Based on the basic biological survey on captured hairtail, Trichiurus haumela in the East China Sea and the Southern Yellow Sea from 1986 to 2000, the hairtail resource in the East China Sea was assessed by using generation analysis and the variation of its productivity and recruitment was discussed. A relationship between environment and recruitment was given through selected environmental factors. Results showed that the minimum body length of maturation, the average body length and the body weight of spawning parents declined, so did the egg diameter; while individual productivity increased, with the ever-developing f ishing power. After the implementation of Summer No-Fishing Season system, the quantity of recruiting co lony increased a lot , and the recruiting quantity per unit of parent s increased by 45% - 60% . That clinched that the Summer No-Fishing Season system had a very good ecological effects. The recruiting quantity was directly proportional to the number of parents, water temperature and most importantly the period of the season. The parent fish in the East China Sea is still insufficient, so it is imperative to further decease fishing power.