OBSTRUCTING EFFECT OF BUBBLE CURTAIN ON RAINBOW TROUT (ONCORHYNCHUS MYKISS)

Rainbow trout (Oncorhynchus mykiss), as a kind of cold water fish with rich nutrition and high value, has become one of the important aquaculture species of large sea cage in China. The underwater bubble curtain has the advantages of low cost, no pollution and no damage in catching and displacing fish. It has been applied in the control of fish in marine ranches, catching and displacing fish in river channels and intakes. In 2021, the “Shenlan 1” fully submersible large-scale steel structure cage developed by China has achieved large-scale rainbow trout farming in the cold water mass of the Yellow Sea. In order to make full use of the cold water mass in the Yellow Sea to cultivate cold water fish, realize the interception and aggregation of rainbow trout in the dark environment after the cage diving, and improve the fishing efficiency, we explored the obstructing effect of bubble curtain on rainbow trout under different conditions. The experiment was carried out in a light-tight room, under the light environment, four kinds of hole spacing (1.0, 2.0, 3.0 and 4.0 cm), four kinds of hole diameter (0.5, 1.0, 1.5 and 2.0 mm) and three kinds of gas flows (60, 120 and 180 L/min) were used to generate bubble curtain. The obstructing experiment of rainbow trout was carried out by single variable method, and the optimal obstructing effect was obtained. On this basis, the obstructing effect of bubble curtain on rainbow trout under the optimal condition of dark environment was tested. The results showed that under the light environment, the optimal obstructing effect was the bubble curtain with hole diameter of 1.0 mm, hole spacing of 2.0 cm and gas flow of 120 L/min, and the obstructing rate was (96.32±3.99)%. In the dark environment, the swimming speed of rainbow trout decreased significantly. The number of fish tail swimming above the bubble curtain pipe was 63.37% in the light environment, and the obstructing rate was (87.48±2.55)%. It was observed that rainbow trout passed through the bubble curtain in passive and active ways. In light and dark environment, there are differences in the behavior and obstructing rate of rainbow trout, indicating that rainbow trout can perceive the bubble curtain in advance through vision, so as to make behavioral response. In dark environment, rainbow trout can not perceive the existence of bubble curtain visually, but it can only perceive bubble curtain through other senses at close range. The visual effect of bubble curtain on rainbow trout plays a certain role in the obstructing process. The bubble curtain with dense bubbles is more like a “bubble wall”, which prevents rainbow trout from passing through easily. However, the bubble curtain with sparse bubbles can not completely block the perception of the environment on the other side. This study explores the bubble curtains on the block mechanism of rainbow trout, the results can be used for inside the cages bubble curtains block fish, achieve the congregation of fish and other fishing gear partial fishing method and for large deep sea trout fish aquaculture control technology and fishing equipment research and development to provide theoretical reference and technical support.