The Significance of Meander Restoration for the Hydrogeomorphology and Recovery of Wetland Organisms in the Kushiro River,a Lowland River in Japan

The meanders and floodplains of the Kushiro River were restored in March 2011. A 1.6‐km stretch of the straightened main channel was remeandered by reconnecting the cutoff former channel and backfilling the straightened reach, and a 2.4‐km meander channel was restored. Additionally, flood levees were removed to promote river–floodplain interactions. There were four objectives of this restoration project: to restore the in‐stream habitat for native fish and invertebrates; to restore floodplain vegetation by increasing flooding frequency and raising the groundwater table; to reduce sediment and nutrient loads in the core wetland areas; to restore a river–floodplain landscape typical to naturally meandering rivers. In this project, not only the natural landscape of a meandering river but also its function was successfully restored. The monitoring results indicated that these goals were likely achieved in the short term after the restoration. The abundance and species richness of fish and invertebrate species increased, most likely because the lentic species that formerly inhabited the cutoff channel remained in the backwater and deep pools created in the restored reach. In addition, lotic species immigrated from neighboring reaches. The removal of flood levees and backfilling of the formerly straightened reach were very effective in increasing the frequency of flooding over the floodplains and raising the water table. The wetland vegetation recovered rapidly 1 year after the completion of the meander restoration. Sediment‐laden floodwater spread over the floodplain, and approximately 80–90% of the fine sediment carried by the water was filtered out by the wetland vegetation.     

The Ability of Aquatic Macrophytes to Assess Fish Farm Pollution in Two Salmon Rivers

The wastewater from freshwater fish farming is responsible for important water quality modifications in receiving ecosystems. These point source pollution cause local problems for the management of the freshwater environment, especially in salmon rivers. The aim of this paper is to study the relationship between plant communities and environmental factors in two rivers basins on which seven fish farms are located and to assess the relative part of water pollution compared to other environmental factors involved in water plant distribution. The disturbance due to fish farming wastewater increased both richness and diversity of aquatic plant communities and modified the distribution of 11 aquatic macrophytes. Nevertheless, the main factors involved in the aquatic plant distribution in the whole data set were not the location upstream or downstream from one point source pollution but the belonging to one river system and the habitat physical features. Relevant prediction of macrophytic communities is a useful tool for bioindication purposes but several groups of variables that manifest themselves at different spatial levels must be considered.     

Stream degradation,fish abundance and the potential viability of ornamental fisheries in south-western Cameroon

Fifteen sites on nine second- and third-order streams in the Mount Cameroon area, with varying degrees of human disturbance, were sampled during wet and dry seasons over 21 months in 2003–2005 to estimate their potential for sustainable exploitation of ornamental fishes. In total, 35 species of fish representing 22 genera and 14 families were captured. By biotope, fish populations per 20 m averaged 528 ± 318.5 fish (8.0 ± 3.02 species) in runs, 86 ± 60.9 fish (2.4 ± 1.06 species) in riffles and 819 ± 480.0 fish (7.8 ± 3.15 species) in pools. Riffles contained significantly fewer individuals and species than either runs or pools. Shannon's index was similar for runs and pools, averaging 1.646 ± 0.429 and 1.548 ± 0.345, respectively, but differed significantly for riffles, averaging 0.652 ± 0.473. There were no significant differences in number of individual fish, number of species or Shannon's index among stream order or season, reflecting the stability of these ecosystems throughout the year. Regression of number of fish per 20 linear m of stream, number of species and Shannon's index against a subjective scale related to stream degradation was significant. In particular, the polluted Limbe River sites had significantly fewer individual fish, fewer species and a lower Shannon index across all biotopes than other sites. Fishing efficiency of local gears was estimated at 27% for easily captured species and 14% for the more difficult ones, and could be used to make relative estimates of fish abundance as a means of monitoring changes in fish abundance. Although species diversity in south-western Cameroon was high, typical of tropical streams globally, total abundance was low, and therefore it is unlikely that a profitable ornamental fish trade could be sustained on the basis of fish captured exclusively from the wild.     

