长江口东滩湿地斑尾刺虾虎鱼的栖息亚生境选择和食性差异

2015年7月至2016年6月每月在长江口东滩湿地西南水域的光滩、盐沼(以海三棱藨草为主)和潮沟3种亚生境进行斑尾刺虾虎鱼的样本采集,分析斑尾刺虾虎鱼的丰度和食性差异.结果表明:6—11月均采集到斑尾刺虾虎鱼样本,以幼鱼为主,其他月份未采集到.其中,7月采集数量最多,为71尾,11月仅采集到3尾.潮沟中共采集到93尾,分别是光滩和盐沼的5.2和4.9倍.6—11月斑尾刺虾虎鱼的平均体长和体质量均呈逐渐增加趋势.斑尾刺虾虎鱼主要摄食虾类、蟹类、昆虫类和多毛类等10大类30小类饵料生物.其中,虾类是最重要的饵料类别,并以安氏白虾等白虾属为主;蟹类以相手蟹属为主;昆虫类以小划蝽等蝽科昆虫成虫为主;鱼类饵料的质量百分比相对较高,但数量比例很低.不同亚生境斑尾刺虾虎鱼的饵料组成差异较大.7—11月斑尾刺虾虎鱼的摄食等级随体长增大而明显增大,秋末(11月)平均摄食等级可达3.不同亚生境间的斑尾刺虾虎鱼丰度差异与其摄食饵料不同有关.     

矛尾复虾虎鱼物种命名有效性探讨

利用形态学和遗传学方法探讨斑尾复虾虎鱼和矛尾复虾虎鱼的亲缘关系及矛尾复虾虎鱼物种有效性.研究结果显示:两种虾虎鱼在量度特征上存在极显著的差异,但分节特征不存在显著差异;与斑尾复虾虎鱼相比,矛尾复虾虎鱼头长相对较小,而尾鳍相对较长.对两种虾虎鱼的线粒体DNA控制区片段序列进行比较分析,得到两种虾虎鱼的遗传距离仅为0.006,与种内距离相当;NJ和MP法构建的系统树也显示两种虾虎鱼间亲缘关系很近,两种间不存在显著差异.综上,矛尾复虾虎鱼并非有效物种,应为斑尾复虾虎鱼的同种异名.     

胶州湾六丝钝尾虾虎鱼的摄食生态特征

根据2011年2-11月在胶州湾海域进行的4个季节的底拖网调查,共收集624尾六丝钝尾虾虎鱼样品进行胃含物分析,对其摄食生态进行了初步研究.结果表明:六丝钝尾虾虎鱼摄食的饵料种类有40余种,其中优势饵料生物有日本鼓虾、经氏壳蛞蝓和细螯虾等.其食物组成存在明显的季节变化,除在4个季节均大量摄食虾类外,春季主要摄食腹足类,夏季主要以鱼类为食,秋季主要摄食虾类,冬季摄食桡足类和端足类等小型甲壳生物的比例较高,这主要与胶州湾饵料生物种类和数量的季节性变化有关.随着体长的增长,六丝钝尾虾虎鱼摄食的饵料生物由小型的桡足类逐渐转变为个体较大的经氏壳蛞蝓、绒毛细足蟹和日本鼓虾等,食物组成呈现出明显的体长变化.典范对应分析(CCA)表明,水温和盐度是影响六丝钝尾虾虎鱼摄食的主要因素,其次是体长和pH.     

全球气候变化对小兴安岭阔叶红松林影响的动态模拟研究

应用林窗模型(Forest Gap Model)及4种大气环流模式(General Girculation Models,GCMs) CO₂加倍\"平衡响应\"数值试验结果模拟了小兴安岭阔叶红松林对未来气候变化的动态响应过程.结果表明,在美国高达空间研究实验室(Goddard Institute for Space Studies,简记GISS)和美国俄勒冈州立大学(Oregon State University,简记OSU)GCMs预测的CO₂倍增未来气候情景下,与本底生物量(目前气候条件下)相比,阔叶红松林生物量逐渐升高,目前云冷杉阔叶红松林将逐渐向枫桦、紫椴和裂叶榆阔叶红松林演变;但在普林斯顿大学地球流体动力学实验室(Geophysical Fluid Dynamics Laboratory,Princeton University,简记GFDL)和英国气象局(United Kindom Meteorological Office,简记UKMO)GCMs预测的未来情景下,由于较大幅度的增温,云冷杉红松林将向以蒙古栎、紫椴和裂叶榆为主要树种的阔叶林演变.未来增温速率决定了阔叶红松林未来的演替方向.     

