Limited evidence of zebra mussel (Dreissena polymorpha) consumption by freshwater drum (Aplodinotus grunniens) in Lake Winnipeg

Freshwater drum (Aplodinotus grunniens) may be a predator of the invasive zebra mussel (Dreissena polymorpha), which established in Lake Winnipeg in 2013. In this study, the diets, trophic position, and growth of 51 freshwater drum collected in 2019 (six years post-zebra mussel invasion) were compared to 64 freshwater drum sampled in 2000. Benthic insect larvae were the dominant food items in both years. Although mollusks occur in high densities in Lake Winnipeg, they were only consumed by a few freshwater drum in either sample year. Zebra mussels were not a frequent prey item in 2019 as they were only consumed by four of the sampled freshwater drum. Stable isotope analysis of white muscle tissue yielded similar δ¹³C and δ¹⁵N values in both years and were consistent with a benthic, insectivorous diet. Length-at-age data derived from otoliths revealed that the 2019 population had at least an equal growth rate to the 2000 population. Weight-at-length data suggested that fish condition was greater in 2019 than in 2000, which coincided with increased benthic macroinvertebrate density in Lake Winnipeg. Based on these findings, Lake Winnipeg freshwater drum continue to feed predominantly on insect larvae and not zebra mussels.     

Giant hogweed at its northern distribution limit in North America: Experiments for a better understanding of its dispersal dynamics along rivers

We studied the reproduction and dispersal of giant hogweed (Heracleum mantegazzianum) at its northern distribution limit in North America (Québec, 2014–2016) to better understand the invasion dynamics of the species along rivers. Seeds were collected from a riparian population to conduct germination, floatation, and dispersal experiments. Data were analysed in comparison with a real invasion case that was initiated about 10 years ago along a river system. In Québec, giant hogweed individuals produce on average 14,000 to 16,000 seeds with a germination rate of 75–85%. Seeds with endosperm that fall in water likely sink within 5 hr. Along a small brook, most disperse over short distances (<40 m) in summer, although some can travel 100–300 m. These data suggest that late‐summer or early‐fall water dispersal of seeds would not explain the magnitude and rapidity of the invasion patterns observed along streams. We suggest that late‐fall and, especially, spring floods are the most efficient dispersal vectors for giant hogweed seeds and are likely responsible for the establishment of populations kilometres downstream from introduction points along river systems. The spread of giant hogweed would consequently be less influenced in the near future by a rise in temperature than by a change in the magnitude or timing of flood events.     

Impacts of Nile Perch,Lates niloticus,introduction on the ecology,economy and conservation of Lake Victoria,East Africa

Nile perch were secretly introduced into Lake Victoria in the 1950s, and officially in the 1960s, amid unresolved controversy. Proponents were of the view that the introduction would improve fisheries production and sport fishing. Although the former objective was achieved, the side effects were dire, including extinction of many native species, especially the ecologically important haplochromines, because of predation. The introduction also changed the habitat, trophic dynamics and water clarity. The change in water clarity is thought to be responsible for hybridization of haplochromines, further contributing to the loss of species diversity among cichlids. The establishment and expansion of the Nile perch also altered the fishery and socio‐economic settings characterizing the lake. A local economy which, until the early 1980s, was based on native fish species has been replaced by an export‐oriented exotic fish processing industry that destroyed the once‐cherished traditional resource. Other socio‐economic issues associated with Nile perch include the high HIV/AIDS prevalence among fishers, and border conflicts attributable to the migratory and transboundary nature of the fishery resource. Conservation measures for the fishery should include establishment of co‐management units that have so far registered both successes and challenges. Other efforts include establishment of the Nile perch Fisheries Management Plans that focus on curbing overfishing and eradicating illegal fishing.     

医用内窥镜系统体内驱动方式的研究

提出了一种新型的医用内窥镜系统的体内驱动方式和相应的驱动机构。此方式利用螺旋旋转时产生的牵引力推动医用内窥镜系统在人体内腔中运行，同时利用螺旋旋转时产生的动压效应建立起动压润滑粘液膜，使医用内窥镜系统在体内运行时不与内腔壁发生直接接触。避免对人体有机组织产生损伤。详细分析计算了用此方法驱动的医用内窥镜系统在不同半径、不同粘度粘液和不同弹性模量的内腔中的轴向运行速度和形成的粘液膜厚度，结果表明，用此方法驱动的医用内窥镜系统在人体内腔中运行时可以形成足够厚的粘液膜把医用内窥镜系统与内腔壁隔开，实现以较快速度的悬浮运行。上述分析结果已被实验研究所证实。     

Genetic diversity of phalaris arundinacea populations in relation to river regulation in the Merkys basin,Lithuania

During the 1950s–1960s, the Merkys river basin, the largest protected area of Lithuania, underwent severe anthropogenic regulations. Within the Baltic States, the genetic diversity of Phalaris arundinacea populations is unknown and how they might be affected by anthropogenic activities such as river regulation. The objectives of this study were to compare molecular parameters (SSRs or microsatellite loci) within and among populations from natural river fragments with populations from regulated river parts. Study populations have greater genetic diversity within, rather than among, populations. The upstream portion of the Merkys basin populations had lower genetic diversity compared with further downstream. The mean number of polymorphic SSR loci was lower for populations from regulated parts of the river basin compared with natural ones. Main principle coordinate analysis revealed populations of regulated rivers at marginal positions. Bayesian clustering showed that current populations are admixtures of 3 distinct genetic groups, based on STRUCTURE analysis (K = 3 groupings) in geographic subdivisions of (a) downstream populations (Var?n?, Verseka, Upper Grūda, Lower Grūda, Upper Merkys, Lower Merkys), (b) upstream populations (Upper ?al?ia, Ber??, Lower ?al?ia, Visin?ia, Lower ?altyk??ia, Nedil?), and (c) the 2 regulated sites in the distinct geographic area of Taurupis and Upper ?altyk??ia. P. arundinacea in the Merkys river basin does not all belong to a single, random‐mating population encompassing its tributaries or among populations across its geographic scales. In several instances, river regulation might impair the genetic diversity of P. arundinacea populations.     

