Hatchery technology restores the spawning ground of phytophilic fish in the urban river of Yangtze Estuary, China

Abstract

Due to the concrete slope protection projects conducted around urban rivers in many megalopolises, increased attention has been paid to fish biodiversity losses accompanying urban development. Hatchery technology is a promising method for restoring fisheries where spawning substrates are degraded and/or lacking. In the current study, a Phragmites australis stereo artificial floating wetland (SAFW) was constructed in an urban river (Tuanwang River, Shanghai), and palm sheets were laid under the SAFW frame to imitate the spawning grounds for phytophilous fish. Fish species with five spawning types were distinguished from nineteen fish species in the study area. After viscid eggs were found to be attached to the palm sheets, the eggs were distinguished by the subunit of the mitochondrial cytochrome C oxidase I gene. All of the eggs belonged to six fish species: Culter ilishaeformis, Cyprinus carpio, Cyprinus auratus, Cultrichthys erythropterus, Rhodeus sinensis, and Hemiculter leucisculus. Cyprinus auratus and Cyprinus carpio accounted for the vast majority, and the number of these species was significantly greater than that of the other species. Dissolved oxygen and light intensity at the water surface were significantly higher than those at the deep water sites (p < 0.05), and all viscid eggs were inclined to be distributed at water depths of -0.5 and − 1.5 m. The results of redundancy analysis (RDA) showed that both water depth and dissolved oxygen were the main environmental variables in all spawning periods. The current study suggested that the relatively inexpensive P. australis SAFW was a useful hatchery technology for creating spawning grounds for phytophilous fish in urban rivers.