LED 적·녹색광 및 파일항타 작업소음에 대한 어류 행동 반응의 분석

Abstract

This study analyzed fish behavior exposed to external stimuli (artificial light and underwater noise), to provide behavioral information to the fisheries. The first study aimed to find an effective light source that increase the growth rate by analyzing the behavioral response of fish exposed to lights. The study was conducted in the laboratory using rockfish (Sebastes inermisa) and olive flounder (Paralichthys olivaceus), and the behavioral responses of fish were measured using a CCTV and related software. The second study aimed to provide basic information for the fisheries resources management by analyzing the behavioral response of fish exposed to pile driving noise during the construction of offshore wind power plants. In the study, black rockfish (Sebastes schlegeli) and olive flounder were targeted to observe their behavior in situ using the acoustic telemetry system. The system consisted of acoustic transmitters, receivers and related software. After the construction was completed, it was analyzed the behavioral response of the test fish before and after periphyton attachment to underwater structure of the power plants. The first study consisted of three experiments for rockfish and two experiments for olive flounder using red and green of LED lights. The lights turned on at 6:00 in the morning and off at 20:00 at night in the first and second experiment. In the first experiment for rockfish, the average swimming speed (cm/s) during 24 hours was measured 4.4 cm/s in red light, 3.2 cm/s in green light and 2.3 cm/s in control (natural light), respectively. In the second experiment, the average swimming speed during 24 hours was 1.7 cm/s in red light, 1.3 cm/s in greed light and 1.0 cm/s in control. In the experiments, it was found that the average swimming speed of rockfish was faster in order of red light, green light and natural light. In the previous study, it was shown that the growth rate of rockfish exposed to red light was lower than green light and natural light. Therefore, it is likely that swimming speed of rockfish negatively affected on growth rate. During 6 seconds immediately after lighting, the average swimming speed in the first experiment was 1.4 cm/s in red light, 6.3 cm/s in green-A light (810 mW), 1.0 cm/s in green-B light (130 mW), 1.0 cm/s in control, respectively. During 1 second after lighting, the swimming speed in the first experiment was 2.8 cm/s in red light, 3.1 cm/s in green-A light, 0.1 cm/s in green-B light and 0.3 cm/s in control, respectively. In the third experiment, the lights turned on during 40 minutes and off during 20 minutes. During 30 minutes after lighting, the average swimming speed was 2.3 cm/s in red light, 4.0 cm/s in green light and 0.6 cm/s in control, respectively. In the first experiment for olive flounder, the lights turned on during 40 minutes and off during 20 minutes. During 30 minutes after lighting, the average swimming speed was 0.3 cm/s in red light, 2.2 cm/s in green light and 0.03 cm/s in control, respectively. During 6 seconds immediately after lighting, the average swimming speed of olive flounder was 0.1 cm/s in red light, 4.5cm/s in green light and 0 cm/s in control, respectively. As a result of behavioral response of rockfish and olive flounder, it was shown that red and green lights affected on increasing swimming activities than natural light. Red of the LED light tended to make both test fishes move continuously while the light turned on. Green of the LED light, however, tended to make both test fishes move actively only the moment the light turned on. It seems that red of the LED light negatively affects on growth rate of the fish by increasing swimming activity, and green of the LED light triggered sensitive behavioral response of the fish the moment the light turned on. Therefore, if green of the LED light is used in the aquaculture farm, it needs to slowly increase the light brightness to reduce the stress on the fish. In the second study, total 11 black rockfish (CBR) and 9 olive flounder (CF) were released three times at a distance of 1 km from the pile driving site of the offshore wind power plant. Underwater noise before and during pile driving works was measured at the release point using a underwater noise recorder, and the result was compared with behavioral response of the test fish tracked by the acoustic telemetry system. The underwater noise level before (no pile driving works) and during pile driving works was measured 118.0-120.0 dB (re 1Pa), and maximum 