Female-biased mortality rate and sexual size dimorphism of migratory masu salmon, Oncorhynchus masou

Abstract –  We examined whether mortality and growth during the migration phase (the lacustrine phase after smolting) differ between sexes in migratory (lake-run) masu salmon ( Oncorhynchus masou ) in a lacustrine population, northern Hokkaido, Japan. The sex ratio of 1+ smolts was more skewed to females than that of the returning adults in three annual cohorts examined, indicating that females have a higher mortality rate during the migration phase. Although there was no difference in smolt length between sexes, female adults were larger in body length than males of the same age: female-biased sexual size dimorphism (SSD) occurs. We suppose that breeding selection favouring a larger body size for females than for males in this population probably requires that females undertake more intensive foraging behaviour with its greater inherent risks but faster growth rates during the migration phase. It therefore seems to be likely that the selection is the ultimate cause of the female-biased mortality rate and SSD.     

The effect of vitamin A supplementation in broodstock feed on reproductive performance and larval quality in Penaeus chinensis

The effect of feeding four semi‐purified diets A1, A2, A3, A4, containing different vitamin A acetate levels 0, 20, 40, 60 mg kg^?1 diet, respectively, on fecundity, egg hatching rate, larval survival rate and vitamin A content in eggs of Chinese shrimp (Penaeus chinensis) broodstock was compared with a fresh clam diet (control) in a 60‐day feeding trial. The broodstock shrimp fed the diet with 60 mg kg^?1 vitamin A acetate added exhibited significantly higher fecundity (P < 0.01). Hatching rate was highest with diet A4 (P < 0.05), whereas hatching rates were similar fed diets A1, A2, A3. Increasing levels of vitamin A in broodstock diet resulted in improvement in larval quality. The vitamin A levels in shrimp eggs from broodstock fed with diet A4 were higher compared with those from broodstock fed with diet A1, A2 (P < 0.01). The fecundity and hatching percentages were positively correlated with the vitamin A content in eggs in the present study. The results of this study showed that higher level of vitamin A in broodstock diet may have positive effects on fecundity and larval quality in P. chinensis.     

Influence of pond fertilization and feeding rate on growth performance, economic returns and water quality in a small-scale cage-cum-pond integrated system for production of Nile tilapia (Oreochromis niloticus L.)

The effects of pond fertilization and feeding rate on growth, economic returns and water quality were investigated to develop a low‐cost cage‐cum‐pond integrated system for production of Oreochromis niloticus (L.). Hand‐sexed male fingerlings averaging 19±0.39 and 32±0.69 g were stocked in cages and open ponds at 150 fish cage^?1 and 2 fish m^?2 respectively. Fish were cultured for 114 days in five triplicate treatments. Cages were installed into ponds and caged fish were fed a 24% protein diet at 3% (T1) and 6% (T2) body weight day^?1 (BWD) without pond fertilization, and 6% BWD with pond fertilization (T3). The open water in the fourth treatment (T4) was not stocked but contained caged fish, which were fed 6% BWD for the first 57 days followed by 3% BWD for the remaining period. Ponds in the control (T5) had no cages and were neither fertilized nor open‐pond fish fed. Feeding rate and pond fertilization significantly (P<0.05) affected fish growth, profitability and water quality among treatments. Fish growth, feed utilization, fish yield, water quality and profits were significantly (P<0.05) better in T3 than the other treatments. It was concluded that fish production and economic returns were optimized at 6% BWD in fertilized ponds.     

Microencapsulation of Peony Oil

目的]探讨牡丹油微胶囊化技术。[方法]利用β-环糊精、阿拉伯胶和大豆蛋白作为壁材采用喷雾干燥技术制备牡丹油的工艺,对牡丹油微胶囊的制备工艺参数进行了单因素和正交实验分析。[结果]得到制备牡丹油微胶囊的最优工艺参数∶壁材β-环糊精∶阿拉伯胶∶大豆蛋白的配比3∶1∶2,固形物含量35%,芯壁材配比3∶1,乳化剂添加量0.2%。在此条件下,牡丹油包埋率达到92%。[结论]在此工艺下牡丹油的包埋率高,为牡丹油的进一步开发打下了基础。     

转基因玉米试管苗移栽影响因素及移栽技术要点

在海南省三亚地区,通过转基因技术获得规模化的转基因玉米试管苗的移栽成活率往往不高,这主要由其自身条件和外界环境引起的。该研究探讨了影响三亚地区转基因玉米试管苗移栽成活率的因素及移栽技术要点,为提高试管苗在三亚地区的移栽成活率提供参考依据。     

UVSG950环保节能型上光机涂布压合系统的关键技术

基于UVSG950环保节能型上光机的关键技术,对涂布压合系统的涂布厚度变动系数、疵斑点率及剥离强度进行试验研究.上光涂布压合系统新增了三辊顺转涂布刮油压合机构、精细涂布计量调节装置及精细压力调节装置,可达到涂布厚度均匀、疵斑点率低、剥离强度满足标准要求的涂布压合效果.     

怎样高枝嫁接落叶松

怎样高枝嫁接落叶松落叶松利用春季进行高枝嫁接，一般成活率可达到９５％以上，当年新梢生长量达１米左右，可使种子园提前１０～１５年建成。具体方法是：１．选择接穗。落叶松芽萌动前，在落叶松优良家系的植株上选择芽饱满的１～３年生枝条，剪后埋在背阴处备用。２．...