硬壳蛤(Mercenaria mercenaria)稚贝中间培育模式的初步研究

PRIMARY STUDY ON MODES OF SEED HARD CLAM MERCENARIA MERCENARIA(LINNAEUS,1758) CULTURE IN FIELD

采用现场测定方法 ,研究了硬壳蛤稚贝野外中间培育的适宜初始规格以及直接底播、袋中加砂底播、袋中加砂笼养和袋中无砂笼养 4种野外培育模式的效果。结果表明 ,硬壳蛤稚贝进行野外中间培育的适宜规格为壳长大于 2— 4mm。在 4种培育模式中 ,直接底播和袋中加砂底播模式效果比较理想。直接底播的稚贝 ( 30 0 0粒 /m2 )经过 2 8天便可由壳长2 .62mm长到 9.47mm ,达到播种规格 ;经过 62天的培育可以长到 1 7.5 1mm ,成活率可达83.3%。利用袋中加砂底播模式培育的稚贝生长速度略低于直接底播的稚贝 ,但成活率略高于直接底播的稚贝 ,可达到 89.8%— 94.5 %。与上述两种培育模式相比 ,袋中加砂笼养和袋中无砂笼养模式培育的稚贝生长速度较慢 ,其中以袋中无砂笼养模式培育的稚贝生长速度最慢 ,成活率最低。在这两种培育模式中 ,下层稚贝生长最慢 ,其次为中层稚贝 。

The hard clam, Mercenaria mercenaria (L.), is distributed from the Gulf of St. Lawrence to the Gulf of Mexico from a depth of 15m to the intertidal zone. The culture of hard clam has a good future since introduced firstly from the United States to China by Institute of Oceanology, The Chinese Academy of Sciences, in 1997. The intermediate culture process is an important stage in the seed culture of hard clam. There are many methods for intermediate culture of hard clam, such as using raceway system, upflow system, downflow system and rafts, trays, cages, nets in field. In this paper, we determined the optimal original size of juvenile hard clam to begin the seed culture process in field and studied the four seed culture modes in field, i.e. sowed the seed in sand directly (mode 1), cultivated in bags with sand (mode 2), cultivated in bags with sand put in cage (mode 3), cultivated in bags without sand put in cage (mode 4). Our results suggested that the 2-4mm juvenile hard clam suit seed culture in field. Among the four modes, mode 1 and mode 2 are the better modes for seed culture in field. The juvenile hard clams cultured in mode 1 (3000clams/m 2) could grow from 2.62mm to 9.47mm after 28d, which achieved the plantable size. After 62d, the juvenile hard clams could grow to 17.51mm, which the survival rate is 83.3%. The growth rate of seed hard clam cultivated in mode 2 is lower than that of mode 1, but the survival rate is higher than that of mode 1, which are between 89.8%-94.5%. Compared with these two modes above, the growth rates of seed hard clam cultivated in mode 3 and mode 4 are relatively low, and the growth rate and survival rate of seed clams are lowest in mode 4. In mode 3 and modes 4, the growth rate of seed clams in underlay is lowest, next is that in middle, and next is that in superstratum.