一类非线性年龄结构鱼群系统的稳定性

讨论了具有年龄结构的鱼群系统的稳定性，证明了其平衡解是全局渐近稳定的．

实验室条件下鱼类视角与个体邻近距离关系的探究

在麦穗鱼鱼群中,随着邻居鱼的靠拢,其影像在本鱼眼睛中占的视角会变大。为了进一步探究其他的鱼群是否也存在相同的规律,本实验选用个体体长较小的喜成群的红吻半线脂鲤[由30尾组成,平均体长:(20.3±0.2)mm]作为对比研究对象,将其放置在水深5 cm的水族缸(78.0 cm×52.0 cm×65.0 cm)中,使用摄像机从正上方拍摄鱼群影像。逐幅提取鱼群影像中各个体的头部、质心(近头部1/3处)、尾部的二维数据,经过数据处理,分析视角与NND间的关系。结果表明:1)红吻半线脂鲤与麦穗鱼的视角均集中在80°内,即本鱼观察邻居鱼的视角不大于80°。2)在体长差异较大的两种鱼群中,邻近个体占据本鱼的视野范围不会因为鱼体的增大而增加。3)邻近个体占据本鱼视野的最大视角与二者NND间满足以下关系:xy=A,y为视角(用弧度表示),x为NND(单位:BL),A为常数。该规律适用于麦穗鱼与红吻半线脂鲤群体。4)该关系式表示,当邻居鱼靠近本鱼时,为了避免碰撞,鱼类个体用视角作为控制的主要参数,调整相互距离。研究表明,视觉在起主导作用,而侧线、嗅觉、电感觉、磁感觉等即使起作用,也处于次要的地位。

The characteristic of phytoplankton community and its variation at artificial reef area of the coastal sea of Tianjin

Three cruises were investigated respectively in May,July and November 2016 in the artificial reef area of 2010,2012,and 2014 and the non-artificial reef area(control area)in the coastal area of Tianjin.Each area had 3 sampling stations,a total of 12 sites.The result showed that 58 taxa of phytoplankton were identified which belongs to 2 phyla 28 genera,Among these species,bacillariophyta including 19 genera 44 species,pyrrhophyta including 9 genera and 14 species.Give priority to with diatom species,accounting for 75.9%of the total species,followed by dinoflagellates,accounting for 24.1%.Dominant phytoplankton species give priority to with coscinodiscus and Chaetoceros of bacillariophyta,mainly including Coscinodiscus wailesii,C.asteromphalus,C.granii,C.oculus-iridis,C.spp.,Chaetoceros castracanei,C.lorenzianus,C.curvisetus,Pseudo-nitzschiapungens,Guianardia delicatula,Rhizosolenia setigera,Proboscia alata f.indica and Noctilluca scintillans.Phytoplankton cell abundance revealed obviously seasonal changes,the average cell abundance respectively was 94.79×10^4 cells/m^4、39.53×10^4 cells/m^4 and 21.5×10^4 cells/m^3.Phytoplankton diversity index has obviously seasonal variation,and in November,shannon-wiener diversity index,Margalef index and Pielou index are higher than in May and July.Comparing the artificial reef areas with the control area,the phytoplankton cells abundance of the control area in May was significantly higher than the artificial reef areas.In July and November,the artificial reef area of 2014 phytoplankton cell abundance was significantly higher than other artificial reef area and the control area.Diversity index of phytoplankton in the control area and the artificial reef of 2012 was lower than the artificial reef area of 2010 and 2014,and lowest in non-artificial reef areas.Obviously,the construction of artificial reef had significant effect for the improvement of the phytoplankton community diversity,but the phytoplankton community diversity is not always increasing and fluctuating to a certain extent as time goes by.

基于LNAFSA算法的WDM系统PMD自适应补偿

提出了一种可应用于波分复用(WDM)系统的偏振摸色散(PMD)自适应补偿方案。该方案以偏振度(DOP)为反馈信号,采用局部邻域结构的人工鱼群算法(LNAFSA)为控制算法,对低于设定阈值的一个或多个信道同时进行PMD自适应补偿。补偿后各补偿信道的DOP均大于0.96,眼图张开度明显增大,系统性能得到了改善。

Community structure of planktonic copepods in artificial reefs of Wenchang,Hainan

To understand the characteristics of population structure of planktonic copepods and their response mechanisms to marine environmental factors in different seasons,the community structure of planktonic copepods in samples obtained from 7 stations in artificial reefs of Wenchang,Hainan Province in March and September 2019 were investigated.A total of 33 species of planktonic copepods belonging to 23 genera within 17 families were identified in artificial reefs,with 27 species and 21 genera in spring,and 23 species and 19 genera in fall,respectively.The identified planktonic copepods were further categorized into estuarine groups,warm temperate groups,warm water coastal groups,and warm water widespread groups.The predominant species in spring were mainly composed of Temora turbinata and Canthocalanus pauper,whereas Tortanus gracilis and Subeucalanus subcrassus were dominant species in fall.The species and abundance of planktonic copepods in spring were higher than that in fall,while the diversity index and evenness were vice versa,with obvious seasonal differences.In addition,there was a correlation between the population of copepods and physicochemical environmental factors.The major warm water group of copepods in spring showed different degree of correlation with environmental factors,such as NO2-N,NH3-N,pH,water depth,temperature etc.,while the population of copepods in fall was affected by limiting factors such as dissolved oxygen,pH,and temperature.In conclusion,copepods species inartificial reefs were rich and diverse,and their community structure tended to be stable.In addition,the surrounding water quality was generally good,and the whole marine ecosystem and ecological environment were in good condition.

