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排序方式: 共有87条查询结果,搜索用时 93 毫秒
51.
An experiment was conducted at the Asian Institute of Technology, Thailand, for 54 days to investigate on the effect of pond water filtration and aggregates (hydroponic substrates) on lettuce (Lactuca sativa L.) production, nutrient uptake and growth. A 2 × 3 factorial experiment consisting of 2 filtration regimes (unfiltered versus partially filtered pond water) and 3 aggregates (styrofoam as control, sand, and gravel). The hydroponic units were placed on a bamboo platform across the pond surface. An earthen pond (226 m2) was stocked with 8000 hybrid catfish with an average initial weight of 6.58 ± 1.72 g. The fish were fed with commercial pelleted feeds containing 30% crude protein. Twenty-one days old lettuce seedlings were transplanted on to hydroponic units after stocking catfish for 4 months in the pond. Pond water was partially filtered by using a settling tank and filtration tank, which contained netting materials to trap solids. Lettuce plots were irrigated twice daily at 0800 and 1600 h using either filtered or unfiltered pond water for 45 min.The highest head weight and yield of lettuce were observed with plants grown on the sand media followed by gravel and the control treatments. Partially filtered pond water treatments had significantly higher lettuce yield (P < 0.05) and filtration increased lettuce yield of the control, gravel and sand treatments by 87, 63 and 52%, respectively, over unfiltered water treatments. Lettuce grown on gravel and the filtered water control treatments had adequate tissue N content. Nutrient rich hybrid catfish (Clarias macrocephalus × Clarias gariepinus) pond water provides an opportunity to use it in the hydroponic vegetable production.Although pond water is mainly constrained by the high suspended solids, and low dissolved oxygen, the study showed that filtration of catfish pond water enhanced the potential to use it for the hydroponic lettuce production. 相似文献
52.
Shu Guan Jianwei He J. Christopher Young Honghui Zhu Xiu-Zhen Li Cheng Ji Ting Zhou 《Aquaculture (Amsterdam, Netherlands)》2009,290(3-4):290-295
Trichothecene mycotoxins are commonly found in cereals worldwide and bring significant threats to the food industry and animal production. The aim of this research was to search for microbes from fish guts capable of transforming trichothecenes into less toxic compounds. Digesta of 62 fishes from nine species were screened for their ability to transform 4-deoxynivalenol (DON). Liquid chromatography-mass spectrometry was used to determine the reduction of DON concentrations and structures of DON-transformation products. The microbial community from one catfish Ameiurus nebulosus, namely microbial culture C133, completely transformed DON to deepoxy DON (dE-DON) at 15 °C in full medium after 96 h incubation. Various media and culture conditions were tested to evaluate their effect on DON transformation. Microbial culture C133 maintained high transformation ability over a broad range of temperatures from 4 to 25 °C and pH values from 4.5 to 10.4. The transformation of DON to dE-DON was enhanced in a rich medium such as full medium, nutrient broth and corn meal broth. Microbial culture C133 was then tested for its ability to transform other trichothecene mycotoxins; most of the toxins were transformed to deacetyl and/or deepoxy products. This is the first report on trichothecene transformation by microbes from the intestinal tract of fish. 相似文献
53.
A double-tagging experiment is presented that estimates tag retention by plastic dart and T-bar anchor tags in a wild population of Clarias gariepinus. It is shown that plastic dart tags are the most suitable tag as there was 100% initial retention and long-term loss of 2% per annum. T-bar anchor tags had an initial tag retention rate of 81% and no measurable long-term loss. A combination of tag design is attributed to the poor performance of T-bar anchor tags as the T-piece of the tag does not properly anchor behind the pterygiophores. 相似文献
54.
