Due to weather or water quality, we occasionally see dead fish by the river. This kind of fish can't be used again, to prevent the toxins in the fish from leaking into the human body. On May 18th, 221, when law enforcement officers of Jiedong Branch of Jieyang City Ecological Environment Bureau inspected the North River of Rongjiang River, they suddenly found a large number of dead fish in Jiedong section of the North River of Rongjiang River. This large number of dead fish incidents has attracted the attention of law enforcement officers. They immediately launched an investigation and reported it to the higher authorities. After receiving the report, Jieyang leaders attached great importance to this matter and conducted a comprehensive investigation of the rivers in Rongcheng District, Jiedong District, Airport Economic Zone and its jurisdiction. In addition, experts from local eco-environmental protection bureau, agriculture and rural areas, water conservancy and meteorological departments were convened to conduct research on this matter. After a series of investigations, it was finally determined that the river section where the dead fish appeared was from the Beihe Bridge in Rongjiang to Shuangxizui, and the dead fish in this incident was mainly concentrated in the river section from Jieyang Louhou Canal to Jiedong District Government. According to the analysis, there are many kinds of fish in the confluence of Rongjiang River in the north, but the fish that died this time are all single species, named spotted fish, which is also called leaf fish, and is an estuary fish, and likes to appear in groups. From April to June, it is a period of concentrated spawning for them. Rongjiang North River connects all the places to the sea, and there is a phenomenon of rising and falling tide. Since the end of last year, there has been drought and lack of rain in Jieyang area, so the salinity of the water in the north of Rongjiang River is generally high, so the leaffish choose to go upstream. On May 17, 221, heavy rain suddenly fell in the Beihe area of Rongjiang River. The salinity of this river section decreases with the water flow, which is why the leaffish died in a large area due to the change of salinity. In order to check the water quality in this area, Jieyang Ecological Environment Bureau sampled the main stream and related tributaries of the North River of Rongjiang River for monitoring. At present, no abnormality has been detected in the water quality of this basin. And there is no dead fish in the upper reaches of the North River Bridge and the South River of Rongjiang River in Jieyang City. Relevant departments have implemented the salvage of dead fish, and will continue to carry out investigation and monitoring of river sections. Therefore, a large number of dead fish appeared in Jieyang Hanoi this time because of the change of salinity, not the water quality problem.