Key functional groups selection in marine ranching fishery resources from the Pearl River Estuary

Functional groups are the foundation of the analysis of food web structure and energy flow in marine ranching ecosystems. Based on filed investigation in Wanshan Islands adjacent sea in 2016 and 2017, and historical data of fishery resources in the Pearl River Estuary, the predominance, biomass and catch rate of fishery resources were studied. The results showed that Caranx kalla, Collichthys lucidus, Metapenaeus joyneri, Eucrate crenata, Coilia mystus, Oratosquilla oratoria, Eucrate solaris and Charybdis acuta were the shared economical species from the top 30 economic species. In terms of feeding habit, seven groups were identified in Pearl River Estuary including zooplanktivores, zooplanktivores/benthivores, benthivores, benthivores/piscivores, piscivores, omnivores, and detritivores. And benthivores (34%) and zooplanktivores (20%) groups were dominant in the Pearl River Estuary. Furthermore, rare fishes, high-yield fishes and shrimp and crab were eventually selected as top economic species of key functional groups in marine ranching fishery resources including Pampus argenteus, E. moara, L. japonicas, N. albiflora, Mugil cephalus, Penaeus monodon , and Scylla serrate . The common features are: (i) native economic species; (ii) great body weight and high yield; (iii) delicious taste and high market value; (iv) capable of artificial reproduction and release; (v) different habitat water layers; (vi) mutualistic. According to tropic levels of these top economical species in food chain, we found that both Epinehelus moara and Nibea albiflora belong to the higher carnivorous species. Epinehelus moara are bottom fishes that mainly feed on small and medium-sized fish, crustaceans and cephalopods, while Nibea albiflora are middle and lower-layer fishes that mainly feed on small and medium-sized fishes (e.g., Decapterus maruadsi, Sardinella aurita ) and shrimps (e.g., O. oratoria, Alpheus japonicas ). In addition, Pampus argenteus, Lateolabrax japonicas and S. serrate belong to the intermediate carnivorous species. To be specific, Pampus argenteus are pelagic fish, mainly feeding on jellyfish, ripple worms, water fleas or other zooplankton. L . japonicas are bottom fishes that mainly feed on fishes (e.g., C.mystus , Setipinna taty ) and crustaceans (e.g., Oratosquilla oratoria. Scylla serrate ) are benthic crustacean and feed on mollusks and small crustaceans. Moreover, M. cephalus inhabits the middle and lower layers and belongs to lower carnivorous species, mainly feeding on debris or diatoms. And Penaeus monodon are bottom-layer omnivorous species that mainly feed on mollusks and zooplankton. In conclusion, we constructed seven key functional groups of marine ranching fishery resources composed of top economic species and organisms in their food chains, including P. argenteus functional groups, Epinehelus moara functional groups, L. japonicas functional groups, N. albiflora functional groups, M. cephalus functional groups, P. monodon functional groups and S. serrata functional groups. The above seven key functional groups can realize poly-dimension utilization of space-time resources in marine ranching, thus are of great importance for sustainable development of marine fisheries and healthy coastal ecosystems.