Extension potential of rice-fish co-culture system: A case study of 10 provinces in South China

Rice fields can provide habitats for a wide range of aquatic animals, including carps, crabs, crayfish, soft shell turtles, which makes it possible to couple rice culture with fish production. This is referred to as the rice-fish co-culture system. The suitability of rice fields in a specific region for the rice-fish co-culture system often depends on local natural and social economic conditions. An understanding of the potential of rice fields for use in the rice-fish co-culture system would aid effective extension of rice-fish co-culture system and maximize the benefits of this extension. In this study, we assessed the effects of natural and social-economic conditions on the extension of the rice-fish co-culture system in 10 provinces of South China, and predicted the potential of fish yield from rice fields in the rice-fish co-culture system extension. We first built a geographical distribution database of all rice fields in the study area by using a geographic information system (GIS) comprising meteorological data and national statistics. We then assessed the extension priority of different rice fields with a hierarchy model of all assessment criteria and the weighted linear combination method. To assess the extension benefits, we further established a simple model that included rice field area, extension rate, and fish yield. The results showed that rice fields in our study region could be divided into four classes of extension priority based on natural and social-economic scores. The area proportions of four classes were:29.6% for class 1 (3.59×10⁶ hm²), 16.9% for class 2 (2.05×10⁶ hm²), 24.2% for class 3 (2.94×10⁶ hm²), and 29.4% for class 4 (3.57×10⁶ hm²). However, the proportions of rice fields in the four classes were different in the ten provinces. For the provinces of Hunan, Sichuan, Jiangxi, and Zhejiang, half of rice fields were grouped into class 1 and 2, whereas all the rice fields of the provinces of Yunnan and Guizhou were grouped into class 3 and 4. The rice fields of class 1 and class 2 were suitable for the extension of the intensive rice-fish co-culture system, and able to produce a maximum yield of 3.77×10⁶ t and 2.15×10⁶ t of fish in a growing season, respectively. The rice fields of class 3 were suitable for extension of the extensive or intensive rice-fish co-culture systems, and able to produce a maximum yield of 0.62×10⁶ t or 3.09×10⁶ t of fish in a growing season, respectively. The rice fields of class 4 were not suitable for rice-fish co-culture system. Our results may provide an important basis for extending the rice-fish co-culture system in South China. The results may also be a reference for rice-fish co-culture system development in other rice culture areas.