水体对网箱养鳜的承载力

Studies on the carrying capacity of water bodies for cage culture of mandarin fish (Siniperca chuatsi)

通过分析浮桥河水库氮、磷含量 ,确定磷为水体营养物的限制性因子 ;根据水库的中 -富营养化现状 ,确定磷浓度 0 .0 6 6mg/ L——水库中游的磷浓度为水体允许的最高磷浓度 ;结合我国现有的实际情况 ,在 Dillon- Rigler模型的基础上建立了包含水体的有效库容系数、营养水平、养殖强度和养殖对象等参数的动态模型 ,并由此模型计算出浮桥河水库的网箱养殖容量 :单一养殖鳜鱼时为 1.6 0‰ ,单一养殖建鲤时为 0 .2 1‰ ;配套养殖时 ,鳜鱼为 0 .31‰ ,建鲤为 0 .2 1‰ ,总容量为 0 .5 2‰ ;对水体网箱容量的磷限制性标准的制定进行了讨论 ,在模型理论的基础上提出了水体环境调控措施 ,并建议养殖水体以食鱼性网箱养殖为主 ,饵料鱼网箱为辅。

In order to investigate the effect of cage-culture of piscivorous fishes on water environment, the Fuqiaohe Reservoir (110°52′30″E, 31°10′N) was selected to study the optimum carrying capacity of mandarin fish (Siniperca chuatsi).Water samples were collected every month ,from July 1998 to October 1998. The parameters monitored were water temperature, water depth, Secchi degree (SD), pH, dissolved oxygen (DO) and main nutrients (various state of nitrogen and phosphorus). Phosphate contents in the body of mandarin fish and Jian carp were measured in molybdenum-blue method. The models of carrying capacity of water body for cage-culture of fishes were build based on the carrying capacity of waters for wastes and the inputs of exotic nutrients. The former was determined by trophic level of waters, water depth, valid coefficient of capacity and delaying coefficient of phosphorus; and the latter was determined by the fish production of cages, wastes from fishes (including the trash fish fed to fish) and food conversion ratio.The results showed that phosphorus in Fuqiaohe Reservoir was the nutritional limiting factor in the water body. According to the mid-eutrophicational status of the reservoir, the phosphorus concentration (0.066 mg/L)in the middle reaches of the Fuqiaohe Reservoir was regarded as the maximum permission concentration. A series of dynamic models were build for evaluating carrying capacities of cage culture, including parameters of valid coefficient of reservoir capacity, trophic level, cultural intensity and species. The models are shown as the following:The carrying capacity of waters for phosphorus wastes: P=a×H×A×r×(1×(1-R)^(-1))×(P_(max)-P_o) ×1‰The carrying capacity of monocultural cages: P_(cage)=(a×H×r×ΔP×h)×( W_f×(1-R) ×(P_m×b^(-1)+ F×P_F-P_f))^(-1)×1‰The carrying capacity of cage-cultured piscivorous fish in the polycultural pattern:P_s=P×(A×W_(fs)×(P_m×b^(-1)+F_s×P_i-P_f)×h^(-1)) ×1000‰The carrying capacity of trash fish fed to fishes in the polycultural pattern:P_c=F_s×P×(A×W_(fc)×(P_m×b^(-1)+F_s×P_i-P_f)×h^(-1))^(-1)×1000‰The carrying capacity of the total cages in the polycultural pattern:P_(cage)=(a×H×r×ΔP) ×((1-R) ×P_t))^(-1)×(1×W_(fs)^(-1)+F_s×W_(fc)^(-1)) ×1‰Where P is the carrying capacity of the water for phosphorus (kg/y); a is the valid volume coefficient(%), namely the amount of valid volume in the total volume; H is the mean depth (m);A is the reservoir area (m^2); r is the yearly exchange rate of the water; R is the retention coefficient of phosphorus (%); P_(max) is maximum concentration of phosphorus allowed in the water (mg/L); P_o is the original concentration of phosphorus in the water (mg/L); P_(cage) is the carrying capacity of the water for cages (‰); ΔP is the allowed increment concentration of phosphorus in the water (mg/L); h is the survival rate of fish in cages (%);W_f is the unit fish production in cages (kg/m^2); P_m is the percentage of phosphorus in the fingerlings (%);b is the multiple of weight growth of fish; F is the feed coefficient; P_F is the percentage of phosphorus in the feed (%); P_f is the percentage of phosphorus in the adult fish (%); P_s is the carrying capacity for cages of piscivorous fish in the polycultural pattern(‰); P_i is the loaded weight of phosphorus of unit trash fish production (kg/kg); P_c is the carrying capacity for cages of cultured trash fish (‰); W_(fs) is the production of piscivorous fish in the polycultural pattern (kg/m^2); F_s is the survival rate of cultured trash fish (%);W_(fc)is the production of cultured trash fish in the polyculture pattern (kg/m^2); On the basis of the above models, the carrying capacities of cage-cultured mandarin fish in the Fuqiaohe Reservoir was 1.60‰ when mandarin fish was monocultured and 0.21‰ when Jian carp was monocultured; and 0.31‰ for mandarin fish and 0.21‰ for Jian carp with a summation of 0.52‰ under the polyculture pattern.