山东沿海腹洞式毛虾单桩张网试验报告

单桩张网在渤海捕捞毛虾时，损害大量经济鱼虾的幼体，严重地破坏了渔业资源。为保护经济鱼虾的幼体，合理利用毛虾资源，作者根据毛虾和其他经济鱼虾幼体的不同习性和游泳能力，设计了腹洞式毛虾单桩张网。该网的主要特点是，在张网腹部开有一个较大的三角洞，经济鱼虾的幼体受惊后可由此下潜逃逸，或在流速较小时由此外返逃逸。两年来的生产对比试验表明，效果显著。腹洞式毛虾单桩张网比现有生产网的平均网次产量增加20．64％。其中，毛虾增产38．14％，释放经济鱼虾的幼体58．94％。

EXPERIMENT ON HOLE-IN-BELLY STAKED NET IN SHRIMP CATCHING OF SHANDONG INSHORE

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.