During the rearing stage of aquaculture fry (such as fish fry and shrimp fry), the fry are usually tiny (e.g., newly hatched fish fry are only 2-5 mm in length, and shrimp fry are mostly 1-3 mm) and extremely sensitive to environmental changes. Traditional manual observation methods (such as sampling with beakers and visual judgment) are not only inefficient but also prone to interfering with the fry-rearing environment due to operational errors, resulting in inaccurate observation results. However, underwater HD cameras, with their high-resolution imaging (usually 1080P and above), macro shooting capability, and low-interference characteristics, have become a "precision observation tool" for fry rearing. Their role in monitoring swimming ability, feeding enthusiasm, survival rate, and subsequent optimization of the environment and bait formula can be broken down in detail as follows:

1. Precisely Monitoring the Core Physiological Status of Fry to Provide Data Basis for Optimization

1.1 Swimming Ability: Judging the Vitality and Health Foundation of Fry

• Normal State: Healthy fry (such as freshwater sea bass fry and Pacific white shrimp fry) swim with a stretched body and flexible direction. They actively distribute evenly in the upper and middle layers of the water body and can flexibly avoid slight water currents (such as those generated by aeration and oxygenation) without abnormal movements like "circling" or "rolling over";
• Abnormal Signals: If the lens shows that the fry swim slowly, stay still against the wall, or swing their tails weakly and tilt their bodies, it usually indicates that the fry may have reduced vitality due to poor water quality (such as excessive ammonia nitrogen), lack of oxygen, or infection with pathogens (such as the early stage of white spot syndrome virus in shrimp fry). Workers can quickly capture these subtle abnormalities through real-time images, avoiding the problem of discovering it only when a large number of fry die.

1.2 Feeding Enthusiasm: Evaluating Bait Adaptability and Feeding Rationality

• Observation of Feeding Efficiency: Under the lens, it can be seen that healthy fry will actively chase the bait, swing their heads quickly when feeding, and the bait is ingested in a short time; if it is found that the fry have no reaction to the bait or only touch it without swallowing, it may be that the bait particle size is too large (such as micro-pellet feed exceeding the fry's mouth gape) or the palatability is poor (such as the smell of artificial feed not meeting the fry's feeding habits), and the bait type needs to be adjusted in time;
• Control of Feeding Amount: By observing the amount of remaining bait in the water body (such as whether the rotifer density is too high or the feed pellets are precipitated), excessive feeding (which causes residual bait to pollute the water quality) or insufficient feeding (which leads to fry competition and uneven growth) can be avoided. For example, if a large number of feed pellets are found precipitated at the bottom of the pond during the mysis stage of Pacific white shrimp fry, the feeding amount needs to be reduced to prevent the increase of ammonia nitrogen.

1.3 Survival Rate: Grasping the Fry Loss Situation in Real Time and Tracing the Root Cause of Problems

• Dynamic Counting and Loss Tracking: Set up a lens in a specific area of the fry rearing pond (such as the water inlet and oxygenation area), record the changes in the number of fry in this area regularly, and calculate the overall survival rate based on the pond volume; if a sudden drop in the survival rate is found, the video can be reviewed to find the cause - such as whether the fry are washed into the drainage outlet by the water flow (it is necessary to check whether the anti-escape net is damaged) or whether there are dead fry (dead fry usually float or sink to the bottom, with white bodies and no swimming movements), and then solve the problem targeted (such as repairing anti-escape facilities and testing water quality indicators);
• Phased Survival Analysis: Record the changes in the survival rate from the "initial feeding stage" to the "larval stage". If the survival rate drops sharply at a certain stage (such as the survival rate of fish fry from the larval stage to the juvenile stage is less than 50%), the environmental data of the same period (such as water temperature fluctuation and salinity change) can be combined to determine whether it is caused by environmental stress, providing a basis for the optimization of the subsequent fry rearing process.

2. Assisting in Optimizing the Fry Rearing Environment and Bait Formula to Improve Fry Quality

2.1 Optimization of Water Quality Parameters: Establishing a Regulation Mechanism of "Visual Observation - Data Linkage"

• Adjustment of Water Temperature Adaptability: Different fry have different requirements for water temperature (such as the suitable water temperature for grass carp fry is 20-28℃, and that for salmon fry is 10-15℃). If the lens shows that the fry swim slowly and eat less, and the water temperature monitoring data shows that it is lower or higher than the suitable range, the heating or cooling equipment should be started in time to avoid the impact of water temperature stress on growth;
• Regulation of Salinity and pH Value: In the rearing of marine fry (such as grouper fry), if the lens shows that the fry "swim wildly" and "have more mucus on the body surface", and the salinity data is abnormal (such as a sudden increase or decrease of more than 5‰), it is necessary to quickly supplement fresh water or seawater to adjust the salinity; if the pH value deviates from the suitable range (such as the suitable pH for shrimp fry rearing is 7.8-8.5), the lens may show that the fry's breathing rate accelerates (the gill cover opens and closes quickly), and it is necessary to adjust by sprinkling quicklime (to increase pH) or organic acid (to decrease pH) to maintain the stability of water quality;
• Management of Dissolved Oxygen and Water Transparency: When the lens shows that the fry cluster near the oxygenation port (a precursor to "floating head"), even if the dissolved oxygen meter shows that the data is close to the critical value (such as the dissolved oxygen required for fry rearing is ≥5mg/L), it is necessary to immediately increase the oxygenation intensity to prevent the sudden drop of dissolved oxygen from causing fish pond die-off; at the same time, observe the water transparency through the lens (such as whether it is turbid or there is a large amount of algae reproduction) to determine whether it is necessary to change water or add water quality improvers (such as photosynthetic bacteria) to create a clear water environment suitable for fry growth.

2.2 Upgrading of Bait Formula: Bait Improvement Direction Based on Visual Feedback

• Adjustment of Nutritional Components: If it is found that the fry eat normally but grow slowly (the size of the fry varies greatly under the lens), it may be that the bait lacks key nutrients such as protein and unsaturated fatty acids (such as rotifers not being nutritionally enriched), and it is necessary to add fish oil, yeast, etc. to the bait to improve the nutritional density;
• Optimization of Physical Properties: For artificial micro-pellet feed, if the lens shows that the feed disperses quickly in water (making it difficult for fry to eat) or sinks too fast (fry cannot chase in time), it is necessary to adjust the proportion of binders in the feed (to improve stability) and density (to extend the suspension time in the upper and middle layers of the water body), so as to enhance palatability and utilization rate;
• Optimization of Bait Combination: For example, during the "feed transition period" of fry (from natural bait to artificial feed), the acceptance of the mixed feeding of "natural bait + artificial feed" by the fry is observed through the lens, and the proportion of the two is adjusted gradually to reduce the survival rate decline caused by feed transition stress, and finally achieve a smooth feed transition.

3. Core Value: Transformation from "Experiential Aquaculture" to "Precision Fry Rearing"

• Early Risk Warning: Before a large number of fry die and the water quality deteriorates seriously, timely intervention is carried out through subtle abnormalities (such as changes in swimming and feeding) to reduce the loss of fry rearing;
• Precise Cost Control: Reduce resource waste (such as residual bait pollution and excessive use of drugs) caused by inappropriate bait and improper water quality regulation;
• Improvement of Fry Quality: The fry produced are energetic, evenly growing, and highly stress-resistant, laying a good foundation for the subsequent adult fish/adult shrimp culture and indirectly improving the aquaculture efficiency.