The summer fishing moratorium system practiced annually by the Chinese government aims to protect fishery resources and restore the marine ecosystem in the East China Sea. To evaluate the effects of the moratorium on the fish community, temporal changes in the structure and function of the fish community in the northern East China Sea were examined based on data from bottom trawl surveys from 2000 to 2007. The results revealed that the fish community has undergone a directional change, in terms of relative biomass composition, following the implementation of the moratorium, with increasing trends in Pseudosciaena polyactis and Lophius litulon and decreasing trends in Pampus argenteus and Acropoma japonicum. However, the changes in species composition have not resulted in the expected positive changes in the functioning of the fish community. The fish community in the study area was still moderately or heavily disturbed, based on abundance-biomass comparison analysis. Moreover, no positive trends were observed in the indicators related to the stability and functioning of the fish community (e.g. the biodiversity and the slope and intercept of the size spectrum). Therefore, the summer moratorium system does not clearly fulfill restorative expectations for the fish community. To protect the health of this ecosystem, a comprehensive set of further fishery restrictions must be imposed in the area.
Marine mollusks are commonly subjected to heat stress. To evaluate the effects of heat stress on the physiological metabolism of the ark shell Scapharca subcrenata, clams were exposed to different high temperatures (24, 28 and 32 °C) for 72 h. The oxygen consumption and ammonia excretion rates were measured at 2, 12, 24, 48 and 72 h. The results indicated that the metabolic rates of the ark shell significantly increased with increasing heat stress, accompanied by mortalities in response to prolonged exposure. A metabolomics approach based on gas chromatography coupled with mass spectrometry was further applied to assess the changes of metabolites in the mantle of the ark shell at 32 °C. Moreover, multivariate and pathway analyses were conducted for the different metabolites. The results showed that the heat stress caused changes in energy metabolism, amino acid metabolism, osmotic regulation, carbohydrate metabolism and lipid metabolism through different metabolic pathways. These results are consistent with the significant changes of oxygen consumption rate and ammonia excretion rate. The present study contributes to the understanding of the impacts of heat stress on intertidal bivalves and elucidates the relationship between individual-level responses and underlying molecular metabolic dynamics.
Summary
Objectives of the study were ascertaining the temporal variation of fish density and biomass as well as the changes in fish species composition in a surveyed area before and after deployment of an artificial reef. The study was initiated within an area of 0.25 km2 in response to a strong demand for fisheries enhancement and resource conservation in Xiangshan Bay, Zhejiang Province, China. This survey data was collected through a SIMRAD EY60 system and bottom trinal nets pre‐ and post‐construction of the artificial reefs, May 2011 to September 2012 in Xiangshan Bay. The raw data were analyzed using fisheries acoustic Echoview (Myriax) software combined with bottom trinal net data. The results showed that estimated fish density, represented by a nautical area scattering coefficient (NASC) at the artificial reef increased by 14.04, 31.10, 17.35% in May, July and September 2012 after construction of the artificial reef, and that the fish biomass increased by 8.92, 29.06, and 18.09% in these three months of 2012 in contrast to 2011. The numbers of fish species varied from 7 to 9 in May, from 10 to 14 in July and from 9 to 12 in September of 2012. These temporal changes in the fishery status were considered as being mainly due to deployment of the artificial reefs in early April 2012.
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