Jian Ping Suen

Investigating the causes of fish community change in the Dahan River (Taiwan) using an autecology matrix

Recent work in river restoration and water resources management has seen the need to change the focus of analysis from reach to watershed scales to better define causes of watershed impairment. However, comprehensive investigations at a watershed scale are hindered by difficulties in using reach data that was collected for analysis at small spatial and short temporal scales. This is especially true for ecological and biological data. The approach assembles assessment and monitoring data and uses an autecology matrix to identify the changes in environmental and ecological conditions that may be associated with community change over spatial and temporal scales appropriate for ecosystem analysis in watersheds. The analysis uses a weight-of-evidence approach based on the percent of the community associated with a matrix factor. We have used the autecology matrix to examine historical fish community data from the Dahan River, Taiwan. The results show that the method provides an improved understanding of historical influences on fish community structure and supports a process-based analysis of community change over watershed scales and historic time periods. Further the method helps identify habitat requirements for the fish communities at each sampling site, supporting management and ecological restoration objectives.

Potential impacts to freshwater ecosystems caused by flow regime alteration under changing climate conditions in Taiwan.

Observed increases in the Earth’s surface temperature bring with them associated changes in precipitation and atmospheric moisture that consequentially alter river flow regimes. Climate-induced flow regime changes are examined using the Indicators of Hydrologic Alteration. This article uses observed daily streamflow data to examine the flow regime alteration and how these changes might potentially affect freshwater ecosystems. Flow data from 23 gauging stations throughout Taiwan show that the annual extreme water conditions (1-, 3-, 7-, 30-, 90-day annual minima or maxima) have increased alteration compared to baseline periods (1961–1990). Specifically, more severe flood and drought events occur in the period after 1991 than the period from 1961 to 1990. The frequency and duration of flood and drought events also show increased fluctuation. Flow regimes are currently being altered by stressors that will continue into the foreseeable future and it is also happing elsewhere in the world. Aquatic organisms not only need to defend themselves from anthropogenic damage to the river system, but also face the on-going threat from climate change-induced thermal and flow regime alteration. This article raises this issue so that water resources managers may identify precautionary measures that reduce the cumulative effects of both anthropogenic flow alteration and changing climate conditions.

Developing fish community based ecohydrological indicators for water resources management in Taiwan

With concerns about the maintenance of both aquatic communities and flow conditions, a number of hydrologic indicators have been developed. These indicators are generally based on the development of hydrologic statistics for flows that are important to the maintenance of aquatic ecosystems. Although the hydrologic basis for indicators is well defined by common techniques in stochastic hydrology, the basis for ecological integration is still being developed. A critical evaluation of hydrologic indicators intended to protect aquatic ecosystems finds that proposed indicators are based more on standard hydrologic statistics and measures of hydrologic alteration than the habitat needs and ecological requirements of local or desired aquatic communities. We argue that hydrologic indicators are not ecohydrological indicators unless direct connections between flow events and aquatic community habitat and ecological needs are the basis of the indicator development and selection. In this article, we identify ecohydrological indicators that are based on habitat and ecological needs of fish communities. The indicator identification process is initiated with the analysis of community needs using an autecology matrix. Hydrologic statistics are then selected that are appropriate to the target fish community. The resulting ecohydrological indicators provide a direct connection to fish community flow requirements and the physical habitat conditions and associated ecology and life history needs of fish species.

Integrative Analysis of Water Quality and Physical Habitat in the Ecological Design of Water Resources Projects

Historical approaches to water quality control are finding new challenges as ecosystem issues are addressed in comprehensive water resources management programs. Important issues include the recognition that physical habitat conditions may be more important than water quality when ecosystem sustainability is the management objective. Although past emphasis has been on the control of continuous discharges, modern watershed management recognizes that achieving ecosystem sustainability requires control of runoff events that are variable in volume, timing, and frequency. This paper will explore how physical habitat management plays a dominant role in the determination of the ecosystem sustainability. Physical habitat is the result of an eco-hydro-geomorphic systems integration. This integration recognizes that magnitude, duration, and frequency, particularly in the hydrologic system contributes to an understanding of sensitivity and vulnerability in channel networks. Other topics of discussion include the critical linkages between contaminant concentration, duration of exposure, and frequency of recurrence in a watershed setting where differing levels of habitat stability are related to landscape use. The paper will also explore ecological engineering and associated ecohydrology and ecohydraulics in the development of modern watershed management.

Ecohydrologic indicators for rivers of Northern Taiwan

In recent years, water resources planning and management activities have expanded from narrowly focusing on flood defense, water quantity improvement and quality control to the better integration of ecosystem needs in management protocols. Because ecosystem needs are still subject to discussion, a reasonable surrogate is the use of the natural flow regime. The natural flow regime integrates ecolog ical, geomorphic, and hydrologic functions in a watershed and provides a flow -based approach to protecting ecosystems (ecohydrology). This paper identifies a suite of ecohydrologic indicators, called the Taiwan Ecohydrology Indicator System (TEIS). This system of indicators considers seasonal change, typhoons, and ecological requirements of resident species in hydrologic indicator selection. The final set of 60 TEIS hydrologic indicators captures the magnitude, frequency, and duration characteristics of natural flow regimes. To facilitate use in policy analysis, a reduced set of indicators was selected. This set includes six parameters that can be used to minimize the complexity of optimization procedures and still reflect ecological considerations in decision making and planning.

