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991.
Nitrification kinetics of biofilm as affected by water quality factors 总被引:12,自引:0,他引:12
Various types of fixed film biofilters have been used in recirculating aquaculture systems under different water quality and operating conditions. The effectiveness of the nitrification process can be evaluated by nitrification kinetics. Nitrification in the bacterial film of the biofilter involves physical, chemical and biological processes that are governed by a variety of parameters such as substrate and dissolved oxygen concentrations, organic matters, temperature, pH, alkalinity, salinity and turbulence level. The impacts of these parameters upon nitrification kinetics make predicting the performance of a biofilter for a given application an engineering challenge. Knowing the performance of a biofilter is critical for both designers and managers. This paper summarizes the current knowledge on nitrification kinetics as affected by the aforementioned factors based on literature and the results from the authors’ laboratories. These factors were ranked according to their significance of impact on biofilter nitrification performance. The information presented can be used as a reference for the design and operation of biofilters in recirculating aquaculture systems. 相似文献
992.
Qinghui Ai Kangsen Mai Beiping Tan Wei Xu Qingyuan Duan Hongming Ma Lu Zhang 《Aquaculture (Amsterdam, Netherlands)》2006,260(1-4):255-263
A growth experiment was conducted to investigate the effects of replacement of fish meal (FM) by meat and bone meal (MBM) in diets on the growth and body composition of large yellow croaker (Pseudosciaena crocea). Six isonitrogenous (43% crude protein) and isoenergetic (20 kJ g− 1) diets replacing 0, 15, 30, 45, 60 and 75% FM protein by MBM protein were formulated. Each diet was randomly allocated to triplicate groups of fish in sea floating cages (1.0 × 1.0 × 1.5 m), and each cage was stocked with 180 fish (initial average weight of 1.88 ± 0.02 g). Fish were fed twice daily (05:00 and 17:30) to apparent satiation for 8 weeks. The water temperature ranged from 26.5 to 32.5 °C, salinity from 32 to 36‰, and dissolved oxygen content was approximately 7 mg l− 1 during the experimental period. Survival decreased with increasing dietary MBM and the survival in the fish fed the diet with 75% protein from MBM was significantly lower than other groups (P < 0.05). There were no significant differences in specific growth rate (SGR) among the fish fed the diets with 0 (the control group), 15, 30 and 45% protein from MBM. However, SGR in the fish fed the diets with 60 and 75% protein from MBM were significantly lower than other groups (P < 0.05). No significant differences in feeding rate were observed among dietary treatments. The digestibility experiment showed that the apparent digestibility coefficients (ADC) of dry matter, protein, lipid and energy of MBM were significantly lower compared with those of FM (P < 0.05). Essential amino acid index was found to be correlated positively with SGR in the present study, suggesting that essential amino acid balance was important. Body composition analysis showed that the carcass protein and essential amino acids were not significantly affected by dietary MBM. The lipid and n-3 highly unsaturated fatty acid (n-3 HUFA) in fish muscle, however, significantly decreased with increasing dietary MBM. These results showed that 45% of FM protein could be replaced by MBM protein in diets of large yellow croaker without significantly reducing growth. It was suggested that the reduced growth with higher MBM was due to lower digestibility and imbalance of essential amino acids. 相似文献
993.
994.
