Unintended consequences and trade‐offs of fish passage

We synthesized evidence for unintended consequences and trade‐offs associated with the passage of fishes. Provisioning of fish passageways at dams and dam removals are being carried out increasingly as resource managers seek ways to reduce fragmentation of migratory fish populations and restore biodiversity and nature‐like ecosystem services in tributaries altered by dams. The benefits of provisioning upstream passage are highlighted widely. Possible unwanted consequences and trade‐offs of upstream passage are coming to light, but remain poorly examined and underappreciated. Unintended consequences arise when passage of native and desirable introduced fishes is delayed, undone (fallback), results in patterns of movement and habitat use that reduce Darwinian fitness (e.g. ecological traps), or is highly selective taxonomically and numerically. Trade‐offs arise when passage decisions intended to benefit native species interfere with management decisions intended to control the unwanted spread of non‐native fishes and aquatic invertebrates, or genes, diseases and contaminants carried by hatchery and wild fishes. These consequences and trade‐offs will vary in importance from system to system and can result in large economic and environmental costs. For some river systems, decisions about how to manage fish passage involve substantial risks and could benefit from use of a formal, structured process that allows transparent, objective and, where possible, quantitative evaluation of these risks. Such a process can also facilitate the design of an adaptive framework that provides valuable insights into future decisions.     

Technology selection—the impact of economic risk on decision making

ABSTRACT

Developing an understanding of economic variance (risk) is critical when evaluating alternative aquaculture production technologies. This article assesses the efficacy of employing a quantitative stochastic analysis technique to support technology selection decision making by undertaking a case study investment assessment of three alternative production expansion strategies (offshore sea-pens, land-based RAS growout and larger post-smolt) for the Tasmanian salmon industry. Results demonstrate that salmon aquaculture is undertaken with considerable underlying levels of economic risk, expansion offshore probably represents the lowest initial capital investment and greatest economic return, and that levels of financial uncertainty increase with land-based RAS production. The study highlights stochastic modeling provides significant “added-value” over single-point deterministic analysis and that developing an appreciation of the input variability is a key component in critically evaluating alternative production technologies.     

CREDIT MANAGEMENT ANALYSIS OF SEMI-INTENSIVE SHRIMP FARMING IN MEXICO

Credit management (funding source with its specific interest rate, its timing, and amount) and its trade, affect feasibility of commercial shrimp farming. To analyze optimal trade credit management, an existing bioeconomic model of a semi-intensive shrimp farm (139 hectares with 44 earthen ponds) located in Sinaloa, Mexico, was extended to create a framework that assesses the decision-making problem related to funding from input suppliers (feed and postlarvae) during one culture cycle, integrating stochastic factors like shrimp mortality and pond water temperature. Through the application of Monte Carlo simulation and genetic algorithm-based optimization techniques, results show that the minimum funding cost is US$15,710 (for an operation budget of US$603,790), 27% lower than alternative funding scenarios (P-value <0.001). Although framed at the firm level, this approach optimizes any funding planning scenario in short-term credit management, particularly in funding schemes involving input suppliers. Further research is needed to relate credit management at the firm level with other elements of the value chain.     

水稻基因差异表达与杂种优势的关系分析

【目的】分析水稻强、弱优势组合的基因差异表达模式特征,探讨其与杂种优势之间的关系。【方法】以扬稻6号、明恢63、特青配置的9个杂种F1为材料,利用差异显示PCR技术（differential display polymerase chain reaction,DD-PCR）分别分析分蘖期（叶片）、孕穗期（幼穗）、抽穗期（剑叶）的基因差异表达模式。【结果】同一时期内强优势组G1（父本扬稻6号）、中优势组G3（父本特青）以及弱优势组G2（父本明恢63）在母本特异表达（UNP1）、父本特异表达（UNP2）、F1特异表达（UNF1）、F1特异缺失表达（ABF1）4个基因差异表达模式上存在明显差异;相关分析表明分蘖期叶片UNP2与单株产量呈极显著正相关,来自父本的基因特异表达有利于提高杂种优势;同一优势组在不同时期的表达模式也存在明显差异,反映了基因的时空表达特征;获得19个G1、G2间特异性差异表达的基因片段,分布在除第12染色体以外的其余11条染色体上,主要涉及物质合成与运输、能量代谢、糖类代谢等重要途径。【结论】水稻强、弱优势组合F1在不同生育期基因表达模式存在显著差异,表型性状的差异可以从基因表达模式上得以反映。     

