Search Results (7)

Fish play an important role in river ecosystems, and the conservation of their diversity is a common goal worldwide. It is still unclear how fish monitoring programs should be developed in order to rationalize the monitoring of fish diversity in rivers. To help address this issue, we conducted a comparative study of fish species richness obtained through three site-interval monitoring programs (SS1: 3 km interval scheme; SS2: 6 km interval scheme; SS3: 9 km interval scheme) in wadeable rivers in northeastern China. Here, a total of 18 fish species and 4 rare species were collected from 3 rivers. The cumulative species-richness curves showed that SS1 had the highest species richness in a single river and in the whole region, and the species richness gradually decreased with increasing site intervals. The results of the cumulative percentage of species richness indicated that SS1 and SS2 could achieve a level of 80% of potential species richness, while only SS1 could achieve a level of 90% of potential species richness in the Lanhe River (where no rare species were present). However, the results of cumulative species richness per unit of effort indicated that SS2 and SS3 had higher input-output benefits. These results suggested that rare species were more susceptible to monitoring programs and that SS2 was more advantageous in terms of obtaining species richness and cost-effectiveness. This study provides a reliable reference for river fish-monitoring program development. Full article

Fish assemblages inhabiting the Taizi River basin have been severely degraded by anthropogenic disturbances, which weaken the basin’s ecological function and limited revitalization of the northeast industrial base. Long-term ecological rehabilitation has been conducted to restore the fish fauna and improve habitat conditions. To explore fish distribution patterns and key factors after this ecological rehabilitation, a comprehensive and detailed survey of fish fauna was conducted twice in 2021 at 33 sampling sites in the Taizi River. A total of 50 fish species from 13 families were collected, and the dominant species were P. lagowskii, Z. platypus, C. auratus and P. parva. Compared to results reported over the last decade, the increasing trend in fish richness and the change in the longitudinal fish organization were detected. The abundance variation for P. lagowskii, Z. platypus, C. auratus, P. parva, R. ocellatus and H. leucisculus along the upstream to downstream axis contributed most to the fish distribution pattern. Species replacement and addition might have jointly caused the longitudinal changes in the fish fauna, but species replacement was the main underlying mechanism. The canonical correspondence analysis (CCA) results show that the fish structure pattern was mainly shaped by cultivated land coverage and urban land coverage. Our study provides reference sites for future fish-based bioassessment and implications for region-specific management in the Taizi River. Full article

Conservation strategies for a reliable set of umbrella species should benefit many co-occurring species and will improve conservation efficiency. The umbrella index (UI) is increasingly applied for umbrella species selection in different ecosystems. We developed a modified river UI to select potential macroinvertebrate umbrella species with a combination of 69 sites in the Taizi River Basin of northeast China. Calculation of UI and comparison of biotic indices between sites of presence and absence of umbrella species were performed to make the final umbrella species list. The umbrella scheme, based on the proportion and composition of sites supporting the confirmed umbrella species, was introduced to illustrate the conservation effectiveness. A total of eight umbrella species were obtained and all of them were aquatic insects, such as caddisfly and mayfly larva. Umbrella schemes supporting the top umbrella species, hosted the majority of co-occurring species and only 7% of beneficiary species were missed by the umbrella schemes of 70% effort. The positive relationship between abundance of co-occurring species and umbrella species, validated the ability of umbrella species to confer protection and co-existence of co-occurring species, and thus indicated the effectiveness of umbrella species conservation. Co-occurring species were located close to umbrella species in ordinations, suggesting they respond to similar environmental variables characterized by high flow velocity, dissolved oxygen and pebble-covered substrate. On account of good performance of umbrella schemes in our study, UI with further improving methods should be promoted for selection of umbrella species and decision for optimizing of conservation sites in the future. Full article

Interactions between groundwater and surface water (GW-SW interactions) play a crucial role in the hydrological cycle; thus, the quantification of GW-SW interactions is essential. In this study, a cumulative exchange fluxes method based on mass balance theory is proposed for a stream-aquifer system. This method determines the curve of cumulative fluxes through the water balance term, which can characterize GW-SW interactions, determine the amount of exchange fluxes, and reveal the dynamic process of interactions. This method is used in a reach of the Taizi River Basin, and the GW-SW interactions observed in 2016 are categorized into seven stages and four types (natural controlled, reservoir and irrigation controlled, irrigation controlled, and irrigation hysteresis type). The natural recharge in the study reach is approximately 3.03 × 10⁵ m³·day⁻¹, and the increase caused by irrigation is 7.8–13.87 × 10⁵ m³·day⁻¹. After the irrigation stops, the impact can be sustained for 48 d with an increase of 3.03 × 10⁵ m³·day⁻¹. The most influential factor of the results is the runoff coefficient. The method is applicable to the stream in the plains with upstream and downstream flow monitoring data and can be used to analyze complex GW-SW interactions under the conditions of reservoir storage and agricultural irrigation. The analysis results will provide guidance for the other study of GW-SW interactions in this reach. Full article

