How to identify fish species? Observing appearance and color is key

First, look at the size specifications of the fish species. Fish of the same species from the same pond should be uniform and even in size when harvested, with little difference in body length and weight. Conversely, poor-quality fingerlings with large individual differences and uneven sizes often result in very low overall survival rates due to competition for food, mixed genetic stock, poor rearing, and other reasons.

Second, look at the body color of the fish species. High-quality fingerlings have vivid, glossy body colors. Generally speaking, high-quality silver carp fingerlings should have a silver-gray back and silvery-white sides and belly; high-quality grass carp fingerlings have a pale golden-yellow body color, with gray-black reticulated scales that are relatively prominent, and the more robust the fish, the more obvious the pale golden-yellow color; high-quality bighead carp fingerlings mostly have a pale golden-yellow body color, with black markings across the body not very prominent. If the fingerling's body color is relatively dark, or even blackish, it indicates that the fingerling is a weak fry or diseased fish; the gloss on the body surface of fingerlings is caused by the mucus layer covering the body surface, which is the fish's first barrier of defense against disease. Diseased fish or weak fry lack the mucus layer, and their body surface has no gloss.

Third, look at the activity of the fish species. High-quality fingerlings are lively in movement, have a strong schooling instinct, quickly gather in groups and dive to the bottom when startled, have a strong ability to compete for food, and swim strongly against the current. When densely grouped, the fingerlings point their heads downward, with only their tails visible constantly swaying. Weak fry or diseased fish with poorer constitution move sluggishly, do not school, swim alone, have a weak ability to compete for food, and swim poorly against the current.

Fourth, randomly sample fingerlings to check their quality. High-quality fingerlings jump vigorously when out of water, are plump and robust, with small heads and thick backs, glossy body color, lustrous muscle, intact scales and fin rays, gill covers that do not open, tails that do not bend, no parasites or wounds on the body surface, and normal body shape without deformities. Conversely, weak fry or diseased fish jump weakly, have incomplete scales and fin rays, show signs of congestion, are thin and weak, with large heads and small tails, backs as thin as knife blades, and may even have "no belly," "sticking to nets," and so on.