东海北部大管鞭虾的食性

根据对2009年6月至2010年5月在东海北部采集到的720尾大管鞭虾胃含物的分析,对不同季节、性别、个体大小以及发育条件下大管鞭虾的摄食习性进行了研究.结果表明: 东海大管鞭虾的饵料生物共有43种(包含未鉴定种),甲壳类、有孔虫类和多毛类为其主要的摄食群类,在食物中所占的数量百分比分别为34.7%、29.4%和12.4%.大管鞭虾的饵料组成具有明显的季节波动,春季以有孔虫、藻类和无脊椎卵为主要食物;夏、秋季以有孔虫、鱼类和多毛类为主要食物;冬季则以多毛类和有孔虫类为主要食物.其摄食强度在春季和夏季较高,秋季较低.不同甲长的个体食性变化显著,小于24 mm的个体主食有孔虫类和藻类,24 mm以上的个体主食有多毛类和十足类;随着性腺发育雌性个体摄食等级呈现减弱的趋势,表明大管鞭虾摄食活动受到繁殖周期的影响.不同性别和不同季节大管鞭虾的食物重叠指数均较高,与栖息环境饵料资源的波动有关.大管鞭虾的营养级为2.67,属低级肉食性动物.     

基于线性混合模型研究海州湾六丝钝尾虾虎鱼摄食生态

随着我国近海多种传统经济渔业资源的衰退,六丝钝尾虾虎鱼已成为海州湾等海域的优势鱼种之一,并在海洋食物网中发挥着重要作用。本研究根据2011年和2013—2016年春季和秋季在海州湾及其邻近海域进行的渔业资源底拖网调查,基于线性混合模型研究了海州湾六丝钝尾虾虎鱼的摄食习性以及影响其摄食的主要因素,并对其摄食策略进行分析。结果表明: 海州湾六丝钝尾虾虎鱼以虾类、双壳类、端足类等14个饵料生物类群为食,其中端足类、虾类、双壳类、蛇尾类是其主要的饵料类群。从饵料生物种类来看,六丝钝尾虾虎鱼摄食的饵料种类有37种,优势饵料生物有钩虾、细螯虾、独眼钩虾、彩虹明樱蛤和鲜明鼓虾等。线性混合模型分析表明,海州湾六丝钝尾虾虎鱼的摄食强度受体长、水深、季节、底层盐度的显著影响,其中,摄食强度与水深和底层盐度呈显著负相关关系,而与体长呈显著正相关关系,且春季的摄食强度显著高于秋季。聚类分析表明,以体长70 mm为界,可将六丝钝尾虾虎鱼划分为食性差异较大的两个体长组,其摄食随体长的变化主要与自身摄食能力与饵料生物丰度的变化有关。摄食策略分析表明,六丝钝尾虾虎鱼的营养生态位具有较高的表型间成分,对食物的种内竞争较低。本研究将有助于揭示六丝钝尾虾虎鱼的生活史特征,并为其资源的可持续利用和科学管理提供参考依据。     

长江口中华鲟幼鱼的食物组成及摄食习性

分析了2004年5-9月长江口水域中华鲟幼鱼的食物组成及摄食的月份变化.结果表明:长江口中华鲟幼鱼以底栖小型鱼类、多毛类和端足类为主要食物,兼食虾类、蟹类及瓣鳃类等小型底栖动物.幼鱼的摄食率和摄食强度较高,且摄食强度存在着月份变化.主要饵料生物组成有明显的月变化,且食物个体有逐渐增大的趋势,其中5月主食多毛类和蟹类,6月主食鱼类和端足类,7月为鱼类和多毛类,8月样本较少且为空胃,9月为鱼类和虾类.与历史资料进行比较发现,曾是幼鱼重要饵料的鲬类所占比例极小,其质量百分比仅占1.81%;而以前未曾记录的虾虎鱼类在食物中所占比例较高, 其质量百分比达50.54%;等足类以前也未曾记录,其出现频率达10.07%.     

