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How to identify high-quality fish fry? Selection tips every farmer must know

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"Good seed is half the profit, good seedlings are half the grain." Robust, high-quality fish fry are not only an important factor in improving the survival rate of fry, but also an important foundation and guarantee for increasing fish yield and boosting economic returns. High-quality fish fry should have: appropriate and uniform size, robustness without injury, lively movement, and strong feeding competitiveness. Specifically, identifying high-quality fish fry can be summarized as "three looks and one sampling." First look: the size of the fry. The harvested size of the same fish species from the same pond should be neat and uniform, with little difference in body length and weight. In contrast, inferior fry with large individual differences and unevenness, due to reasons such as food competition, mixed germplasm, and poor feeding, often have a very low overall survival rate. Second look: the body color of the fry. High-quality fry have bright and glossy body color. Different species and different feeding methods produce fry with different body colors. Generally speaking, high-quality silver carp fry should have a silver-gray back and silvery-white sides and belly; high-quality grass carp fry have a light golden-yellow body color, with gray-black net-like scales relatively obvious, and the more robust the fish, the more prominent the light golden-yellow; high-quality bighead carp fry mostly have a light golden-yellow body color, with black markings all over the body not very obvious. If the body color of the fry is darker, or even blackish, it indicates that the fry are weak or diseased. The gloss on the body surface of the fry is caused by the mucus layer covering the body surface, which is rich in proteases, lysozymes, etc., and has the function of protecting the scales and skin of the fry from invasion by diseases and pests; fish or weak fry lack a mucus layer, so the body surface has no gloss. Of course, when fry are attacked by external diseases and pests, they will also secrete a large amount of mucus and lose their gloss. For example, when fish are attacked by Ichthyophthirius multifiliis, the body surface will be covered with a thick layer of mucus, which is a stress response made by the fry to external invasion. Third look: the activity of the fry. High-quality fry are lively in movement, strongly gregarious, quickly gather in groups and dive to the bottom when startled, have strong feeding competitiveness and strong upstream swimming ability. When crowded, the fry heads point downward, and only the tails can be seen constantly fanning; while weak or diseased fry with poor constitution move slowly, do not form groups, swim alone, have weak feeding competitiveness, and poor upstream swimming ability. One sampling: randomly sample fry to check their quality. High-quality fry jump violently when out of water, are plump, with small heads and thick backs, glossy body color, moist muscles, intact scales and fin rays, gill covers not open, tails not bent, no parasites or wounds on the body surface, and normal body shape without deformities. In contrast, weak or diseased fry jump weakly, have incomplete scales and fin rays, congestion, emaciated bodies, large heads and small tails, backs as thin as a knife edge, and even those with "no belly" or that "stick to the net" are considered inferior fry.

"Good seed is half the profit, good seedlings are half the grain." Robust, high-quality fish fry are not only an important factor in improving the survival rate of fry, but also an important foundation and guarantee for increasing fish yield and boosting economic returns. High-quality fish fry should have: appropriate and uniform size, robustness without injury, lively movement, and strong feeding competitiveness. Specifically, identifying high-quality fish fry can be summarized as "three looks and one sampling." First look: the size of the fry. The harvested size of the same fish species from the same pond should be neat and uniform, with little difference in body length and weight. In contrast, inferior fry with large individual differences and unevenness, due to reasons such as food competition, mixed germplasm, and poor feeding, often have a very low overall survival rate. Second look: the body color of the fry. High-quality fry have bright and glossy body color. Different species and different feeding methods produce fry with different body colors. Generally speaking, high-quality silver carp fry should have a silver-gray back and silvery-white sides and belly; high-quality grass carp fry have a light golden-yellow body color, with gray-black net-like scales relatively obvious, and the more robust the fish, the more prominent the light golden-yellow; high-quality bighead carp fry mostly have a light golden-yellow body color, with black markings all over the body not very obvious. If the body color of the fry is darker, or even blackish, it indicates that the fry are weak or diseased. The gloss on the body surface of the fry is caused by the mucus layer covering the body surface, which is rich in proteases, lysozymes, etc., and has the function of protecting the scales and skin of the fry from invasion by diseases and pests; fish or weak fry lack a mucus layer, so the body surface has no gloss. Of course, when fry are attacked by external diseases and pests, they will also secrete a large amount of mucus and lose their gloss. For example, when fish are attacked by Ichthyophthirius multifiliis, the body surface will be covered with a thick layer of mucus, which is a stress response made by the fry to external invasion. Third look: the activity of the fry. High-quality fry are lively in movement, strongly gregarious, quickly gather in groups and dive to the bottom when startled, have strong feeding competitiveness and strong upstream swimming ability. When crowded, the fry heads point downward, and only the tails can be seen constantly fanning; while weak or diseased fry with poor constitution move slowly, do not form groups, swim alone, have weak feeding competitiveness, and poor upstream swimming ability. One sampling: randomly sample fry to check their quality. High-quality fry jump violently when out of water, are plump, with small heads and thick backs, glossy body color, moist muscles, intact scales and fin rays, gill covers not open, tails not bent, no parasites or wounds on the body surface, and normal body shape without deformities. In contrast, weak or diseased fry jump weakly, have incomplete scales and fin rays, congestion, emaciated bodies, large heads and small tails, backs as thin as a knife edge, and even those with "no belly" or that "stick to the net" are considered inferior fry.

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