Compatibility of silver barb Puntius gonionotus (Bleeker) with Indian major carps in a grow-out polyculture

The compatibility and growth performance of silver barb Puntius gonionotus (Barbonymous gonionotus) with the three Indian major carps, i.e., Catla catla, Labeo rohita and Cirrhinus mrigala, were assessed in a 10‐month carp polyculture trial. Treatments T‐1, T‐2, T‐3 and T‐4 were stocked with three of the above four carp species, with an absence of silver barb, mrigal, rohu and catla, respectively, while all four species were stocked in treatment T‐5. The treatments were stocked at 6000 fingerlings ha⁻¹, with an equal species ratio maintained in each treatment. Incorporation of silver barb into the polyculture system neither affected the survival of any carp irrespective of species combination nor yielded significant changes in biomass production among treatments, except for the one without catla, where it was significantly low. The study revealed a higher extent of competition between silver barb and rohu, perceptible from the lower growth of one in the presence of the other. Although a certain level of competition of silver barb with mrigal was evident, competition with catla was not perceptible. Irrespective of species combination with silver barb as a component species, similar total biomass production in treatments revealed the feasibility of its incorporation into the Indian major carp‐based polyculture practice without affecting the total yield.     

Screening of gastrointestinal bacteria of Indian major carps for a candidate probiotic species for aquaculture practices

Probotic selection could be detrimental for the success of aquaculture practices. While, in most of the cases emphasis is given to the production of antibacterial compounds, and in vitro inhibitory activities of a bacterium for choosing a probiotic strain, however, other criteria like non‐antibiotic resistant, non‐haemolytic nature and non‐pathogenic potentiality of probiotic strain are often overlooked. We have screened gastrointestinal bacteria isolated from all the three species of Indian major carps viz., Labeo rohita, Catla catla and Cirrhinus mrigala for a suitable probiotic. Bacteria like Aeromonas (Aeromonas species, A. hydrophila), Micrococcus, Corynebacterium, Plesiomonas, Bacillus (Bacillus species, B. subtilis) and Pseudomonas (Pseudomonas species, P. aeruginosa) exhibited antibacterial activities against different pathogens. Among these, B. subtilis was found to grow at a wider range of temperatures, pH and salt concentrations and was non‐haemolytic, non‐antibiotic resistant, non‐pathogenic and inhibited all the tested primary and secondary pathogens. Dietary supplementation of the bacteria at 10⁸ CFU g^?1 feed also enhanced the growth of Indian major carp, L. rohita. Based upon these characteristics, we aimed to develop a suitable probiotic for aquaculture practices.     

Experiments on second spawning of major Indian carps in the same season by hypophysation

The major Indian carps, rohu (Labeo rohita), catla (Catla catla) and mrigal (Cirrhinus mrigala), were hitherto known to breed only once a year—during the monsoon season—either in their natural habitat or by hypophysation in captivity. It has been found possible to mature and induce these carps to spawn twice in the same season, within an interval of about 2 months, and thus augment the spawn production. The technique in brief is as follows. (i) The fish are bred by hypophysation early during the monsoon, in June. (ii) After the first spawning, prophylactic measures are adopted. (iii) The fish are fed supplementary feed consisting of groundnut oil cake and rice bran at a ratio of 1 : 1 and 2–5% body weight of the fish. The spent fish, under favourable weather conditions, were found to mature for a second time and were ready for a second spawning, using hypophysation, in about 2 months. This finding is a breakthrough in the field of fish culture at it helps to obtain more spawn from the same specimens in one season. These results demonstrate the possibility of extending this practice to other cultivated species and thereby augmenting the supply of quality fish seed.     

