CATDOLL : CATDOLL: Is grouper from the sea or the river?

Does grouper come from the sea or the river?

Grouper is a tropical fish in the sea, which can be divided into wild and farmed.

Wild: The skin is lighter in color, and the meat is firmer when pressed by hand. The fish tastes fragrant, and the meat fibers are coarse and not very loose.

Farmed fish are the opposite, their bodies are darker, their meat is softer, their taste is lighter, with only a hint of fish smell (because they only eat fish food), and their meat is smoother.

Farmed grouper grows in freshwater and can also grow in seawater with a salinity of less than 10‰. Its suitable temperature range is between 25-30℃. When the water temperature drops to 20℃, its food intake decreases significantly, and when the water temperature drops to 15℃, its body loses balance. Therefore, areas where the water in the pond drops below 15℃ during winter are not suitable for farming this fish.

Is there any book specifically explaining ocean salinity and temperature? If anyone has studied ocean salinity and temperature, please leave a message!

Fish live in water, whether fresh water or sea water. The aquatic environment affects the growth and reproduction of fish, and affects the physiology and ecological balance of fish. There are many kinds of variable factors in the aquatic environment. If these variable factors exceed the limit that the fish can tolerate, they can make the fish sick or endanger its survival.

The physical and chemical factors of the ocean, such as temperature, salinity, pH, dissolved oxygen, water flow, water pressure, etc., and understanding the changing patterns of these factors are the scientific basis for improving marine fish farming production.

1. Water temperature

Fish are cold-blooded animals, and their body temperature changes with the surrounding water temperature. The body temperature of most fish is about 0.1~1℃ different from the surrounding water temperature. All kinds of fish have their upper and lower limits of heat resistance and their optimum temperature. Within the optimum temperature range, fish have vigorous feeding, breathing, and digestive functions, enhanced metabolism, and rapid growth. Exceeding the optimum temperature range can lead to metabolic disorders, growth inhibition, and even death.

According to the adaptability of fish to temperature, they can be divided into tropical fish, warm water fish and cold water fish. Tropical fish are suitable for higher water temperature (25~30℃), but cannot tolerate low temperature, and it is difficult to survive below 15~30℃. Such as tilapia, milkfish, sharp-nosed perch and some coral fish. Warm water fish are suitable for temperate waters (15~25℃), such as mullet, barracuda, grouper, etc., while cold water fish are suitable for low temperature growth, such as salmon and trout, which are suitable for water temperature of 10~18℃. The water temperature should not exceed 20℃ during breeding.

Groupers mostly live in tropical and temperate seas with rocky bottoms. Their optimum water temperature is 24~30℃, but there are differences between various groupers. For example, the upper limit of the half-lethal temperature of salmon grouper is 38.5~39.5℃, and the lower limit is 11.5~13.0℃. The optimum temperature of red-spotted grouper is 22~28.5℃. If the water temperature exceeds 32℃, the grouper will lose balance, and the red-spotted grouper will easily die at 32.2℃. 32℃ is the upper limit of these groupers, and the lower limit is 15℃. At 15℃, the fish lose balance, stop eating, and do not move. When the water temperature drops to 14℃, the weak and the spotted grouper are prone to death, especially the spotted grouper produced in Thailand and the Philippines, which cannot tolerate low temperatures.

The suitable temperature for tilapia is 25-30℃. It is easy to die at temperatures below 12℃ and above 35℃. At 12℃, the fish is in a depressed state and lies on its side at the bottom of the water. If the temperature drops further, it will die. Above 35℃, the fish's breathing rate speeds up, leading to death.

Large yellow croaker will not eat when the water temperature is below 12℃, and will die when the water temperature is 5.8~6℃. The high temperature cannot exceed 33℃.

The suitable water temperature for yellowtail is 18~29℃. It stops growing below 13℃ and has difficulty surviving below 9℃. The water temperature for wintering cannot be lower than 10℃.

The suitable water temperature for red sea bream is 20~28℃. They eat a lot and can survive in summer when the water temperature reaches 30℃. Their growth stagnates when the water temperature is 12℃, they stop eating when the water temperature is below 10℃, and they die when the water temperature is below 4℃.

The barramundi is a tropical fish that cannot tolerate low temperatures. It stops eating below 17°C, becomes unresponsive at 15°C, loses balance at 14°C, and begins to die in small quantities. However, the sea bass can tolerate low temperatures, and can survive temperatures as low as 9-9.5°C and water temperatures as low as 13.5-14°C without dying.

Based on the above situation, breeders in various regions need to understand the local annual temperature and water temperature changes and stock suitable breeding species to avoid losses after production.

2. Salinity

The dissolved salts in water vary depending on the water body, and the classification standards are also inconsistent. Water with a salinity of 31~41‰ is generally called seawater or alkaline water, while water with a salinity of ∠0.5‰ is fresh water.

Fish have certain physiological regulation mechanisms for water with different salinities, but they are limited to a certain range. Exceeding this range will affect their survival. According to the adaptability of fish to salinity changes, they can be divided into two categories: euryhaline and stenohaline. Red grouper and black sea bream are euryhaline fish, which can tolerate greater changes in salinity.