Trophic gradients of two minnow species with similar eco-type and their relations to water chemistry and multimetric biological integrity

Abstract

The objectives of this study were to determine tolerance ranges and trophic gradients of two fish populations of Zacco koreanus (Zk) and Zacco platypus (Zp) in relation to chemical water quality and ecological stream health, based on the biological integrity metric (BIM) model. Seventy-six streams and rivers were sampled for the analysis. The population of Zk had a narrow chemical tolerance with a low phosphorus limit (< 300 μg/L as total phosphorus), whereas the Zp population occurred within a high limit (up to 1,100 μg/L). Similar patterns in the two populations were shown in nitrogen, biological oxygen demand, suspended solids, and other parameters. The population of Zp had significantly (t=5.25, p<0.001) greater chemical tolerance than the population of Zk. The population of Zk had a positive functional relation (R2=0.43, p<0.001) with insectivore species, but the Zp population had negative linear function (R2=0.50, p<0.001), indicating a trophic difference in the food chain of two populations. Application of the biological integrity model indicated that the values of BIM, as an index of ecological health, were significantly greater (t=13.67, p<0.001) in the population of Zk than the population of Zp.