拟穴青蟹大眼幼体和第Ⅰ期仔蟹对隐蔽物的选择

采用实验生态方法,以攀附率为指标,研究了青蟹大眼幼体和第Ⅰ期仔蟹对不同材质(棉布、尼龙筛绢、PVC和竹木)、放置方式(水平或垂直)和构型(3种结构×3种规格)隐蔽物的选择性.结果表明:大眼幼体和仔蟹对各种隐蔽物材质选择差异不显著(p＞0.05),对垂直放置隐蔽物的选择性显著高于水平放置者(p＜0.01),对不同结构(草丛型、洞穴型和折角型)和不同规格(5,7和10 mm)隐蔽物选择差异均极显著(p＜0.01).其中,对草丛型、洞穴型和折角型隐蔽物的选择性依次降低,对5,7和10 mm隐蔽物的选择性也依次降低.随着规格增大,大眼幼体和仔蟹对草丛型隐蔽物的选择性下降幅度最大,对5 mm草丛型隐蔽物的攀附率为30.92%和25.9%,对10 mm草丛型的仅为0.46%和1.4%. 综上所述,在研制或使用青蟹大眼幼体和仔蟹的隐蔽物时,材质选择主要应考虑耐腐蚀、对水质无不良影响、不易钩挂幼体和仔蟹附肢等因素. 隐蔽物的结构以草丛型为佳,当其亚结构的最小空隙接近大眼幼体或仔蟹全长时,应可达到最好的使用效果.

Shelter Preference of Megalopae and First Juvenile of Mud Crab,Scylla paramamosain (Estampador,1949)

There are two important stages in the development process of mud crab Scylla paramamosain:megalopae and first juveniles.In the present study,the two stages of S.paramamosain were collected to investigate their preferences of different materials (cloth,net,PVC and bamboo sheet),layouts and conformations (3 structures × 3 sizes) shelters by employing experimental ecological methods based on the index of sheltering rates.The results showed that there was no obvious preference of different materials for megalopae and first juveniles ( p > 0.05 ),however,horizontal shelters attracted both megalopae and first juveniles more than vertical ones (p< 0.01 ),shelter structures (grassy type,cavity type and knuckling type) and sizes ( 5,7,10 mm ) had significant effects on the preferences of them ( p< 0.01 ).Structure preferences of megalopae and first juveniles decreased consequently among grassy type,cavity type,knuckling type shelters and also decreased with increasing sizes (5,7,10 mm ).Meanwhile,the decreasing extent of the preference of grassy type shelters was the greatest:30.92% & 25.9% respectively for 5 mm sized ones and 0.46% & 1.4% for the 10 mm sized ones.Therefore,materials with corrosion resistance,without harmful effects to water quality or appendage of the megalopae and first juveniles should be mainly considered when developing or using shelters.A better effect may be gained when grassy type shelters were used,especially when the smallest inter-space of the sub-structure of the shelters approximates to the total length of megalopae and first juveniles.