Abstract
Fish species tolerance used as a component of fish-index of biological integrity (F-IBI) can be problematic as it is usually classified using the historical data, data from literature or expert judgments. In this study, fish assemblages, water quality parameters and physical habitat factors from 206 sampling sites in the Huntai River Basin were analyzed to develop tolerance indicator values (TIVs) of fish based on a (Fb-TIVs) and the weighted averaging (WA) method (FW-TIVs). The two quantitative methods for fish tolerance were then compared. The FW-TIVs and Fb-TIVs of fish species were calculated separately using a WA inference model based on ten water quality parameters (WT, pH, DO, SC, TDS, NH3, NO2−, NO3−, TP, Cl−, and SO42−), and six biological traits (lithophilic spawning, benthic invertivores, cold water species, equilibrium or periodic life history strategies, families of Cottidae, and species distribution range). Fish species were then classified into biological traits approach three categories (tolerant species, moderately tolerant species, and sensitive species). The results indicated that only 30.3% fish species have the same classification based on FW-TIVs and Fb-TIVs. However, the proportion of tolerant species based on two methods had a similar response to environmental stress, and these tolerant species were correlated with PCA axes 1 site scores obtained by (FW-TIVs, p < 0.05, R2 = 0.434; Fb-TIVs, p < 0.05, R2 = 0.334) and not correlated with PCA axis 2 site scores (FW-TIVs, p > 0.05, R2 = 0.001; Fb-TIVs, p > 0.05, R2 = 0.012) and PCA axis 3 site scores (FW-TIVs, p > 0.05, R2 = 0.000; Fb-TIVs, p > 0.05, R2 = 0.013). The results of linear regression analyses indicated that Fb-TIVs can be used for the study of fish tolerance. Fish tolerance assessments based on FW-TIVs requires long-term monitoring of fish assemblages and water quality parameters to provide sufficient data for quantitative studies. The Fb-TIV method relies on the accurate identification of fish traits by an ichthyologist. The two methods used in this study can provide methodological references for quantitative studies of fish tolerance in other regions, and are of great significance for the development of biological assessment tools.
Highlights
Aquatic organisms are commonly used as biological indicators of river ecosystem health [1]and are used to assess the state of a system relative to its reference conditions
Fish tolerance classification based on Fb -tolerance indicator values (TIVs) values found that 26 species (78.8%) were tolerant, six species (18.2%) were moderately tolerant and a single species (3%) was sensitive
One-way analysis of variance (ANOVA) revealed that there was a significant different between fish tolerance classification based on the two methods (F = 28.5, P = 0)
Summary
Aquatic organisms are commonly used as biological indicators of river ecosystem health [1]. The degree of sensitivity and capacity of a species to adapt to changing environmental conditions is often species specific [12] This subjective classification ignores the interspecific differences of tolerance within the same genus. Fish species may be in the same genus, a temporal small-scale disturbance can separate their spatial niches and change their living environment [14] This indicates that fish species within a genus may have different variability or environmental tolerance under the same circumstances. Fish tolerance assessment based on FW -TIVs requires a large amount of data on individual fish species and environmental stress factors, which requires long-term aquatic ecology monitoring. This data is not currently available for many areas. The quantitative results of fish tolerance arising from this study will be of great use in the development of fish diversity tools
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