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海水实验围隔中放养罗非鱼的生态学效应 总被引:4,自引:0,他引:4
围隔实验和在围隔内进行的其他实验结果表明,台湾红罗非鱼(简称罗非鱼)对食物的选择性及其生态学效应与食物资源状况有关。放养罗非鱼的围隔中浮游植物生物量和生产力往往较高,但罗非鱼密度超过8000尾/hm2后可明显压制海洋原甲藻等大型鞭毛藻类。当罗非鱼食物丰富时其对围隔中桡足类的压制作用相对较弱,当其他食物资源缺乏时往往选择捕食个体较大的桡足类。放养罗非鱼对围隔水中氮浓度和COD的影响较小,但加快了磷的循环,罗非鱼密度超过8000尾/hm2的围隔中PO4-P浓度明显高于对照围隔。 相似文献
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不同养殖方式对海水实验围隔底泥中氮、磷和有机碳含量的影响 总被引:5,自引:1,他引:4
①对养殖池塘底质的研究目前尚较少[2]。由于放养生物对投入的饵料和肥料的利用率很低,经过多年养殖的池塘底部往往会形成很厚的淤泥,底泥中有机质大量积累后容易形成厌氧微环境[3],对底栖生活的养殖种类造成危害,因此,减轻养虾池底质中有机质的积累是改善对虾养殖环境的重要内容。作者1995,1996年进行了两次围隔养殖实验。本文初步讨论了不同养殖方式对海水实验围隔底泥中有机碳和氮磷含量的影响,以期为今后对虾池养殖生态系统结构优化提供基础资料。1材料和方法实验的时间、地点、围隔构造以及放养和管理的有关细节… 相似文献
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April to October, 1997 comparative studios on the nitrogen budgets of closed shrimp polyculture systems showed that, in all the studied polyculture systems, nitrogen from feeds and fertilizers were the main input items, which comprised 70.7% - 83.9% of the total input nitrogen, 3.2% - 7.4% of which was provided by nitrogen fixation. It was in monoculture enclosures (Y-4, Y-11 and Y-12) that the percentage reached the maximum value. The output nitrogen in harvested products comprised 10.8% - 24.6% of total input nitrogen, and the highest percentage, 24.6%, was found in shrimp-fish-tagelus polyculture systems. In shrimp monoculture and shrimp-fish polyculture systems, they were 19.1% and 21.9%, respectively. The nitrogen utilization efficiency was different and varied from 12.2% to 20.1%. The highest, 20.1%, was found in shrimp-fish-tagelus polycultttre systems, and the average of 20.0% was found in shrimp-tagelus polyculture systems. The lowest, 12.2%, was found in shrimp monoculture systems.All the nitrogen utilization efficiencies in shrimp-fish systems or shrimp-scallop systems seemed to be higher than that of the monoculture system, but they showed little statistical difference. The main outputs of nitrngen were found in sediment mud, and comprised 48.2% -60.8% of the total input, the lowest percentage was found in shrimp-fish-tagelus polyculture systems, and the highost percentage in shrimp-scallop systems.During the experiment, nitrogen lost through denitrification and ammonia volatilization comprised 1.9% - 6.2%, averaged 2.8%, of the total input, and the loss through seepage comprised 5.9% - 8.9% of the total.The estimated nitrogen attached to the enclosure wall comprised 3.7% - 13.3% of the total, and was highest in shrimp monoculture systems. Compared with the classic shrimp farming industry, the closed shrimp polycul-ture systems may improve the nitrogen utilization efficiency, and hence reduce the environmental impacts on coastal waters. The nitrogen discharging rates for all the studied polyculture systems ranged from 3.0% to 6.0% of total input nitrogen. 相似文献
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