Integrating ecological flow regimes in water resources management using multiobjective analysis

Water resources management has shifted from flow regulation applications designed to protect public health to applications that include restoration of natural flow regimes and protection of aquatic ecosystems. The ecological flow regime uses a regime-based approach that considers hydrologic variability instead of focusing on identifying flows or flow targets for aquatic ecosystems. It determines environmental flow by embracing the multitude of species within an ecosystem rather than emphasizing a single species. In addition, the ecological flow regime recognizes that flow magnitude, duration, frequency, timing, and predictability must be incorporated into any flow management strategy. This paper provides a multi-objective approach to integrating ecosystem and human needs in water resources management. The ecological flow regime analysis provides a surrogate for ecosystem needs in analyzing the trade-offs with human water usage. The non-dominated sorting genetic algorithm (NSGA II) is used to find the Pareto set of operating rules for evaluation of reservoir operation for the Dahan River basin in Taiwan. It provides decision makers with the trade-offs between shortages in water available for human needs and ecological flow regime maintenance.

Comparing Habitat Suitability Indices (HSIs) Based on Abundance and Occurrence Data

Abstract Suitability-based physical habitat modeling is sensitive to the choice of habitat suitability index. We compared the effects of using abundance versus occurrence data on suitability indices along environmental gradients for four fish species collected by means of prepositioned electrofishing in a mountain stream in southern Taiwan. The results indicate that abundance data provide more sensitive outcomes than occurrence data in terms of both mean values and habitat suitability. The mean values of flow velocity and water depth from the abundance data separated the four fish species into four distinct flow groups and two depth groups; the occurrence data did not produce similar groupings. Habitat suitability curves from the abundance data provided clearer outcomes than those from the occurrence data. The differences were greater for species with differential densities along environmental gradients that were related to species characteristics. Advancements in point abundance sampling methodology, suc...

Reconstructing riverine mesohabitat unit composition using fish community data and an autecology matrix

This research proposes a simplified method for estimating the mesohabitat composition that would favour members of a given set of aquatic species. The simulated composition of four types of mesohabitat units (deep pool, shallow pool, deep riffle and shallow riffle) could guide the design of in-stream structures in creating pool-riffle systems with ecological reference. Fish community data and an autecology matrix are used to support the development of a stream mesohabitat simulation based on regression models for reaches in mid to upper-order streams. The fish community-mesohabitat model results constitute a reference condition that can be used to guide stream restoration and ecological engineering decisions aimed at maintaining the natural ecological integrity and diversity of rivers.

Aquaculture Water Quality Index: a low-cost index to accelerate aquaculture development in Indonesia

Due to a lack of the related data, there were no simple water indexes available for indicating water quality. Motivated by the fact that many lakes and reservoirs in Indonesia have been polluted because of aquacultural activity, this paper proposed a Water Quality Index, called the Aquaculture Water Quality Index (AWQI), and presented the development of practical tool to aid the development of aquaculture in Indonesia. Specific purposes included: (a) providing a brief summary of the assessment results of the existing WQI; (b) developing the AWQI method for applying in an aquacultural context; (c) implementing the AWQI method in Depok Area (Indonesia) as study area. An AHP method was also processed to define the weights of selected water quality parameters: DO, ammonia, pH, and fecal coliform. The AWQI had several features: (a) a low-cost water quality monitoring program that could be used by developing countries; (b) a useful tool for water resource agencies, especially for local agencies, to manage waterbodies and to raise public awareness of water pollution for its data, as its data could be easily understood and interpreted.

Dependency and independency among fish density and electivity indices in a stream fish assemblage

Habitat preferences can be identified from population density and electivity indices, which can be derived from either abundance or occurrence data. This study examined the preference detectability and independency of density and electivity indices from different data sources -- abundance and occurrence. Eight scenarios comprising four fish species along two environmental gradients (flow velocity and water depth) in an undisturbed mountain stream were used in this study. Fish density and seven electivity indices were calculated from abundance and occurrence data for the eight scenarios. The correlation analyses illustrated that abundance electivity indices were positively correlated with density in all eight scenarios while occurrence electivity indices were positively correlated with density in only three scenarios. Electivity indices were positively correlated with each other within the same data quality (abundance or occurrence) but not between. The Chesson’s L index was less correlated with other indices and should be used cautiously. Natural historical traits, such as social interactions among organisms, may affect the preference performance of density and electivity indices. In conclusion, density is a good preference indicator. Abundance electivity indices can represent density while occurrence electivity density should be used cautiously for fast assessment. Three electivity indices, Ivlev’s E and E′ and Jacobs’ D, were recommended for their ease of understanding.