Supporting Evidence for the “Ten-Year Fishing Ban”: Different Modes of Fishing and Pollution Induce a Fish Diversity Decline between the Pearl River and Its Estuary

Abstract

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.