Capture depth related mortality of discarded snapper (Pagrus auratus) and implications for management

Variables affecting the short-term survival of snapper (Pagrus auratus) captured using commercial fish traps and subsequently released were investigated by holding the fish in cages. A logistic regression model showed that capture depth had the greatest affect on short-term survival of snapper, with no mortalities observed from depths of less than 21 m and 2% from depths of less than 30 m. Mortality of snapper increased rapidly after 30 m and was 39% between capture depths of 30 and 44 m and 55% between capture depths of 45 and 59 m. Survival was also effected by fish length, with smaller fish being more likely to die. The rate of ascent of captured snapper and the density of fish in cages were kept reasonably constant and did not appear to affect survival. The number of snapper swimming upside-down prior to being returned to the sea floor in cages was not a good predictor of mortality. Future studies that use cages to assess discard mortality rates would benefit from underwater video observations of fish behaviour. The results demonstrate that the discard mortality of snapper should be considered when managing the fishery in New South Wales, Australia.     

Investigation of movement and factors influencing post-release survival of line-caught coral reef fish using recreational tag-recapture data

Six species of line-caught coral reef fish (Plectropomus spp., Lethrinus miniatus, Lethrinus laticaudis, Lutjanus sebae, Lutjanus malabaricus and Lutjanus erythropterus) were tagged by members of the Australian National Sportsfishing Association (ANSA) in Queensland between 1986 and 2003. Of the 14,757 fish tagged, 1607 were recaptured and we analysed these data to describe movement and determine factors likely to impact release survival. All species were classified as residents since over 80% of recaptures for each species occurred within 1 km of the release site. Few individuals (range 0.8–5%) were recaptured more than 20 km from their release point. L. sebae had a higher recapture rate (19.9%) than the other species studied (range 2.1–11.7%). Venting swimbladder gases, regardless of whether or not fish appeared to be suffering from barotrauma, significantly enhanced (P < 0.05) the survival of L. sebae and L. malabaricus but had no significant effect (P > 0.05) on L. erythropterus. The condition of fish on release, subjectively assessed by anglers, was only a significant effect on recapture rate for L. sebae where fish in “fair” condition had less than half the recapture rate of those assessed as in “excellent” or “good” condition. The recapture rate of L. sebae and L. laticaudis was significantly (P < 0.05) affected by depth with recapture rate declining in depths exceeding 30 m. Overall, the results showed that depth of capture, release condition and treatment for barotrauma influenced recapture rate for some species but these effects were not consistent across all species studied. Recommendations were made to the ANSA tagging clubs to record additional information such as injury, hooking location and hook type to enable a more comprehensive future assessment of the factors influencing release survival.     

稻农低碳生产行为的双路径干预策略研究——基于50余万字深度访谈资料的扎根分析

农业绿色低碳发展是中国构建现代化经济体系的重要组成部分。本文以湖北省102户稻农50余万字深度访谈资料为基础,运用扎根理论方法进行开放式编码、主轴式编码和选择式编码分析,探究稻农低碳生产行为的有效干预策略。研究结果显示,“宣传推广教育+低碳情境变革”双路径通过影响稻农低碳生产态度、行为效能感知、生产实施成本和社会环境因素,实现对其低碳生产行为的有效干预。前者属于信息型干预策略,能够提供低碳生产信息、教育和榜样示范等内容,旨在改变稻农低碳生产认知和规范;后者属于结构型干预策略,能够提供经济激励、土地流转、低碳标识和市场监管等内容,旨在改变稻农低碳生产行为决策的情境。因此,应重视低碳农业宣传教育,培育低碳农业经营主体,完善低碳农业补贴机制,加快建立低碳产品标识,进而实现农业低碳化转型。     

Measurement of the shear modulus of wood by asymmetric four-point bending tests

We conducted asymmetric four-point bending tests of wood and obtained the shear moduli on the basis of Timoshenko's theory of bending. Akamatsu (Japanese red pine,Pinus densiflora D. Don) and shioji (Japanese ash,Fraxinus spaethiana Lingelsh.) were used for the tests. Asymmetric four-point bending tests were undertaken by varying the depth/span ratios; and Young's modulus and the shear modulus were calculated by Timoshenko's bending theory. Independent of the asymmetric bending tests, we also conducted three-point bending tests, free-freeflexural vibration tests, and numerical calculations by the finite element method. Young's and shear moduli obtained by these methods were compared with those derived from the asymmetric bending tests. Based on these comparisons, we concluded that the shear modulus can be properly obtained by the asymmetric four-point bending tests when the span is 20 times larger than the depth.     

