黄河三角洲河道演变与景观格局分析

以黄河三角洲地区东营市部分为研究区域,研究了黄河三角洲河道演变规律与景观格局分布规律,并着重研究了该地区河道演变与景观格局分布的联系。结果表明:近20年间黄河总取水量呈上升趋势;2002~2010年裸地沼泽面积明显减少,植被面积增多。2010~2019年,建设用地面积明显增加;土地利用景观格局的形式从沿海区域开始向内陆演变呈现一定的规律,最外环为海洋、向内依次为是浅海滩涂、滩涂、水产湿地、盐田、旱地、沼泽湿地、植被、建设用地;受季节影响较大的图可以利用ENVI提取其对应的植被覆盖图来消除影响。在NDVI植被归一化指数的基础之上建立植被覆盖图,通过NDVI指数分析植被的长势和营养状况。     

Effect of dietary protein content on growth rate,survival and body composition of juvenile cauque river prawn,Macrobrachium americanum (Bate 1868)

We determined the effect of four concentrations of dietary crude protein, 30.7, 37.2, 41.8 and 46.8% on growth rate, survival and body composition of the juvenile cauque river prawn (Macrobrachium americanum). The prawns were hatched in the laboratory from the spawn of one wild ovigerous female. Prawns consuming 37.2% crude protein reached a final weight of 0.58 g (feed conversion ratio of 2.15), which was significantly better than the other treatments. Survival was 100% in all treatments. Protein content in the diets had no significant effect on whole body proximate composition and amino acid profile. Juveniles consuming the 37.2% crude protein diet grew faster than those fed the other diets. Specific growth rate was adjusted to the two‐slope broken‐line regression analysis model to estimate the optimal protein requirement. In conclusion, these results demonstrated that the 37.2% protein level diet is optimal for juvenile cauque river prawn M. americanum in the experimental conditions of this study.     

Effect of an intensive mechanical removal effort on a population of non‐native rainbow trout Oncorhynchus mykiss in a South African headwater stream

1. Invasions by non‐native species can compromise the conservation value of otherwise pristine headwater streams. While both developed and developing countries recognize this threat, few of the latter have suitable budgets to implement control programmes.
2. This study assessed the effectiveness of a mechanical project to remove non‐native rainbow trout Oncorhynchus mykiss from a 6 km section of the upper Krom River, a small headwater stream in the Cederberg Mountains in South Africa's Cape Floristic Region (CFR).
3. From October 2013 to February 2014, 354 O. mykiss were removed by angling (58%), fyke netting (28%) and gill netting (14%). This resulted in a marked reduction, but not eradication, of the O. mykiss population (fish relative abundance decreased from 0.53 ± 0.09 fish per net per night in October 2013 to 0.21 ± 0.09 fish per net per night in February 2014). Following the cessation of manual removals, the relative abundance of O. mykiss had increased to 0.56 ± 0.18 fish per net per night by March 2016, suggesting that without sustained removal effort, the population will rapidly return to its pre‐removal abundance level.
4. Further work is needed to refine the methodology and test the effectiveness of mechanical removal of non‐native freshwater fish in a variety of ecological settings in the CFR. This approach holds potential for meeting the dual goals of reducing the ecological impacts of non‐native fishes and generating employment opportunities in line with the policy objectives of developing nations.

     

Implications of piscine predator control on the federally listed fountain darter

One strategy for protecting the federally listed fountain darter, Etheostoma fonticola (Jordan & Gilbert), during low flow conditions is the removal of piscine carnivores [in this case, largemouth bass, Micropterus salmoides (Lacepède)]. However, headwater spring communities of the Comal and San Marcos rivers include another potential predator [red swamp crayfish, Procambarus clarkii (Girard)]. Removal of piscine carnivores could produce cascading effects by increasing crayfish consumption of benthic fish. The purpose of this study was to evaluate if piscine carnivore removal will lessen predatory pressure or induce a trophic cascade with crayfish increasing and causing declines in fountain darter. The numbers of fountain darter consumed were quantified among three predator treatments (red swamp crayfish only, largemouth bass only and red swamp crayfish and largemouth bass combined) and vegetation treatments (vegetated and non‐vegetated) at three temperature regimes (18, 22, 27°C). Vegetation had no effect on fountain darter predation. Among temperature trials, largemouth bass only and red swamp crayfish and largemouth bass combined consumed similar numbers of fountain darter, and red swamp crayfish only consumed the least numbers of fountain darter, except at 22°C. Largemouth bass did not consume more red swamp crayfish than fountain darter. Therefore, largemouth bass removal appears to be a viable option for reducing fountain darter predation during periods of low flow.     

