Integrated rice field aquaculture, a practice normally used by rural small-scale farmers, is not only supporting farms and livelihoods but is also reducing poverty and is playing a more and more important role in China. It is also becoming one of the main freshwater aquaculture systems, in addition to ponds, lakes, reservoirs, streams, and other aquaculture systems. During the past 40 years, both the production and areas of integrated rice field aquaculture in China have significantly increased from 0.13 million t and 0.74 million ha in 1990 to 3.25 million t and 2.56 million ha in 2020, respectively. Advances in ecology research on integrated rice–fish aquaculture were one of the main contributors to this achievement. In this paper, we systematically reviewed the advances in ecology research on three major integrated rice field aquaculture systems in China, namely rice–fish, rice–crab, and rice–crayfish coculture systems, the contribution of the research, and future prospects. We found that progress in ecology research on theories, biological studies, models, and eco-engineering techniques, coupled with policy support promoted the development of the rice field aquaculture industries. This review could assist individual small-scale farmers to make better use of rice field space to produce safer aquatic and rice products at a lower cost and help aquaculture scientists to further study the ecology of integrated rice field aquaculture systems.

The Danjiangkou Reservoir (DJKR) serves as the water source for the world’s biggest water diversion project, the Middle Route of the South-to-North Water Diversion Project (MR-SNWDP) in China, and this project concerns the water security of tens of millions of people in northern China. Hence, the maintenance of ecosystem health and optimization of management necessitate studies to assess the composition and dynamics of key aquatic living resources. Zooplankton represent a critical component of the reservoir ecosystem and are sensitive to environmental changes and anthropogenic disturbances. In this study, the zooplankton compositions in DJKR were quantified and compared in May, August, and November 2017. Simultaneously, the effects of water trophic states on the zooplankton community structure were analyzed at three levels (overall, taxonomic, and functional groups). A total of 65 zooplankton taxa were recorded, with the taxonomic richness of Rotifera (28 taxa) being the highest among taxonomic groups, which were further classified into 10 functional groups. The community was characterized by low diversity and high evenness. Compared with historical studies, the biomass had increased remarkably, while the abundance showed a decreasing trend in DJKR, and there were more large-bodied zooplankton in this study. The multivariate analysis revealed that zooplankton compositions changed significantly among the three sampling months without distinguishable spatial variations. Moreover, the zooplankton compositions at all three levels correlated significantly with total nitrogen, water transparency, and permanganate index in most situations, as verified by db-RDA and Mantel’s test. However, the contributions of chlorophyll a and total phosphorus were only significant for the LCF group, implying that the bottom-up effects of phytoplankton on zooplankton were weak in DJKR. Therefore, analysis based on functional groups may reflect a more accurate snapshot of the relationships. Our findings will contribute to enriching the long-term fundamental ecological knowledge of the DJKR and the MR-SNWDP, as well as provide key taxonomic information for ecosystem assessment and management.

The reproductive biology of three yellow catfish congeners was studied in the Three Gorges Reservoir of the Yangtze River, China. We compared reproductive traits among the lentic, transitional, and lotic zones. A total of 4502 individuals of the three species was collected, and the sex ratio, size at 50% maturity, spawning season, fecundity, and egg size were determined. Results showed that populations inhabiting the lotic zone spawned earlier than those inhabiting the lentic zone. For the three species, fecundities were significantly higher for populations in the lotic zone than for those in the lentic and transitional zones (P < 0.05). Pelteobagrus vachelli (Richardson) and P. fulvidraco (Richardson) displayed an obvious trade-off between egg size and fecundity, whereas P. nitidus (Sauvage et Dabry) produced the largest eggs in the lotic zone. Sex ratios were significantly different among zones (P < 0.05, for each species), but the bias patterns were different. Sizes at 50% maturity of female P. nitidus and P. vachelli were the largest in the lotic zone and the smallest in the transitional zone, but was similar among zones for P. fulvidraco. Overall results suggest that the three yellow catfish species developed different reproductive traits among the three habitats in the TGR, whereas the variations reflected further interspecific differences. Our study indicates the importance of riverine habitats for the conservation of species of fish, even for species such as these eurytopic catfish inhabiting the upper reach of the Yangtze River. This study further suggests that species-specific responses should be considered when evaluating the influences of new hydropower projects, even for such closely related species of fish.

The impoundment of the Yangtze River and construction of the Three Gorges Dam and Reservoir created an unnatural flow regime with a 30 m water-level fluctuation and four artificial seasons that differ from the river's natural flow-regime timing. Using stable isotopes, we selected 15 common benthic fish species representing five trophic guilds to analyze seasonal variation in production sources, trophic niche width, and niche overlap. We hypothesized that, similarly to a natural flow regime, artificial hydrological seasons effectively influence fish trophic niches. We found consistency in seasonal shifts in the contribution of aquatic and terrestrial producers to fish biomass. δ¹³C and δ¹⁵N depicted seasonal changes in intra-guild trophic niche width and intra- and inter-guild niche overlap. Considering that the Three Gorges Reservoir's flow regime is artificially regulated, our findings suggest that water-level fluctuation is one of the key mechanisms driving such trophic shifts and allowing multiple species to coexist. Given the increased cascaded large reservoir construction and the concomitant creation of unnatural flow regimes in large rivers worldwide, these findings are timely. Our findings contribute to improving water-level management by optimizing rhythmicity while balancing flood control and fish protection.