Growth,feed conversion and body composition of fingerling stinging catfish Heteropneustes fossilis (Bloch) fed varying levels of dietary l‐threonine

An 8‐week feeding trial was conducted to assess the effects of dietary l ‐threonine on growth, protein utilization, threonine retention efficiencies, nucleic acid indices and body composition of fingerling Heteropneustes fossilis (6.6 ± 0.1 g; 10.9 ± 0.2 cm). Casein–gelatin based isonitrogenous (38% crude protein; CP) and isocaloric (15.3 kJ g^?1 digestible energy; DE) amino acid test diets with six levels of dietary l ‐threonine (0.75%; 1.0%; 1.25%; 1.5%; 1.75%; 2.0% dry diet) were prepared and hand‐fed to quadruplicate groups of fingerling to apparent visual satiation twice daily. Weight gain (WG; 46.3 g fish^?1), feed conversion ratio (FCR; 1.98), protein utilization efficiency (PUE; 0.25), threonine retention efficiency (TRE; 0.69), lipid productive value (LPV; 0.45), body protein (18.2%) and RNA/DNA ratio (3.6) of fish fed graded levels of dietary threonine increased significantly (P < 0.05) up to 1.49% threonine of dry diet. To generate precise information, the WG, RNA/DNA and LPV data were subjected to broken‐line and quadratic regression analyses. The two models were superimposed and requirement was determined by establishing the point, where the quadratic curve first intersected the plateau of broken‐line. Based on the above mathematical analyses, optimum dietary threonine requirement of fingerling H. fossilis was estimated to range between 1.62% and 1.69% of the diet, corresponding to 4.26–4.44% protein.     

人工饲养银鲑幼鱼的试验

在人工饲养的条件下，银鲑幼鱼以全长74mm为生长拐点，生长拐点前为幼鱼Ⅰ，生长拐点后为幼鱼Ⅱ。银鲑幼鱼Ⅰ（44-74mm)和幼鱼Ⅱ（74-103mm)全长与日龄均呈线性相关，银鲑幼鱼Ⅰ和幼鱼Ⅱ体重与日龄均呈幂函数相关，幼鱼Ⅰ生长快于幼鱼Ⅱ，同期内体重增长始终比体长增长较为明显。     

Effects of silver carp and the small indigenous fish mola Amblypharyngodon mola and punti Puntius sophore on fish polyculture production

A sustainable semi-intensive pond aquaculture technology including major carp species as cash-crop and small indigenous fish species (SIS) as food for the farmers' families is being optimized in Bangladesh. The inclusion of silver carp (Hypophthalmichthys molitrix), a cheap large species affordable by poor farmers, is now being considered. As part of a study on the effects of this filter feeder on polycultures including the large carps rohu (Labeo rohita), catla (Catla catla) and common carp (Cyprinus carpio) and the SIS punti (Puntius sophore) and mola (Amblypharyngodon mola), an experiment was carried out under farm conditions to test the effects of silver carp and of each SIS species on the growth, survival and yield of the large and small species and on pond ecology.The experiment was performed in 38 farmers' fishponds of different sizes, from 220 m² to 1200 m². The results show that the larger the fish pond the better rohu performance, the larger punti fry weight and the lower punti fry harvested biomass. Pond size did not affect other fish species. The addition of 250 mola and/or punti per 100 m² fishponds affected rohu and catla and did not affect common and silver carps. The addition of mola alone reduced rohu's parameters by 15%. The addition of SIS in the three combinations tested (250 mola, 250 punti, 125 of each species) reduced catla's parameters by 20-24%. Punti fry were larger when both SIS were stocked and punti fry biomass was larger when only punti were present. Total mola harvested biomass and yield were larger when the entire SIS stocked were only mola.The addition of 10 silver carp over the 99 large carps stocked per 100 m² fishponds negatively affected rohu and catla growth and yield by about 15-21% and 45-50% respectively but not their survival, did not affect common carp performance, did not affect punti and mola reproduction in the ponds, reduced punti yields by 25%, reduced mola performance by about 35%, and silver carp own biomass increased total yield and total income in about 12% each. These effects are explained and discussed considering fish interactions through the food web. The decreased income from selling the more expensive large carps is more than compensated by that obtained from silver carp, which allows the option to the farmer to sell part of the silver carp to complete the cash income that would have been obtained from large carps only if silver carp would not be stocked, and consume the rest with the family.     

