Summary of the Trial on Introducing and Farming the Giant Mudskipper

The giant mudskipper is a small warm-temperate, humid-tropical coastal economic fish. It prefers to inhabit harbors and estuarine brackish waters and intertidal muddy flats, living in burrows it digs. Its flesh is delicious and nutritious, making it a specialty species with development prospects. To fill the gap in local aquaculture, in 2006 we actively introduced giant mudskipper fry and conducted farming trials. After several months of exploration, the trial succeeded, and we have basically mastered the farming techniques for the giant mudskipper. The farming method for the giant mudskipper is briefly described below.

I. Basic information of the trial

The trial site @#@185@#@ was in the aquaculture zone of Rongxing Township, Dawa County, Liaoning Province. Two standard ponds were used, with a total farming area of 10 mu. Per mu, 3,000 giant mudskipper fry of 4 cm in size were stocked. After 153 days of artificial farming, harvest by capture @#@136@#@ began in early October.

II. Specific implementation steps

1. Early-stage preparation work: First, clear the mud from the pond bottom, then dig a "field"-shaped ring ditch with a depth of 0.5 m. Use quicklime at 100 kg/mu, mix with water, and splash it over the whole pond for disinfection. After exposure to the sun for 3 days, fill with water and wash the pond. Begin fertilizing the water 1 week before releasing fry, using fresh rice bran at 30 kg/mu to fertilize the water, then fill with water to 20 cm. Three days before releasing fry, propagate the benthic algae. Finally, install anti-escape facilities by surrounding the dike with plastic film, the same as @#@235@#@.

2. Fry stocking: Fry were released on May 2, with fry size 4 cm and 3,000 fry per mu. Before release, they underwent strict inspection and disinfection treatment. The fry had complete fins, intact scales, no mechanical injuries, and strong vitality. They were soaked in a 30 mg/L potassium permanganate solution for 20 minutes.

3. Farming management

(1) Feed organisms: The giant mudskipper feeds on benthic diatoms or blue-green algae and does not directly consume feed such as rice bran or fish paste. Cultivating benthic diatoms well and ensuring the giant mudskipper can eat enough food is necessary to maintain its growth rate, so drying the flat and applying fertilizer must be done frequently. After a period of cultivation and management following fry stocking, when the total length reaches more than 5 cm and the fish can already dig burrows and live in them, the benthic diatoms disappear and the water quality becomes turbid. At this time, drainage, flat drying, and fertilization must be carried out to promote the diatoms to reproduce again. For drainage and flat drying plus fertilization, leave water only in the central ditch and ring ditch, choose clear weather and dry the flat for 2-3 days, then apply rice bran. The amount of fertilizer applied should be flexibly controlled according to how much residual benthic diatom remains. Usually, 20-30 kg of rice bran is applied per mu. Dry the flat and apply fertilizer once every 15-20 days.

(2) Water quality regulation: The giant mudskipper is a eurythermal and euryhaline fish with low requirements for seawater salinity. It likes to live in brackish waters, with pond water salinity of 5-15 and water temperature of 24-30°C being more suitable. In the early stage after stocking, before the fry have burrowed deeper, to prevent excessive fluctuations in water temperature, the pond water on the flat surface should be kept above 20 cm. When the fish body length is more than 5 cm, the fish dig relatively deep burrows, and the water depth should be kept at 5-10 cm. During cold wave invasions on cloudy days, inject new water and maintain a relatively deep water level. During periods of heavy rainstorms or long drought, change the water or add fresh water in a timely manner to regulate pond water salinity.

(3) Daily management: During the grow-out period, patrol the pond every day to observe the fish's feeding and growth conditions and the reproduction status of benthic diatoms, and carry out anti-escape, anti-theft, and anti-predator work at all times. When problems are found, take measures promptly.

(4) Disease and pest control: The main predators during the giant mudskipper grow-out period are harmful birds and parasites. Old gill nets can be used as overhead nets to prevent harmful birds such as egrets from flying into the pond and preying on the giant mudskippers. When parasites such as abdominal flukes are found on the fish, an infusion of dipterex can be splashed over the whole pond to kill them, with a commonly used amount of 0.3-0.4 g/cubic meter.

4. Results: In early October, 614 kg of commercial giant mudskippers were harvested, totaling 26,010 fish, with a recapture rate of 86.7%, an average size of 23.6 g, and an average monthly weight gain rate of 156.7%.

The total cost was 26,000 yuan, including 15,000 yuan for fry, 1,000 yuan for rice bran, 2,500 yuan for labor, 1,000 yuan for anti-escape measures, 1,500 yuan for water and electricity, 2,000 yuan for infrastructure, 61,000 yuan for drugs, and 2,000 yuan for other expenses.

The average selling price was 60 yuan/kg, creating a total output value of 36,800 yuan and achieving a total profit of 10,800 yuan.

III. Observations

The results show that the giant mudskipper has strong adaptability to the environment and a high farming survival rate; it grows quickly, with a monthly weight gain rate above 150%, suitable for the needs of aquaculture production; its food chain is short and it directly feeds on benthic algae, reducing feeding costs; it has few diseases, and no diseases were found during the farming process; the farming technology is relatively simple and easy to promote; and its economic value is relatively high, with farming benefits higher than other conventional species.

Although the trial succeeded, there are still some shortcomings: First, regarding fry, if large-scale farming is to be carried out, a large number of giant mudskipper fry will be needed, and centralized transport from the south is inconvenient and expensive, increasing farming costs. Therefore, this problem must be solved locally. We have already selected and retained some larger giant mudskippers for overwintering, preparing to carry out trials on artificial seedling rearing of giant mudskippers in soil ponds next spring. In the next two years, we will successfully master the technology for artificial seedling rearing of giant mudskippers in soil ponds and then carry out large-scale production to provide healthy and high-quality giant mudskipper fry for this region and surrounding areas. Second, regarding sales prices, consumers in northern regions currently do not have sufficient awareness of the nutritional and medical value of the giant mudskipper, and further publicity and guidance are needed, so that sales prices are far lower than in southern provinces. If the same price were reached, we would obtain better economic benefits. In addition, in the early stage of the trial, the issue of bird damage was neglected in anti-escape and anti-predator work. Because the farming water surface was relatively shallow, many water birds entered the pond to prey on giant mudskippers, causing some losses. After the problem was discovered, countermeasures were taken promptly, and old gill nets were set up over the pond as overhead nets, so harmful birds could not fly in, and the effect was good.