Experience and Techniques for Polyculture of River Crabs and Bass in Summer

This polyculture model of river crabs and bass fully utilizes the water body space, forming a composite ecosystem where fish and crabs coexist in a mutually beneficial relationship, reducing the disease rate, greatly improving the market quality of commercial crabs, and increasing farming income. The technical key points are summarized below:

Pond Cleaning and Preparation

After the pond has been exposed to the sun, use 80 kg of quicklime per mu to disinfect the pond, killing harmful organisms and pathogenic bacteria. Seven days before stocking crab seedlings, fill with water 0.5 m deep, apply 60 kg of chicken manure per mu to cultivate plankton feed, making the water color yellow-green with a transparency of 30 cm depth, and plant some aquatic plants for river crabs to inhabit.

Seedling Stocking

Crab seedlings: In mid-May, stock 1000 juvenile crabs per mu, with a size of 160-200 per kg. Crab seedlings should be robust, with complete limbs, free of parasites and diseases.

Bass fry: In late June, stock 30 desalinated bass fry per mu, with a body length of 2.5-3 cm. Bass fry should be uniform in size, agile in movement, with normal body color, free of parasites and other diseases.

Precautions: Bass are naturally aggressive. In fish-crab polyculture, attention should be paid to controlling the time difference in stocking. Only when crab seedlings have grown to a size of 60-80 per kg can bass fry be put into the pond, to avoid juvenile crabs being harmed. At the same time, large-sized crab seedlings should be stocked as much as possible.

Feed Feeding

River crab feeding adheres to the principle of “meat and vegetable pairing, combining green and concentrated feed.” Before bass fry are put into the pond, juvenile crabs are mainly fed animal-based bait to quickly grow them to a size of 60-80 per kg. Throughout the farming process, the proportion of complete formula feed for river crabs accounts for about 30% of the feeding amount. The feeding amount should be flexibly controlled according to the growth, feeding and weather conditions of river crabs. Molting hormone should be regularly added to the bait to prevent molting failure. Bass are fed complete fish pellet feed, adhering to the “four fixed” principle.

Water Quality Regulation

River crabs prefer a fresh water quality environment, with transparency controlled at 35 cm depth. In the high-temperature season, add water 10 cm deep daily until the maximum water level is reached, and splash EM biological preparation over the entire pond 1-2 times to improve the water environment.

Disease Prevention and Control

Monthly, appropriately splash quicklime and monocalcium phosphate to improve water quality, with a dosage of 10 kg per mu. Bass are carnivorous fish. Fish-crab polyculture can consume excess small miscellaneous fish and shrimp, keeping the water quality clean and greatly reducing the occurrence of diseases.

Pond Patrol Management

Observe water color, escape, feeding, molting and disease conditions daily, so as to take timely countermeasures.