臺中市境內包含河川、灌排渠道等水域密布,居民傍水而居,因而每每發生死魚事件,便讓臺中市民對水域水質安全存有疑慮,然而事實上多數死魚事件與氣象有關。過去對於死魚事件的原因紀錄,常包括「水位過低基流量不足」、「溶氧不足」、「水流停滯」及「污染排放」等,然而除了污染排放是在經由追查後發現水體水質或是魚體檢測異常,可確定明確原因外,其他對於造成死魚事件的因素皆僅止於環境狀態描述,未能精準確定實質導致死魚之原因,在原因不明下,便無法施以有效的管理與應變。因此,本研究為釐清確切造成死魚之原因,藉由歷年的死魚資料、水質、氣象數據進行交叉比對分析,發現可定義出數個臺中市境內水域的明確死魚類型,包括「連續低日照無雨」、「潮汐變化」、「季節轉變」、「大雨過後魚隻在高灘上擱淺」、「釣客放生不適於該環境魚隻」、以及「污染」等,不同死魚原因發生於不同環境條件,釐清各明確條件下所導致死魚問題,將有助於未來死魚預測、預警與防制。
Taichung City is densely covered with rivers, irrigation and drainage channels and other water areas. Over the years, large-scale dead fish incidents have occurred frequently in various water areas, which has exhausted the relevant management units of the water areas and made Taichung citizens have doubts about the water quality safety of the water areas. In the past, the causes of dead fish incidents were often recorded, including "low water level, insufficient base flow", "stagnation of water flow", and "pollution discharge". However, except that the pollution discharge was found to be caused by abnormal water quality or abnormal fish body detection after investigation, the other factors that caused the dead fish incident were only described in the environmental state, and the actual cause of the dead fish could not be determined accurately. Therefore, in order to clarify the exact cause of the dead fish, this study conducted a cross-comparison analysis of the dead fish data, water quality, and meteorological data over the years, and found that several clear dead fish types can be defined in the waters of Taichung City, including "continuous less of sunshine without rain", "salinity changes in the tidal zone", "seasonal changes", "fish stranded on high beaches after heavy rain", "irrigation water gate adjustment", "fish not suitable for the environment released by fishermen", and "pollution". The causes of fish occur in different environmental conditions. Clarifying the problem of dead fish under each specific condition will help in the prediction, early warning and prevention of dead fish in the future.