The catches of different lamps using on the falling-net fishing vessels in South China Sea

Falling nets are a type of fishing gear that appeared and developed rapidly in the northern of South China Sea in the early 1990s. We have developed Light-emitting diode (LED) fishing lamps to replace metal halide (MH) lamps that reduce fuel consumption without reducing the catches. We conducted marine light-fishing experiments in the northern South China Sea from September 20 to 26, 2019, and August 29 to 31, 2021. The results in the first fishing experiment show that there is no significant change in catch of the falling-net fishing vessel when the white LED lamps (with a total power of 36 kW) were used instead of MH lamps (with a total power of 120 kW). Squid catches of the falling-net fishing vessel increased significantly when white LED lamps (with a total power of 36 kW) and cyan LED lamps (with a total power of 6.0 kW) were used. The results in the second fishing experiment show that the total weight of catches of the cyan LED fishing lamps is more than that of the white LED fishing lamps, and the cyan LED light can attract Penaeus merguiensis and Thryssa dussumieri more effectively than the white LED light.

Methods
A total of 120 MH lamps (power P = 1 kW) were used on the nights of September 20 and 21, 2019, and the lamps were fixed vertically on two cross bars above the falling-net vessel; 120 white LED fishing lamps (P = 300 W) were used on the nights of September 23 and 24, 2019, and the LED lamps were fixed at almost the same position as the MH lamps. The direction of luminous COB Chip On Board) of the LED lamps was downward, diverged at about 30 degrees from the horizontal direction; in addition to the 120 white LED fishing lamps, 20 cyan LED fishing lamps (P = 300 W) were fixed on the two vessel sides on the nights of September 25 and 26, and the direction of luminous COB of the cyan LED lamps was downward diverging at about 45 degrees from the horizontal direction. The fishing lights were turned on to gather fish at ~8 pm every night. Four net-fishing operations could be completed every night, which means that we had eight net catches under each lighting condition. After each net collection, the catches were classified and weighted, and species and weight of catches were recorded. The data of each net catch can be found in the document "Data of the First Experiment".

The second experiment was conducted from August 29 to 31, 2021, in order to compare the fishing effect of cyan light LED lamp and white light LED lamp. White LED lamps and cyan LED lamps are equipped on two ships respectively, and the fixed positions are almost the same (fixed on the two cross bars above each falling-net fishing vessel). The total power of LED lights on each vessel is 36 Kw. The experimental sites of the two vessels are about 3 kilometers apart. The fishing lights were turned on to gather fish at ~8 pm every night. Four net-fishing operations could be completed every night, which means that we had eight net catches under each lighting condition. After each net collection, the catches were classified and weighted, and species and weight of catches were recorded. The data of each net catch can be found in the document "Data of the Second Experiment".

After identification, there is little difference between the catch species of the white LED fishing lamps and that of the cyan LED fishing lamps. There are 37 catch species of the white LED fishing lamps and 36 catch species of cyan LED fishing lamps (the data can be found in the document "Species and Probability of Catches").