Abundance and Distribution of Fish in the Zilan Stream (Van/ Turkey) Its Relationship with Some Physicochemical Parameters

In the recent decades, river regulation attempts, dams and wastewater discharge have not only influenced the water-quality and physical-habitat-structures of the rivers in a bad way but they have also threatened fish-stocks. The aim of this study is to examine the multi-relationship structure between the fish-species-density living in the Zilan-Stream, the largest stream of Lake-Van, and the physicochemical-parameters in this stream. Fish-density was found out with the records from the 12-stations located on Zilan-Stream. From the stations, water-temperature, habitat-score, pH, conductivity, dissolved-oxygen (DO), phosphate (PO4), nitrate (NO3), turbidity and height values were obtained. The correlation structure of the obtained parameters with fish-density was analyzed by canonical-correspondence-analysis (CCA). CCA axes fully explained the response of fish-density to physicochemical-parameters. As a result of the CCA, it was observed that the species concentrated in environments with less-conductivity and low nitrate/pH levels. Species were hypersensitive to altitude, and were found more intensely at mid/low altitudes. In addition, it was observed that the species concentrated in high-habitat score and oxygen-rich stations. It was observed that the species prefer medium/low temperature more and concentrate in environments with low-solids content. It is expected that the data obtained from this study will contribute to the management of areas to be protected in Zilan-Stream.