quality parameters (except transparency and chlorophyll a) did not vary significantly (P>0.05) among treatments. Mean final weights of both silver carp and catla were decreased with the increasing of their own stocking density. The treatment SC₁₅₀₀C₁₀₀₀ resulted in 25–32% increased net production of silver carp plus catla (461 kg ha^?1) and 20–21% increased net production of all species combined (874 kg ha^?1) as compared with the other treatments, although the differences in production of prawn and mola among treatments were not significant.     

Evaluation of freshwater prawn‐small fish culture concurrently with rice in Bangladesh

An integrated aquaculture of freshwater prawn (Macrobrachium rosenbergii) and self‐recruiting small fish mola (Amblypharyngodon mola) was conducted in farmers' rice fields at Mymensingh, Bangladesh. There were four treatments with three replications. Four stocking densities, 10 000, 15 000, 20 000 and 25 000 ha^?1, of freshwater prawn were applied. The stocking density of mola was the same (20 000 ha^?1) in all treatments. During land preparation, triple super phosphate (TSP) and murate of potash (MP) were applied at the rate of 150 and 75 kg ha^?1 respectively. Urea was applied at the rate of 200 kg ha^?1 in equally distributed three installments after 16, 45 and 65 days of rice plantation. Prawns were fed with commercial pelleted feed at 3–8% body weight. All water quality parameters were found to be within the suitable range for freshwater prawn culture. There was a homogenous abundance of plankton communities in all treatments. The results of a 4‐month culture period showed that the average production of prawn ranged from 222 to 388 kg ha^?1, mola 51 to 68 kg ha^?1 and rice 2 880 to 3 710 kg ha^?1. Significantly higher production of both prawn and mola was recorded in the plots where the freshwater prawn stocking density was 15 000 ha^?1. This treatment resulted in a net profit of USD 1100 ha^?1.     

广西区1999年审定的水稻新品种

(1 )培 S2 75:　系广西农科院杂交水稻研究中心育成的两系感温型中迟熟组合。 1 998年北流市试种2 57hm2 ,抽样验收平均单产 52 4 .1 kg/ 667m2。全生育期 1 30天 ,晚稻翻秋栽培 1 1 5天。株高 1 0 5 cm,株型紧凑 ,分蘖力中等 ,千粒重 2 3g。米质优 ,饭味可口。抗性鉴定 :穗瘟 5级 ,白叶枯病 3级 ,稻飞虱 9级。(2 )枝优 0 1 :　系博白农科所育成的感温型中熟组合。据统计 ,到 1 997年止全广西种植面积达 1 3.2万 hm2 ,一般单产都在 40 0 kg/ 667m2。全生育期桂南稻作区早稻 1 1 5天 ,晚稻 1 0 0～ 1 0 5天 ,桂中稻作区早稻 1 1 7～ 1 2 0天…     

改善米质重在早籼

早籼稻在我区粮食生产具有举足轻重的地位,也是我区最重要的商品粮源,国家定购比重大,产量比较稳定,是其他粮食作物不可替代的.近年来,各地实施科技兴粮,改良品种,主攻提高单产等战略,粮食连年获得了丰收.但是,随着农产品供求格局的变化,人们对大米的品质要求越来越高,从讲吃饱到要求吃好.因此,早籼稻米因品质比晚籼稻米差,消费者不愿吃,市场不受欢迎,造成大量压库,已经成为事实.因此,改善早籼米品质,成为我区粮食品质提高的当务之急.     

Effects of selective harvesting and claw ablation of all‐male freshwater prawn (Macrobrachium rosenbergii ) on water quality,production and economics in polyculture ponds

The effects of selective harvesting (SH) and claw ablation (CA) of blue‐clawed (BC) prawns on an all‐male freshwater prawn–finfish polyculture system were compared with control (Co) in quadruplicate. Ponds were stocked with all‐male freshwater prawn Macrobrachium rosenbergii, silver carp Hypophthalmichthys molitrix, catla Catla catla and mola Amblypharyngodon mola at 12 000, 2000, 500 and 20 000 ha^?1 respectively. Prawns were fed with pelleted feed. Ponds were fertilized regularly with urea, triple super phosphate and cow‐dung. SH of BC prawns in treatment SH and CA in treatment CA started on the 60th day during a 137‐day culture and continued at 15‐day intervals until the final harvest. Water quality parameters and plankton abundance did not vary significantly (P>0.05) among the treatments. Treatment SH resulted in a higher (P<0.05) net production of freshwater prawn (437 kg ha^?1), with better survival and mean weight, followed by CA (354 kg ha^?1) and Co (322 kg ha^?1). The combined net production of prawn plus finfish was also higher in SH (1244 kg ha^?1) as compared with CA (1161 kg ha^?1) and Co (1137 kg ha^?1), although the finfish production did not differ significantly. The periodic SH of BC prawns showed a better economic return with a BCR of 1.71.     

Potential of mixed culture of freshwater prawn (Macrobrachium rosenbergii) and self-recruiting small species mola (Amblypharyngodon mola) in rotational rice–fish/prawn culture systems in Bangladesh

The effects of different stocking densities of freshwater prawn (Macrobrachium rosenbergii) on its growth and production in relation to the presence of small self‐recruiting species mola (Amblypharyngodon mola) were investigated in modified rice fields after rice harvest at Mymensingh, Bangladesh. Keeping the stocking density of mola fixed at 20 000 ha^?1 in each treatment, four densities of freshwater prawn (treatments) were maintained: 10 000, 15 000, 20 000 and 25 000 ha^?1 respectively. The rice plots were limed (CaCO₃) and fertilized with urea, triple super phosphate and cowdung regularly. The prawns were fed daily with commercial pellets. Water quality parameters such as temperature, dissolved oxygen, transparency, pH, total alkalinity, inorganic nitrogen (nitrate, nitrite and total ammonia), chlorophyll a and orthophosphate were determined fortnightly. Numerical analysis of plankton communities was performed monthly. All water quality parameters were found to be within the suitable range for freshwater prawn culture, except high temperature, in the peak summer months. There was a homogenous abundance of plankton communities in all treatments throughout the experimental period. Mola started to breed in the second month of the original stocking with partial harvesting after the second month and continued until the final harvest. The total production of mola ranged between 124 and 152 kg ha^?1 during the 4‐month culture period. The average prawn survival ranged from 49% to 57% without any significant difference among treatments. Freshwater prawn production ranged from 294 to 596 kg ha^?1 with significantly higher production in the treatment where 20 000 ha^?1 freshwater prawn were stocked. This treatment also resulted in a higher net profit margin (74%), indicating that stocking at a combination of 20 000 ha^?1 freshwater prawn and 20 000 ha^?1 mola could be the optimum proposition for prawn–mola culture in modified rain‐fed rice fields after rice cultivation.     

杂交水稻制种生产中影响种子纯度的主要问题及对策

就我区杂交水稻制种生产中,对种子纯度存在的几个主要问题、采取相应的对策.