花生播种期施用绿僵茵防治蛴螬的研究

本文研究金龟子绿僵菌MetarhiziumanisopliaeM202．1菌株对花生蛴螬的防治效果。室内生物测定表明,在含有绿僵菌5×10^6、10×10^6和20~10。孢子．g^-1土壤中,暗黑鳃金龟Holotrichiaparallela幼虫死亡率分别为22．4％、41,1％和74．4％,高浓度下LT50为11．9d。盆栽试验中,在播种花生时进行土壤施菌。施药处理,并在花生开花时进行接虫对比处理,结果显示：对照土壤中接虫处理的蛴螬为害可造成花生好果数减少29．2％,果重减轻26．1％,虫果增加率达28．1％;土壤施菌后接虫条件下虫果增加率为20．7％,比对照减少7．4％;但不论接虫与否,花生好果数及果重与对照土壤不接虫处理的差异均不显著;辛硫磷处理对蛴螬有较好的直接控制作用,但使花生结荚数减少;1／2剂量绿僵菌加1／2剂量辛硫磷混合处理不能很好控制虫害。田间试验显示,播种时绿僵菌能有效控制蛴螬为害,收获期花生的好果数和果重都提高40％左右,显著高于对照,虫果率降低10．9％;绿僵菌的防治效果显著高于辛硫磷。     

条石鲷仔稚鱼发育过程中消化酶活性的变化

研究了条石鲷（Oplegnathus fasciatus）从初孵仔鱼到孵化后33日龄稚鱼期间的胰蛋白酶、酸性蛋白酶、淀粉酶和脂肪酶活性变化。结果显示：条石鲷初孵仔鱼体内可检测到胰蛋白酶、酸性蛋白酶、淀粉酶和脂肪酶活性,但胰蛋白酶、酸性蛋白酶和淀粉酶活力均很低。9日龄仔鱼胰蛋白酶总活力（U/larva）有显著升高,并随发育的进行逐渐升高。28日龄稚鱼酸性蛋白酶和脂肪酶的总活力有显著增大,33日龄稚鱼的蛋白酶和脂肪酶总活力较28日龄稚鱼显著增大。9日龄仔鱼的淀粉酶总活力显著升高,并随发育的进行逐渐增大,但进入稚鱼期后淀粉酶活力随稚鱼生长发育而显著降低。研究表明条石鲷仔稚鱼消化酶活性与其发育阶段及食性密切相关,在早期仔鱼阶段,胰蛋白酶和淀粉酶是起主要消化作用的内源性消化酶。     

兴安落叶松鞘蛾第四龄幼虫和蛹的空间分布

1987年春天,于东北林业大学哈尔滨实验林场、海林林业局三部落经营所、海林县杨子荣烈士陵园及海林县海南林场,共选五块标准地,各抽样调查了30株标准树,每一标准树取4个样枝,以样枝上的叶丛为调查样方,实测样方上的虫数和频次。用分布型频次法和指数法检验结果表明,兴安落叶松鞘蛾第四龄幼虫和蛹属负二项分布和聚集分布。     

提高罗氏沼虾单位水体出苗量试验

１９９１－１９９２年利用对虾育苗进行了提高罗氏沼虾单位水体出苗量试验。１５个试验池总水体７９．５ｍ＾３，共出虾苗４０４．２３万尾，平均５．０８万尾／ｍ＾３，最高６．３５万尾／＾３．１９９２年１２月专家鉴定认为，本成果达国内先进水平。     

几种因子对中国鲎胚胎和幼体发育的影响

以人工授精所获得的中国鲎胚胎及其幼体为实验材料,研究了授精后的静置时间、温度、盐度、重金属等对中国鲎胚胎和三叶幼体发育的影响.结果表明,在试验范围内,授精后静置时间1min即可,不必长达1h;中国鲎胚胎发育的最适温度为28℃,最适盐度20;中国鲎三叶幼体发育的最适温度为30℃,最适盐度30～35;4种重金属离子对中国鲎胚胎发育的毒性效应表现为pb2+＞Zn2+＞Cu2+≈Cd2+;中国鲎三叶幼体比胚胎更容易受重金属污染而影响其正常生长发育.     

Oxygen consumption and ingestion rate of Penaeus setiferus larvae fed Chaetoceros ceratosporum, Tetraselmis chuii and Artemia nauplii

The effects of the density and type of food on oxygen consumption and ingestion rate of larvae of the white shrimp Penaeus setiferus fed diatoms Chaetoceros ceratosporum, flagellates Tetraselmis chuii and Artemia franciscana nauplii were analysed. Diatoms, flagellates and Artemia nauplii were fed at five densities from 10 to 5 × 10³ cells mL^?1, 0 to 4 × 10³ cells mL^?1, and 0.1, 0.5, 1.0, 1.5 and 2 nauplii mL^?1, respectively. In three experiments, two of three types of food were maintained constant at concentrations of 30-40 × 10³ cells mL^?1 (diatoms), 2 × 10³ cells mL^?1 (flagellates) and 1 Artemia nauplii mL^?1. The oxygen consumption in three experiments increased with larval stage, reaching maximum values in Mill except at lower feed concentrations. A maximum ingestion peak in MI was recorded in larvae fed diatoms, whereas that peak was observed in Mil in larvae fed flagellates. The maximum ingestion rate of Artemia nauplii was observed in Mill. Feed concentrations that produced an optimum metabolic rate as a consequence of equilibrium between ingested food and larval stages were obtained with 20 and 30 × 10³ cells mL^?1 of C. ceratosporum, 2 and 3 × 10³ cells mL^?1 of T. chuii, and 1.0 Artemia nauplii mL^?1. These concentrations would be the most suitable for producing P. setiferus postlarvae.     

