Spatial-temporal variations in eco-service values of pond aquaculture in Shanghai

Pond aquaculture was a critical fishery production system in China. At present, eco-service value research focused on the positive aspects while negative service values (e.g., environmental cost) were neglected. Pond aquaculture performed multiple functions, including aquatic product supply, air conditioning and temperature adjustment, culture recreation services, etc. At the same time, this system can also bring forth environmental costs. For further clarification of changes in eco-service values and to realize sustainable development of pond aquaculture, this paper established a comprehensive eco-service value evaluation system. On this basis, eco-service values and their the spatial-temporal variations in pond aquaculture eco-service values in Shanghai (including Jiading, Qingpu and Fengxian Districts) were estimated by Market Valuation Method (MVM), Travel Cost Method (TCM), Contingent Valuation Method (CVM) and Shadow Engineering Method (SEM). The main results of the paper were summarized as follows: 1) The total values of pond aquaculture eco-service in Jiading, Qingpu and Fengxian Districts were approximately 8.228×10⁷ Yuan·a^-1, 8.462 8×10⁸ Yuan·a^-1 and 1.558 84×10⁹ Yuan·a^-1, respectively. This respectively amounted to 9.408×105 Yuan·hm^-2·a^-1, 2.000×105 yuan·hm^-2·a^-1 and 3.273×105 yuan·hm^-2·a^-1; which were 2.69, 1.94 and 2.17 times of pond aquaculture economic values in 2011. This showed that significant differences existed among the spatial-temporal variations in pond aquaculture. 2) Pond aquaculture eco-service values were high, but this huge potential values were not optimally exploited. Unrealized eco-service values were respectively about 5.46, 1.23 and 0.46 times of net food supply values in the Jiading, Qingpu and Fengxian Districts. 3) Driven by temporal variations in economic efficiency, pond aquaculture varieties were adjusted from 2010 to 2011. Conventional fish aquaculture reduced significantly while freshwater shrimp and Penaeus vannamei became the main aquaculture species in the studied districts. 4) There was significant difference and flucturation in temporal variations in eco-service values due to different spatial distributions among eco-services. Recreation culture service value was highest from April to September, air conditioning value highest from July to December and temperature adjustment value highest from May to September. 5) Pond scales had significant impact on spatial-temporal variations in eco-service values. Pond aquaculture eco-service value was subjected to scale economy. Spatial-temporal distributions of different types of eco-service values were dissimilar and no clear general mechanism was noted. It was necessary to adjust and optimize management strategies of pond aquaculture based on the eco-service value distributions and to develop recreational fisheries to improve eco-service values. It is important for government to develop and implement necessary ecological compensation policy to achieve environmental equity and sustainable development.