小江不同食性鱼类氮磷排泄及其对养分循环的影响

Nitrogen and Phosphorus Excretion of Fishes with Different Feeding Habits and Their Role in Nutrient Cycling in Xiaojiang River

探究小江流域不同食性鱼类排泄对初级生产养分循环的作用,为三峡库区支流鱼类群落调控及养分再循环提供理论参考。2019年在小江设置5个断面对水质、浮游物、鱼类进行监测和采样,并选取小江4种典型食性鱼类,即滤食性鱼类鳙、草食性鱼类草鱼、杂食性鱼类鲫和肉食性鱼类黄颡鱼,分析其氮磷排泄率的差异及其与温度的关系,通过模型反演估算不同食性鱼类排泄对小江藻类初级生产的贡献。结果表明:(1)滤食性鱼类氮排泄率最高,滤食性鱼类和肉食性鱼类磷排泄率相对较高;(2)不同食性鱼类氮磷排泄率随水温升高均有所增大,且杂食性鱼类氮排泄率受水温变化影响最大,而草食性鱼类磷排泄率受水温变化影响最小;(3)小江鱼类总生物量约11.08t,氮、磷排泄率分别为16.92、2.11ng/(L·d);(4)小江鱼类氮磷排泄对藻类养分循环贡献均较小,分别占初级生产力所需氮、磷含量的0.015%和0.022%;(5)在4种食性鱼类中,肉食性鱼类对初级生产力的贡献率最高。

In this study,we investigated the impact of excretions from fish with different feeding habits on primary production and nutrient cycling in Xiaojiang River.Four typical fishes with different feeding habits(filter-feeding bighead carps,herbivorous grass carps,omnivorous crucian carps and carnivorous yellow catfish)were selected as representative species.We first investigated the variation of nitrogen and phosphorus excretion rates of the four species at different water temperatures and analyzed the relationship of excretion rate and temperature,and then we estimated the contribution of nitrogen and phosphorus excretions by each species to primary productivity using model inversion.In 2019,water quality was monitored monthly at five transects in Xiaojiang River,and plankton and fishery resources were surveyed in July.Results show:(1)The nitrogen excretion rate of the filter-feeding species was highest,and the phosphorus excretion rates of the filter-feeding and carnivorous species were highest.(2)The nitrogen and phosphorus excretion rates of all species increased with water temperature,and the nitrogen excretion rate of omnivorous fish was most affected by water temperature,while the phosphorus excretion rate of herbivorous fish was least affected by water temperature.(3)The total biomass of fish in Xiaojiang River was 11.08 t,the excretion rate of nitrogen was 16.92 ng/(L·d)and that of phosphorus was 2.11 ng/(L·d).(4)The contribution of nitrogen and phosphorus to the nutrient supply of algae was small in Xiaojiang River,accounting for 0.015% of the nitrogen and 0.022% of the phosphorus required for primary production.(5)Among the four different feeding habits,the carnivorous fish contributed the most to primary production.The results of this study provide a theoretical reference for managing the fish community and nutrient cycling in the tributaries of Three Gorges Reservoir.