Bin Xie

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.

Artificial reefs are widely recognized for their role in improving the ecological environment and creating protected habitats for marine organisms, ultimately enhancing biodiversity within the food web and fisheries resources. This study utilizes stable isotopes to analyze fish samples ranging from 3.4 to 1067 g in body mass, collected within the artificial reef area of Haizhou Bay. The objective is to determine if the δ¹⁵N-based fish body mass acts as a driving factor in shaping the food web structure. The results showed a certain level of overlap among all trophic guilds, suggesting that most trophic guilds within this region share similar living environments and feeding habits. The multiple linear regression showed a slight increasing trend between δ¹⁵N values and body mass. Furthermore, the predator–prey mass ratio (PPMR) was calculated to be 430:1 based on the δ¹⁵N–body mass relationship. This implies that larger reef fish within this artificial reef ecosystem tend to have higher δ¹⁵N values compared to smaller fish, indicating a shorter food chain in this ecosystem. In summary, this analysis provides valuable insights into the fish community structure within artificial reef ecosystems. Therefore, it is recommended that future studies focus on further characterizing the fish community structure using body mass information.

After more than ten years of offshore wind farm (OWF) construction, the total installed capacity of China ranks first in the world. The effect of OWF on fish communities—to attract or banish—differs among fish species and wind farms. Studies on the effects of OWFs are limited in China and results from other regions may not be transferable due to different environmental and biological conditions. In October 2019, an acoustic survey was conducted in Jinwan OWF, outside the Pearl River Estuary, northern South China Sea, China, to assess the fish resources (biomass and abundance), community diversity, and distribution information of this area. According to the Index of Relative Importance (IRI), Harpadon nehereus and Brionobutis koilomatodon were the dominant fish species in the study area. The mean Shannon–Weiner diversity index was 1.74. The mean Margalef richness index and Pielou uniformity index were 2.51 and 0.84, respectively. The ABC curve indicated that the fish community was undisturbed. The mean acoustically-derived biomass and abundance densities were 195.40 ± 254.32 kg/km² and 6506.83 ± 11,098.96 individuals/km², respectively. The fishery resources had evident aggregate distribution patterns, and the southern part of the study area had more biomass than the northern part. Seven environmental factors were selected by canonical correspondence analysis (CCA) analysis to reveal the correlation between fish assemblages and environmental factors, including nitrate (NO₃⁻), ammonium (NH₄⁺), dissolved oxygen (DO), water depth, pH, Chlorophyll a (Chl a), and phosphate (PO₄⁺). However, the CCA only accounted for 45.49% of the total variation, indicating that other unexplained stresses affect the fish assemblage in Jinwan OWF. This is the first study to examine the fish distribution patterns and community structures of the Jinwan OWF area. In addition, it will help all sectors of society to more scientifically and objectively understand offshore wind farm projects. In future studies, control areas with more trawl samples can be set up to explore the long-term impact of OWF facilities on local fish communities.