涨渡湖水生态系的结构和生产力的研究

STUDIES ON THE AQUATIC ECOSYSTEM STRUCTURE AND PRODUCTIVE POTENTIALITY OF ZHANGDU LAKE

１９９１年对湖北省新洲县涨渡湖的水环境和水生物资源进行了调查。该湖平均水深１．３１ｍ，透明度平均３１．３ｃｍ，总氮、总磷含量分别为１．００４，０．１１８ｍｇ·Ｌ-１。浮游植物对光能利用率为０．１８％。牧食链中Λ１、Λ２、Λ３、Λ４的年生产能最分别为８４０９．４４，３９８．４７，４０．８，１２．１３ｋＪ·ｍ-２。Λ２／Λ１、Λ３／Λ２、Λ４／Λ３的能量利用率分别为４．７４％、１０．２４％、２９．７３％。全部鱼类对浮游植物生产能量的利用率为１．６７％。根据浮游生物的生产力估算鲢、鳙鱼产力为２３３ｋｇ·ｈｍ-２，同年它们的渔获量为２４３．１９ｋｇ·ｈｍ-２）。渔获量已达估算鱼产力的１０４．３７％，因此该湖鲢、鳙已无增产潜力。１＋龄鲢生长指标不达０．５ｋｇ，现有鲢的放养数量应予降低。水草资源由于草食性鱼类的过度利用，其种群结构已受到破坏，影响到水生动物的生产，应设法恢复。

The water environment and hydrobiant resources in Zhangdu Lake were surveyed in 1991. The lake had an average water depth of 1. 31 m, an average transparancy of 31. 3 cm and gross nitrogen and phosphorus concentrations of 1. 004mg·L-1 and 0. 188 mg·L-1 respectively. The efficiency of phytoplankton in capturing radiant energy was 0. 18%. The annual production forces of first to fourth trophic level in grazing food chain (namely Λ1,Λ2,Λ3, and Λ4)were 8409. 44, 398. 47, 40. 8, and 12. 13 kJ·m-2 respectively. The efficiency of energy utilization of Λ2/Λ1,Λ3/Λ2 and Λ4/Λ3 were 4. 74, 10. 24, and 29. 73%, respectively. The efficiency of fishes in using plankton production is 16.7%. The productivity of silver carp and bighead carp estimated on the basis of the productivity of plankton was 233 kg·hm-2. The catch of these two fishes in the same year was 243. 19 kg·hm-2. which was 104. 37 percent of the estimated value. It suggests that there is no further production-increasing potentiality in the lake. As the growth rate of 1+year silver carp lower than 0. 5 kg, the present culture amount of the carp should be decreased. Aquatic plants was over-utilized and its community structure was destroyed by cultured herbivorous fishes, which has being produced a negative effect on the production of aquatic animals. It is, therefore , necessary to recover the plant resources.