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To settle the emerging debate on whether a "ten-year fishing ban" is too long or an annual fishing moratorium is enough for fish resource restoration in the Yangtze River, a long-term comparison between the 1980s and the 2020s in the Pearl River was performed. Significant declines in fish biodiversity were determined among both the Pearl River and its estuary over the past decades. The trophic level increased from 4 to 5 in the estuary, whereas it remained at 4 in the Pearl River. Interestingly, an opposite trend in interspecies networks of fish was observed between the Pearl River and its estuary. A reduced density and increased links were detected in the Pearl River as its interspecies networks became complex, which was in contrast to that in the estuary. Furthermore, fishing and pollution were both confirmed to participate in the fish biodiversity decline in the Pearl River, whereas pollution was the dominant factor inducing the fish biodiversity decline in the estuary. Our case indicated that an annual fishing moratorium is not enough for fish resource restoration and supports the strategy of "ten-year fishing ban". Moreover, pollution should also be brought under control so that we can facilitate fish resource restoration.

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An investigation of the waters around Macau collected 43 phytoplankton species belonging to 29 genera and 5 phyla, including 32 species from 22 genera of Bacillariophyta, 7 species from 3 genera of Pyrrophyta, 2 species from 2 genera of Cyanophyta, and 1 genus and 1 species from both Euglenophyta and Chromophyta. The dominant phytoplankton species in the study areas were Skeletonema costatum (Greville) Cleve, Aulacoseira granulata (Ehrenberg) Simonsen, Thalassiothrix frauenfeidii Grunow, and Thalassionema nitzschioides Grunow. The phytoplankton abundance in the waters around Macau was between 46,607.14 and 1,355,000 cells/m3, with the highest abundance noted in station S8. Diatoms were the main contributor to phytoplankton abundance in station S8, accounting for 96.2% of the total abundance. Station S4 exhibited the lowest phytoplankton abundance of 46,607.1 cells/m3, with diatoms and Chromophytaaccounting for 58.6% and 29.9% of the total phytoplankton abundance, respectively. Biodiversity analysis results showed that the phytoplankton richness index was 1.18–3.61, the uniformity index was 0.24–0.78, and the Shannon–Wiener index was 0.94–3.41. Correlation analysis revealed that ammonia nitrogen was significantly negatively correlated with the phytoplankton richness, uniformity, and Shannon–Wiener indices. Nitrite nitrogen, nitrate nitrogen, inorganic nitrogen, salinity, turbidity, and pH were positively correlated with the phytoplankton evenness index and Shannon–Wiener index. Cluster and non-metric multidimensional scaling analyses demonstrated that the phytoplankton community structure in the waters around Macau could be divided into three groups, with A. granulata, S. costatum, T. frauenfeidii, T. nitzschioides, Chaetoceros curvisetus Cleve, and Chaetoceros diadema (Ehrenberg) Gran being predominant in different grouping communities (contribution% > 10%). Biota-Environment Stepwise Analysis (BIOENV) showed a significant correlation between the phytoplankton community and nitrite nitrogen content in the waters around Macau (correlation: 0.5544, Mantel test: statistic 0.4196, p = 0.009), which was consistent with the results of the canonical correspondence analysis.