旷野风速对林网内风速分布及防风效能的影响

为了揭示旷野风速对农田林网内风速分布及防风效能的影响,通过空间多点实地观测,利用传统统计分析、Surfer软件、地统计学等方法对3种风速(5.4,7.2和10.3m/s)条件下的林网内风速分布及防风效能进行了分析。结果表明,3种旷野风速下主林带的背风面均形成一个较大范围的降风区;3种旷野风速下林网平均降低风速效能为26.1,23.3和25.7%,平均有效防护面积比为50.8%,41.7%和47.7%,林网的总体防护效能在风速为5.4m/s时为最大,风速为7.2m/s时为最小;3种不同旷野风速下林网风速空间变异函数均可以较好地拟合为球状模型,3种旷野风速下网格内风速块金值与基台值的比值较小,均小于25%,林网内风速均具有强烈的空间自相关性。旷野风速对林网内风速分布及防风效能的影响比较复杂,并不是单一的随着风速的增大而增大或减小,受林带结构及疏透度的影响较大。     

双侧竖缝式鱼道水力特性研究

研究分析不同水池长宽比条件下双侧竖缝式鱼道的水池流场结构及其水力学指标,为双侧竖缝式鱼道布置参数的优化选择提供技术依据。基于单侧竖缝式鱼道体型参数的研究成果,选取导板长度与水池宽度之比为0.25、竖缝宽度与水池宽度之比为0.15、导向角度为45°作为研究的基本体型;鱼道来流边界设置为压力进口,上游水深设置为2 m,出流边界设置为压力出口,下游水深设置为2 m;模型顶部设置为压力进口,进口压强为1.01×105Pa,边墙设置为固壁边界。采用三维数值模拟的方法研究分析了水池长宽比分别为4∶8、5∶8、5.5∶8、5.75∶8、6∶8、6.5∶8、7∶8、8∶8、9∶8的条件下双侧竖缝式鱼道的水池流场结构及其水力学指标。在不同水池长宽比条件下,鱼道常规水池内存在3种典型流场结构,其主流轨迹线、主流流速沿程衰减规律以及回流区分布等水力学指标均有不同,典型长宽比取值区间分别为4∶8~5.5∶8、5.75∶8~6.5∶8及7∶8~9∶8;对比发现,长宽比在5.75∶8~6.5∶8区间范围时,主流区宽度相对较大,水池空间利用较为充分,沿程流速衰减情况也较好,回流区主要分布于主流两侧且大小适中。初步认为长宽比5.75∶8~6.5∶8的水池流场结构较为合理。     

有机培肥土壤对优势流中养分淋失的影响

为研究有机培肥对土壤优势流中养分淋失的影响,采用原状土柱模拟淋溶的方法,对土壤优势流中养分淋失的情况进行研究.结果表明,土壤经有机培肥后,明显降低了优势流中各种养分的淋失速度,从而使养分的淋失总量减少,为未施秸秆处理的1/3左右.有机培肥土壤对于淋溶液中养分浓度的影响表现为,在淋溶液中养分浓度总体降低的同时,各种养分的浓度降低的幅度又有所不同,其中对水溶性K和铵离子的效果最明显,而对硝态氮（NO-3-N）保持作用则相对差些.上述结果说明,有机培肥对减少土壤优势流造成的土壤养分淋失以及降低地下水污染都有一定的作用.     

植被斑块格局对砒砂岩坡面土壤侵蚀强度的影响

选取水力侵蚀极其剧烈的砒砂岩区为研究对象,基于野外径流小区的连续监测试验,采用三维激光扫描、无人机航拍与方差均值比率法相结合,对比分析砒砂岩坡面3种典型自然植被格局(聚集分布、均匀分布、随机分布)下的产流产沙特征与坡面微地形的演变规律。结果表明:(1)均匀分布格局对减缓水力侵蚀条件下砒砂岩坡面土壤侵蚀强度的效果最明显,与裸坡相比,减流率达到64%,减沙率达到72%,土壤流失量最少,为0.05 kg/m²。径流泥沙量之间存在多项式曲线关系,拟合函数为y=-0.0462X²+0.5355X-0.865,R²=0.736。(2)均匀分布格局的侵蚀区面积最小,为12.28 m²;沉积区面积最大,为3.44 m²,土壤侵蚀强度较其他坡面弱,以轻度侵蚀为主。(3)均匀分布格局的径流泥沙量与平均沉积深度之间的相关性较强,与径流量呈显著正相关(p＜0.05),相关系数为0.603;与泥沙量呈极显著正相关(p＜0.01),相关系数为0.771。     

Site of acid-base relevant ion transfer in the gills of rainbow trout (Oncorhynchus mykiss) exposed to environmental hypercapnia

