abstract:The harvest of mackerel purse-seine fishery in Taiwan fell sharply by 47.75% following the strong El Niño of 1997/1998. In this study, we try to incorporate El Niño barometric readings and sea surface temperature measurements into analysis for predicting the biomass. Using daily logbook records of the mackerel purse-seine fishery from 1982 to 1999, we identify the factors that influence the catch of mackerel purse-seine fishery in Taiwan. Based on an empirical model and the results of a fishing fleet cost survey, we estimate the average cost and the welfare loss associated with an El Niño. A time-series simulation shows that adding the El Niño barometric readings information improves the accuracy of biomass forecasts. It also shows that about 14 months after the strong El Niño has occurred, the biomass index is 13.2% lower and the number of fishing day is 10.4% higher. The estimated welfare loss of all mackerel purse-seine fleets during September to January in the year subsequent to the El Niño is about US$6 million. Policy implications of the study are also discussed.