High variability in spawning migration of sea trout,Salmo trutta,in two northern Swedish rivers

Abstract Telemetry was used to examine spawning migration of sea trout, Salmo trutta L. (n = 126), in two rivers in northern Sweden. The spawning areas defined by radio‐tagged fish differed between the river systems. In the River Vindelälven, sea trout spawned in the main stem and 80% of tagged individuals returned to areas where hatchery‐reared juveniles had been previously stocked. In the River Piteälven, 74% of tagged sea trout ascended tributaries for spawning. Tagged fish were categorised into three groups of migratory pattern. cart (classification and regression tree) analysis indicated that distance from tagging location to spawning site (S_dist) explained the migratory patterns. Large S_dist separated fish with stepwise upstream migration from those with up‐ and downstream migrations and one‐directional direct migration. Fish tagged early in the season migrated the longest distance to spawning areas. Stocking locations and sex explained the large search behaviour up‐ and downstream in the rivers. The findings are important for the sustainable management of sea trout in the Gulf of Bothnia.     

Spawning movements of humpback whitefish in interior Alaska rivers

This study was conducted to describe the spawning movements and identify spawning areas for humpback whitefish Coregonus pidschian in the Minto Flats–Chatanika River complex, Alaska, during 2008 and 2009. Radio transmitters were surgically implanted in humpback whitefish in 2008 (N = 60) and 2009 (N = 100), and fish positions were determined through a combination of boat and aerial surveys and fixed receiving stations. Two spawning areas were identified: one in the Chatanika River downstream of the Elliot Highway Bridge and the other in the Tanana River near Fairbanks. Humpback whitefish dispersed from the wetland complex of Minto Flats in June, moved upstream through late August, arrived at the spawning areas in early September and began moving downstream in early October. In 2009, spatially segregated movements were observed when approximately 40% of the radio‐tagged humpback whitefish moved to the Tanana River, suggesting that humpback whitefish in Minto Flats are comprised of mixed spawning stocks. These study results provide a complete account of humpback whitefish movements and their associated spawning habitats, which will allow for better‐informed management strategies.     

Movement patterns of adult pike (Esox lucius L.) in a Belgian lowland river

Northern pike, Esox lucius, needs different habitats to survive and reproduce and thus depends on the availability and accessibility of these habitats. To efficiently manage pike, information is needed on its spatial and temporal patterns of migration. In this study, we investigated the occurrence of adult pike migration and which environmental variables influenced migration. From December 2010, we followed 15 pike for 1 year by use of radio telemetry in the River Yser, a typical lowland river characterised by anthropogenic impacts such as artificial embankments. Pike migrated most in February and March, which could indicate they frequented spawning habitat in this period. Four environmental variables significantly affected pike migration, ranging from the location where pike were observed (strongest effect), over water temperature and flow to diel water temperature change (weakest effect). The relation between migration and the location where pike were observed could demonstrate that pike preferred specific regions in the river. Increasing water temperature triggered migration for both sexes, and males started migrating at lower temperatures than females, which suggests that males start migrating earlier. This was the only substantial difference observed between male and female pike migration. The results suggest that migration was inhibited by high flow, as no migration was observed at high flow. River managers can use this information to efficiently manage their pike populations, for example, by removing or temporarily opening hydraulic structures like valves, weirs and sluices. This may facilitate access to suitable habitats at moments pike needs these habitats to fulfil its life cycle.     

射频识别技术在粮食供应链体系中的应用研究

将射频识别技术应用于粮食供应链系统中,力求实现供应链体系运行的快速与高效.介绍了射频识别技术的基本原理及特点,在此基础上构建了粮食供应链管理系统的系统模型,并给出了粮食供应链管理系统的系统架构,以及基于射频识别技术的实现过程,最后对现存的问题和相应对策进行了概述.     

基于无线测距的农业机器人导航定位方法

针对农业机器人应用中的自主导航问题,提出了一种基于无线测距的导航定位方法。首先,分析了机器人的机械模型和位姿描述;然后,阐述了超宽带测距的原理,并分析了基于超宽带测距的定位模型;最后,设计了基于卡尔曼滤波器的多信标传感器信息融合算法。该方法稳定性高,操作简便,解决了农业机器人在恶劣和未知作业环境中的导航定位问题。     

基于无线和短信环境安全型猪舍监控技术研究

通过无线和短信结合,实现了对环境安全型猪舍的监控。系统由无线智能传感器、无线或短信通信终端、监控中心和执行节点四部分组成,采用集散控制方法。监控中心是整个系统的核心,对数据进行集中管理、分析和处理,其他部分负责数据采集、传输和执行。     

广播电视体制对节目生产和播出内容的影响

世界各国的广播电视体制可以划分为三种类型:商业体制、公共体制和国营体制。不同的广电体制对广播电视节目生产和播出内容有着直接的影响。本文在概括三种体制的理论渊源和特点的基础上，着重分析了不同体制所产生的正负面影响。     

喷水推进转向式遥控渔药喷施机的设计

为解决人工泼洒渔药工作劳动强度大、施药效率低且施药过程中渔药对施药人员身体的危害大等问题,利用Solid Works软件进行建模,设计了由直流自吸水泵驱动,自动混药、施药的新型无线遥控喷水推进转向式遥控渔药喷施机。喷施机由船体、动力装置、喷水推进转向系统、施药系统、无线遥控系统以及配套的水管管路系统组成,样机机身质量约为26 kg,并对样机进行测试。结果表明,该渔药喷施机运行平稳可靠、噪音小,作业时的平均行驶速度为1.0 m/s,最大喷施效率约为2.4 hm2/h(传统的人工泼洒效率约为0.4 hm2/h),喷施效率约是人工的6倍。通过遥控控制喷施机完成渔药的喷施,保证了操作人员的安全,同时对渔药进行在线混合,从而避免喷施药液配置过多造成浪费和污染环境,适用于水产养殖。