How to Increase Oriental River Prawn Yields in Mixed Shrimp-Crab Ponds

Mixed shrimp-crab culture is the main aquaculture model promoted under the fishery science and technology outreach program in Xiangcheng District. In recent years, while river crab prices have repeatedly been hit by the market, oriental river prawn prices have remained relatively firm. Therefore, while ensuring river crab growth, tapping the production potential of oriental river prawn has become an effective way to achieve high efficiency in mixed shrimp-crab culture. Below is a brief discussion of the technical points for increasing oriental river prawn yields in mixed culture ponds:

1. Optimize the stocking structure and seize the production potential of spring prawns

As for the stocking structure, it is necessary to adapt to local conditions on the basis of learning advanced models, and choose a reasonable stocking model according to the conditions of one's own pond. Since river crabs are smaller in size and lower in biomass from March to June, the production potential of spring mysid prawns should be fully utilized at this time. The river crabs can first be enclosed in the ring ditch for culture, while the large space outside is used for planting aquatic plants and culturing oriental river prawns. In this way, not only can the aquatic plants grow fully, but the oriental river prawns also gain sufficient growth space. In addition, feeding should start early in spring; once the water temperature reaches above 15°C, a small amount of highly nutritious feed should be given to replenish the strength of the oriental river prawns, so that they can smoothly molt and grow, go on the market early, and gain a price advantage.

2. Persist in supplementing autumn prawns

Some farmers believe that oriental river prawns will reproduce in the pond, so they do not stock autumn fry, and as a result the autumn prawn yield is very low. In fact, due to asynchronous timing, pond water quality and environmental conditions, the survival rate of self-bred oriental river prawn fry is not high, and the size is not uniform either. Therefore, it is necessary to supplement about 25,000 autumn prawn fry per mu to ensure a good yield of autumn commercial prawns and mysid prawns.

3. Pay attention to water quality

River crab culture requires relatively clear water, while the growth of oriental river prawns requires a certain degree of fertility; the water needs to be lively and refreshing, and water that is too lean is not conducive to the growth of oriental river prawns. Therefore, biological fertilizers and microbial preparations should be used to regulate water quality and control the water fertility at a moderate level, so as to meet the growth needs of oriental river prawns without affecting the growth of river crabs.

4. Reasonably combine aquatic plants

Shrimp-crab ponds in Xiangcheng District generally plant Elodea. Elodea is easy to establish, but it is not tolerant of high temperatures, so multiple aquatic plants need to be planted to complement each other. Generally, it can be combined with hydrilla, tape grass, and so on.

5. Feed nutrition and feeding

In mixed shrimp-crab ponds, to ensure that both shrimp and crabs get enough feed, the feeding technique can be improved. Feed with a slightly lower protein content (for example, 36%-38% protein) can first be given to the river crabs (accounting for 70% of the total feeding amount), and then feed with a slightly higher protein content (for example, 38%-40%) can be given to the oriental river prawns (accounting for 30% of the total feeding amount), so that both shrimp and crabs obtain sufficient nutrition.

6. Use microporous aerators

Since oriental river prawns have relatively high dissolved oxygen requirements, the dissolved oxygen in the pond must be kept sufficient. In view of the fact that paddle-wheel aerators easily injure or kill nearby shrimp and crabs, it is recommended to use microporous aerators for aeration.