Temporal and spatial comparison of food web structure in marine pastures in the Pearl River Estuary: Implications for sustainable fisheries management

Abstract

The biological and ecological integrity of marine ecosystems in the Pearl River Estuary (PRE) has been compromised due to overfishing and water pollution. Fishing moratorium and artificial reef construction have been implemented in Wanshan and Miaowan for resource protection and restoration. Therefore, food web structure and trophic pathways of Wanshan, Miaowan, and Wailingding in different temporal and spatial situation will be determined using the Ecopath model, as well as the keystone species affecting these ecosystems, which can provide a basis for fishery management. The results showed that the energy transfer efficiency of IV and V trophic levels (TL) was higher than that of II and III‐TL before and after fishing moratorium, and the energy transfer efficiency of artificial reefs II and III‐TL was only slightly higher than that of nonartificial reefs in Wanshan. In addition, the mean values of ecosystem property indicators (consumption, respiration flow, total system throughput, and total biomass) after the fishing moratorium were significantly higher than those before the fishing moratorium. The average value of the ecosystem attribute indicators (consumption, respiration flow, total system throughput, and total biomass) of artificial reefs is lower than those of nonartificial reef areas, which may be related to the differences in community composition between artificial reefs and non‐artificial reefs. Finally, Nemipterus japonicus and Gastrophysus spadiceus are keystone species that distinguish the Wanshan and Miaowan artificial reefs from other areas. Overall, the fishing moratorium has a positive effect on the short‐term restoration of fishery resources, mainly restoring short‐life cycle organisms. However, the construction of artificial reefs will be more conducive to the persistence of ecosystem restoration. In addition, reasonable proliferation, release and fishing of N. japonicus and G. spadiceus will be beneficial to the sustainable utilization of fishery resources.

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

“…It was well noted that a fishing moratorium provides benefits by facilitating the restoration of fishery resources in the short term, which would mainly restore the short life cycle organisms at low trophic levels. 22 Previous research showed that improving predation conditions and expanding the distributed scope were necessary for the sole cetacean Yangtze finless porpoise (Neophocaena asiaeorientalis). 46 Therefore, the ten-year fishing ban in the Yangtze River was implemented in 2020.…”

“…Here, socio-economic indexes were analyzed together, and it was found that fishing was one of the key drivers of the fish diversity decline in the Pearl River. Previous studies (focusing on fishery resources and fish communities) had reported that large dynamics of the fishery ecosystem in subtropical rivers and lakes were caused by overfishing, ,− and the response strategy of different ichthyological groups to overfishing events varied along with feeding structure and trophic level changes. During the past forty years, a steep decrease in fish and dietary organism diversity was observed in the Pearl River, which was consistent with the decrease in the fish, interaction density, and food web indexes (system omnivory index, Finn’s cycling index, and MPL ).…”

“…To compare the fish biodiversity, the method of stable isotopes of carbon and nitrogen was applied to understand the biogeochemical processes associated with fish population dynamics and habitat degradation processes. , The stoichiometric variations of isotopic stable carbon and nitrogen can reflect the nutrient cycling rates and energy flows levels, and thus manifest the variations in the structure and function of aquatic ecosystems. − During the process of element transfer and energy flow, both intra- and inter-species changes in the keystone species of the fish community can irreversibly lead to ecosystem stability and fishery resource sustainability collapse, − thereby disrupting trophic levels of aquatic organism regulation. ,− Furthermore, a reconstruction of the food web can display fish interactions clearly by using carbon and nitrogen isotope technology and further provides benefits for evaluating the impacts of human activities on fish biodiversity alterations. , …”

Bioaccumulation and Trophic Transfer of Organophosphate Flame Retardants and Their Metabolites in the Estuarine Food Web of the Pearl River, China

“…Seventeen fish species were identified including Cynoglossus joyneri ( n = 4), Cynoglossus macrolepidotus ( n = 2), Moolgarda cunnesius ( n = 3), Nemipterus japonicus ( n = 4), Siganus fuscescens ( n = 2), Ambassis urotaenia ( n = 3), Collichthys lucidus ( n = 3), Ilisha elongata ( n = 3), Leiognathus brevirostris ( n = 6), Johnius belangerii ( n = 5), Trypauchen vagina ( n = 4), Thryssa kammalensis ( n = 4), Sillago sihama ( n = 1), Dendrophysa russelii ( n = 3), Platycephalus indicus ( n = 2), Muraenesox talabonoides ( n = 1), and Argyrosomus argentatus ( n = 3). The collected components that could form an estuarine food web in this study were mainly dominated by benthic species (Table S2), all of which represent typical estuarine species in the PRE ecosystem. ,,− After collection, the samples were transported to the laboratory and stored in a refrigerator at −20 °C. In addition, 21 surface water samples and 10 surface sediment samples were collected from the sampling region.…”

First Evidence of the Bioaccumulation and Trophic Transfer of Tire Additives and Their Transformation Products in an Estuarine Food Web

“…Recognition and categorization of biota samples were based on databases such as China Animal Science Database, EOL, Fishbase, SeaLifeBase, and WoRMS . Based on previous reports, these biota samples collected in this study belonged to the representative species of the PRE. − To minimize the microbial activity and transformation of targeted chemicals, the pH of water samples was acidified to 3.0 immediately upon collection, and 1 mL of glutathione solution (1 M) and 5% methanol (v/v) were added. , All samples were preserved in a −20 °C refrigerator and then delivered to the laboratory promptly. Information on sampling locations, water quality, and biota samples is provided in Figure S1 and Tables S2–S4 in the Supporting Information.…”