Response of Planktonic Copepods to Seasonal Fishing Moratorium in Erhai Lake, Yunnan, China

Copepods were sampled monthly from February to November in 2009 in a subtropical plateau lake,Erhai,Yunnan,China,in which a moratorium on spring and early summer fishing was imposed by local government,in order to investigate the seasonal dynamics of Copepod community.The biomass of Copepods showed a bimodal seasonal distribution,the first peak in the mid fishing moratorium and the second peak in the mid fishing season.The omnivorous cyclopoid Mesocyclops dissimilis was dominated in the mid fishing moratorium,while a filter-feeding calanoid Phyllodiaptomus tunguidus was dominated in the mid fishing season.The seasonal fishing moratorium affected not only the predation pressure from fish on copepods,but also changed the competitive pressure from Cladocera on copepods by influencing the community structure of Cladocera.Under low predation pressure but high food-competitive pressure,the dominant species of copepods were omnivorous cyclopoids,while under high predation pressure and low food-competitive pressure,the filter-feeding calanoid took over in dominance.