Daily Management Essentials for Cage Culture of Yellow Catfish

The daily management of yellow catfish raised in cages includes cage inspection, fish growth inspection, cage net cleaning and disease prevention and control.

1) Routine inspection

Routine inspection includes cage net inspection and inspection of fish growth inside the cage.

1. Cage net inspection Cage net inspection includes inspection before and after stocking fingerlings and inspection during the rearing process, and both are very important. After fingerlings are stocked, inspect the cage body once in the morning and once in the evening each day to see whether the netting is damaged. The inspection method is to slowly lift the four corners of the cage in turn and carefully check whether the netting is damaged, whether the mesh has been bitten through by water rats, whether it has been pierced by dorsal and pectoral spines, and whether the cage body has been damaged during operations. If problems are found, repair them promptly. To prevent fish from escaping through broken netting, a double-layer cage is generally used; when inspecting, check the inner cage first, then the outer cage.

2. Inspection of fish growth inside the cage Because cage culture of yellow catfish requires graded rearing, and the important basis for graded rearing is whether the fish have grown to a certain stage. Only by regularly inspecting the fish can their growth condition be understood, which not only provides a practical basis for feeding but also provides reliable data for estimating production. Growth inspection is generally required every 5-7 days in the early stage and once every half month in the later stage, analyzing existing problems and promptly taking corresponding measures. The method for checking fish growth is generally to use a dip net to scoop the yellow catfish from the cage into a small basin or bucket, then use a ruler to measure the fish. At the same time, observe the plumpness of the fish so as to adjust feeding in time.

2) Cleaning of cage-body fouling

Generally speaking, 3-5 days after the cage is placed in the water, a large amount of fouling will attach to it, and afterward filamentous algae, diatoms and algae such as Mougeotia will attach as periphytic algae (also called attached algae), clogging the mesh, thereby affecting water exchange inside and outside the cage and being unfavorable for yellow catfish culture. In this case, manual removal is necessary. At present, domestic cage fish culture uses the following methods to clean the netting:

1. Manual cleaning When there is relatively little attachment on the cage, first lift the netting by hand, then shake off the fouling, or directly immerse the netting in water and scrub it. When there is too much attachment, scrub it with a hard brush, or directly immerse the netting in water and beat it with a bamboo strip to shake it off. Operate carefully to prevent injuring fish and breaking the net.

2. Mechanical cleaning When the scale of cages is relatively large, a water spray gun or submersible pump can be used to wash off the fouling on the netting with a strong water current.

3. Cage sinking method Various filamentous green algae are generally difficult to grow and reproduce below a water depth of 1 m. Therefore, sinking a closed cage to 1 m below the water surface can reduce attachment on the netting. However, this method often affects feeding and management and is unfavorable to fish growth, so when using this method, adapt it to local conditions and decide after weighing the pros and cons.

4. Biological cleaning method By using the habit of fish such as xenocyprinids (such as fine-scaled yellowtail xenocyprid and yellowtail xenocyprid) of liking to scrape and eat attached algae and swallow filamentous algae and organic debris, appropriately stock yellowtail xenocyprid, fine-scaled yellowtail xenocyprid and other fish in the cage and let them scrape and eat the organisms attached to the cage, so as to keep the netting clean and the water flow unobstructed. Using this biological method to clean fouling can not only make full use of the bait organisms in the cage but also increase the cultured species, raising fish yield and economic benefits.

3) Management during disastrous weather and keeping good log records

1. Management during disastrous weather Disastrous weather mainly refers to strong winds, rainstorms and floods. Strong winds often occur together with rainstorms. Cages set in lakes and large water areas may sometimes be overturned or submerged by wind and waves, so before strong winds blow, the frame and support posts of the cage must be checked for firmness. For fixed cages, strengthen the ropes and appropriately raise the height of the part of the cage exposed above the water. For floating cages, prevent the bottom of the cage from touching the lake bottom during strong winds, so as to prevent line breakage and net damage caused by friction. Floods can accelerate the water flow in the cage-setting area, cause the cage fixing stakes to be washed away and floating cages to drag anchor and shift, and rising water levels can submerge fixed cages and allow fish to escape; when necessary, add a cover to open cages to seal the top. Whether strong winds, rainstorms or floods, inspect immediately afterward, and once problems are found, repair and rescue immediately.

2. Keep a good rearing log The culture log is important reference material for checking work, accumulating experience, formulating plans and improving technology. To practice scientific fish farming, one must keep a log for each cage, and this is the most basic management work. The cage log should include items such as date, weather, water temperature, stocking, fishing records, fish growth records, feed type and quantity, fish activity and fish disease prevention and control measures. Analyzing problems and summing up experience and lessons based on the log is an important link for smoothly carrying out cage culture of yellow catfish.