This investigation was performed to monitor hexachlorocyclohexane isomers (HCHs), dichlorodiphenyltrichloroethane (DDT, and
its metabolites, refered to as DDTs), plasma levels of estradiol-17β (E2), and the gonadosomatic index (GSI) between sampling
sites of unpolluted ponds of Gujartal, Jaunpur (control site) and the polluted rivers Gomti (Jaunpur) and Ganga (Varanasi),
which affect the reproductive physiology of some edible catfish and carp during the pre-monsoon season. HCHs and DDTs were
measured by gas liquid chromatography (GLC) and hormones by radioimmunoassay (RIA). The results indicated that the level of
HCHs and DDTs was very high in both the catfish and the carp captured from the polluted rivers compared with the fish captured
from the control site. The GSI and E2 values were lower in both groups of fish when compared to the fish from the control
site. The results also indicate that catfish showed greater bioaccumulation of HCHs and DDTs than carp, above the permissible
limit, as compared to the fish from the control site. In conclusion, fish from the Gomti and Ganga rivers were highly polluted
when compared with fish from the control site, as was evident from high levels of tissue bioaccumulation of HCHs and DDTs
and decreased levels of plasma E2, inhibiting the reproductive physiology of these species at the receptor level. The levels
exceeded the maximum residue limits (MRL) as recommended by Codex, hence it is suggested that the fish should be avoided for
food purposes. 相似文献
55.
56.
Carole R. Engle Brent SouthworthPratheesh O. Sudhakaran Adam Nanninga 《Aquacultural Engineering》2011,45(1):1-8
Periodic grading and harvesting of fish has been shown to increase production of some species by removing larger fish throughout the growing season, reducing overall biomass, and increasing growth of smaller fish. Two two-year studies measured production and economic effects of the UAPB grader as compared to traditional live car grading and assessed effects of frequent harvesting and grading. Multi-batch production systems were used in both studies. In Study 1, fingerlings grew significantly better in ponds graded with the UAPB grader (0.97 g d−1) as compared to the traditional live car (0.80 g d−1) and resulted in 14% fewer under-sized (<0.57 kg) fish sent to the processor. In Study 2, increased frequency of harvest up to four harvests a year resulted in significantly fewer over-sized fish (>1.51 kg), more frequent receipt of revenue, and improved cash flow. Economic analysis showed that: (1) it was economically advantageous for catfish farmers to switch to the UAPB grader under a variety of farm size and processor dockage scenarios; and (2) increasing the frequency of harvest up to four harvests/year resulted in fewer over-sized fish, less dockage at the processing plant, improved cash flow, and more favorable economic outcomes. 相似文献
57.
Xue Changhuo 《中国水产科学》1995,(3)
COMPARISONOFLIPIDSANDNITROGENOUSEXTRACTIVESOFDANUBLANWELSANDCHINESECATFISHXueChanghuo(OceanUniversityofQingdao,266003)WangJia... 相似文献
58.
[目的]确定苯甲酸雌二醇诱导黄颡鱼性转化的条件.[方法]分别以浮游动物和微颗粒饲料作为激素载体,研究了添加不同浓度的苯甲酸雌二醇对黄颡鱼性转化诱导过程中成活率、雌性率以及体长的影响.[结果]浮游动物与微颗粒饲料作为载体进行投喂对黄颡鱼鱼苗成活率、雌性率和体长具有较明显差异,浮游动物组成活率为43.1% ~66.5%,而微颗粒饲料组成活率为17.1% ~52.1%;过高的激素浓度处理会导致死亡率升高,而过低的激素浓度处理会导致雌性率大大降低;不同载体和激素处理浓度对黄颡鱼鱼苗生长均具有明显的抑制作用.[结论]以浮游动物或微颗粒饲料为载体,苯甲酸雌二醇的最适浓度分别为150 μg/L和50 mg/kg. 相似文献
59.
Willard C. Losinger 《Aquaculture International》2006,14(5):415-419
Analysis of data from a cross-sectional survey of 571 catfish farmers in the four major catfish-producing states in the United States showed that variability in production fell as farm size increased. Increasing pond size was associated with increasing variability in production. The variance of production was higher on operations that had watershed ponds than on operations with levee ponds. 相似文献
60.