Effects of environmental change and exploitation on marine communities around the Zhoushan archipelago: A functional group perspective

Abstract Temporal changes in environmental conditions and fishing pressure in Zhoushan Archipelago were markedly different among different months caused by fisheries management. The bottom trawl surveys at 80 stations covering the whole Zhoushan Archipelago were performed to examine the fish and macro-crustacean species response to these dynamics during the November of 2015 and May of 2016, which roughly corresponds to the beginning and closure of the trawl fishing season, respectively. We identified two distinct habitats (bay and offshore) based on salinity, temperature and turbidity. Species composition within these habitats varied significantly by month in terms of their abundance and body size. The average abundances for the Hn., planktivore, shrimp, and crab groups decreased over the study period by an average of 68%; the average abundances for the Ah. and benExAH. increased by 3600%. The average sizes for all the groups except Hn. decreased by 57%. The decreasing numbers of large size species ( Harpadon nehereus ) and increasing numbers of small size species ( Amblychaeturichthys hexanema and benExAH.) from autumn to spring were observed. Temporal dynamics of these groups community are likely related to both water temperature and changes in fishing pressure. Salinity, turbidity, primary production determined mostly the aggregation of Hn. and shrimp groups inside the bay areas, and concentration of Ah., benExAH., planktonviore and crab groups in the offshore areas. Our results suggest that temporal size variation of the marine species are likely driven by the reproduction strategy related to temperature and changes in fishing pressure resulting from the summer fishing moratorium.