人工海水培育尖吻鲈Lates calcarifer(Bloch)稚幼鱼的生长特性

对尖吻鲈Lates calcarifer(Bloch)稚鱼，早期幼鱼进行人工海水培育生长特性研究结果，个体均全长0.83cm，均重0.006g，的稚鱼经室内水池和室外土池的47d培育，终均全长5.16cm，均重2.15kg；全长日均增长率3.89%，与培育时间的关系式为L=0.8511e^0.0367d；体重日均增长率12.51%，与培育时间的关系式为W=0.0093e^0.1121d；全长与体重的回归方程为W=0.0168L^2.8899，幂指数b接近3，表明体重与全长的立方呈正相关，属于均匀生长型。     

尖吻鲈Lates calcarifer（Bloch）养殖技术及其发展前景

尖吻鲈系咸淡水养殖的一种重要经济鱼类,主要分布于中国南海,东海南部,印度,缅甸,印度尼西亚,菲律宾,大洋洲。近二十年来,特别是泰国,马来西亚,新加坡,印度尼西亚及香港,台湾等地区相继发展尖吻鲈养殖业,初具生产规模,对尖吻鲈繁殖生物学,养殖技术的研究已有许多报道,作者搜集了一些文献作扼要概述。     

尖吻鲈Lates calcarifer（Bloch）人工繁殖技术现状及其发展前景

尖吻鲈是咸淡水养殖的主要经济鱼类。最近几年来,泰国、新加坡、马来西亚和菲律宾等国家和地区对尖吻鲈养殖已引起极大的兴趣,已深入开展尖吻鲈养殖生物学和繁殖机制的研究。本文着重概述东南亚海洋渔业开发中心研究尖吻鲈Lates calcarifer(Bloch)人工繁殖技术现状及其发展前景。     

池养尖吻鲈和花鲈的生长特性

尖吻鲈（Ｌａｔｅｓｃａｌｃａｒｉｆｅｒ）、花鲈（Ｌａｔｅｏｌａｂｒａｘｊａｐｏｎｉｃｕｓ）为河口性鱼类,可作为池塘养殖的对象。尖吻鲈的适宜生长水温为２５℃～３４℃,快速生长年龄在Ⅰ～Ⅱ龄;花鲈在珠江口地区一年四季均能生长,快速生长年龄在Ⅲ～Ⅳ龄。应用ＶｏｎＢｅｒｔａｌａｎｆｙ方程求得它们在人工饲养条件下体长、体重生长方程：尖吻鲈Ｌｔ＝７０６．５５５３［１－ｅ－０．５１２８（ｔ＋０．２０３２）］,Ｗｔ＝６５５４．４６４９［１－ｅ－０．５１２８（ｔ＋０．２０３２）］３．０３３５;花鲈Ｌｔ＝８８７．４９５８［１－ｅ－０．４０２５（ｔ＋０．０２０９）］,Ｗｔ＝１０８８２．１８８４［１－ｅ－０．４０２５（ｔ＋０．０２０９）］３．１４２７。它们的体重生长拐点分别位于１．９６和２．８２龄处。商品鱼的合理起捕时间应选在生长转折点。参照生物学指标,珠江口地区池养尖吻鲈、花鲈的上市商品鱼应为Ⅰ～Ⅱ龄和Ⅲ～Ⅳ龄,这不仅符合经济原则,也适应当地的消费习惯。     

尖吻鲈Latescalcarifer(Bloch)营养学研究的现状

尖吻鲈Lates calcarifer(Bloch)系水产养殖的重要对象。据文献记载,印度尼西亚、马来西亚、菲律宾、新加坡、泰国、我国台湾省和香港等国家和地区长期从事尖吻鲈养殖。目前许多国家和地区对尖鲈营养学研究已深入地开展起来,泰国沿岸水产养殖研究所对尖吻鲈营养学已进行较深入的研究,现将该所研究的最新的营养学研究成果作扼要地概述,供我国开展尖吻鲈营养学研究者的参考。     

尖吻鲈的生物学及其养殖

尖吻鲈Lates Calcarifer (Bloch)，在东南亚和太平洋热带地区是一种重要的经济鱼类。其生长迅速，肉味鲜美，在东南亚、广东省、香港和台湾地区的沿海地区均有大规模的养殖。     

