A Field Trial to Study the Effects of Stenella attenuata Deterrent on the Catch of a Light-Falling Net Fishery

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Abstract
The incidental capture (bycatch) of protected cetaceans in fishing gear has become a serious problem worldwide. Bycatch has also had many serious consequences for pantropical spotted dolphins (Stenella attenuata) in the light-falling net fishery within this research area. We provided a self-developed acoustic deterrent device and conducted trials to investigate the long-term deterrent effects on Stenella attenuata and assess the influence of external factors on fishing catch. In 2022, 50 deterrence trials were conducted, of which 38 were effective and 12 were ineffective. In 2023, 30 deterrence trials were conducted: 24 effective and 6 ineffective. No dolphin bycatch occurred within a two-year period. Overall, the catch per unit effort (CPUE) of the effective deterrence nights was 4.96 ± 3.06 kg/min, while the CPUE of the ineffective nights was 3.78 ± 3.10 kg/min. There was a significant difference (p = 0.041, >0.05) between the two conditions. On the nights when dolphins did not appear, the average CPUE was 5.04 ± 4.44 kg/min. This CPUE was not different from the night on which deterrence was successful (p = 0.981, >0.05), but was considerably higher than night on which deterrence was unsuccessful (p = 0.028, <0.05). General additive model results indicate that month, longitude, flow direction, latitude, wind direction, dolphin number, and wind speed affect fish catch. The ADD may be improved by manually controlling the pulse frequency, transmission interval, and type to improve deter efficiency.
Funding Information
  • Financial Fund of the Ministry of Agriculture and Rural Affairs, China (NFZX2024, CF-MEEC/TR/2024-15, 2021SD18, 42106181, 2022J02003)
  • CNOOC Marine Environment and Ecological Protection Welfare Foundation (NFZX2024, CF-MEEC/TR/2024-15, 2021SD18, 42106181, 2022J02003)
  • Central Public-interest Scientific Institution Basal Research Fund, South China Sea Fisheries Research Institute, CAFS (NFZX2024, CF-MEEC/TR/2024-15, 2021SD18, 42106181, 2022J02003)
  • National Natural Science Foundation of China (NFZX2024, CF-MEEC/TR/2024-15, 2021SD18, 42106181, 2022J02003)
  • Natural Science Foundation of Fujian Province of China (NFZX2024, CF-MEEC/TR/2024-15, 2021SD18, 42106181, 2022J02003)

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