Stroke optimization of a novel multi-station rotary polishing robot based on workspace analysis

In order to meet the polishing requirement of faucets and other products,a novel multi-station rotary polishing robot is designed,which is a PPPR + RR type of degree of freedom( DOF) distribution structure,and is similar to dual-arm robot. Forward and inverse kinematic analysis is carried out by robot modeling. In order to make this robot structure more compact,first of all,X,Y and Z three moving degrees of freedom( DOF) limit stroke polishing need is calculated by using an artificial fish swarm algorithm,which analyzes dexterous workspace of this robot. Then,on the basis of the above analysis,the three DOF stroke is optimized. Simulation and polishing experimental results verify that this polishing robot with optimized stroke parameters can meet the polishing needs of faucets and other bathroom pieces.

Spatial and seasonal variations in the trophic spectrum of demersal fish assemblages in Jiaozhou Bay, China

Trophic structure of fish communities is fundamental for ecosystem-based fisheries management, and trophic spectrum classifies fishes by their positions in food web, which provides a simple summary on the trophic structure and ecosystem function. In this study, both fish biomass and abundance trophic spectra were constructed to study the spatial and seasonal variations in the trophic structure of demersal fish assemblages in Jiaozhou Bay, China. Data were collected from four seasonal bottom trawl surveys in Jiaozhou Bay from February to November in 2011. Trophic levels(TLs) of fishes were determined by nitrogen stable isotope analysis. This study indicated that most of these trophic spectra had a single peak at trophic level(TL) of 3.4–3.7, suggesting that demersal fish assemblages of Jiaozhou Bay were dominated by secondary consumers(eg. Pholis fangi and Amblychaeturichthys hexanema). The spatial and seasonal variations of trophic spectra of Jiaozhou Bay reflected the influence of fish reproduction, fishing pressure and migration of fishes. Two-way analysis of variance(ANOVA) showed that seasonal variations in trophic spectra in Jiaozhou Bay were significant(P <0.05), but variations among different areas were not significant( P >0.05). The trophic spectrum has been proved to be a useful tool to monitor the trophic structure of fish assemblages. This study highlighted the comprehensive application of fish biomass and abundance trophic spectra in the study on trophic structure of fish assemblages.

Status of two Coreius species in the Three Gorges Reservoir,China

Dam construction alters natural flow regimes which,in turn,cause significant changes in fish communities during and after impoundment. The construction of the Three Gorges Reservoir,from impoundment of the Changjiang(Yangtze) River,China,may have affected native fish species. Thus,the status of two lotic freshwater fish species,Coreius heterodon and C.guichenoti,were monitored in the Three Gorges Reservoir,including fish abundance,individual composition,growth,condition,and mortality. Data on both species were gathered from upstream,midstream and downstream areas of the reservoir and,where available,from studies published before and after dam construction. Lower abundance,slower growth,a less diversified age structure,poorer fish condition(indicated by hepatosomatic index) and higher mortalities were recorded in sites nearest the dam compared with upstream areas. Furthermore,after final impoundment,individual Coreius species inhabiting the area changed,with young individuals becoming more abundant,while upstream of the reservoir the two Coreius species became smaller at a given age. The results show that the status of the two Coreius species was subject to dramatic changes after impoundment.

Fish Community Structure and Habitat Preference in Hinval Freshwater Stream of Garhwal Himalayas, India

Fish diversity in different habitats and their preference for a particular habitat was studied in a freshwater stream Hinval in Western Himalayas of Garhwal region. A total of 7 fish species belonging to 2 orders were recorded. The maximum fish diversity and dominance was reported in the cyprinids. Two species of order Cypriniformes, Tot putitora （Ham.） and Barilius bendelisis （Ham.） were recorded at all the three sites, although they were more abundant at sites I and II. Among the Barilius spp., Barilius bendelisis （Ham.） was the most common at all the study sites, while Barilius barna （Ham.） and Barilius vagra （Ham.） were only found at Ⅰand Ⅱsites. The pool habitat was the most preferred habitat of almost all the species with （＇H＇=0.521-0.594） tbllowed by rapid and riffle habitat respectively.

Preliminary notes on brain weight variation across labrid fish species with different levels of cooperative behaviour

Brain size and weight vary tremendously in the animal kingdom. It has been suggested that brain structural develop- ment must evolve balanced between the advantages of dealing with greater social challenges mad the energetic costs of maintain- ing and developing larger brains. Here we ask if interspecific differences in cooperative behaviour （i.e. cleaning behaviour） are related to brain weight variations in four close-related species of Labrid fish： two are obligatory cleanerfish throughout their en- tire life （Labroides dimidiatus and L. bicolor）, one facultative cleaner fish Labropsis australis and one last species that never en- gage in cleaning Labrichthys unilineatus. We first search for the link between the rate of species＇ cooperation and its relative brain weight, and finally, if the degree of social complexity and cooperation are reflected in the weight of its major brain sub- structures. Overall, no differences were found in relative brain weight （in relation to body weight） across species. Fine-scale dif- ferences were solely demonstrated for the facultative cleaner L. australis, at the brainstem level. Furthermore, data visual exami- nation indicates that the average cerebellum and brainstem weights appear to be larger for L. dimidiatus. Because variation was solely found at specific brain areas （such as cerebellum and brainstem） and not for the whole brain weight values, it suggests that species social-ecological and cognitive demands may be directly contributing to a selective investment in relevant brain areas. This study provides first preliminary evidence that links potential differences in cognitive ability in cooperative behaviour to how these may mediate the evolution of brain structural development in non-mammal vertebrate groups .