Abstract: Investigation showed that in the earliest stage of exploitation, catches greatly exceeded recruitments, population structure changed obviously.Afterwards, the structure kept stable, the growth rate became quicker,sexual maturity was earlier than before,reproduction capacity was increasing and sexual structure changed to favour the females, egglaying stock became younger. In order to properly utilize the stock, it is considered that the mesh of fishnets must be enlarged to prevent over - fishing.

Key words: Mechanized cultivation, Soil, Ecological factors, Biological effect