Effects of increasing the stocking density of large carps by 20% on 'cash' carp–small fish polyculture of Bangladesh

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 on fish performance and on the environment of adding 20% large fish to the basic ‘cash crop’ carp–small fish polyculture consisting of 10 000 fish ha^?1 of the large carp rohu Labeo rohita (Hamilton), catla Catla catla (Hamilton) and common carp Cyprinus carpio (L.) at a species ratio 1:1:1, and 15 000 fish ha^?1 of each small indigenous fish punti Puntius sophore (Hamilton) and mola Amblypharyngodon mola (Hamilton) (control). The treatment ponds were stocked with additional 2000 large fish ha^?1, either all rohu, or all catla, or all common carp, or half rohu and half common carp, or half catla and half common carp. The results obtained and the analysis of interactions through the food web that affect food resource availability of the different fish species and account for the trends and differences observed among treatments confirm the positive effect of common carp on rohu reported in previous experiments and show that a 20% increase in large carps stocking neither affect the survival of the large carps nor reduce harvesting biomass of the small fish for the farmer's family consumption. Increased stocking densities of each large carp species did not significantly reduce its own harvesting weight and mean growth rate, while significantly increased rohu and catla (but not common carp) harvesting biomass and yield. The complex relations between species led to inter‐ and intraspecific competition, which in some treatments increased growth or yield of one species and in other treatments of other species, so that the gains on one species and the losses on the other led to no significant total harvested biomass differences between treatments. Yet, the results herein reported may help farmers to select their species stocking ratios. Thus, if the main target of the farmer is rohu, then a stocking density increase of 10% common carp and 10% rohu would improve rohu growth rate (due to common carp) and result in 50% higher rohu harvesting biomass and yield. If the main target of the farmer is catla, then a 20% increase in catla stocking density would lead to 20% higher catla harvesting biomass.     

Grow‐out performance of Kuria labeo,Labeo gonius (Hamilton), with major carps in carp polyculture system

A year‐long grow‐out carp polyculture trial was conducted in nine earthen ponds to study the growth performance of Kuria labeo (Labeo gonius) with the different major carps such as catla (Catla catla), silver carp (Hypophthalmichthys molitrix), rohu (Labeo rohita) and mrigal (Cirrhinus mrigala). Suitable water quality parameters were maintained in ponds through intermittent liming, manuring and fertilization. Three different species combinations of carps were evaluated using silver carp and catla as the common species and varying other carp components as rohu–Kuria labeo, mrigal–Kuria labeo and rohu–mrigal in the three treatments. The ponds were stocked at a combined density of 7500 fingerlings ha^?1. Silver carp and catla showed similar growth performances in all the three combinations, suggesting that other carps in the combination do not have any differential influence on their growth. Kuria labeo was compatible with rohu, while competition was observed with mrigal. Although growth performance of Kuria labeo was inferior to that of mrigal, better compatibility of Kuria labeo with rohu helped this combination to yield a biomass equivalent to the mrigal–rohu combination, suggesting feasibility to use Kuria labeo as an alternative species to mrigal in the major carp polyculture system without compromising the total biomass yield.     

淡水池塘黄鳍鲷与南美白对虾混养技术

黄鳍鲷又名黄脚立、黄加拉、赤翅,属鲈形目、鲈亚目、鲷科、鳍鲷属,肉质佳美,营养丰富,经济价值较高,黄鳍鲷适应力强,在河口区半咸水域均有分布,为杂食性鱼类,生长快。近年来,我县淡水池塘养殖南美白对虾通过不断探索鱼虾混养新技术来摆脱困境,2009年4月至9月,黄鳍鲷与南美白对虾混养试验取得成功,效益显著,现将技术情况介绍如下。     

对虾池混养缢蛏高产技术

缢蛏肉味鲜美,营养丰富,是我国沿海群众喜爱的海味佳品.养殖缢蛏具有生产周期短,易管理,成本低,效益高,投资少,见效快等特点.在对虾塘里混养缢蛏,可充分利用水体,不但可以增加贝类的产量;还可避免因残饵腐败引起的水质恶化,减少虾病发生;贝类的排泄物又能促进浮游生物和底栖硅藻的繁殖,为对虾提供天然饵料,有利于对虾生长,形成良性循环,达到虾贝双丰收的目的.     