尖吻鲈、花鲈和大口黑鲈在池塘的集约化养殖

<正> 尖吻鲈又称雷子鱼,是东南亚热带和亚热带国家的经济鱼类,早期生活在海水和咸淡水海区,成鱼可在海水或淡水中养殖。其幼鱼为杂食性,成鱼为肉食性。尖吻鲈在泰国的性成熟年龄为3周龄。花鲈俗称七星鲈,在我国有丰富的天然种苗资源。花鲈为广温近岸浅海凶猛鱼类,喜栖于河口咸淡水区,也生活于淡水,秋末冬初到河口产卵。大口黑鲈俗称加洲鲈,原产美国加里福尼亚洲,是适温较广的肉食性鱼类。在盐度12‰以下的咸淡水和淡水中均可养殖。鱼苗阶段以浮游动物为饵科,成鱼为肉食性。     

Nucleotide Degradation Profiles of Iced Barramundi (Lates calcarifer) and Nile Perch (Lates niloticus) Muscle

Adenine nucleotides and their related compounds were determined in muscle extracts from two species of fish that were stored in ice after thawing. The fish were the closely related species, Australian barramundi (Lates calcarifer) and Kenyan Nile perch (Lates niloticus) which had different process histories. For all samples, adenine nucleotides did not exceed 6% of the total nucleotide pool. Inosine monophosphate (IMP) decreased steadily with storage. Hypoxanthine (Hx) was the major product of adenosine triphosphate (ATP) degradation in both barramundi and Nile perch, showing a steady increase with days of iced storage. The Hx level did not reach a maximum during the 9d storage period. The K-value also increased regularly with time of storage and for the later stages (i.e., 7 and 9d) and was significantly different (P < 0.01) for the species. The iced storage life of these typical samples of barramundi and Nile perch was estimated to be 3d after thawing using a K-value of < 30% to indicate excellent quality. Despite the differences in process history the nucleotide profiles were remarkably similar during storage. This precludes the use of nucleotide levels as a means of differentiating between these species.     

Characterization and comparison of variations in reproductive performance of Chitralada strain Nile tilapia, Oreochromis niloticus (L.)

In an attempt to better understand and characterize the variability in the female reproduction of individual Thai‐Chitralada strains of Nile tilapia, Oreochromis niloticus (L.), tagged mature females (n=68) from a single population were monitored in a hapa‐in‐pond system over a 12‐month experimental period. Spawn female⁻¹, eggs female⁻¹ day⁻¹, eggs kg female⁻¹ day⁻¹, day spawn⁻¹ and weight (g) at first spawning of individual females were determined from the regular weekly sampling of weight (g) and eggs per spawn. For analysis, the females were grouped into two, high spawning (HSF) and low spawning frequency (LSF) classes based on their spawning frequency (SF) record. Moreover, nested under these two classes were two groups each based on growth rate, i.e., high frequency – large size (HL), high frequency – small size (HS), low frequency – large size (LL) and low frequency – small size (LS). There was no difference in eggs spawn⁻¹ among all females. The HSF group produced 68% and 361% more eggs female⁻¹ day⁻¹ than the population mean and LSF group respectively. Eggs female⁻¹ day⁻¹ and spawn female⁻¹ remained high in the HSF group and low in the LSF group throughout the 12‐month experimental period. This suggests that individual female spawning activity is consistent within a population in a common environment. The inter‐spawn interval increased with age in all four groups, and day spawn⁻¹ was shorter by 130% in HSF females compared with day spawn⁻¹ in LSF. The HSF group also spawned more successively (≥3), while the LSF group of females had fewer successive spawns (≤2). Body weight (g) had no influence on the number of eggs produced. The study indicates that separating frequently spawning females could be used as an important strategy to improve commercial seed production of Nile tilapia.     