N肥深施深度对小麦吸收利用N的影响

本文应用＾１５Ｎ示踪技术，在川中紫色土上进行了聚土的表层施肥（施肥深度１－２ｃｍ）、中层施肥（深施２５ｃｍ）、底层施肥（深施４５ｃｍ）和平作表层施肥不同处理小麦吸Ｎ特性等的研究。结果表明：Ｎ肥利用率是“平＋表施”〉“聚＋底施”〉“聚＋中施”〉“聚＋表施”，处理间Ｎ肥利用率最高是２３．７８％，小麦一生有３８．７－４４．１％的Ｎ来自肥料。小麦拔节以前无论是聚土还是平作，其表层施肥地上部分ＮＤＦＦ值极显     

Performance evaluation of tillage tines operating under different depths in a sandy clay loam soil

The study investigated the performance of three model tillage tools (tines). The experimental tillages were made from flat 8 mm plain carbon steel. They were designated T1, T5, and T20, corresponding to tine widths of 1, 5, and 20 cm respectively. Experiments were carried out in a soil bin filled with sandy clay loam soil at average moisture content 11.5% (dry basis) and 600 kPa average cone index. The plastic limit and liquid limit and plasticity index of the soil are 20%, 31% and 11% respectively. Tests were conducted at forward speeds of 0.28, 1.0, and 2.5 m/s. Depths of operation considered were 35, 70, 150, 200 and 250 mm. Draught measurements were made for the different tines and were also calculated using soil mechanics equation. There was reasonable agreement between measured and predicted draught forces. The effects of depth of operation on draught force of the tines were studied and evaluated. It was observed that draught increased at an increasing rate with depth; the relationship was a curvilinear one best fitted by exponential function. The soil disturbance created as a result was also evaluated and reported in this paper. The parameters used to define soil disturbance of a single tine were: ridge-to-ridge distance (RRD), maximum width of soil cut (WFS), maximum width of soil throw (TDW), after furrow depth (df), height of ridge (hr) and rupture distance (f). They all increased as the depth of operation of the tool increased but less proportionately. The critical depth of the tines was also estimated.The results of analysis of variance showed that tool type and operating depth significantly affected draught at 5% level of significance (p < 0.05) and that, there was interaction between the two factors.     

各种优化目标的最佳地下水埋藏深度探讨

首次引入地下水分生产效率、盐分修正地下水分生产效率和雨水的地下水转化率概念，讨论了地下水埋藏深度与作物产量、地下水蒸发量、耕层土壤盐分、地下水分生产效率、盐分修正地下水分生产效率和雨水的地下水转化率之间的关系，根据各关系，确定了以土地生产效　率、地下水分生产效率、盐分修正地下水分生产效率和雨水的地下水转化率为优化目标的最佳地下水埋藏深度范围，为干旱、半干旱盐化潮土地区的旱、盐、渍综合治理提供较合理的　指标．     

沙壤土地区排水沟道的沟深沟距试验研究

在低洼易涝地下水位埋深较浅地区,采用适宜的排水措施是排除涝水和降低地下水位的一项行之有效的工程措施。本文通过野外试验,进行水文地质参数(渗透系数和给水度)的确定,并从理论上分析了排水沟的沟深与沟距。根据试验与理论分析认为,在沙壤土地区,合理的沟深约为1.2m,合理的沟距以45～50m为宜。     

蕙兰不同盆栽深度对其生长影响初探

以中国蕙兰下山驯化苗为试材,研究北方日光温室中不同盆栽深度对其生长的影响.结果表明:浅栽(假鳞茎处于基质表面)有促进植株提前老化和衰退的趋势;传统栽培深度(假鳞茎基部在基质表面以下)下其叶片生长充分,根系较长,但病害发生较严重;深栽(基质表面位于叶片分批处)促进兰株生长健壮,有利于植株的更新复壮,但新芽萌发较少.     

AN ANALYSIS OF AND APPROACH TO THE METHOD FOR TESTING THE PARALLELISM OF SAW GUIDE MOTION LOCUS AGAINST THE BLADE

UNDERSTANDINGoFTHESTANDARDSIntheWoodworkingBandSawing--MachineandCarriagePrecision(GBlo956-89),thetechnicaldemandsoftheparallelismofsawguidemotion1ocusagainstthebladeareasfollows:usingthetestingsteelbandandindicatortotestandmeasure,itsparallelismtoleranceiso.lommatalengthof3oomm.ltstestingmethod,referto"Theindicatorisfixedtothemotioncomponent,andmovestogetherwithitaccordingtotheregularrange,itsmeasuringheadtouchestheplanetested,andslidesalongit;themaximumdifferencevalueoftheindic-…