Abstract: Shrimps (Acetes sp.) catchingin the Bo Hai Sea, the single staked nets damage alarge quantity of the fishes and prawns of commercial value. It has heavily destroyedfisheries resources. Based upon the behaviour and the swimming ability of the dif-ference between young fishes, young prawns (Penaeus orientalis) and shrimps.the authors designed a modified hole-in--belly single staked net in 1981 in order toprotect young fish resources from the shrimps catching operations. The main featureof the newly designed net is a large triangle hole opened in the belly, thus the youngfishes and prawns might escape from the hole, either by diving downwards or bywithdrawing from the net mouth.The modified net exhibets noteble effects in experiments. The average yield pernet increased by 20.64% as compared with the original net, among which shrimpcatch increased by 38.14%, and young fishes and prawns were saved by 58.84%.For making clear understanding of reaction of shrimp to irritation, an observa-tion in an aquarium (105×51×46cm) with the water depth 25--32cm was takenplace. It wns found that when irriated, all shrimps spring upwards or slantwise, noone of downwards at all. The distance of each stride was 4--8 cm, and the continuousspring could reach over 30 cm.