基于SPEI_PM指数的渭河流域气象干旱时空演变特征

利用渭河流域25个气象站点1980−2018年月值气象数据集，基于Penman-Monteith蒸散模型计算多个时间尺度的标准化降水蒸散发指数（SPEI），分析渭河流域气象干旱的演变、趋势、影响范围、发生频率和持续时间等时空变化特征，以期为渭河流域防灾减灾管理提供科学依据。结果表明：（1）近39a来渭河流域有明显的干湿周期变化，但整体上呈变干的趋势，干旱时段主要集中在1995−2009年，其中以2000−2009年的干旱站次比最大，平均达到36%，且干旱持续时间最长，约3.6个月，1980−1989年干旱持续时间最短，约1.6个月；（2）渭河流域秋季总体呈湿润变化趋势，而春季和夏季干旱在不断加剧，是区域年际干旱的主要驱动力；（3）渭河流域干旱以危害性较小的轻中旱为主，但2000年前后出现严重及极端干旱的站次相对较多，其中1997年研究区内发生的干旱程度较高，影响范围较广；（4）不同时间尺度各等级干旱发生频率的变化规律表现一致，均呈现出干旱等级越高发生频率越低的态势，且极端干旱在年际尺度内发生次数较为频繁，从空间上看渭河流域东北部是干旱多发区。总之，近39a来渭河流域总体干旱较为严重的时段为2000−2009年，且研究区内干旱呈北重南轻特征，因此北部地区仍需加强防灾管理。     

苏州城区河道大型水生生物分布特征

为研究苏州城区河道大型水生生物时空分布特征,于2020年5月开始,对苏州古城区主要河道23个断面的大型水生生物及水质指标进行为期一年监测,分析其理化因子时空分布差异,并探讨与大型水生生物相关的影响因素,体现苏州河道恢复程度。结果表明,水温、pH、溶解性总固体、电导率、溶解氧、透明度与氨氮在不同月份间呈显著性差异（P<0.05）,总氮和总磷在不同月份间具有极显著性差异（P<0.01）。研究期间苏州城市河道中共检出5种沉水植物,10种大型底栖无脊椎动物,7种鱼类。其中沉水植物辛普森指数最高,结构最均匀,各断面中沧浪亭桥玛格列夫指数最高,物种最丰富。有无沉水植物分组间流速呈显著性差异,总氮、氨氮存在极显著差异。大型底栖无脊椎动物有无的河道在流速、水深、透明度和溶解氧存在极显著性差异。按是否存在鱼类对比,水质指标均无显著性差异。冗余分析（RDA）结果也表明,氨氮、水温、溶解氧和透明度是影响城区河道大型水生生物分布的主要水质指标。     

疏勒河流域2001~2010年水足迹动态特征及评价

随着人口增长、城市化进程的发展和社会经济发展,以及全球气候变化等因素的影响,疏勒河地区生态用水不断被挤占,造成地下水位下降,天然植被也因缺水而退化,水资源供需矛盾突出,为了有效改善水资源利用效率,利用水足迹模型研究了疏勒河流域2001~2010年的水足迹动态特征。结果表明:疏勒河流域2001~2010年总水足迹呈增长趋势,人均水足迹从2001年的772.537m3增加到2010年的1 304.476m3。疏勒河流域水资源集约利用度呈增长趋势,从2001年的6.053增加到2010年的10.875,说明疏勒河流域水资源利用效率提高了。疏勒河流域水资源压力指数从2001年的0.447增加到2010年的0.747,说明疏勒河水资源利用压力虽处于水资源可承载范围内,但其水资源压力不断上升。农田灌溉用水和农田种植面积均与农畜产品虚拟水足迹呈显著正相关关系(P0.05)。未来还需从实施节水农业战略等方面提高流域水资源利用效率,以及通过虚拟水贸易方式优化产业结构,以实现疏勒河流域水资源可持续利用和经济社会可持续发展。     

Shedding light on the migratory patterns of the Amazonian goliath catfish,Brachyplatystoma platynemum,using otolith 87Sr/86Sr analyses

