The impact of the hard clams cultured in ponds was grew slower and slower that result in overfeeding and higher stocking densities in grow-out ponds.Most of growers losing their income not only longer culture periods for harvesting but also mass mortality occurring frequently and the half-dying adult clams were sold cheaper.The first progeny of the fastest growing strain of each batch hard clams from grower farm will be hatchery reared by following generations to generations and the fastest growing strain will be selected also.Each bath selective breeding strain juveniles will be planted on sub-areas in the same nursery ponds that isolated by block distance.Experimental sub-ares containg selected anf non-selected clams were cultivated at the same densitv and at the same site.
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