池塘饲养鱼类优化结构及其增产原理——Ⅱ.池塘主养鱼类合理群落结构及其能量转换效率

THE RATIONAL DESIGN OF POND FISH CULTURE WITH REFERENCE TO THE PRINCIPLES OF YIELD INCREASE Ⅰ. Rational structure and energy conversion efficiency of the community of major cultured fishes in ponds

池塘对比试验(1987—1989)和室内补充试验结果证明了“一草养三鲢”的常规混养法不能充分发挥高产池中草鱼和鲢鳙鱼种间的协调互利作用,使池塘能量转换效率偏低,这主要由于鲢鳙鱼密度太大,饵料不足,需经常过量施肥,易造成水质恶化,诱使草鱼体弱多病诱致。依草鱼摄食后所排粪量的供饵能力和作用于滤食性鱼的主要能流途径,将草鱼与滤食性鱼种放养重量调整为1.5—2.5:1,以青料为主,适当配喂颗粒饲料,其主体鱼的种群生长率、池塘能量转换效率均明显高于常规饲养法。池塘内不增施外源肥料,青、精饲料输入量保持与草鱼生物学特性相适应的情况下,每生产单位重量的草鱼,可带动生产40—80％重量的鲢鳙。

Pond culture experiments (1987—1989) and indoor supple-mental experiments showed that the commonly used stocking ratio of 1 grass carp to 3 filter-feeding fish in polyculture systems fails to fully utilize the interspeeifie benefits among the grass carp, silver carp and bighead carp, resulting in a low energy conversion efficiency in the pond system. Because of the low food availability caused by high densities of silver carp and bighead carp, over-fertilization is frequently practised, resulting in deterioration of water quality and diseases and poor condition in the grass carp. Based on the food-supply potential of the feces produced by grass carp, and the energy flow pathyway acting on the filter-feeding fish, the weight ratio of stocked grass carp to filter-feeding fish was adjusted to (1.5—2.5) : 1 Ⅰ. Green plants were used as the major food, supplemented with pellet feeds. The growth rates of major cultured fishes and energy conversion efficiency of the pond were apparently higher than those in ponds using routine culture methods. With no exogenous fertilization and suitable green and pellet feed inputs in accordance with the biological characters of the grass carp, each unit weight of grass carp produced could yield 40—80% of its weight of filterfeeding fishes.