Biological functional traits help to understand specific stressors that are ignored in taxonomic data analysis. A combination of biological functional traits and taxonomic data is helpful in determining specific stressors which are of significance for fish conservation and river basin management. In the current study, the Taizi River was used as a case study to understand the relationships between the taxonomic and functional structure of fish and land use and water quality, in addition to determining the thresholds of these stressors. The results showed that taxonomic structure was significantly affected by the proportion of urban land and specific conductivity levels, while functional metrics were influenced by the proportions of farmland and forest. Threshold indicator taxa analysis found that Phoxinus lagowskii, Barbatula barbatula nuda, Odontobutis obscura, and Cobitis granoei had negative threshold responses along the gradients of urban developments and specific conductivity. There was a significant change in fish taxonomic composition when the proportion of urban land exceeded a threshold of 2.6–3.1%, or specific conductivity exceeded a threshold of 369.5–484.5 μS/cm. Three functional features—habitat preference, tolerance to disturbances, and spawning traits—showed threshold responses to the proportion of farmland and forest. The abundance of sensitive species should be monitored as part of watershed management, as sensitive species exhibit an earlier and stronger response to stressors than other functional metrics. Sensitive species had a positive threshold response to the proportion of forest at 80.1%. These species exhibited a negative threshold response to the proportion of farmland at 13.3%. The results of the current study suggest that the taxonomic and functional structure of fish assemblages are affected by land use and water quality. These parameters should be integrated into routine monitoring for fish conservation and river basin management in the Taizi River. In addition, corresponding measures for improving river habitat and water quality should be implemented according to the thresholds of these parameters. Full article

Identifying priority zones for river restoration is important for biodiversity conservation and catchment management. However, limited data due to the difficulty of field collection has led to research to better understand the ecological status within a catchment and develop a targeted planning strategy for river restoration. To address this need, coupling hydrological and machine learning models were constructed to identify priority zones for river restoration based on a dataset of aquatic organisms (i.e., algae, macroinvertebrates, and fish) and physicochemical indicators that were collected from 130 sites in September 2014 in the Taizi River, northern China. A process-based model soil and water assessment tool (SWAT) was developed to model the temporal-spatial variations in environmental indicators. A support vector machine (SVM) model was applied to explore the relationships between aquatic organisms and environmental indicators. Biological indices among different hydrological periods were simulated by coupling SWAT and SVM models. Results indicated that aquatic biological indices and physicochemical indicators exhibited apparent temporal and spatial patterns, and those patterns were more evident in the upper reaches compared to the lower reaches. The ecological status of the Taizi River was better in the flood season than that in the dry season. Priority zones were identified for different hydrological seasons by setting the target values for ecological restoration based on biota organisms, and the results suggest that hydrological conditions significantly influenced restoration prioritization over other environmental parameters. Our approach could be applied in other seasonal river ecosystems to provide important preferences for river restoration. Full article

Numerous studies have sought to clarify the link between biological communities and environmental factors in freshwater, but an appropriate model is still needed to predict the effect of water quality and hydromorphology improvement on biological communities and to provide useful information for ecological restoration planning. In this study, a support vector machine (SVM) was used to predict the bio-indicators of an aquatic ecosystem (i.e., macroinvertebrates, fish, algae communities) in the Taizi River, northeast China. Environmental factors, including physico-chemical (i.e., dissolved oxygen (DO), electricity conductivity (EC), ammonia nitrogen (NH₃-N), chemical oxygen demand (COD), biological oxygen demand in five days (BOD₅), total phosphorus (TP), total nitrogen (TN)) and hydromorphology parameters (i.e., water quantity, channel change, morphology diversity) were used as the input variables to train and validate the SVM model. The sensitivity of the input variables for the prediction was examined by removing a variable from the SVM model. Results revealed that the SVM model reproduced the variation in bio-indicators of fish and algae communities well, based on the input variables. The sensitivity for the input variables applied in SVM showed that in the Taizi River the most sensitive variables for predicting macroinvertebrate and algae communities were channel change, DO, TN, and TP, while the most sensitive variables for predicting fish communities were DO and BOD₅. This study proposed an effective method for predicting biological communities, which will improve freshwater quality and hydromorphology management schemes. The outputs can guide the decision-making process in river basin management, support the prioritization of actions and resource allocation, and help to monitor and evaluate the effectiveness of interventions. Full article