Genetic diversity and population structure of spottedtail goby (Synechogobius ommaturus) based on AFLP analysis

Larval dispersal may have an important impact on genetic structure of benthic fishes. To examine population genetic structure of spottedtail goby Synechogobius ommaturus, samples from five different locations of China and Kunsan population in Korea were analyzed by using amplified fragment length polymorphism (AFLP) technology. A total of 253 bands were identified from 91 individuals by 5 primer combinations and the percentage of polymorphic bands was 43.87%. The average gene diversity was 0.0794 ± 0.1470 and Shannon’s information index was 0.1279 ± 0.2138. The pairwise F_st values ranged from 0.022 to 0.201. The results of AMOVA analysis indicated that 90.54% of the genetic variation contained within populations and 9.46% occurred among populations. The gene flow estimates (Nm) demonstrated that different gene flow existed among populations from 0.994 to 11.114. No significant genealogical branches or clusters were recognized on the UPGMA tree. The results support the hypothesis that larval dispersal ability can be responsible for the genetic diversity and population structuring.     

Population dynamics of alien gammarid species in the River Odra estuary

During the period of 1988–2000, three alien gammarid species, i.e. Gammarus tigrinus Sexton, 1939, Pontogammarus robustoides G. O. Sars, 1894, and Dikerogammarus haemobaphes (Eichwald, 1841) were recorded in the Odra estuary. This study, the first record of G. tigrinus and P. robustoides in Poland, focuses on the distribution, abundance, and biomass as well as on population structure of the three new species found in the coastal zone of the estuary. G. tigrinus and P. robustoides were first sampled in the Szczecin Lagoon (mid-part of the estuary) in 1988. The densities of both species were high from the time they were first recorded and exceeded 10 000 ind. m^–2, while the biomass was 25 and 140 g m^–2, respectively. G.tigrinus occurred at higher densities in northern and eastern parts of the Lagoon, while P. robustoides was particularly abundant in the south-eastern part, most heavily affected by River Odra discharge. In 1999, the third gammarid, D. haemobaphes, was recorded in the southern part of the estuary. Both in 1999 and 2000, the species was found in qualitative samples (dredge collections of Dreissena polymorpha) taken from the western branch of the river. As estimated from quantitative samples, densities and biomass in the eastern branch were rather low and did not exceed 150 ind. m^–2 and 2.7 g m^–2, respectively. The Szczecin Lagoon population of G. tigrinus produces at least two generations within a year: a summer one and an overwintering one. The latter is dominated by older and larger specimens. The species may reproduce in the Lagoon from April until November.     

Ontogenetic diet shift, feeding rhythm, and daily ration of juvenile yellowfin goby Acanthogobius flavimanus on a tidal mudflat in the Tama River estuary, central Japan

To ascertain the feeding habits of benthic juvenile yellowfin goby Acanthogobius flavimanus, the gut contents of 599 specimens (15–41 mm in standard length, SL), collected on a tidal mudflat in the Tama River estuary throughout the diel cycle, were examined. The major prey items changed from harpacticoid copepods to errant and sedentary polychaetes at ca. 20 mm SL. Prey width increased with fish size. Fish of 26–28 mm SL fed mainly from sunset to morning, with highest feeding intensity during twilight hours and/or high tide. Based on the gut evacuation rate estimated from a forced feeding experiment in the laboratory and data for the diel change of mean gut-content volume in the field, the daily ration of juvenile yellowfin goby (26–28 mm SL) was calculated to be 13.8 mm³ fish⁻¹ day⁻¹. This volume is approximately equivalent to 3.9 individuals of the errant polychaete Ceratonereis erythraeensis (9.7 mm in body length, BL) or 8.1 individuals of the sedentary polychaete Prionospio japonica (14.8 mm BL), both species occurring abundantly on the mudflat during the study.     