Effects of adding different proportions of the small fish punti (Puntius sophore) and mola (Amblypharyngodon mola) to a polyculture of large carp

This experiment was carried out in the framework of a project to develop a viable fish polyculture technology under Bangladeshi conditions that allows simultaneous fish production of small indigenous species for the farmers' family consumption and of large carp species as a cash crop. The objectives of this experiment were to assess the effects of adding punti and mola in different proportions on the large carp and on the environment, and to assess the effects of punti on mola and mola on punti. The polyculture included the large carp rohu, catla and common carp (as cash crop fish), and the small indigenous fish punti and mola (as food for the small‐scale farmer family). The total large carp stocking density was 10 000 fish ha^?1, at a species ratio of 1:1:1. The total small fish stocking densities were 0 in the control and 30 000 punti and mola ha^?1 in the treatments, these at rates 2:1, 1:1 and 1:2. Stocking punti and mola at the density and all ratios tested were viable solutions to obtain simultaneously large carp cash crops and small fish to feed the farmer's family. Statistically marginal differences in large carp production were obtained in stocking small fish in the different proportions. These marginal differences could be explained by food competition between punti and common carp and between mola and rohu, which had different outcomes depending on the proportions of the small fish stocked. Stocking punti and mola at a 1:1 ratio would result in more small fish for the farmer's family, while the individual size of rohu, the most expensive large carp, would be somewhat smaller, but not necessarily small enough to decrease its selling price. Stocking one of the small fish in higher proportion than the other (2:1 or 1:2) would result in less mola for the family consumption, while harvesting of common carp would be somewhat lower and of smaller fish. Since common carp is the cheapest of the large carps, this small reduction would not necessarily affect the family income in an important way. With these results, farmers would now be able to reorganize their stocking practices with large carps and small fish and decide the appropriate small fish stocking ratios to meet their needs.     

几种常用水产药物对大鳞副泥鳅苗种的急性毒性试验

以规格(1.53±0.32)g重的大鳞副泥鳅(Paramisgurnus dabryanus)苗种为试验对象,采用静态急性毒性试验法,进行了硫酸铜、聚维酮碘、敌百虫、甲醛的急性毒性试验。结果表明,硫酸铜24、48、96 h的半致死量分别为1.23、0.55、0.40 mg/L,安全浓度为0.03 mg/L;聚维酮碘24、48、96 h的半致死量分别为429.58、396.36、388.47 mg/L,安全浓度为101.23 mg/L;敌百虫24、48、96 h的半致死量分别为16.72、7.94、4.80 mg/L,安全浓度为0.54 mg/L;甲醛24、48、96 h的半致死量分别为110.00、96.59、45.45 mg/L,安全浓度为22.35 mg/L。结论:硫酸铜的毒性最大且安全浓度远低于常用浓度,应禁用;敌百虫的安全浓度处于常用浓度范围内,但使用时需控制使用剂量;聚维酮碘和甲醛可按常规浓度安全使用。     

Growth,Feed Conversion,and Nutrient Retention Efficiency of African Catfish,Clarias gariepinus, (Burchell) Fingerling Fed Diets with Varying Levels of Protein

Growth, feed conversion, and nutrient retention efficiencies of African catfish fingerling, Clarias gariepinus (5.22 ± .07 cm; 8.22 ± 0.03 g), fed diets with varying levels of protein were assessed by feeding seven casein/gelatin based isocaloric (17.62 kJ/g GE) experimental diets with graded levels of dietary protein (20%, 25%, 30%, 35%, 40%, 45%, and 50% of the diet) to triplicate groups of fish to apparent satiation for eight weeks. Effects of feeding these diets on live weight gain (LWG%), feed conversion ratio (FCR), protein efficiency ratio (PER), protein retention efficiency (PRE%), and energy retention efficiency (ERE%) were assessed. Maximum LWG% (867%), PER (2.01), highest PRE (32%), ERE (69%), best FCR (1.39), and maximum body protein were recorded in fish fed diet containing 35% protein. On the basis of the second-degree polynomial regression analysis of the above response variables, it is recommended that the inclusion of protein in the range of 34.4%–39.6% is optimum for maximizing growth potential, feed conversion, and nutrient retention in African catfish fingerling, Clarias gariepinus.     

