FUNCTIONAL GROUP COMPOSITION AND FUNCTIONAL DIVERSITY OF NEKTON COMMUNITY IN THE XIANGSHAN BAY
JIANG Ya-Zhou;LIN Nan;YUAN Xing-Wei;JIAO Hai-Feng;LI Sheng-Fa;East China Sea Fisheries Research Institut Chinese Academy of Fisheries Sciences;Ningbo Academy of Oceanology and Fisheries;
A functional group is a group of species that occupy the same niche in ecology and share resources in a similar way. In the concept of functional group, we simplify the structure and dynamics of nekton community to examine the energy flow and biomass within food webs in the Xiangshan Bay based on the data collected from beam-trawl and single-trawl surveys in April, July, and November of 2011. In terms of feeding habit, seven functional groups were identified: planktivores, planktivores/benthivores, benthivores, benthivores/piscivores, omnivores, piscivores, and detritivores. Similarity analysis revealed that there was no significant seasonal difference in structure of nekton community at functional group level. Benthivores/piscivores, benthivores, piscivores, and detritivores were dominant in biomass of the nekton community. The functional diversity in the bay was 1.303 in April, 1.261 in July, and 1.185 in November, with no significant monthly difference. A strong positive relationship was revealed between functional diversity and total biomass of these individuals whose body weights exceed 50g. A linear relationship between species and functional diversity could be well described in regression. In addition, the number of species in some given functional groups was small, indicative of a low level of functional redundancy. Currently, under the intense fishing pressure, some commercially important species might extinct locally, which might further lead to the removal of the whole functional group from the bay and irreversible degradation of ecosystem functions.