含除草剂非织造布的研制及其技术规范

含除草剂非织造布兼有防草和保温作用 ,是一种用于农业生产的浮面覆盖材料。本试验研究的滴渗法涂药工艺为设施农业提供了低污染技术 ,并提出了含除草剂非织造布的生产和使用技术规范。     

Implications of an invasive fish barrier for the long‐term recovery of native fish assemblages in a previously degraded northeastern Illinois River system

Barriers to fish movement have been used to prevent the spread of invasive fishes but may also limit the movements of native fishes. We evaluated the potential consequences of a proposed barrier on the Illinois River Waterway, meant to inhibit the spread of silver and bighead carps, to the continued recovery of native fishes in the Des Plaines River following water quality improvements. We compared changes in upstream cumulative species richness and community structure from 1983 to 2013 in the DuPage River, an adjacent tributary with an impassable dam, to the area upstream of a newly proposed barrier on the Des Plaines River where fish can currently pass through a navigational lock. Fewer species displayed truncated distributions upstream of the passable lock and dam (n = 18) compared with the impassable dam (n = 23). Due to water quality improvements in the Illinois River as a whole, cumulative species richness downstream of both dams steadily increased over time. Richness also increased upstream of the passable dam but plateaued upstream of the impassable dam. Fifteen to 18 species accounted for differences in community structure between areas downstream and upstream of either dam. Most species (78–100%) were found in greater relative abundance downstream of the impassable dam, and only 53% were found in greater relative abundance downstream of the passable dam. The truncation in species richness and abundance at the impassable dam foreshadows the potential consequences of an indiscriminate barrier on native fishes and the continued recovery of native assemblages.     

Sex ratio and reproduction of invasive red devil, (Amphilophus labiatus: Cichlidae) in Lake Sentani,Indonesia

The Red Devil Cichlid Amphilophus labiatus (Günther 1864), native to Lake Nicaragua and Lake Managua in Central America, is widely cultivated as an attractive, yet aggressive, aquarium fish that has been introduced to several freshwater locations around the world. It was recently introduced into Lake Sentani in Indonesian New Guinea, a naturally rich aquatic habitat home exhibiting a diverse fauna with high endemism. To better understand the invasive potential and impacts of A. labiatus, the present study was undertaken to describe the sex ratio and reproductive potential of A. labiatus in Lake Sentani through determination of its gonad maturation stages, gonado‐somatic index and fecundity. The fish were collected using floating gill nets at six locations around the lake between June and August 2019. Sex identification, gonads type, gonad stage and weight, fecundity were observed in the laboratory. Of the total 542 of A. labiatus collected during the survey, 345 individuals were sampled for sex ratio and reproduction. The overall male:female ratio was skewed towards males in a ratio of 3.28:1. The males were generally found to be in the gonad maturation stage I, while the females were commonly found in gonad maturation stages III and IV for all sampling locations during the study period. The highest male mean GSI value was found for the Yakonde site (0.24 ± 0.21) and at the Ayapo site (1.11 ± 1.01) for the females, with a fecundity of 191–2,720 eggs. The fish have spread to most parts of the lake, being conditioned to potentially spawn at any location, thereby providing an explanation for the observed rapid increase of the A. labiatus population over the last ten years. The results of the present study suggest a high invasive potential for this species in this and other similar lake habitats, warning that their careful management should be undertaken to restrict their further spread in Indonesia and elsewhere.     

用于微创外科手术的遥控机器人系统研究现状及趋势

用于微创外科手术(Minimally Invasive Surgery 简称MIS)的主从式遥控机器人 系统是医疗中的MIS技术与遥操作技术的结合, 本文主要对具有力觉临场感的比率遥控机器 人用于MIS时的控制特点要求和控制理论技术的研究现状进行了综述,强调了用于MIS和用于 生物工程、微机械等领域的遥控机器人系统在控制上的异同, 对用于MIS的比率遥控机器人 系统控制中有待研究的一些关键问题提出了见解.     

A time-sequence-based fuzzy support vector machine adaptive filter for tremor cancelling for microsurgery

Hand tremors may cause some blemishes in precision and stability of a minimally invasive surgery (MIS). To track the tremor signals accurately, there are two main problems left to be settled. First, it is not practical to collect the sample data of tremor in large scale in practical applications. To deal with the hand tremors, a learning method based on small samples sizes and high dimensional input space is needed. Second, the hand tremors have time-varying characteristics. This fact is neglected by traditional learning methods, which could lead to imprecision and instability of a MIS. In this work, a time-sequence-based fuzzy support vector machine adaptive filter (TSF-SVMAF) for tremor cancelling is proposed. The proposed method is based on support vector machine and time series. It is suitable for solving the problem that the inputs are time-varying and the samples are small-scale. To cancel the time-varying hand tremors, different learning-weight-functions are designed for tremor signals with different frequencies. From the simulation results, compared with the existing methods such as back propagation (BP), weighted-frequency Fourier combiner (WFLC) and bandlimited multiple Fourier linear combiner (BMFLC), the proposed method has better performance when learning the time-varying hand tremors with small sample sizes.