2000—2015年拉萨河流域NPP时空变化及驱动因子

拉萨河流域是西藏政治、经济和文化核心区,具有青藏高原典型的高寒湿地及西藏主要的耕作区,受人类活动及气候变化的影响,流域生态安全及生态健康面临威胁和破坏。植被净初级生产力（NPP）作为衡量生态系统健康的重要指标,能够反映生态系统的可持续发展。利用2000-2015年MODIS-NDVI数据,基于光能利用率模型估算了拉萨河流域的NPP,分析了NPP的时空格局、动态变化特征及NPP与气候因子的相关性,探讨了影响NPP变化的驱动因子并明确了驱动分区。结果表明：近16年拉萨河流域NPP年均值为165.614 gC m^-2 a^-1,总体分布具有明显的空间异质性,与该地区植被类型的分布规律相似,不同植被类型的NPP存在差异。NPP变化在总体上呈下降趋势,平均年变化趋势斜率为-1.804 gC m^-2 a^-1。NPP与气温和降水的相关性具有明显的地域性差异,草本湿地与气温呈显著负相关,灌丛与降水呈显著正相关。NPP变化受气候因子驱动的区域占比20.81%,非气候因子占比79.19%。     

A historical view of schistosomiasis japonica in the Chikugo river basin. What can we learn from autopsy?

Three hundred and forty-nine autopsy cases of schistosomiasis japonica were divided into two groups, based on the pathomorphology. Frequent regressive hepatic lesions such as active schistosomal lesion and destruction of limiting plates characterized the first group. The second group showed reparative hepatic lesions such as regeneration of the collapsed parenchyma, newly formed limiting plates and subsequent narrowing and disappearance of fibrous septa. Complications of liver cirrhosis and hepatocellular carcinoma related to viral hepatitis B and/or C also increased. Clonorchiasis was consistently found in both groups.     

Optimum energy intake and gross efficiency of energy conversion for brown trout, Salmo trutta, feeding on invertebrates or fish

1. The chief objectives were to determine the daily optimum energy intake ( C OPT cal day−1) for growth and the gross efficiency ( K G%) for converting energy intake into growth for brown trout, Salmo trutta . Energy budgets for individual fish were obtained from experiments with 292 trout (initial live weight 1–318 g) bred from wild parents, and kept at five constant temperatures (5, 10, 13, 15, 18 °C) and 100% oxygen saturation. Most trout (252) were fed over a period of 42 days on a fixed ration of shrimps, Gammarus pulex , the ration levels varying between zero and maximum, but 40 of the larger trout were fed to satiation on freshly-killed sticklebacks ( Gasterosteus aculeatus ).
2. Energetics models developed in earlier studies on the same data were summarized briefly and were used to predict the relationship between the change in the total energy content of a trout ( C G cal day−1) and its energy intake ( C IN cal day−1), and hence to estimate C OPT. The models were also used to predict the relationship between K G and C IN. In both comparisons, there was good agreement between observed values from the experiments and expected mean values predicted from the models. For trout feeding on invertebrates, C OPT lay closer to the maximum, rather than the maintenance, energy intake. When the diet changed from invertebrates to fish, there was a marked increase in C IN, C G and K G.
3. For trout feeding on invertebrates, K G exceeded 30% within 7–11 °C, with a maximum K G of 31.8% at 8.9 °C. For piscivorous trout, K G exceeded 30% within 4–16 °C and 40% within 6.5–12 °C, with a maximum K G of 41.8% at 9.3 °C. These differences were discussed in relation to the results of previous workers, and the models used in the present study provided a method of exploring the limitations of the ' K -line' hypothesis for the relationship between K G and C IN.     