Modelling the effect of buoyancy on the transport of anchovy (Engraulis capensis) eggs from spawning to nursery grounds in the southern Benguela: an IBM approach

An individual‐based model (IBM) was used to investigate the effects of physical and biological variables on the transport via a jet current of anchovy (Engraulis capensis) eggs from spawning to the nursery grounds in the southern Benguela ecosystem. As transport of eggs and early larvae is considered to be one of the major factors impacting on anchovy recruitment success, this approach may be useful to understand further the recruitment variability in this economically and ecologically important species. By coupling the IBM to a 3D hydrodynamic model of the region called Plume, and by varying parameters such as the spatial and temporal location of spawning, particle buoyancy, and the depth range over which particles were released, we could assess the influences of these parameters on transport success. A sensitivity analysis using a General Linear Model identified the primary determinants of transport success in the various experimental simulations, and model outputs were examined and compared with patterns observed in field studies. Model outputs compared well with observed patterns of vertical and horizontal egg distribution. Particle buoyancy and area of particle release were the major single determinants of transport success, with an egg density of 1.025 g cm^?3 maximizing average particle transport success and the western Agulhas Bank being the most successful spawning area. This IBM may be useful as a generic prototype for other upwelling ecosystems.     

Partial replacement of fishmeal with sunflower cake and corn oil in diets for tilapia Oreochromis niloticus (Linn): effect on whole body fatty acids

The objective of this study was to determine the effect of replacing fishmeal with high‐fibre and low‐fibre sunflower cakes (HFSC and LFSC) on whole body fatty acid composition in tilapia Oreochromis niloticus (Linn). Sex‐reversed O. niloticus males with an initial weight of approximately 16g ± 0.95 (SD) were used. A control diet based on herring meal and soybean meal was formulated. Six test diets were formulated such that low‐fibre (LF) and high‐fibre (HF) sunflower cakes (SC) contributed 30%, 60% and 80% of the dietary protein, and the diets were designated as LFSC‐30, LFSC‐60, LFSC‐80, HFSC‐30, HFSC‐60, and HFSC‐80 respectively. All fish were held at 25–28°C. They were fed three times daily their prescribed experimental diets for 70 days. At the end of this period they were starved for 24 h and weighed. Five fish representing the average weight of each replicated group (n=3) were frozen in plastic bags at –22°C for determination of fatty acid composition. Fatty acids in the fish were significantly influenced by diet. Palmitic, oleic and linoleic acids were the most abundant fatty acids in both the diets and the fish. Linoleic acid (18:2 ω6) was the most abundant fatty acid in diets based on sunflower cake. The levels of this fatty acid were also higher in fish fed diets with high contents of the sunflower cakes (LFSC‐60, LFSC‐80 and HFSC‐80) (31.3%, 34.7% and 29.7% respectively) than fish fed the control diet (13.8%). Percentages of long chain polyunsaturated acids of the ω‐3 family viz., docosahexaenoic (22:6 ω3) and eicosapentaenoic (20:5 ω3) were low in the diets and in the fish bodies. Fish fed the control diet had a higher level of 22:6 ω3 than those fed the other diets. The possible implications of the preceding findings for human health will be discussed.     

Implications of interannual variability in euphausiid population biology for fish production along the south-west coast of Vancouver Island: a synthesis

This is a synthesis of published and unpublished research on euphausiid and fish populations using the south-west coast of Vancouver Island. Overall, the studies covered 1985–98, when there were two ENSO events and considerable variation in upwelling. The population biology of the dominant euphausiids ( Thysanoessa spinifera , Euphausia pacifica ) was monitored during 1991–98. The species abundance trends differed. Results of simple correlation analyses suggested that variations in temperature, salinity and upwelling do not explain variations in the abundance of larval or adult euphausiids, or in the abundance of portions of euphausiid populations on which fish feed. I found significant interannual variations in daily ration of the dominant planktivorous fish species, but euphausiids remained the most important prey. Pacific hake ( Merluccius productus ), the dominant planktivore, fed on larger (>17 mm) T. spinifera , even though the biomass of this part of the euphausiid biomass decreased by 75% between 1991 and 1997, but Pacific herring ( Clupea pallasi ) may have begun feeding on smaller E. pacifica . Therefore, any study of the relationship between fish production and krill biology must consider that part of the euphausiid biomass exploited by fish. In addition, some fish species and/or life history stages appeared to adapt to changes in euphausiid availability, while others did not. Such variation in adaptations also has to be described and considered to understand how changes in euphausiid biology affect fish productivity.