In order to delineate the contribution of primary vs. secondary circulatory circuits in the gill for acid-base and ionic regulation, the flow and composition of the fluids in the central venous sinus (CVS) and the systemic circuit of rainbow trout were studied by application of a previously developed microcannulation technique during normocapnic and hypercapnic conditions. The average haematocrit (Hct) of blood from dorsal aorta (DA) and sinus venosus (SV) ranged from 20.1 to 26.7%, whereas average Hct in the fluid from the branchial vein (BV), representing drainage from the central venous sinus (CVS), was in the range of 4.2 to 7.0%. Under normocapnic conditions, the largest fraction of cardiac output, 92.9%, was directed through the systemic vascular circuit, whereas the CVS circuit was perfused with 7.1 % of cardiac output. Hypercapnia did not significantly affect the blood flow distribution between the two circuits. The pattern of acid-base regulation in dorsal aortic blood reflected the characteristic response of fish exposed to environmental hypercapnia. Upon initiation of environmental hypercapnia (2% CO₂), plasma P_{CO 2} was elevated in all three flow compartments (CVS, DA, SV), inducing an extracellular respiratory acidosis of about 0.4 pH units. pH and [HCO₃ ^-] values in the DA were consistently lower, than those for both CVS and SV sites throughout the hypercapnic period. During the 8h of exposure plasma bicarbonate concentration was elevated by about 12 mM, complemented by a fall in extracellular [Cl^-] of about 10 mM in all three compartments. The amount of HCO₃ ^- gained at the CVS site during 8h of hypercapnia (3.3 mmol · kg^-1) exceeds the amount accumulated in the extracellular space (2.1 mmol·kg^-1), suggesting the CVS as the main site of ionic acid-base regulation in trout.     

流式细胞术在水产动物研究中的应用

流式细胞术(Flow Cytometry,FCM)是20世纪70年代发展起来的对细胞的物理和化学性质进行快速测定的技术.它以大量的单个细胞为检测单位,研究结果客观准确,它还具有快速、灵敏和同时检测多个参数等优点.     

应用于鱼道设计的新疆木扎提河斑重唇鱼的游泳能力测试

为了探究斑重唇鱼的游泳能力,给过鱼设施设计和鱼类游泳行为学研究提供基础参数,本研究以木扎提河野生斑重唇鱼(全长TL=12～16 cm)为研究对象,测定了其在(16.6±1.6)℃水温下的感应流速、临界游泳速度、爆发游泳速度及持续与耐久游泳能力。结果显示,斑重唇鱼感应流速为(0.18±0.02)m/s,相对感应流速为(1.40±0.23) BL/s (BL为体长);临界游泳速度为(1.02±0.15) m/s,相对临界游泳速度为(8.58±1.65) BL/s;爆发游泳速度为(1.39±0.17) m/s,相对爆发游泳速度为(10.92±1.86) BL/s;最大持续游泳速度为0.87 m/s,最大耐久游泳速度为1.37 m/s,与平均爆发游泳速度相近。其持续游泳时间与流速呈负相关(l g T=?5:136X+8:504)。当以斑重唇鱼为主要过鱼对象时,建议为吸引鱼类进入鱼道,进口流速设计为1.02～1.39 m/s,休息池主流设计为0.20～1.02 m/s,鱼道竖缝处流速宜低于0.85 m/s。鱼道长度为1 000 m时,鱼道内平均水流速度应低于0.78m/s。本研究结果可为新疆木扎...     

Performance and welfare of Atlantic salmon,Salmo salar L. post-smolts in recirculating aquaculture systems: Importance of salinity and water velocity

Producing a larger post-smolt in recirculating aquaculture systems (RAS) could shorten the production time in sea cages and potentially reduce mortality. Knowledge of the biological requirements of post-smolts in closed-containment systems is however lacking. In the present study, the effects of salinity and water velocity on growth, survival, health, and welfare of Atlantic salmon reared in RAS were examined. Salmon smolts were stocked in three separate RAS with salinities of 12, 22, and 32‰ and subjected to high (1.0 body lengths per s⁻¹) or low (0.3 body lengths second⁻¹) water velocity. Growth performance, survival, welfare, and physiological stress responses were monitored until the fish reached a bodyweight of around 450 g. Growth rate was higher at lower salinity and higher water velocity generally had a positive effect on growth in all salinities. Feed conversion ratio was lower at 12‰ compared to the 22 and 32‰ when the fish were between 250 and 450 g. Higher mortality, elevated plasma cortisol levels, higher incidence of cataract, and a higher expression of stress-induced genes in the skin (iNOS, Muc5ac-like) indicated a negative effect of higher salinity on fish welfare. Male maturation was low (<1%), and not affected by salinity or water velocity.