What types of grouper are there? What are the key points for farming them?

Grouper is a medium-to-large marine fish, mainly distributed in coastal areas. Its flesh is tender and nutritious, tasting somewhat like chicken, and it is deeply loved by people. Most of what is on the market today is farmed. So what types of grouper are there? What are the key points for farming them?

I. What types of grouper are there?

1. Leopard coral grouper (common in Hainan)

The leopard coral grouper comes in colors including blue, red, brown and yellow. Its body is more slender than that of ordinary groupers, with a small head. Its blue eyes have jet-black pupils, and its body is covered with tiny white spots, resembling stars in the sky, which is why it is called “star grouper”; as for the “eastern” part of its name, that is because it is produced in the Dongsha Islands in eastern China.

2. Speckled grouper

The speckled grouper generally has a body length of 25 cm to 30 cm, and its body surface as well as all fins except the pectoral fins are covered with gem-like spots. The pectoral fins bear reddish streaks, and the caudal fin is slightly concave with a white edge. It is a warm-temperate, mid-to-lower-layer fish, mostly living in sea areas with a rocky reef substrate, with sex reversal, being first female then male. Growth is relatively slow. Grouper is ferocious and alert, feeding mainly on meat, preferring fish, shrimp and crabs; it does not like to form schools, and when hungry it may engage in cannibalism. The speckled grouper is distributed in the Indian Ocean and the western Pacific Ocean, and in China it is produced in the South China Sea. Several provinces in China carry out artificial cage farming of it.

3. Green grouper

The green grouper has several orange-red spots on the lower part of its body, and 6 dark brown vertical stripes on its flanks, with the widest gap between the 3rd and 4th bands. Only the caudal fin bears spots. It is a warm-water, mid-to-lower-layer fish. Juveniles and larvae feed on plankton, while adults feed on fish, shrimp and crabs. It is hermaphroditic, with females maturing first, and sex reversal occurring at a body length of 250 mm to 400 mm; males all mature sexually at 6 years old (a few at 5 years old). Absolute fecundity is 80,000 to 250,000 eggs, and the spawning period is from late May to July, with spawning beginning at 20°C and peaking at 22°C to 24°C; it lays pelagic eggs. At a water temperature of 22°C to 25°C, it takes 23 hours to 30 hours for larvae to hatch. Its flesh is delicious, making it a valuable fish, and live fish are sold in large quantities to Hong Kong, China and Macao, China. It is a target species for shallow-sea farming in China and Southeast Asia, and can be farmed in cages. It is distributed in Taiwan, China, the East China Sea and the South China Sea, as well as Japan.

4. Orange-spotted grouper

The orange-spotted grouper has a short, blunt snout, 8 to 11 spines in the dorsal fin, no black spots at the base, 5 indistinct transverse bands on its flanks, and spots scattered on its flanks and various fins. It is a tropical, mid-to-lower-layer fish that prefers to inhabit sea areas with a rocky reef substrate, and is a valuable fish of the South China Sea. It is ferocious and feeds mainly on meat, preferring fish, shrimp and crabs, and engaging in cannibalism when hungry. It can live in waters with a salinity of 11‰ to 41‰, with an optimum water temperature of 22°C to 28°C; below 18°C its appetite decreases, and below 15°C the fish loses its balance. It can be farmed in cages. It is distributed in sea areas such as the East China Sea and the South China Sea of China.

II. What are the key points for farming grouper?

1. Selection of fry and broodstock

For broodstock, artificially farmed adult fish or adult fish caught from natural sea areas can be used. For females, choose those weighing 5 kg to 8 kg with a swollen and soft abdomen; for males, choose those weighing more than 8 kg from which semen can flow out when the abdomen is gently pressed. Female and male broodstock are matched at a ratio of 3:1 to 8:1, and the grouper broodstock are kept or held temporarily in indoor cement ponds. Through artificial intensive rearing, with daily water changes and siphoning of waste, the broodstock can naturally spawn and fertilize without hormone-induced spawning, yielding high-quality fertilized eggs.

2. Daily management

Choose reasonable cage and fish-raft densities to prevent oxygen-deficiency accidents. During the farming process, in addition to feeding, frequently observe and check the fish's growth, feeding, activity and body color, and also frequently check whether the cages are damaged and how much fouling organism is attached. Regularly remove the fouling organisms attached to the cages to keep the water flow inside and outside the cages unobstructed, regularly monitor water quality, and protect the farming environment. Monitor the farming water according to the first-class seawater quality standard issued by the state, which is conducive to the normal growth of grouper and the deliciousness of its flesh, and prevents accidents caused by water quality deterioration.

3. Bait feeding

Under normal conditions, some bait organisms such as rotifers and copepod nauplii should be kept in the pond for the larvae to feed on. Check the density of live bait in the pond water three times a day, in the morning, at noon and in the afternoon. If the density of live bait is found to be insufficient, appropriately supplement live bait such as rotifers and copepods to keep the pond's bait organisms abundant; if there is no live bait, appropriately splash compound feed such as spirulina powder and shrimp flakes (use a 200- to 80-mesh silk screen to filter according to the size of the fry before feeding), to reduce cannibalism among the fry and increase the survival rate of the fry.

In the later stage of fry rearing, an appropriate amount of minced fish and shellfish meat can be added, or 0.15 to 0.3 ppm powdered compound feed can be fed directly. Check the bait density 2 to 3 times a day, and feed just enough for the fry to reach satiation.