金衢地区双季稻周年高产品种搭配与种植方式研究

为了解决目前金衢地区双季稻生产存在的早晚稻生育期衔接矛盾、早晚稻适宜高产主栽品种不突出以及双季稻周年高产高效种植问题,通过开展双季稻周年高产高效研究,探讨适宜金衢地区的双季稻周年高产品种结构和种植方式。结果表明,早稻‘中嘉早17’直播搭配晚稻‘甬优15’手插模式的周年产量最高,达到18175.5 kg/hm2,周年效益达19519.5元/hm2;早稻采用‘中嘉早17’直播搭配‘甬优15’机插模式的周年产量为28584.0 kg/hm2,周年效益为14854.5元/hm2;早稻采用‘株两优609’直播搭配晚稻‘钱优0506’机插模式的周年产量为15549.0 kg/hm2,周年效益为16867.5元/hm2。金衢地区种粮大户早稻采用直播方式选择生育期相对较短的‘株两优609’或‘金早09’等,搭配机插晚稻‘甬优15’或‘钱优0506’;大户选用双季机插模式,早稻可选择‘中嘉早17’等中、迟熟品种,搭配‘甬优15’或‘钱优0506’等品种,即可获得较高的收益,又可合理安排播插和收获时间。     

不同栽培方式下香型优质稻渝香203的产量分析

[目的]研究不同栽培方式下优质稻渝香203的产量差异,探讨挖掘品种的高产潜力的栽培技术。[方法]研究手栽秧、机栽秧、抛秧、直播4种栽培方式下渝香203产量及相关性状的差异。[结果]手栽秧种植方式下产量最高,之后依次为机栽秧、抛秧,直播栽培方式下产量最低。[结论]4种栽培方式有各自的优缺点。其中手栽秧产量水平最高,但其劳动强度大,种植成本高;机插秧和抛秧正逐渐取代手插秧。     

宝天曼锐齿槲栎-华山松林样地物种组成及空间分布格局

为了深入理解宝天曼自然保护区树种多样性的形成和维持机制,对核心区内1 hm2锐齿槲栎-华山松固定监测样地的物种组成及空间分布格局进行了研究.结果表明,样地内共有胸径≥1 cm的木本植物58种2 214株,隶属于28科49属,其中,锐齿槲栎(Quercus aliena var.acutiserrata)和华山松(Pin...     

遥感信息技术在大麦生产中的应用研究

大麦生产中应用调优栽培信息化技术,是把传统农业与高新产业结合的技术,通过实际应用,可以提高大麦单产,改善籽粒品质,增加大麦生产抵御自然灾害的能力,提高经济效益,同时可以减少麦芽生产企业收购成本,使收购更具有针对性.大麦调优栽培信息化技术在我国北方地区具有很好的推广价值.     

杂交紫长茄瑞丰3号优化栽培模式研究

【目的】研究不同施肥措施及栽培密度对茄子新品种瑞丰3号产量的影响,为瑞丰3号紫长茄高产栽培提供科学参考。【方法】采用＂416-B＂最优混合设计,探讨种植密度和氮、钾、磷肥施用量与瑞丰3号紫长茄产量、利润及产投比的关系,并建立三元二次回归模型,分析各因子对产量形成的影响及相互作用效应。【结果】4个因素对茄子产量影响的顺序依次为氮肥〉钾肥〉种植密度〉磷肥,说明氮肥和钾肥施用量是制约紫长茄产量的主导因素。【结论】在该试验条件下,其最佳栽培措施是：施氮量297.33kg/ha,施钾量371.44kg/ha,施磷量95.68kg/ha,种植密度36908株/ha,紫长茄最优产量为100937.7±13239.5kg/ha。