Julie M. Macaranas Liza Q. Agustin Ma. Carmen A. Ablan Ma. Josefa R. Pante Ambekar A. Eknath Roger S. V. Pullin 《Aquaculture International》1995,3(1):43-54
Four African wild strains (Egypt, Ghana, Senegal and Kenya) and four established Asian farmed strains of Nile tilapia, Oreochromis niloticus (popularly known in the Philippines as Taiwan, Thailand, Singapore and Israel) were analysed electrophoretically at 30 protein loci to estimate genetic differences among the strains. All strains shared alleles at 14 monomorphic and 16 variable loci. Among the African strains, characteristic allele frequency differences were observed at AAT-1
*
46 for Ghana and Senegal, ADH
*
83 for Kenya, ADH
*
120 for Senegal, G3PDH-2
*
300 for Egypt, IDDH
*
67 for Senegal, sMDH-1
*
120 for Kenya and SOD
*
150 for Senegal. Genetic distance values among the strains revealed a clustering of the farmed strains with Egypt and Ghana O. niloticus, a slight separation of the Senegal strain and a larger separation of the Kenya strain. This profile may reflect the origins of the few founder populations of this species previously introduced to Asia. It also confirms the wider genetic divergence of the Kenya strain (O. niloticus vulcani) from the others studied here, which are all O. n. niloticus. Observed heterozygosities of the strains ranged from 0.026 to 0.071, with the African wild strains the lower values (mean Ho = 0.036) and the farmed strains the higher ones (mean Ho = 0.056). The implications of these results to the ongoing tilapia genetic improvement programme in the Philippines are discussed. 相似文献
995.
采用常规石蜡切片,组织染色法和放射免疫测定方法(RIA)对石鲽(Kareius bicoloratus)精巢的发育状况和生殖季节血浆睾酮(T)对注射外源促黄体激素释放激素类似物(LHRH-A)的反应进行研究。结果表明,石鲽精巢为小叶型,精巢发育分为6个时期。性腺成熟系数(GSI),肝重指数(HSI)和肥满度(CF)呈现显著的季节变化。注射LHRH-A后6h,T含量显著上升,之后的12h、24h逐渐下降,48h又显著回升,几乎达到注射前的8倍;对照组血浆T含量在注射后6h显著下降,12h变化不大;24h又显著回升,48h继续回升,但低于处理组。 相似文献
996.
绥芬河污染对大麻哈鱼、滩头雅罗鱼及水生生物影响的调查监测 总被引:1,自引:0,他引:1
绥芬河为中俄共有河,是黑龙江省的产鱼区之一,本介绍了该河流水质常规分析,工厂污水分析、鱼体残毒分析、浮游动物、浮游植物、底栖生物、着生藻类定性、定量及鱼类急性致毒性试验结果,同时进行了水质评价。结果表明:该河流经环境治理,水质状况得以改善,属于寡污带河流,基本达到渔业水质标准,是我国少有的清洁河流,对该河流洄流的四种大麻哈鱼、两种滩头鱼和生存的其它水生生物不构成危害性影响。 相似文献
997.
西瓜未授粉子房的离体培养 总被引:1,自引:0,他引:1
为了探讨西瓜未授粉子房诱导率的影响因素,以‘早春红玉’、‘西农9号’和‘小绿皇’为供试材料进行西瓜未授粉子房的离体培养,研究供体植株的黑暗热激处理、基因型、不同取样时间、2,4-D浓度和不同激素浓度组合等因素对其芽点诱导率的影响。结果表明:西瓜未授粉子房离体培养以33℃的条件下黑暗热激4 d效果最佳;以开花前1 d的子房诱导率最高为17.2%;3个品种中仅‘早春红玉’获得了再生植株,且在激素组合为4.0 mg·L-12,4-D+2.0 mg·L-16-BA+0.5 mg·L-1NAA时芽点率最高为15.0%;根据再生植株的根尖染色体数目,初步鉴定再生植株中有单倍体植株,还有二倍体和四倍体植株。 相似文献
998.
脊尾白虾营养丰富,除鲜食外还可加工成干品。在对虾、梭子蟹养殖池塘收获后,通过池塘收获后留下的部分达不到规格的个体或纳苗、亲体自繁获取白虾苗种,养殖到春节前后出售,这种养虾方法具有成本低、周期短、易管理、能充分利用池塘生产力等特点,使秋冬季节闲置的池塘得到充分利用。一、脊尾白虾主要生物学特性 相似文献
999.
1000.
利用数理统计的方法,对乳山湾东流区6-9月间的水化学,水文和生物观测数据进行处理,结果表明6-9月间硝酸盐与盐度有着极显著的负相关关系,6月和9月亚硝酸盐和氮氨与盐度呈显著性相关,而7月和8月养殖高峰期间呈弱相关关系。 相似文献