虾池养殖大西洋牙鲆技术探讨

大西洋牙鲆是分布于北美洲大西洋沿岸的一种底层鱼类,是一种极具发展潜力的养殖新品种。它对环境的适应能力比较强,能适应不同的养殖条件。利用对虾养殖池养殖大西洋牙鲆有非常广阔的前景。将对虾养殖池经过清淤、消毒进水,于5月下旬前后投放10cm左右的大西洋牙鲆鱼苗,经过投饵、水质管理等措施;到11月下旬前后出池,出最大个体达756g,平均437g。     

无公害蟹池套养鳜鱼生产技术要点

1 池塘条件 水源要求水量充足,水质良好,符合NY5051标准,进排水系畅通.面积以6 000～20 000m2为宜.水深在1.2～2.0m之间.形状以东西走向为佳.底质以粘土为好,粘壤土次之,淤泥在10～15cm之间.     

海水池塘虾蟹贝生态养殖中后期管理技术

山东省日照市东港区涛雒镇朝阳村养殖场创新养殖模式,实行虾、蟹、贝生态健康养殖,实现了良好的经济效益与生态效益,带动了周边海水池塘养殖发展,2008年被确定为农业部水产健康养殖示范场。     

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.     

Production performance of Labeo calbasu (Hamilton) in polyculture with three Indian major carps Catla catla (Hamilton), Labeo rohita (Hamilton) and Cirrhinus mrigala (Hamilton) with provision of fertilizers,feed and periphytic substrate as varied inputs

Inclusion of kalbasu, Labeo calbasu as a candidate species in the Indian major carps based polyculture system was evaluated through a six-month grow-out trial in earthen ponds of 0.08 ha each. Species performance was assessed through provision of varied inputs viz., fertilizers (T-1), fertilizers + supplementary feed (T-2) and fertilizers + supplementary feed + periphytic substrate (T-3) as the three treatments, which were evaluated in replicates. Catla (35%), rohu (35%), mrigal (15%) and kalbasu (15%) were stocked at combined density of 7500 fingerlings/ha. While ponds were fertilized with cowdung, urea and single super phosphate, mixture of groundnut oilcake and rice bran at 1:1 (w/w) was provided as supplementary feed. The periphytic substrate, comprised stripe bamboo mat, was provided at 10% of the pond surface area. Provision of each additional input caused significantly higher increase in overall mean survival, growth, SGR and net biomass yield of carps. Among the carp species, while only rohu and kalbasu showed significantly higher weight gain (234.4 g and 170.3 g, respectively) in T-3, no such increase was noticed either in catla or mrigal. The net production in T-3 (1516.1 ± 24.3 kg ha^− 1 6 months^− 1) was 13.0 and 73.2% higher than those of T-2 (1341.7 ± 15.5 kg ha^− 1 6 months^− 1) and T-1 (875.2 ± 15.6 kg ha^− 1 6 months^− 1), respectively. The study revealed the relative advantage of using periphytic substrates in carp polyculture systems with kalbasu as a component species.     

Inhibitory effect of <Emphasis Type="Italic">Pistia</Emphasis> tannin on digestive enzymes of Indian major carps: an in vitro study

Aquatic weeds are one of the major unconventional feed ingredients tested for aquafeed formulation. Tannin content in the water lettuce, Pistia, has been quantified (26.67 mg g⁻¹; dry weight) and graded levels of which (12.5–200 μg) have been incorporated in the reaction mixtures to evaluate any change in the in vitro activity of the principal digestive enzymes from the three Indian major carps (IMC), namely rohu (Labeo rohita), catla (Catla catla) and mrigala (Cirrhinus mrigala). Result of the experiment revealed that the Pistia tannin (PT) significantly inhibit/lower the activities of the digestive enzymes from three IMCs in a dose-dependant manner, even at very low concentration. Significant variation in the reduction of the enzyme activities was noticed between the three fish species, as well as between the three enzymes studied. Among the three species studied, digestive enzymes from L. rohita were found to be the most sensitive to the PT, whereas enzymes from C. catla were found to be comparatively least affected. On the other hand, protease and lipase activities were comparatively more affected than the amylase activity. The results of the study suggest that more stress should be given on the elimination of tannin while incorporating feed ingredients of plant origin in fish diets.     

