Grass carp is used to the water temperature of 20 ~ 32℃. In this water temperature range, grass carp eat more frequently. When the water temperature is 27 ~ 30℃, grass carp eats the most. When the temperature is higher than 35℃, the upper water temperature is higher than 30℃. In order to escape from summer, grass carp will forage in the middle and lower layers, so they can choose to fish at the bottom or 10~30 cm away from the bottom.

Grass carp (Ctenopharyngodon idellus) is a fish of CYPRINIDAE and Ctenopharyngodon, with a long body, a slightly blunt nose and mouth, a short gill rake, a yellowish brown body, a grayish-white abdomen, a grayish-black pectoral fin and ventral fin, and light-colored other fins. It lives in rivers and lakes in plain areas, and generally likes to live in the middle and lower layers of water and coastal areas with more aquatic plants. It has many activities, swims fast and often feeds in groups.

Morphological characteristics of grass carp;

Body length is 3.4 ~ 4.0 times of body height, 3.6 ~ 4.3 times of head length, 7.3 ~ 9.5 times of tail stalk length, 6.8 ~ 8.8 times of tail stalk height, head length is 3.0 ~ 4. 1 times of kiss length, 5.3 ~ 7.9 times of eye diameter and eye spacing is 65438+. The length of the tailstock is 0.8 ~ 1. 1 times the height of the tailstock.

The body is long, the front is nearly cylindrical, the tail is flat, the abdomen is round, there is no abdominal margin, the head is wide and medium-sized, the front is slightly flat, the kiss is short and blunt, slightly longer than the eye diameter, the position of the mouth end, the mouth crack is wide, the mouth is slightly longer than the mandible, the end of the maxilla extends below the nostril, the posterior labial groove is interrupted, the distance is wide, and it is located in the front half of the head, and the eye is wide.

The branchial foramen is wide and extends forward to the lower part of the posterior edge of the anterior branchial lid. The gill cover is connected with the isthmus, which is wide and round with large scales. The front of the lateral line is curved and the back is straight, reaching the base of the caudal fin. The dorsal fin has no hard spines, the outer edge is straight, and it is located above the ventral fin, and the distance from the starting point to the base of the caudal fin is closer than that of the snout.

The gluteal fin is located behind the dorsal fin, and the distance from the starting point to the base of the caudal fin is close to the starting point of the ventral fin. The tip of the fin reaches the base of the caudal fin and the pectoral fin is short and blunt. The distance from the end of the fin to the beginning of the ventral fin is greater than 1/2 of the length of the pectoral fin. The caudal fin is shallowly forked, the upper and lower leaves are about the same length, the gill rakes are short and few, the hypopharynx is moderately wide and slightly hooked, the hind arm is slightly larger, and the mandible is slightly hooked.

Comb-shaped, with grooves on the side, straight crown and 1 narrow groove in the middle. The swim bladder has two chambers, the front chamber is thick and short, the rear chamber is longer than the front chamber, the distal end is pointed, the intestine is long, and it has many circles, which is more than twice as long as the body. The peritoneum is black, the body is yellowish brown, the abdomen is grayish white, the scales on the side of the body are grayish black, the pectoral fins and ventral fins are grayish yellow, and the other fins are pale.