Suitable habitat shifts and ecological niche overlay assessments among benthic Oplegnathus species in response to climate change

Climate change has had a significant impact on many marine organisms. To investigate the effects of environmental changes on deep-water benthic fishes, we selected the genus Oplegnathus and applied species distribution modeling and ecological niche modeling. From the last glacial maximum to the present, the three Oplegnathus species (O. conwayi, O. robinsoni, and O. peaolopesi) distributed in the Cape of Good Hope region of southern Africa experienced fitness zone fluctuations of 39.9%, 13%, and 5.7%, respectively. In contrast, O. fasciatus and O. punctatus, which were primarily distributed in the western Pacific Ocean, had fitness zone fluctuations of -6.5% and 11.7%, respectively. Neither the O. insignis nor the O. woodward varied by more than 5% over the period. Under future environmental conditions, the range of variation in fitness zones for the three southern African Oplegnathus species was expected to be between -30.8% and -26.5%, while the range of variation in fitness zones for the two western Pacific stonefish species was expected to remain below 13%. In addition, the range of variation in the fitness zones of the O. insignis was projected to be between -2.3% and 7.1%, and the range of variation in the fitness zones of the O. woodward is projected to be between -5.7% and -2%. The results indicated that O. fasciatus and O. punctatus had a wide distribution and high expansion potential, while Oplegnathus species might have originated in western Pacific waters. Our results showed that benthic fishes were highly adaptable to extreme environments, such as the last glacial maximum. The high ecological niche overlap between Oplegnathus species in the same region suggested that they competed with each other. Future research could explore the impacts of environmental change on marine organisms and make conservation and management recommendations.

Comparative analysis of climate-induced changes in distribution of representative fish species in the Yellow Sea

Climate changes are posing remarkable impacts on marine fish and fisheries. Although many studies have addressed the distributional effects of climate change on single fish species or taxa in recent years, comparative studies focusing on different types of fish are still lacking. In this study, we applied dynamic bioclimate envelop models (DBEM), based on three earth system models, to predict sea surface and bottom temperature, as well as the spatial and temporal distribution of nine representative fishes in the Yellow Sea, contain two habitats, i.e., continental shelf benthopelagic (CBD) and continental shelf pelagic-neritic (CPN) fishes, and two thermophilies, i.e., warm temperate (WT) and warm water (WW) fishes. Under a low emissions scenario (RCP 2.6) and a high emissions scenario (RCP 8.5) between 1970 and 2060, results reveal that: a) CPN fishes show a distinct tendency to move to higher latitudes than CBD fishes, and WW fishes show a significant tendency to migrate more widely to the north than WT fishes; b) The relative abundance of CPN fishes is expected to be higher than that of CBD fishes, while there is no apparent difference in relative abundance between WW fishes and WT fishes. The main reasons for this difference are presumed to be: variance of temperature rise between the sea surface and bottom layers, divergent adaptations of the species, and disparate degrees of anthropogenic influence.

Climate change projections show shrinking deep-water ecosystems with implications for biodiversity and aquaculture in the Northwest Pacific

The increased availability of environmental data with depth deriving from remote-sensing-based datasets permits more comprehensive modelling of the distribution of marine ecosystems in space and time. This research tests the potential of such objective modelling of marine ecosystems in four dimensions, spatial and temporal, to provide projections of how climate change may affect biodiversity, including aquaculture. This approach could be replicated for any regional seas. The Bohai Sea, Yellow Sea, and East China Sea (BYECS) are marginal seas in the Northwest Pacific bounded by China, Korea, and Japan. Despite providing important ecological and economic services, their ecological conditions and ecosystems distribution have not yet been systematically mapped. This analysis used 13 marine environmental variables, measured on a three-dimensional and monthly basis during 1993-2019, to classify and map the BYECS region by k-means clustering using cosine similarity as distance function. There were 13 distinct areas identified that fit the definition of "ecosystems" that is, enduring regions demarcated by environmental characteristics. Of these 13 ecosystems, the Yellow Sea Cold Water (YSCW) Ecosystem is significant in relation to seasonal species composition and the newly developing deep-sea salmon caging aquaculture in the region. Projections of the potential size of this water mass under various climate-change scenarios based on analysis using the Non-Parametric Probabilistic Ecological Niche (NPPEN) model show that its volume may decrease 31 %-66 % in the future. Such a decrease would have impacts on the seasonal species' abundances in the BYECS marginal sea region and threaten the deep-sea cold-water salmon farming.