Applying Habitat Environment Variables of Upper Creeks to Evaluate Ecological Carrying Capacity Index of Fish Species in Dry Seasons
Date Issued
2015
Date
2015
Author(s)
Su, Tzu-Chieh
Abstract
The purpose of this study is to analyze the habitat environmental variables affecting dry-season creek fish, and evaluate ecological carrying capacity index (ECCI) in dry-season creeks. The research targeted on seven creeks in Taiwan which have less contamination and more ecological potential resoration. The samples were conducted in seven creeks in Taiwan. By collecting the environmental variables and the fish-distribution variables, this main research determined ECCI formula by 214 study sites during dry seasons from January 2006 to April 2008. After investigating in the field, the target fish species could be found at almost all sites in dry seasons. Six target fish species were Nile mouthbreeder (Tilapia), Acrossocheilus paradoxus, Microphysogobio brevirostris, Onychostoma barbatulum, Rhinogobius brunneus, and Rhinogobius gigas. Analyzing fish distributions by statistics, the research concluded that five fish body variables (minimum body length, maximum body length, difference length (difference between minimum body length and maximum body length), average length, and total fish number) would change notably by different creeks (spatial scale), and three fish body variables (minimum body length, average length, and total fish number) had notable differences in different dry-season months (temporal scale). This research considered 10 environmental variables: water depth of habitat, water width, water length, pH, electrical conductivity, water temperature, current water velocity, rainfall, elevation, and substrate diversity. Pearson’s correlation coefficient matrix and three-factor loading plots showed that current flow velocity, rainfall, and elevation affected on fish variables similarly, and water length (logarithmic) and water width (logarithmic) had the positive and similar influences in fish variables. Using the principal component analysis (PCA), varimax rotated factor analysis (FA), and the regression in product-exponential model (PEM), ECCI was formulated by these 10 environmental variables. In brief, ECCI was reasonable and calculated simply by the environmental variables of fish habitats. Habitat evaluation levels were classified 5 groups, namely, very poor habitat, poor habitat, fair habitat, good habitat, and then very good habitat. The results of this study can be applied extensively to evaluate the conditions of fish habitats in dry-season creeks for habitat recovery projects. This study is useful for fish conservation and restoration in dry-season creeks in Taiwan
Subjects
dry-season
fish species
habitat assessment
carrying capacity
ecological carrying capacity index
factor analysis
principal component analysis
Type
thesis
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