Simulation of Nile tilapia (Oreochromis niloticus niloticus L.) culture in ponds, through individual-based modelling, using a population dynamic approach

A simulation model for the production of the Nile tilapia (Oreochromis niloticus niloticus L.) for mixed‐ or mono‐sex culture and for poly‐culture with the African catfish (Clarias gariepinus Burchell 1822) or African snakehead (Parachanna obscura Günther 1861) is presented. The model is based on an exponential decay model used in population dynamics and follows an individual‐based approach. The model consists of a tilapia sub‐model representing population dynamics, growth and recruitment and a predator sub‐model representing the predation process and population dynamics and growth of the used predator. The model was calibrated with data on mixed‐ or mono‐sex culture of Nile tilapia and for poly‐culture with the African catfish or African snakehead obtained in Congo Brazzaville and validated with similar data from the Philippines, Thailand and the Ivory Coast. The model visualized major underlying processes in tilapia farming and aspects for further improvement of the model; growth is one of the most sensitive input parameters and should be quantitatively related to feeding level and feed quality; length at first maturity and quantification of the recruitment of Nile tilapia has a relatively large influence and recruitment should be related to the length of the females; prey–predator relations are too coarse and should be more fine‐tuned with the relation between prey size and predator size. Incorporation of these features would provide the basis of a model that can serve as a predictive and decision‐making support tool.     

Spontaneous diploidization of the maternal chromosome set in Nile tilapia (Oreochromis niloticus L.) eggs

Spontaneous diploidization of the maternal chromosome set (SDM) in Oreochromis niloticus is described here for the first time. The SDM phenomenon was observed in progeny of only one XY neofemale out of 11 such neofemales from which eggs had been fertilized with UV‐irradiated sperm: this treatment produced only the expected haploid embryos from the other females. SDM progeny were produced from three different batches of eggs from this female. No significant differences in survival at different stages of embryonic development were observed between the SDM and the diploid control group. The maternal inheritance of SDM progeny was verified using multilocus DNA fingerprinting. Only diploid karyotypes were observed in these fish and diploid control groups. In both the SDM and control groups, sex ratios were significantly skewed towards males (93.3% and 65.0% males respectively). The actual mechanism of SDM in eggs from this particular female remains unknown.     

Time related alterations in digestibility and faecal characteristics as affected by dietary composition in the Nile tilapia (Oreochromis niloticus L.)

After being shifted to a new diet, time related alterations in digestibility, faecal waste production and faeces recovery in Nile tilapia were assessed in relation with dietary ingredient composition. Four experimental diets were formulated according to a 2 by 2 factorial design: two starch inclusion levels (20 or 40%) and two maize starch types (native versus gelatinized). After introduction to the experimental diets, faeces were collected weekly from Week 2 till 6 using settling tanks. Digestibility of ash, organic matter and dry matter increased with time (P < 0.001). For organic and dry matter the time related alteration in digestibility were different between both starch types (P < 0.05). All faecal waste characteristics altered with time (P < 0.01). The incline in faeces recovery with time was affected by starch type (P < 0.01); being the largest at the 40% gelatinized maize diet. In conclusion, the minimal length of the adaptation period in digestibility studies for obtaining unbiased digestibility estimates is dependent on diet composition, in this study with Nile tilapia 4 weeks for diets with gelatinized starch and 6 weeks with native starch.     

Increased spawning activity of female Nile tilapia (Oreochromis niloticus) (L.) after stocking density and photoperiod manipulation

This study was conducted to evaluate the effects of stocking density and photoperiod in increasing the reproductive performance of Oreochromis niloticus. In experiment 1, a change in stocking density (from 47.7 to 6.8 kg m^?3) was performed, with groups of 48 females moved to single compartments. In experiment 2, 36 females experienced a 6L:18D photoperiod for 21 or 28 days (stocking density: 31.3 kg m^?3) before being placed in individual compartments (stocking density of 6.9 kg m^?3, 12L:12D photoperiod). The spawning rates in experiment 1 (32.2%) and in experiment 2 (21 days: 65.2%, 28 days: 36.1%) were significantly higher than those in the control (17.7%). On the other hand, hatching and swim‐up fry rates were significantly lower in experiment 2 – 21 days (41.3%, 40.4%) but not in experiment 1 (64.0%, 56.3%) compared with the control (67.0%, 62.3%). The spawning rate in experiment 2 – 21‐day treatment group was the highest, while the number of eggs collected per female was significantly lower than that in the control. In experiments 1 (20.8%) and 2 (21 days: 44.4%, 28 days: 19.4%), the daily spawning rates were the highest 3 days after maintaining females in single compartments. The current experiment demonstrates how specific stocking density changes can be used to induce higher spawning rates in Nile tilapia.     

Apparent digestibility coefficient of duckweed (Lemna minor), fresh and dry for Nile tilapia (Oreochromis niloticus L.)

