Aquaculture economics research in Asia: Proceedings of a workshop held in Singapore, 2–5 June 1981: IDRC,Ottawa, Canada, 1982. 128 pp., ISBN 639-3-003-(5). Available in the U.S.A. from Unipub,New York,NY, $15.00; in other countries from IDRC,Ottawa, Canada, $12.00

Propeller-aspirator-pump aerators of 0.38, 1.5, and 2.24 kW transferred averages of 1.73 to 1.91 kg oxygen/kW · h in standardized oxygen transfer tests (tap water; 20°C; 0 mg/l dissolved oxygen) conducted in a shallow basin (1.04 m of water depth). In comparison tests, spray-type surface aerators transferred 1.34 to 1.41 kg oxygen/kW · h and a diffused-air system transferred 1.08 kW · h. The water-mixing capabilities of aerators were estimated from the time to completely mix salt (NaCl) throughout the volumes of ponds, and from the time required to spread a dye over surfaces of ponds. The propeller-aspirator-pump was effective in mixing pond water. A 1.5-kW propeller-aspirator-pump spread dye over a 0.4-ha pond in 32 min and mixed salt throughout 3000 m³ of water in 90 min. A larger spray-type surface aerator (2.24 kW) required 1.5 h to spread dye and 1.75 h to mix salt in the same pond.     

Rearing of marine fish larvae in Japan: Katsuzo Kuronuma and Kunihiko Fukosho. IDRC,Ottawa, Ont., 1984. 109 pp., illus., ISBN 0-88936-406-0, IDRC-TS47e (also available as microfiche)

Serotonin induced spawning in six bivalve species using individual spawning techniques without any additional stimuli. Intragonadal injection of serotonin induced spawning in the bay scallop Argopecten irradians, the American oyster Crassostrea virginica, and the surf clam Spisula solidissima. Injection of serotonin into the anterior adductor muscle of the ocean quahog Arctica islandica, the ribbed mussel Geukensia demissa, and the hard clam Mercenaria mercenaria induced spawning. The dosage of 0.4 ml of 2 mM serotonin solution used in this study stimulated bivalves to spawn within 15 min.     

Aquaculture: The legal framework: Bruce H. Wildsmith. Emond-Montgomery Ltd., Toronto,Canada, 1982, 313 pp. U.S. $ 45.00, ISBN 0-920-722-08-3

In the present communication the gross symptoms of severe riboflavin deficiency are reported as observed in six experiments conducted with four independent stocks of rainbow trout fry and fingerlings. Unlike other reports on salmonids, ocular opacities were infrequently observed, and neither their rate of incidence nor their severity was related to dietary riboflavin content. Compared with both satiety-fed and pair-fed controls, riboflavin-deficient trout exhibited lethargy, apparent muscular weakness, reduced appetite and growth rate, severe fin erosion (all fins), rapid opercular movements, light greenish-yellow skin coloration and high mortality rate. These symptoms, although due to riboflavin deficiency per se, are nonspecific. As the cataracts produced by others in riboflavin-deficient trout appear to be a specific, diagnostic symptom, it is important to identify those conditions which can preclude their development in riboflavin deficiency.     

Effect of fish species combinations on water chemistry and plankton composition in earthen fish ponds

Fish-environment relationships in ponds with several different combinations of fish species are analysed. The study was carried out in 18 earthen fish ponds in a farm at Lohamei HaGetaot, Israel, during the 1986 fish culture season. Water was analysed for temperature, dissolved oxygen, pH, ammonium, nitrite, nitrate, and phyto- and zooplankton. Factor analysis was applied to the physico-chemical and plankton datasets to identify respectively the main ecological processes and species groups in the ponds. The general linear model was applied to analyse the effect of fish species combination and month on the ecological and plankton factors identified. The main source of water quality variability was accounted for by three factors: pond loading (CHF1), oxygenation of the water (CHF2), and pH effect on the second step of nitrification (CHF3). The main source of variability in the plankton composition was due to presence or absence of a blue-green algal bloom (PLF1). Another four plankton factors were identified. Each factor was differently affected by the fish species combination in the pond and the month. The complex nets of interactions between common carp, tilapia and mullet, and how these fish in different cominations affect pond water quality and food webs are discussed.     

鱼蚌混养对池塘水质、藻相结构及三角帆蚌生长的影响

2012年4月26日—2012年12月12日通过在鲢鳙鱼养殖池塘中放养不同密度的三角帆蚌,研究不同三角帆蚌放养比例对鲢鳙鱼养殖池塘中水质、藻相结构及三角帆蚌生长的影响。实验中,鲢鳙放养比例统一为3∶7,总密度为1.5尾/m3。三角帆蚌放养密度则设置4个水平,分别为单养鲢鳙鱼池塘(0只/m3),低密度三角帆蚌混养池塘(0.8只/m3),中密度三角帆蚌混养池塘(1.0只/m3)和高密度三角帆蚌混养池塘(1.2只/m3)。结果显示,混养三角帆蚌池塘的水化指标(TP、PO4-P、NH3-N、NO2-N和NO3-N)均显著低于单养鱼池塘。中密度三角帆蚌混养池塘除NH3-N和化学需氧量(COD)与低密度三角帆蚌混养池塘无显著差异外,其他各项水化指标均显著低于其他3个池塘,并且极显著低于单养鲢鳙鱼池塘。单养鲢鳙鱼池塘藻类平均密度均极显著高于鱼蚌混养池塘,其中在鱼蚌混养池塘中浮游植物密度与三角帆蚌密度成负相关关系。单养鲢鳙鱼池塘的浮游植物生物量均极显著低于中、高密度鱼蚌混养池塘,并且显著低于低密度混养池塘。浮游植物生物量与三角帆蚌密度成正相关关系,鱼蚌池塘中绿藻和裸藻的生物量在养殖过程中上升显著。低、中密度三角帆蚌混养池塘三角帆蚌存活率均显著高于高密度三角帆蚌混养池塘;低密度混养池塘中蚌湿重、壳长及壳宽相对增长率均为最大,显著高于中、高密度三角帆蚌混养池塘。研究表明,养鱼池塘混养三角帆蚌不仅能改善养殖池塘的水质,还能控制藻类数量,促使绿藻和裸藻等大型藻类的生长,提高养殖水体浮游植物的生物量总量,最终还能有效提高三角帆蚌的存活率及生长率。从改善水质,藻相结构,蚌成活率及生长等指标角度考虑,在鲢鳙鱼养殖池塘中,三角帆蚌最佳放养密度为1.0只/m3。