Low-frequency band noise generated by industrial recirculating aquaculture systems exhibits a greater impact on Micropterus salmoidess

The effect of underwater noise environment generated by equipment in industrial recirculating aquaculture systems (RAS) on fish is evident. However, different equipment generate noise in various frequency ranges. Understanding the effects of different frequency ranges noise on cultured species is important for optimizing the underwater acoustic environment in RAS. Given this, the effects of underwater noise across various frequency bands in RAS on the growth, physiology, and collective behavior of juvenile largemouth bass (Micropterus salmoides) were comprehensively evaluated here. In this study, three control groups were established: low-frequency noise group (80-1000 Hz, 117 dB re 1μPa RMS), high-frequency noise group (1-19 kHz, 117 dB re 1μPa RMS), and ambient group. During a 30-day experiment, it was found that: 1) industrial RAS noise with different frequency bands all had a certain inhibitory effect on the growth of fish, which the weight gain rate and product of length and depth of caudal peduncle in the ambient group were significantly higher than those of the two noise groups, with the low-frequency noise group showing significantly lower values than the high-frequency noise group; 2) industrial RAS noise had a certain degree of adverse effect on the digestive ability of fish, with the low-frequency noise group being more affected; 3) industrial RAS noise affected the collective feeding behavior of fish, with the collective feeding signal propagation efficiency and feeding intensity of the noise groups being significantly lower than those of the ambient group, and the high-frequency noise group performing better than the low-frequency noise group as a whole therein. From the above, the underwater noise across different frequency bands generated by equipment operation in industrial RAS both had an impact on juvenile largemouth bass, with the low-frequency noise group being more severely affected.

Impact of underwater noise on the growth, physiology and behavior of Micropterus salmoides in industrial recirculating aquaculture systems

The operation of the equipment in industrial recirculating aquaculture systems (RAS) affects the underwater soundscape of aquaculture tanks where fishes live. This study evaluated the influence of commercial industrial RAS noise on the growth, physiology, and behavior of juvenile largemouth bass (Micropterus salmoides). In this study, two experimental groups, the RAS noise group (115 dB re 1 μPa RMS) and the ambient group (69 dB re 1 μPa RMS), were studied. The water quality and feeding regime for each group were kept the same during the 60-day experiment. Results showed that there was no significant difference in the average daily feed intake of the fish between the two treatments, while the rate of weight gain of the ambient group (755.27 ± 65.62%) was significantly higher than that of the noise group (337.66 ± 88.01%). In addition, the RAS environmental noise also had an adverse effect on the anti-oxidation and immune systems of the fish based on results of analysis of blood, liver, and intestinal samples. Moreover, environmental noise affected the swimming behavior of the fish school. The mean angle and distance between the focal fish and its nearest neighbor fish in RAS noise group were 33.3° and 92.1 mm, respectively, which were larger than those of the ambient group with 24.4° and 89.5 mm, respectively. From the above results, RAS noise did influence the welfare of largemouth bass, and the soundscape in RAS hence should be managed in real production.