Dry matter (DMD), protein (PD), ash (AD), fat (FD), gross energy (ED) and phosphorus (PhD) digestibility coefficients were determined for five different iso‐N fish diets fed to Nile tilapia (Oreochromis niloticus). The control diet contained fishmeal (35%), corn (29%), wheat (20%), wheat bran (10%), fish oil (3%), diamol (2%) and premix (1%). Partial replacement of dry matter of fishmeal, corn grain, wheat grain, wheat bran and fish oil by 20% and 40% of dry matter of duckweed, in a dry and fresh form, was performed. Diets of treatments 1 and 2 included 20% and 40% of duckweed, respectively, in a dry form. In treatments 3 and 4, tilapia received formulated diets 4 and 5 in addition to 20% and 40% fresh duckweed providing the same amount of dry matter and protein as in control. The specific growth rates (SGRs) of tilapia were 1.51±0.07, 1.38±0.03, 1.31±0.06, 1.44±0.02 and 1.33±0.05, in control and treatments 1–4. There was no significant difference between SGR for the control diet and the diet with 20% fresh duckweed, while the other treatment groups had significantly lower SGR. All the treatment diets provide good values for feed conversion ratios (FCRs) and protein efficiency ratio (PER). Dry matter of diets ranged from 61.8% in treatment 4 to 85.2% in control. All the diets have high PD (88.4–93.9%) and high‐energy digestibility (78.1–90.7%). Dry matter of duckweed were 66.8, 63.3, 45.8 and 28.3 in treatments 1 to 4 respectively. Protein values were 78.4, 79.9, 77.6 and 75.9, while ED values were 59.8, 60.9, 64.5 and 58.4 in treatments 1 to 4 respectively. Analysis of body composition shows that tilapia fed diets with duckweed contain significantly (P<0.05) higher phosphorus and protein content and significantly (P<0.05) lower lipid content. In contrast, tilapia fed control diet had a significant higher (P<0.05) dry matter content and lower ash content.     

尼罗罗非鱼幼鱼对食物中镉的积累的研究

罗非鱼幼鱼饲喂含1ppm Gd^2 2的饲料20天后改用不含镉的饲料12天。在一定的时间间隔分别用直接和经1N盐酸浸泡1小时去掉体表吸附的Cd后测定鱼体镉的积累。测定结果表明：在食物施加镉的过程中鱼体的镉浓度逐渐上升到第20天的0．129ppm，而停用镉后在12天内逐渐降低到原来的86％。因生长因素降低浓度占60％，排出占21％。鱼体镉的吸附量占携带总量的20－30％。     

The use of tuna industry waste in the practical diets of juvenile Nile tilapia (Oreochromis niloticus,L.): effect on growth performance,nutrient digestibility and oxidative status

A 45‐day feeding trial was conducted to study the effect of replacing dietary fish meal (FM) with a tuna by‐product meal (TBM) on the growth, feed efficiency, carcass composition and stress oxidative status of juvenile Nile tilapia, Oreochromis niloticus L.). Triplicate groups of fish (2.21 ± 0.01 g) were fed on four iso‐nitrogenous and iso‐energetic diets. The control diet (A₀) used FM as the sole source of animal protein. In the other three diets (A₁₀–A₃₀), 33%–100% of FM was substituted by TBM at 10% increments. There were no significant differences (P>0.05) in growth performance among fish fed on diets A₀, A₁₀ and A₂₀. Fish fed these experimental diets (i.e., A₀, A₁₀ and A₂₀) showed significantly (P<0.05) better daily mass gain, specific growth rate and protein efficiency ratio than those fed on diet A₃₀. Feed conversion ratio increased with increasing TBM content, but only the value found in fish fed on diet A₃₀ differed significantly (P<0.05) from the other treatments. The fish accumulated increasing quantities of lipids and decreasing levels of ash in their carcasses with increasing levels of dietary TBM. At the end of the experimental period, a significant increase (P<0.001) in catalase and glutathione S‐transferase activities was seen only in groups fed on diet A₃₀. Similarly, a significant enhancement in glutathione peroxidase and superoxide dismutase activities was observed in groups fed on diets A₂₀ and A₃₀ compared with the other groups. The results show that this product can be included up to 20% in practical Nile tilapia diets without any detrimental effects.