双齿围沙蚕-牙鲆网箱综合养殖模型碳、氮收支的实验研究

摘要

The culture of fish in cages has been shown to be economically efficiency; however, it produces large amounts of fish feces and uneaten food. These organic waste materials, containing significant levels of carbon, nitrogen, phosphorus, etc., can cause environmental damage and may result in decreased dissolved oxygen levels within cages, negatively affecting fish production. During an exploration of benthic taxa beneath cage culture, numerous nereids were recorded, including Perinereis aibuhitensis, an important seashore species of polychaete, feeding in the sediments. In the present study, a system of fish cage culture and P. aibuhitensis were combined in a 40-day laboratory experiment to investigate the carbon/nitrogen budget and its effect on environmental optimization. The experimental design involved four treatments at the same fish density within the cage (Japanese flounder, Paralichthys olivaceus, about 21 g/ind, 5 ind/cage) and different densities of P. aibuhitensis (0, 50, 70 and 90 g;designated C, S1, S2 and S3). There were three replicates for each treatment. The cage was 60 cm in diameter by 30 cm deep. The fish and P. albuhitensis were starved for 24 h before being weighed. Five Japanese flounders and 20 g of P. albuhitensis were in the initial sample. All specimens were fed twice a day with artificial pellets at 07:30 and 18:00 during the experimental period. The amount of food was similar in each group and was adjusted according to the uneaten food in the control group. Uneaten food and fish feces were left in the system. The system had a steady flow rate of 250-300 L/day and light aeration was provided continuously. A simulated natural photoperiod (14:10, light/dark) was used throughout the experiments. At the end of the experiment, all animals were sampled, weighed after 24 h starvation, and oven-dried at 70℃ for 48 h for analysis. The results showed that the levels of carbon and nitrogen in the sediment were higher in the control (C) than in other treatments. There was no significant difference among treatments in the amount of carbon lost in respiration, or for the net output of organic carbon and nitrogen in water (P>0.05). The input of carbon and nitrogen was principally from food. In addition, there was no significant difference among treatments of the proportion of nitrogen for net output in water (P>0.05). The proportion of nitrogen output from the system was highest in the control, but there was no sig-nificant difference between C, S1 and S2 (P>0.05). The proportion of nitrogen accumulated in sediment was higher in the control than in either S2 or S3 (P<0.05). The proportion of carbon accumulated in sediment was highest in the con-trol (P<0.05). The proportion of organic carbon for net output in water was higher in C and S1 than in S3 (P<0.05). The proportion of carbon output for the system was significantly lower in S3 than in S1 or the control (P<0.05). Both the carbon and nitrogen output ratios were lowest in the control. In the present experiment, P. aibuhitensis was shown to be a significant consumer of uneaten food and feces in our model of“Japanese flounder cage culture and P. aibuhitensis”. Our novel model could be valuable in reducing carbon and nitrogen accumulation in the sediment beneath Japanese flounder cage culture and thereby improving the environment and enhancing fish production.%在实验室条件下,设计相同的牙鲆(Paralichthys olivaceus)鱼苗网箱养殖密度(密度5尾/箱,鱼苗体质量约21 g),分别与不同数量的双齿围沙蚕(Perinereis albuhitensis,0 g,50 g,70 g,90 g)混合养殖,4个实验组分别记作C、S1、S2和S3,网箱规格为Ф60 cm×30 cm。各实验组设3个平行组,实验进行40 d。牙鲆和沙蚕在称重前均饥饿24 h,同时取5尾牙鲆和20 g沙蚕作为实验初始样品。实验期间,每天07：30和18：00分2次投喂配合饲料,根据对照组饵料剩余情况适时调整投喂量,每个实验单元的投饵量基本一致,此过程中不处理残饵和粪便。实验单元采用微流水,流量为250~500 L/d。实验期间,24 h持续微量充气。至实验结束时,全部生物饥饿24 h。将其全部取出,擦干体表水分,称重后置于70℃干燥箱中烘干至衡重,研磨、分析。结果表明,对照组(C)的底质积累碳、氮量最高,各实验组水体净输出的氮和有机碳量以及呼吸碳量分别无显著差异(P>0.05)。饲料是碳、氮输入的主要来源。在输出各项中,各个实验组水体净输出氮占输出氮比例无显著差异(P>0.05),而系统净排放氮以对照组所占比例最高,但与S1和S2组无显著差异(P>0.05)；对照组底质积累氮所占输出氮比例显著高于S2和S3组(P<0.05)。对照组底质积累碳所占比例显著高于其他各实验组(P<0.05)；对照组和 S1组的水体净输出有机碳比例显著高于 S3组(P<0.05),而 S3组碳净排放占碳输出的比例显著低于对照组和 S1组(P<0.05)。碳、氮产投比均以对照组最低。在本研究条件下,双齿围沙蚕在综合养殖模型中可利用牙鲆网箱养殖产生的残饵和粪便,减少底质碳、氮积累,提高产投比,综合养殖模型既可以降低碳、氮排放,又可以增加产品产出。结论认为,网箱养殖牙鲆搭配双齿围沙蚕的综合养殖模型理论上具有可行性,双齿围沙蚕可以作为牙鲆网箱养殖产生的残饵和粪便的一道有效处理屏障,此模型在港湾和围堰鱼类网箱养殖中更有意义。