珠江三角洲地区大口黑鲈池塘养殖系统的能值评估

为评价珠江三角洲地区大口黑鲈池塘养殖系统的生态经济性能,实验以能值理论为基础,定量分析该系统的能流和物流特点,通过建立能值评价指标体系,综合评估该系统的环境影响及可持续性。结果显示,大口黑鲈养殖系统投入的资源分为可更新资源(太阳能、风能、雨水能、地球循环能和河水能)和购买的外部资源(设施、苗种、电能、饵料、药品、劳动力、租金、维护费)两部分。养殖系统投入的总能值为4.51×10~(17)sej/(hm~2·a),其中可更新资源能值总和为1.24×10~(16) sej/(hm~2·a),占总投入能值的2.75%。河水能在可更新资源中所占比例最大,为9.77×10~(15) sej/(hm~2·a),占总投入能值的2.17%。购买的外部资源能值总和为4.38×10~(17) sej/(hm~2·a),占总投入能值的97.25%。饵料投入在购买的外部资源中所占比例最大,其能值为3.49×10~(17) sej/(hm~2·a),占总投入能值的77.33%,其次是劳动力,能值为2.29×10~(16) sej/(hm~2·a),占总投入能值的5.08%。大口黑鲈池塘养殖系统太阳能值转换率TR为2.18×106 sej/J,产出能值交换率EERY为2.028,能值产出率EYR为1.028,环境负载率ELR为35.39,能值持续性指数ESI为0.029,可持续性发展的能值指数EISD为0.059。大口黑鲈池塘养殖系统经济效益较高,但过多依赖购买的外部资源,对环境压力较大,可持续性较差。减少饵料投喂量、提高饵料利用率(如选择优质配合饲料及添加剂、改进投喂策略等)以及开展综合养殖是提高珠江三角洲地区大口黑鲈养殖系统持续性、减小环境负载率的有效途径。

Emergy evaluation of largemouth bass (Micropterus salmoides) aquaculture system in the Pearl River Delta, China

In this study, emergy analysis method was used to evaluate the benefits and driving forces of largemouth bass (M. salmoides) aquaculture system from ecological and economic points. For analysis, a number of different inputs have been identified and grouped in two categories:renewable environment resource inputs and purchased external resource inputs. The first group counted five natural, free and renewable inputs (solar radiation, wind, rain, earth cycle and river water), while the second group included eight external inputs (construction, fingerlings, electricity, feed, medicine, labor, rent and maintenance). Emergy indices for the largemouth bass aquaculture system calculated from the emergy evaluation, such as Transformity (TR), Emergy Yield Ratio (EYR), Environmental Loading Ratio (ELR), Emergy Exchange Ratio of Yield (EER_Y), Emergy Sustainability Index (ESI) and Emergy Index for Sustainable Development (EISD), were applied to characterize the resource utilization, environmental impact and the overall sustainability of the largemouth bass aquaculture system. These indices were compared with those of four other fish farming systems:the large yellow croaker (Larimichthys crocea) aquaculture system around Dongji Island in Zhoushan, China, the eel aquaculture systems on wetlands surrounding the Pearl River Estuary, China, the polyculture system of ophicephalus and mullet on wetlands surrounding the Pearl River Estuary, China and the dike-pond agro-ecological engineering system in Sanshui city of the Pearl River Delta. The results showed that the total emergy inputs was 4.51×10¹⁷ sej/(hm²·a). The renewable emergy inputs was 1.24×10¹⁶ sej/(hm²·a), which accounted for 2.75% of the total emergy inputs. The external emergy inputs was 4.38×10¹⁷ sej/(hm²·a), which accounted for 97.25% of the total emergy inputs. More than 70% of the emergy inputs into the largemouth bass aquaculture system was feed (77.33%). Labor was the second largest emergy input to the system (5.08%). The river water emergy was the major renewable environment resource input for largemouth bass aquaculture system (2.75%). The TR of this system was 2.18×10⁶ sej/J, EER_Y was 2.028, and EYR was 1.028. The ELR was 35.39, ESI was 0.029, and EISD was 0.059. The lower ESI with EISD and the higher ELR showed that the purchased external resource emergy inputs achieved a greater effect than renewable environmental resource emergy in largemouth bass aquaculture system, and the system had more dependence on purchased external resource emergy inputs, which indicated that the largemouth bass aquaculture system was less sustainable. The result showed that measures which reduced feed inputs and improved the feed utilization efficiency, such as using feed and additives with low feed coefficient, increasing feeding frequency, etc., could reduce the purchased external resources inputs, and then elevate the ESI and EISD of the largemouth bass aquaculture system. Integrated aquaculture was another method which could get the same result.