Abstract:The parasite Rhadinorhynchus chongmingnensis infects the digestive tract of the carp, the intestines wall tissue is damaged immediately, a lot of epithelial cells proliferated from the intact tissues to cover damaged positions. At same time, the damaged tissues grow granulation tissue and form granuloma, and the adherence of internal organs occurred. Other organs of the diseased fish such as liver, pancreas and kidney are also damaged to varying degrees. The process of forming, developing and disappearing concerned with granuloma is observed and described.The contents of K, Na, Cl, CRE and BUN in serum of diseased fish are almost the same as the healthy fish. Only GOTs and no GOTm exists in the serum whether the diseased or the healthy fish, the total GOT actively in serum of diseased fish is distinctly higher than that of the healthy ones. The neutrophil content showed by percentage in leucocyte quantities of diseased fish is higher than that of healthy fish.The middle host of Rhadinorhynchus chongmingensis is Moina dubis. Using quick lime (CaO) or beaching powder (CaOCl₂) to sanitize fish pond before stocking is efficacious in prevention.

Abstract:Silver pomfret is an economically valuable fish, which has a wide distribution in China from Bohai Sea down to South China Sea. Specimins of this experiment were collected monthly from the East China Sea. The observations of annual ovarian histological changes show as follows:1. The spawning season of the fish in the East China Sea is from May to June. After spawning,the ovary soon degenerated, by the end of this it will develop into stage ll'and remain in this stage over the whole winter. The ovary begins to develop once more in the last ten days of the next March; it will not approach to stage Ⅳ until April.2. During the development of oocytes oil-globule structures occur in the inner spaces of the cytoplasm, while the yolk granules appear in the early time of the large growth stage in the outer space of the cytoplasm.3. The two egg membrane layers, zona radiata and gluey membrane co-exist in the whole development course of the oocytes. In the matured stage zona radiata disappeared, there is only gluey mambrane left.4. According to the spawning behavior of silver pomfret, the fish should be classified into short-term batech-reieasing pattern.

Abstract:Four groups of Tilapia nilotica were fed in different ranges of temperature (constant temperature of 28℃ and 30℃; periodic fluctuating temperature of 28±4℃ and 30±4℃)in the laboratory. The increasing body weight and oxygen consuming rate were measured. The energy assimilating rate and tissue growing rate (K₂) were calculated. The results indicated that the growth of fluctuating temperature groups was faster, and the daily increase weight and percentage increase weight were higher than that of the controlled ones. In addition, the energy assimilating rate and tissue growing rate in the fluctuating temperature groups were higher than that of the controlled groups, except that the tissue growing rate in the fluctuating temperature group at 30±4℃ was lowest. The mechanism that fluctuating temperature promoted the growth of Tilapia nilotica and its significance in productive practice were discussed and analysed.

Abstract:The structures and properties of polysaccharide fromEucheuma gelxtinae were studied, and according to the results of experiment, the gelation mechanism was deduced.The polysaccharide gel in the presence of K⁺, Rb⁺, Gs⁺, Mg⁺⁺, Ca⁺⁺, Sr⁺⁺, Ba⁺⁺ and NH₄⁺ forms gel which has higher strength than the original. The strength of gel increases with concentration of adding salt, and it attains the maximum value as the ratio of cation number to galactose residue is 1:2, and then starts decreasing The polysaccharide reacted with compounds contain two aminogroups such as urea, alkaline amino-acid and ethylenediamine to form higher strength gel.The polysaccharide also reacted with gelatin to form complex which was a high strength elastomer. The complex could react with the formaldehyde to form a very high strength gel. Its strength was about twice as that of the original complex gel.The scanning electron microscope revealed that the shape and aggregating compactness of section of gel after freeze-drying agree with the order of dehydrating tendency. From above results, it may be considered that the reaction mechanism of cation on the polysaccharide was different from that of diamine and gelatin.The research into various polysaccharide gel by scanning electron micrscope. indicated that the polysaccharide gel was like the sparse twisting fiber cluster and aggregated each other in a same direction; the polysaccharide-KCI was like the untwisting fiber cluster; th and aggregated in a same direction; the polysaccharide ethylene diamine was like some chains aggregating in a same direction; and polysaccharide-gelatin was like sponge.According to above evidence, the gelation mechanism was deduced as follows:1) When the temperature of polysaccharide sol-gel lows, the Brownian movement of molecules is weakened. In addition, the polysaccharide molecule exl (?)bits asymmetry because it is alternately linear comprised by galactose residues and 3,6-anhydro-D-galactose residues, with repeated structure. The neighbor molecule. segments were held together regularly to form a three dimentional framework by hydrogen bonds.2) The polysaccharide gel particles, in presence of cation (K⁺), dehydrated due to the hydration of cation. In addition, the negatively charged gel particles were neutraIized by cation. Then the macromolecuIe gel particles further approaches to each other, and regularly associated to develop a cohesive network by cation "salt bridges".3) In case of adding the compound which contain two amino-groups such as ethylenediamine, the amino-groups of the compound reacted with sulfate groups in the poiysaccharide to form amino-group salts, crosslinking to network structure.4) In case that gelatin was added, multiple amino-groups in gelation reacted with sulfate groups in the polysaccharide to form amino salts and develop a cohesive network involved both macromolecules.