160 dB (re 1Pa), respectively. In the 200-400 Hz frequency band, the underwater noise level during the pile driving works was on average 43.03.0 dB higher than when no pile driving works. In order to calculate the position of the fish tagged an acoustic transmitter using an presence/absence receiver (VR2W receiver), the error and drift amount of the internal clock of the receiver was compensated using a reference acoustic transmitter and the results of experiments in air (indoor) and outdoor water tank. The position of the acoustic transmitter was calculated using the hyperbolic positioning method. On 18 July 2018, the black rockfish (CBR2-1) was released at a distance of about 1,026 m from the pile driving site. The swimming speed of CBR2-1 was 28.4 cm/s when there was no pile driving work, and 39.6 cm/s during 5 minutes after starting the first pile driving work. It was about 1.4 times higher than when no pile driving work. During the final two pile driving works on the rocky seabed (about 1 minute), the swimming speed was 33.2 cm/s and 30.1 cm/s, respectively. The speed increased about 1.1 and 1.0 times than when no pile driving work. The CBR2-1 tended to move away from the site of the pile driving work, and its average swimming direction was 119.6˚. As a result of Rayleight's z-test, there was a significant directionality in the swimming direction of CBR2-1 (n=24, Z=7.7). The black rockfish CBR2-2 and CBR2-3 respectively stayed about 34 minutes and 18 minutes within a radius of 400 m from the release point and then moved away from the site of the pile driving work. On 13 September 2018, the olive flounder (CF2-1) was released at a distance of about 983 m from the site of the pile driving work. The swimming speed was 18.8±11.6 cm/s when no pile driving work (about 85 minutes), and 21.0±9.0 cm/s during the pile driving work (about 45 minutes). The speed increased about 1.1 times than when no pile driving work. During 5 minutes after starting the first pile driving work, the swimming speed was 26.7 cm/s. It was about 1.4 times higher than when no pile driving work. The olive flounder CF2-2 stayed about 10 minutes within a radius of 400 m from the release point, and then moved away from the site of the pile driving work. In this study, it was found that both black rockfish and olive flounder escaped from the site of the pile driving work. The avoidance reaction of fish can be one of significant reason affecting on fisheries resources. It can cause to avoid the habitat and change the migration route. Therefore, the construction site in the ocean should be selected after conducting sufficient scientific survey to reduce negative effects on habitat, migration route and so on. In addition, after completion of the construction work in the ocean, it is thought that continuous monitoring of the effects of marine structures on the surrounding ecosystem. In this study, it was analyzed the behavioral response of the black rockfish and olive flounder before (below 1 year after construction) and after (above 1 year after construction) the periphyton attachment to underwater structure of the power plants. On 26 July 2019, before the periphyton attachment, the black rockfish CBR3-2 and CBR3-3 respectively stayed about 24 minutes and 37 minutes within the initial point (a radius of 400 m from the release point), and then about 8 hours and 8 hours within the site of the offshore wind power plant (a radius of 400 m of each wind power plant (No. 1 to 20). On 26 September 2020, after the periphyton attachment, the black rockfish CBR4-2 and CBR4-3 respectively stayed bout 7 minutes and 18 minutes within the initial point, and then about 39 minutes and 6.1 hours within the site of the offshore wind power plant. On 15 October 2019, before the periphyton attachment, the olive flounder CF3-1 and CF3-2 respectively stayed about 20 minutes and 47 minutes within the initial point, and then about 3 days and 13 days within the site of the offshore wind power plant. On 31 October 2020, after the periphyton attachment, the olive flounder CF4-1 and CF4-2 respectively stayed about 1.9 hours and 1.8 hours within the initial point, and then about 3 days and 6 days within the site of the offshore wind power plant. In this study, it was shown that the periphyton occurrence on the underwater structure of the power plant affected on the stay duration of olive flounder. However, it did not affect on the stay duration of black rockfish. Therefore, the follow-up study is necessary to find the differences between the two species.