Progress in Fishery Sciences (Apr 2023)
Spatiotemporal Variation of Biodiversity and Mean Temperature of the Biomass of Fishery Resources in the Yellow Sea in Fall
Abstract
Due to climate change, the biomass and biodiversity of fishery resources are increasing at higher latitudes and decreasing at lower latitudes (reflected by the mean temperature of the biomass, MTB). Studies have shown that the change in catch composition of marine fisheries at the global scale is largely related to seawater temperature. It remains important to accurately analyze biodiversity and biomass distribution to inform the sustainable utilization and adaptive management of fishery resources. To evaluate the long-term spatiotemporal dynamics of biodiversity and MTB of fishery resources in the Yellow Sea, we selected species that account for more than 0.05% of the total biomass as representative species based on scientific bottom trawling data in autumn (October) of 2000, 2009, and 2018. A total of 117 stations (39 stations each year) were surveyed by R/V Beidou. Considering that sea surface temperature (SST) is the most accessible oceanographic variable and has been shown to affect marine biomass, the impact of SST on the biodiversity of benthic fisheries in the Yellow Sea was analyzed. Therefore, the spatiotemporal distribution of fish, crustaceans, and cephalopods, their relationship with SST, and the spatiotemporal distribution of biomass and MTB were analyzed. The Shannon-Wiener, Berger-Parker, and Margalef biodiversity indices were used to evaluate distribution changes. Location-related data were matched at the same resolution (0.5°×0.5°) for further analysis. Data processing and plotting were performed using R. The results showed that 39 species in 2000, 37 species in 2009, and 46 species in 2018 were representative of the total biomass collected by bottom trawling. The increase in diversity observed in 2018 may have resulted from a decrease in the abundance of dominant species. Although Liparis tanakae was dominant between years, there were significant differences in biomass proportions: 27.00% in 2000, 37.85% in 2009, and 22.82% in 2018. Fish showed the highest richness around 33°~34°N, and that of the southern Yellow Sea was higher than the northern Yellow Sea; crustaceans showed higher richness south of 34°N, and gradually increased from 2000 to 2018. For cephalopods, Japanese flying squid (Todarodes pacificus) was the only species occupying more than 0.05% of the total biomass. Except for cephalopods, the richness of all categories increased northward. According to the species accumulation curve, approximately 20 random stations were needed to represent Yellow Sea species richness. The Rényi profile further verified that 1) species were not evenly distributed, 2) species richness decreased from 2000 to 2009 and increased in 2018, and 3) the proportion of the most dominant species was highest in 2009 and lowest in 2000. In terms of biomass, high biomass stations occupied only one-third of the total stations and were mainly distributed around 35°~37°N in 2000, while high biomass stations occupied half of the total stations in 2009 and 2018. The proportion of fish was > 70% in all years with a downward trend, followed by an upward trend; the proportion of crustaceans increased from 11.45% to more than 25%; the proportion of cephalopods was the lowest (less than 1%) with a downward trend. Previous studies have also shown that crustaceans gradually dominate over time in both abundance and biomass. In particular, the abundance of Crangon affinis was dominant in all years, accounting for 53.25% in 2000, 75.40% in 2009, and 63.81% in 2018. In terms of the spatiotemporal distribution of biodiversity indices, the Berger-Parker index and Shannon-Wiener index showed contradictory distribution trends; high Shannon-Wiener and Margalef index values were mainly distributed in the southern Yellow Sea, whereas high Berger-Parker index values were mainly distributed in the middle and southern Yellow Sea. For the same diversity index, Berger-Parker had the lowest values in 2018, while the Shannon-Wiener index and Margalef index values increased over time, and no obvious longitudinal or latitudinal change was found for any of the indices. There was no significant linear relationship between the SST and biodiversity indices (P > 0.05). SST had a weak positive correlation with species richness, the Margalef index, and the Shannon-Weiner index, while SST had a weak negative correlation with the Berger-Parker index. Therefore, we concluded that bottom species are not sensitive to changes in SST, and bottom sea temperature should be compared to diversity indices in future studies. In terms of MTB, it was higher in the southwest and lower in the northeast with an obvious change around 34°N; it was lower in the deep-water area than in the coastal area; the lowest value appeared in the northern survey area, while the highest value appeared in the southern survey area. Considering the weak relationship between SST and diversity indices, SST is not feasible for diversity studies of bottom species. Research on the relationship between bottom sea temperature and diversity and the spatiotemporal distribution of bottom temperature-based MTB are needed in the future.
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