草鱼集约化养殖中的磷循环

Phosphorus Cycling in Intensive Grass Carp Culture

理解养殖生态系统中的磷循环途径可为提高养殖效益和降低磷排放提供理论依据,为此,开展不同磷含量饲料对草鱼生长、饲料效率及系统中磷循环的影响试验。设置两个试验处理组,并分别投喂含磷量为1.02%和0.52%的配合饲料,进行为期10周的观测。试验结果表明,含磷量1.02%组的饲料效率为68.4%,草鱼质量增加率为72.3%;含磷量0.52%的饲料组的饲料效率为77.3%,草鱼质量增加率为74.3%;低磷饲料组比高磷饲料组具有更高的饲料转换率,且收获更高的渔获量。低磷饲料组中观测到更高的浮游植物生物量,表明浮游植物可能存在对沉积物中磷的泵吸作用,并通过食物链加速了水体中物质循环效率,这释明低磷饲料处理是具有更高饲料利用率并获得更高渔获量的原因。草鱼集约化养殖过程中,单纯增加饲料磷含量并不利于渔获量的提高,反而导致沉积物磷滞留和养殖水体磷污染;合理的磷含量(0.52%)可以更好的发展水体中浮游植物的生长,提高饲料利用率,达到养殖增产和保护环境的双重效益。

Understanding of the phosphorus cycling approach in aquaculture ecosystem provides theory basis with improvement of cultural benefits and decrease in phosphorus emissions. We therefore manipulated different phosphorus concentrations in fodder to study the influences of phosphorus concentration on growth, feed efficiency and phosphorus cycling in intensive aquaculture ponds of grass carp Ctenopharyngodon idellus. Fish in two treatment groups （A and B groups） were fed compound feed containing phosphorus content of 1. 020/00 and 0. 52%. A ten-weeks observation showed that the feed efficiency was 68.4% and mass increasing rate was 72.3% in group A. In contrast, the feeder efficiency was 77. 3% and mass increasing rate was 74. 3~ in group B. There were significantly higher fodder efficiency and greater yield in group B than those in group A. Treatment with low phosphorus fodder led to more phytoplankton biomass, suggesting that it could pump phosphorus from sediments and accelerate the efficiency of material circulation through food chain. The result explained the reason why treatment with low phosphorus fodder led to higher fodder efficiency and greater fish field. Increasing phosphorus concentration in fodder was not beneficial to improve fish field in intensive grass carp. On the contrary, it could lead to more phosphorus retention in the sediment and pollution in the water. Suitable phosphorus contents in fodder can accelerate the growth of phytoplankton directly, ultimately getting satisfied fish field and protecting environment simultaneously.