The fry are too small to uproot the seedlings and because this is the peak period for plankton, fry growth is enhanced. It is best to release the fry as early as possible to take full advantage of this peak in plankton growth. If the artificial hatching of fry is delayed, the application of base manure and the transplanting of early rice should also be delayed to maximize the mutual benefits that can be achieved. At present, large fish-fry breeding farms have advanced the season of fry hatching to late April and the rice growers on these farms delay the transplanting of rice seedlings. But the practice has not gained much popularity.
Additional effort is needed to disseminate the idea and launch demonstration projects.
Along the Yangtze and Zhujiang Rivers, where people catch river fry, it is better to put these fry into early ricefields because it makes it easier to regenerate fish of the same family. It eliminates the need to buy summer fry, means that ponds are not needed for summer fry, and maximizes the mutual benefits of growing rice and fish together. It is an economical, practical method that yields better and faster results. Ctenopharyngodon idella , with its ability to eliminate weeds and worms, can help increase rice output and reduce the need for labour. Even in ricefields overgrown with weeds, it is feasible to grow C. idella along with some C. carpio and C. auratus .