Effects of saltmarsh invasion by Spartina alterniflora on arthropod community structure and diets

Invasive plants strongly affect physical and biotic environments of native ecosystems. Insects and other arthropods as one of the major components of many ecosystems are very sensitive to subtle changes in abiotic and biotic environments. We examined the effects of exotic Spartina alterniflora invasion on community structure and diets of arthropods in a saltmarsh previously dominated by native Phragmites australis in Yangtze River estuary through net sweeping and plant harvesting methods and stable isotope analysis. Our results showed that diversity indices were not significantly different between exotic and native plant communities, but the total abundance of insects estimated through plant harvesting method was found to be lower in Spartina monoculture than that in Phragmites monoculture. Community structure of insects in Spartina monoculture was dissimilar to that in Phragmites monoculture and Phragmites–Spartina mixture. Moreover, stable carbon isotope patterns of arthropods were significantly different between Phragmites and Spartina monocultures. Although some native arthropods (perhaps generalists) shifted their diets, many native taxa did prefer Phragmites to Spartina even in Spartina monoculture. Spartina invasions resulted in reduced abundances of some arthropds, and increased dominance of others feeding preferably on Spartina. This study provides evidence that invasive plants can change the community structure and diets of native arthropods, which will eventually alter the arthropod food web, and affect the integrity and functioning of native ecosystems within a nature reserve that has been set aside for conserving the native biodiversity and maintaining the ecosystem integrity. In this sense, Spartina invasions in the Yangtze River estuary need to be managed appropriately.     

Distribution and diet of the roughskin sculpin, <Emphasis Type="Italic">Trachidermus fasciatus</Emphasis>, larvae and juveniles in the Chikugo River estuary,Ariake Bay,Japan

Larvae and juveniles of the roughskin sculpin Trachidermus fasciatus were collected during four cruises in March and April 2001 to study the distribution and diet of the fish in the Chikugo estuary in the northern Ariake Bay, Japan. Sampling was conducted at seven stations covering an area approximately 30 km in length along the estuary, with salinity ranging from nearly 0 to about 30 PSU. Gut contents were analyzed by separating, identifying, and counting the prey organisms. Plankton samples were collected during each cruise to study the numerical composition and abundance of copepods in ambient water. A total of 1790 larvae and juveniles of T. fasciatus were collected; they were distributed in the five uppermost stations, covering approximately 20 km and ranging in salinity from 0.4 to 27.4 PSU. The fish fed almost exclusively on a single calanoid copepod species, Sinocalanus sinensis, which was numerically the most abundant in the ambient water at the upper part of the Chikugo River. At the lower part of the river, the fish positively selected S. sinensis while negatively selecting other species. T. fasciatus larvae experienced a high proportion of empty guts and low feeding intensity at around 9.0 mm body length, which appears to be associated with commencement of exogenous feeding. The proportion of empty guts reduced sharply at subsequent stages and was accompanied by an increase in feeding intensity. The oligohaline and mesohaline areas are important nursery grounds, and S. sinensis is an important prey copepod species for the larval and juvenile T. fasciatus in the Chikugo estuary.     

Local competitive effects of introduced Spartina alterniflora on Scirpus mariqueter at Dongtan of Chongming Island, the Yangtze River estuary and their potential ecological consequences

Dongtan of Chongming Island, Shanghai, China is a wetland of international importance, in which dominant vegetation is Scirpus mariqueter community that supports a great diversity of bird species. Spartina alterniflora, native to the eastern and gulf coasts of the USA, was intentionally introduced to the tidelands of Dongtan in May 2001. Field work were conducted at Dongtan from March 2002 to May 2003 to determine how introduced S. alterniflora affects S. mariqueter population dynamics. The results obtained here show that S. alterniflorahad strong competitive effects on S. mariqueter, and that the introduction of S. alterniflora to S. mariqueter community resulted in a significant decreases of S. mariqueter's abundance, coverage, seed and fresh corm output after two growing seasons. A concomitant consequence might be the decline in bird diversity. It is suggested that further introduction of S. alterniflora should be avoided to conserve the wetlands and their associated birds. A plan for controlling further spread of existing S. alterniflora populations in the Yangtze River estuary is urgently needed.