Efficiency of oxbow lake management systems in Bangladesh to introduce cage culture for resource-poor fisheries

A total of 5488 ha of oxbow lakes in Bangladesh has recently gained importance as a potential fishery resource. The growing need to utilize this resource to a fuller potential requires consideration of cage culture by resource-poor fishing communities as a compliment to existing stock enhancement programmes. In the present study, the existing management systems of eight lakes are reviewed. Water quality was analysed with reference to the largest lake, i.e. Lake Baluhar. During the present study, > 100 cm transparency indicated the suitability of a lake for cage culture. Other water quality parameters, especially dissolved oxygen, ammonia and nitrite concentrations, also indicated suitability for cage culture. Non-fisheries activities, such as the use of agricultural pesticides in the lake catchment and jute retting in its basin, were identified as the most harmful to fish by the majority of the fishermen. An integrated pest management programme using rice–fish based rearing systems in the lake catchment is recommended. It is further recommended that a unified management system should replace the existing dispersed systems under different management bodies.     

An investigation of the possible causes for the loss of productivity in genetically improved farmed tilapia strain in Fiji: inbreeding versus wild stock introgression

Four microsatellite markers and a mitochondrial DNA (mtDNA) fragment were used to investigate two possible explanations for a reported decline in productivity of genetically improved farmed tilapia (GIFT) in Fiji: (i) a decline in genetic diversity (GD) and (ii) genetic introgression from feral tilapia populations. Genetic diversity was estimated using θ and allelic richness, while Bayesian clustering was used to assign individuals to genetic groups (K=2 or 3) to test for introgression. Differentiation among groups was estimated using F_ST analysis. Results indicate that genetic diversity had declined compared with a GIFT reference stock from WorldFish Centre, while there was little evidence for introgression from feral tilapia populations. Loss of genetic diversity most probably resulted from practices that have not actively managed genetic resources in the hatchery. While GIFT is considered to be an improved line of Nile tilapia (Oreochromis niloticus), mtDNA analysis here revealed haplotypes assigned previously to three discrete Oreochromis species (O. niloticus, Oreochromis mossambicus and Oreochromis aureus) in both the Fijian strain and the WorldFish Centre strain. Possible sources for the three divergent lineages are discussed. Results have implications for the management and future expansion of the tilapia culture industry in Fiji as well as in other Pacific island nations.     

Indirect selection for growth and life-history traits in Indian carp aquaculture: 1. Effects of broodstock management

Artificial selection for genetic improvement is not carried on in Indian fish hatcheries. However, the process of selection of potential breeders and artificial propagation involves indirect selection, the nature of which will be determined by the type of breeders selected for breeding.The present study is focused on females belonging to two carp species, Labeo rohita and Cirrhinus mrigala, from two fish farms in Karnataka State, south India. Quantitative estimates of pre-reproductive growth rate, age at first spawning and size at first spawning were obtained by a confirmatory factor analysis of measurements made on fish scales. Phenotypic correlations and the resulting correlated selection intensities during a single episode of selection have been estimated. The intensity of indirect selection was negative for pre-reproductive growth rate and positive for age at first spawning. This indicates an undesirable tendency to breed slower growing and later maturing individuals in both farms.     

The potential of deoiled sal (Shorea robusta) seed meal as a feedstuff in pelleted feed for Indian major carp, rohu, Labeo rohita (Hamilton), fingerlings

Ten isonitrogenous (350 g kg^1-crude protein) diets incorporating raw and soaked deoiled sal (Shorea robusta) seed meal at 200, 300,400, 500 and 600 g kg^?1 into a fish-meal-based diet were fed to rohu, Labeo rohita (Ham.), fingerlings for 60 days and fish performance was studied. Tannin from raw salseed meal could be reduced from 34 to 7 g kg^?1 by soaking in water for 16 h at room temperature. In terms of growth response, food conversion ratio and protein efficiency ratio, a diet containing 200 g kg^?1 soaked salseed meal resulted in significantly (P < 0.01) the best performance of the fish. Apparent protein digestibility (APD) values decreased with increasing level of oilseed meal. Carcass protein was highest in fish fed diets containing 200 g kg^?1 soaked salseed meal. The results showed that deoiled salseed meal can be incorporated in carp diets up to 200 g kg^?1 and 300 g kg^?1 in raw and treated forms respectively.