1. In the Amazon, migratory catfishes of the genus Brachyplatystoma are apex predators that are important for fisheries and conservation. The life cycle of Brachyplatystoma platynemum Boulenger, 1898 is poorly known, although it has been hypothesized to be very similar to that of Brachyplatystoma rousseauxii Castelnau, 1855, which uses the entire length of the Amazon basin to complete its life cycle (from the Andes to the estuary). This study provides the first data on the migratory patterns of B. platynemum at the individual level using otolith microchemistry.
2. In total, 94 individuals were sampled close to major breeding areas in the Amazon basin (78 fish from the middle and upper Madeira River and 14 fish from the upper Amazon), and their lifetime movements were assessed by measuring variations in ⁸⁷Sr/⁸⁶Sr along transverse sections of their otoliths (ear stones), using laser ablation multi‐collector mass spectrometry (LA‐MC‐ICP‐MS).
3. The migrations of B. platynemum are not as extensive as those of B. rousseauxii, and do not involve natal homing. Furthermore, the estuary is not a nursery area, at least for fish hatched in the Madeira. Nevertheless, B. platynemum migrates several thousand kilometres within the Amazon basin, with transboundary displacements between at least Bolivia, Brazil, and Peru.
4. Current and planned hydroelectric development in the Amazon basin will severely disrupt both migration and access to breeding grounds, ultimately affecting the recruitment and population dynamics of these apex predators.
5. The conservation of B. platynemum is crucial for the stability of the Amazonian aquatic food webs. This requires building effective fish passage on the two existing Madeira dams and considering alternative options to the large‐scale hydropower development in the Amazon basin.

     

Living in an amphidromous world: Perspectives on the management of fish passage from an island nation

1. Amphidromy is a form of migratory life history typified by the reproduction of fish in freshwater environments, the early downstream dispersal of post‐hatch larvae to marine environments, and the return of small‐bodied young juveniles to freshwater environments for growth to adulthood. Island freshwater fish communities are frequently dominated by fish species with amphidromous life histories.
2. Amphidromous life cycles leave fish communities highly susceptible to habitat modification and disruptions to connectivity across marine and freshwater environments. This means that managing waterway connectivity is fundamental to their conservation; however, the unique and often geographically restricted amphidromous communities that characterize many small island nations have received little consideration in the development of strategies for the management of fish passage.
3. The ecology and locomotory capabilities of amphidromous species are often poorly studied, partly because their small size at migratory life stages renders current state‐of‐the‐art in situ biotelemetry methods unsuitable. The small size of fish also means that seemingly small obstructions can severely impede migrations.
4. The steps necessary to advance the management of fish passage for island fish communities are: curating and maintaining barrier inventories; evaluating barrier permeability; developing effective barrier mitigation options; and prioritizing restoration and conservation efforts.
5. New methods for understanding the ecology and locomotory capabilities and behaviour of amphidromous fishes are required to advance the management of fish passage for island fish communities. Fish passage solutions that imitate natural streams, such as those promoted in new guidelines in New Zealand, may be the most effective way of improving waterway connectivity; however, integrated approaches to freshwater fish conservation that account for meta‐population dynamics, in combination with the management of fish passage, are necessary to optimize conservation outcomes for amphidromous species.

     

Detecting the undetectable: Characterization,optimization, and validation of an eDNA detection assay for the federally endangered dwarf wedgemussel,Alasmidonta heterodon (Bivalvia: Unionoida)

1. Environmental DNA (eDNA) assays are valuable tools for monitoring the presence and distribution of cryptic species.
2. Like many freshwater mussels, the numbers of dwarf wedgemussel, Alasmidonta heterodon, have dwindled and its range has diminished. As of its listing in 1993, only 10–20 locations were known to persist out of the 70 Atlantic slope locations known historically.
3. A quantitative polymerase chain reaction (qPCR) assay to detect the presence of A. heterodon was developed that uses two probes to accommodate a single‐nucleotide polymorphism (SNP) in the probe‐binding site within the cytochrome c oxidase subunit I (COI) gene. This SNP defines northern and southern major phylogenetic lineages.
4. The primers match exactly the previously determined COI sequences of 20 dwarf wedgemussel individuals representing Atlantic slope populations from North Carolina, Virginia, Maryland, New York, and New Hampshire. Other than for the qPCR assay described here, these primers can be used for sequencing or metabarcoding to further delineate dwarf wedgemussel populations phylogenetically.
5. A simple eDNA preparation method is introduced using flocculation to concentrate free DNA in solution as well as cellular material (including shed animal cells, bacteria, viruses, and dissolved DNA).
6. In addition to the specific application described here, the methodological approaches used in this study are widely applicable to conservation, including, but not limited to, general aquatic biodiversity, phylogenetic studies, and the detection of pathogenic microbes.