1．调查了解育苗生产单位亲蟹及蟹苗情况。看着亲蟹的来源、质量情况，如果亲蟹个头较小或不是长江水系的，产出的苗的质量不会好的。了解育苗池内蟹苗的密度和淡化处理过程，选购盐度在0．3％以下，淡化5～6日龄健壮的蟹苗，要求无死苗、无杂质、无附着物。2．称重计数鉴别。 1. Investigate and understand seedling production units crab and crabs situation. Looked at the source of crabs, the quality of the situation, if the crabs head smaller or not the Yangtze River, the quality of the output of the seedlings will not be good. Understand the density and desalination process of the crab seedlings in the nursery pond, and choose the salinity below 0.3% to dilute the robust crab seedlings aged from 5 to 6 days without dead seedlings, no impurities and no attachments. 2. Weighing count identification.