Responses of Fish to Experimental Introduction of Structural Woody Habitat in Riffles and Pools

The declining condition of river systems associated with rapid development of human societies has led to substantial declines in fish diversity. One cause of decline is the loss of in‐stream Structural Woody Habitat (SWH), an important component of stream ecosystems, particularly as fish habitat. As a result there has been an increase in the number of rehabilitation programs that introduce SWH into rivers. This paper assesses fish responses to SWH introduction in riffles and pools in the Hunter River, eastern Australia, using a Multiple‐Before‐After‐Control‐Impact (MBACI) experimental and analytical design. In the riffle experiment, species richness was comparable among all control and treatment riffles across the entire study period. However, there were significant differences in assemblage structure, fish abundance, and biomass between control and treated riffles. The introduction of SWH (bank embedded deflector jams) appeared to create additional habitat which was utilized by one native fish species (Retropinna semoni—Australian smelt) and one alien species (Gambusia holbrooki—mosquito fish). In pools there were no significant changes in fish species richness, abundance, or biomass following introduction of SWH (pool jams). These findings have important practical and cost implications in terms of the design and implementation of rehabilitation strategies using SWH to restore fish assemblages in degraded streams.     

Importance of phytoplankton carbon to heterotrophic bacteria in the Ohio,Cumberland, and Tennessee rivers,USA

The flux of carbon and nutrients through aquatic systems is largely dependent upon interactions between autotrophic and heterotrophic processes. As a means of assessing the relative importance of autotrophy and heterotrophy in large rivers, we compared phytoplankton production, heterotrophic bacterial production and community respiration in three regulated rivers of the Midwestern USA. Samples were collected monthly (March to December 1999) from impoundments of the Ohio (McAlpine Pool), Cumberland (Lake Barkley), and Tennessee (Kentucky Lake) Rivers. Bacterial production was tightly coupled to phytoplankton production at each site (r ² = 0.63–0.85). Ratios of phytoplankton production to bacterial production ranged from <1 to 15 in the Tennessee and Cumberland Rivers and 2 to 90 in the Ohio River. The ratio of primary production to community respiration (P:R) ranged from 0.03 to 2.76 across all sites, with average P:R values lower in the Ohio River (0.14) than the Tennessee River (0.39) and the Cumberland River (1.10). P:R values above unity (P > R) were observed only in the Tennessee and Cumberland Rivers during seasonal (April–July) spikes in primary production. We estimate that 3, 6, and 20% of annual bacterial carbon requirements were met by exudates from in situ phytoplankton in the Ohio River, Tennessee River, and Cumberland River, respectively. Our findings indicate that heterotrophic bacteria were largely dependant upon allochthonous carbon. Autochthonous sources provided supplemental organic matter (up to 40% of bacterial carbon demand) during summer low flow. Handling editor: J. Padisak     

Diel distribution patterns of fishes in a temperate large lowland river

During the day, juveniles and typical inshore species in the lower Oder River, Germany, inhabited the littoral (0·05–1·50 m deep) while potamal species inhabited the mid‐channel (40–100 m from the banks). During the night, two behavioural groups were distinguished: 1) potamal species and large individuals of other species, moved from offshore to the littoral, and 2) nocturnal foraging species, became active and increased in inshore and offshore habitats. Inshore, the most significant differences at night was the increasing density of silver bream Blicca bjoerkna increasing both total biomass and total length of fishes caught. Offshore, the increasing density of whitefin gudgeon Gobio albipinnatus at night was most significant. Additional night electrofishing improved the assessment of the abundance, age and size structure of typical potamal fish species. It should be incorporated in large river fish monitoring programmes.     

Spatial and seasonal distribution patterns of fish assemblages in the Río Champotón, southeastern Mexico

Río Champotón in the Yucatán Peninsula is within the Usumacinta Province, the most diverse in fish fauna in Mexico, and is part of the Mesoamerican hotspot, with high endemism and exceptional habitat loss. The spatial and seasonal variability of its fish fauna and their relation to physical habitat characteristics were studied, finding 53 taxa. Canonical correspondence analysis shows salinity, distance from the river mouth, and substratum type differentiate an estuarine and a freshwater region. Fish fauna replacement was observed, with taxa exclusive to each region: 26 estuarine and 27 freshwater species. Six freshwater species enter the estuarine region when the high river flow depletes salinity. Estuary showed greater seasonal differences in specific richness than the freshwater region, which have sites with higher local specific richness. Despite its small drainage, Río Champotón has a highly diverse fish fauna and some areas are affected by human activity and the hurricane season. Its conservation is of critical importance.