Abstract:Bacteria are abundant and form floccule by agglutination in fertile fish ponds, most of ¹⁴C was used to investigate the digestion and absorption rate of bacteria floccules Results obtained were 45.1% and 81.4% by Hypophthalmichthys molitrix and Oreochromis niloticus respectively. Beef extractpeptone, leaf extract of Eichhornia sp. and organic residue of pond as organic source were used to culture bacteria. The floccules thus analysed contained 50.1%, 36.5% and 36.7% crude protein respectively and all necessary amino acids for fish larva growth. Floccules were employed to feed fish larva successfully. After 13 days of feeding, the wight of H. molitrix (338. lmg) and O. niloticus (252.7mg) increased by 67.3%and 104.1% respectively. The above results show the satisfactory effects of fluccole as fish feed and confirm its role as an important producer in pond ecosystem. They also suggest that apart from the generally conception of phytoplankton-zooplankton-fish food chain, there may be other processes of organic mass flow beginning from bacterium such as bacterium-protozoan-fish, bacterium-zooplankton-fish and bacterium-fish in pond ecosystem, which are ignored at present

Abstract:In this experiment, the blood of 185 healthy fish including grass carp, black carp, wuchang fish, silver carp and bighead carp were measured, 1367 data including erythrocyte, hemoglobin, blood sugar, total protein, albumin, urea nitrogen, cholestrol and triglyceride were obtained. Through the reliable analysis, the average error rate of all the data was less than that of the biological tests in investigutions except that the blood sugar has a relative error above 5%. The results of experiments have shown as follows:1. The blood indexes of fish are variable with species Except for the erythrocyte, the value of other seven indexes is in the following order: carnivorous fish herbivorous and omnivorous fishesfiltering feeders.2. The blood indexes of fish are affected by the environmental conditions The values of blood sugar, total protein, albumin, hemoglobin and urea nitrogen of wuchang fish and grass carp reared in running water are much higher than those of the pond fish.3. The blood indexes also related to the nutrtive availability. Fish of higher nutritive value can be cultured by taking natural organisms as the main food source and the commercial food as supplementary.

Abstract:Cysts of Brine shrimp (Artemia salina) were collected from three different places in China, from Chengkou Salterns of Shandong, Yinggehai Salterns of Hainan Island and Salt Lake of Qinhai, The chorion thickness of he cysts of the three strains were 9.7μm, 11.4 μm and 13.2μm respectively. The highest hatchabilities were obtained by incubating the cysts in freshwater for 2,3 and 4 hours respectively before hatching in sea water. The optimal hatching temperature were 25.5-28.5°, 27.0-30.0° and 27.0-33.0℃ with the optimal salinities 30, 20 and 35‰, the hatching period were 6.5, 6.4 and 7.4 hours separately.The cysts were collected in 24 hours after production and cultured under laboratory condition. The effects of different deactivation treatments on the hatchability were studies. The most effective treatments were as follows:1. For the chengkou cysts, the hatchability of 91—94% was achieved by soaking the cysts in saturated crude salt solution for 2—3 months.2. For the Yinggehai cysts, the hatchability of 80—90% was achieved by soaking the cysts in saturated crude solution for 2—5 months.3. For the Salt Lake cysts, the hatchability of 96—98% was achieved after pre-incubation the cysts in 11° Bé brine at 5℃ for 2—3 months.However, the newly produced cysts could not be activated by soaking in 3% H₂O₂ or formaldehyde solution. Moreover, the hatchability of the cysts collected naturally can be increased by soaking in 3% H₂O₂, 3% formaldehyde, or decapsulation treatment.

Abstract:This paper deals with the regularity of diurnal fluctuation and vertical distribution of non-ionized ammonia concentration at different water depth in the high-yield fish ponds. The concentration of non-ionized ammonia is higher at sunny day than at cloudy day. Early in the morning of sunny day, the concentration is at minimum and it shows little difference in different water layers. In the afternoon, the photosynthesis approaches to the peak. The pH value rises and the concentration of non-ionized ammonia reaches to maximum, though the concentration of the total ammonium decreases. The concentration of nonionized ammonia is the highest in the upper water layer and the lowest in the bottem layer. At dusk when the photosynthesis of phytoplankton becomes lower, the pH value and concentration of non-ionized ammonia decreases in the water layers, especially in the upper and middle layers, though the concentration of the total ammonium increases. At cloudy day, however, the diurnal fluctuation and the vertical distribution of non-ionized ammonia concentration at different water depth have little difference. At windy day, the variation of non-ionized ammonia concentration is also intense, but at fine day with light breeze the concentration among the different water layers has less difference. The effects of photosynthesis of phytoplankton, the respiration and excretion of fish and the decomposition of fish feces on non-ionized ammonia concentration are also discussed.