Species traits determined different responses to "zero-growth" policy in China's marine fisheries

Ensemble predictions of high trophic-level fish distribution and species association in response to climate change in the coastal waters of China

As climate change shifts marine ecosystems, understanding distribution changes of high trophic-level fish is critical for ecological and fisheries management. This study examined the distribution changes of five high trophic-level fish species in China's coastal waters from 1990 to 2023, using species distribution models (SDMs) combined in an ensemble modeling framework to predict future trends under RCP26 and RCP85 scenarios. The ensemble approach integrated multiple SDM algorithms to reduce uncertainty and improve predictive accuracy. The analysis incorporated ecological metrics like niche breadth, niche overlap, and species association indices to assess habitat suitability and interspecies interactions. The ensemble model performed well, particularly for monkfish (Lophius litulon) and whitespotted conger (Conger myriaster), both of which are demersal species. Key environmental factors influencing habitat distribution included bottom water temperature and depth. Under climate change scenarios, the spatial niche breadth of only the largehead hairtail (Trichiurus lepturus) was expected to increase, while the niche breadth of the other species was projected to decrease, especially under high emissions. Fish habitats were predicted to shrink under future climate scenarios, especially under high emissions, with significant losses projected by 2100, ranging from -47 % for the Slender lizardfish (Saurida elongata) to -24 % for the Monkfish, although habitat suitability was expected to improve in southern coastal areas and near the Korean Peninsula. This study emphasizes the profound effects of climate change on the distribution and ecological niches of high trophic-level fish, offering insights for future fisheries management and climate adaptation strategies.

Global sustainability assessment of cephalopod fisheries based on pressure-state-response framework

Cephalopods are growing in commercial importance due to their unique biological characteristics; however, uncertainty about the pressure facing cephalopod fisheries poses a challenge to the health of fisheries and to policy development. Therefore, identifying and quantifying the dynamics of the sustainability of global cephalopod fisheries becomes critical. This study focuses on twenty major cephalopod producing countries around the world, using a pressure-state-response (PSR) framework together with an uncertainty assessment methodology. The results suggest that the sustainability of cephalopod fisheries varies greatly among countries; with developed countries characterized by low pressure and high response while developing countries show the opposite characteristics. Although there were large differences in the sustainability of this fishery among countries, the level of sustainability tightened slightly over time. The results emphasize that key response indicators, such as mitigating stressors on fisheries and improving the governance capacity of government departments, contribute to the sustainable use of cephalopod resources.

Stock Assessment of the Commercial Small Pelagic Fishes in the Beibu Gulf, the South China Sea, 2006-2020

Long-term variations in population structure, growth, mortality, exploitation rate, and recruitment pattern of two major commercial small pelagic fishes (CSPFs) (Decapterus maruadsi and Trachurus japonicus) are reported based on bottom trawl survey data collected during 2006-2020 in the Beibu Gulf, South China Sea. All individuals collected during each sampling quarter over a period of 15 years were subjected to laboratory-based analysis. In this study, the stock of D. maruadsi and T. japonicus inhabiting the Beibu Gulf was assessed using length-based methods (bootstrapped electronic length frequency analysis (ELEFAN)) to complete stock assessment in different fishery management periods (the division of fisheries management periods was based on China's input and output in the South China Sea offshore fisheries over 15 years, specifically divided into period I (2006-2010), period II (2011-2015), and period III (2016-2020)). The results showed that the mean body length, dominant body size, and estimated asymptotic length of two CSPFs decreased, whereas their growth coefficient decreased, indicating miniaturization and slower growth, respectively. Estimated exploitation rates and catching body length for two CSPFs indicated that both stocks in the Beibu Gulf were overexploited in period I and moderately exploited after 2011. These stocks were taking a good turn in status in period III, with the exploitation rate much lower than the initial period and reversing the downward trend in catching body length. Furthermore, the variations in the spawning season of the two CSPF stocks and their barely satisfactory expected yield indicated the complexity of the current fishery management in the Beibu Gulf. These results suggest that management measures to reduce fishing pressure may have a positive influence on the biological characteristics of those CSPFs in the Beibu Gulf; however, the stock structure already affected by overfishing will be a huge challenge for the conservation and restoration of fisheries resources in the future. Given that the current stocks of D. maruadsi and T. japonicus in the Beibu Gulf still have low first-capture body length (Lc) and high fishing mortality (F) (compared to F0.1), we identify a need to refine population structure by controlling fishing efforts and increasing catchable size, and more consideration should be given to the local fishery resource status in fisheries management.