蓝鳃太阳鱼苗种耗氧率与窒息点的研究

在 2 4℃水温条件下 ,对蓝鳃太阳鱼 (Lepomismacrochirus)苗种的耗氧率与窒息点进行了测定。结果表明 :蓝鳃太阳鱼苗种的耗氧率和窒息点随鱼体的增大而降低 ,平均体重0 62g的鱼苗耗氧率 0 645mg/(g·h) ,窒息点 0 5 90mg/L ;平均体重 31 90g的鱼种耗氧率0 1 62mg/(g·h) ,窒息点 0 5 0 0mg/L。蓝鳃太阳鱼苗种的耗氧率有明显的昼夜变化节律。     

大规格吉富罗非鱼种塑料大棚越冬技术

【目的】探讨大规格吉富罗非鱼种塑料大棚越冬技术,为我国南方罗非鱼产业提供低成本、高收益的安全越冬模式。【方法】在柳州市沙塘试验基地的两个池塘上搭建塑料大棚,其中1个池塘在越冬期陆续抽取地下水补水调温,分别定期检测大棚内外池塘水温及大棚内池塘水体溶解氧、氨氮两个水质指标。【结果】越冬期,大棚内池塘水温比较稳定,抽取地下水补水的池塘水温保持在17.0～22.5℃,未抽取地下水补水的池塘水温也能保持在16.0～21.5℃;大棚内池塘水体溶解氧变化范围为2.5～5.0mg/L,氨氮变化范围为0.47～0.93mg/L;两个池塘大规格吉富罗非鱼种成活率分别为98.0%和99.0%,越冬培育后其规格分别为0.40和0.38kg/尾。【结论】采用塑料大棚越冬模式,大规格吉富罗非鱼种能安全越冬且生长效果良好,其方法简便、效果良好,若能同时搭配抽取地下水补水调温,效果更佳,但必须控制好放养密度。     

胭脂鱼仔幼鱼发育及苗种培育技术

对胭脂鱼仔幼鱼发育的形态特征及其主要生活习性进行了描述,探讨了胭脂鱼苗种的不同培育方法,其培育成活率为５５．２％－９７．４％,采用水蝗蚓,鳗鱼饵料,鱼虾蚌肉,动物肝脏及豆制品等多种饵料喂养胭脂鱼鱼种,其综合饵料系数为４．３－５．６,日均增长长度为０．８７－１．０１ｍｍ,日增增生体重为０．０９－０．４５ｇ,全长与全长／体高的关系呈负相关。     

The effect of common carp, Cyprinus carpio (L.) and mrigal, Cirrhinus mrigala (Hamilton) as bottom feeders in major Indian carp polycultures

A polyculture experiment with the large carp rohu, Labeo rohita (Hamilton), catla, Catla catla (Hamilton) and either mrigal, Cirrhinus mrigala (Hamilton) or common carp, Cyprinus carpio (L.) (as cash crop fish), and the small indigenous fish punti, Puntius sophore (Hamilton) (as food for the small‐scale farmer family) was carried out at the Field Laboratory of the Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh. The main objective was to compare polycultures of large carp in which the bottom feeder is either the native mrigal or the exotic common carp. Secondary objectives were to assess the effects of adding the small indigenous species punti to polycultures of large carp, and to compare the effects of mrigal and common carp on punti production and reproduction. It was found that (i) common carp damaged embankments, had no effect on catla, improved rohu performance by 50% and total fish production by 20%; (ii) punti addition did not affect rohu, catla and total yield, improved mrigal performance by 50%, and decreased common carp performance by 20%; and (iii) punti was not affected either by common carp or by mrigal. However, its performance was not satisfactory, probably owing to frequent netting, which might have hindered growth and breeding. In spite of the embankment damage caused by common carp, this bottom feeder seems to be more promising than mrigal, because it leads to higher fish production. The addition of punti to the large carp polyculture is a viable proposition, as it does not reduce cash crop production, and might be a good food source for a small‐scale farmer's family.