Study On The Resource Utilization Status And Ecological Niche Of The Major Small-scale Fishes In Zhushan Lake

In aquatic ecosystems,the study of fish population parameters,trophic structure of food web and ecological niche characteristics is of great significance for resource utilization assessment and ecological management of lakes.This study conducted a one-year fixed-site sampling in Zhushan Lake,Taihu Lake,selected dominant small-scales fishes,used ELEFAN?and LBB methods to evaluate their population parameters and utilization status,and analyzed food sources such as phytoplankton and plants.The relationship with fish,the trophic,spatial and temporal niche breadth and overlap of dominant small-scales fishes are discussed,which provides reference for evaluating the utilization of fishery resources in Zhushan Lake and provides support for fishery management.The results are as follows:1.In the fishery resource survey conducted in Zhushan Lake,a total of 55 species of fishery organisms were identified,including 6 orders,8 families,36 genera and 49species of fish,accounting for 89.09%of the total number of fishery organisms.The dominant species included Pseudorasbora parva,Hemiculter bleekeri,Hypophthalmichthys molitrix,Coilia nasus,Aristichthys nobilis,Cyprinus carpio,and Exopalaemon modestus.The analysis of population parameters shows that the body length of H.bleekeri is 44.17?181.87 mm,the growth equation is L_t=194.25^{[1-e-0.36(t+0.46)]};the body weight is between 0.88?70.30 g,and the growth equation is W_t=99.50[1-e^{-0.36(t+0.46)}]^3.058;body length-weight relationship W=1.0×10^-5L^3.058,showing a uniform growth;the relative total death coefficients estimated by ELEFAN?and LBB are 7.08 and 5.30.C.nasus body length range is 46.02?292.87 mm,L_t=309.75^{[1-e-0.58(t+0.25)]};weight range is 0.10?92.90 g,W_t=77.89[1-e^{-0.58(t+0.25)}]^3.0452;The relational formula is W=3.0×10^-6L^3.0452,which grows at a uniform rate;the relative total death coefficients estimated by ELEFAN?and LBB are 4.09 and 5.10.P.parva body length range is 31.42?123.40 mm,L_t=137.60[1-e^{-0.33(t+0.55)}];weight range is 0.55?24.74 g,W_t=33.89[1-e^{-0.33(t+0.55)}]^2.9132.The relational formula is W=2.0×10^-5L^2.9132,which grows at a uniform rate;the relative total death coefficients estimated by ELEFAN?and LBB are 5.45 and 4.25.2.The analysis of stable isotope?¹³C and?¹⁵N value characteristics showed that there were highly significant differences(P<0.01)between the?¹³C and?¹⁵N values of the three fishes and their food sources.Primary producers such as attached algae and aquatic plants had relatively low ¹⁵N values and were located at the bottom of the food web;fish had relatively high ¹⁵N values and were at the top of the food web;and invertebrates(Bellamya aeruginosa and zooplankton)were in between.The?¹³C values of fishes were within the range of?¹³C values of food sources,with rich nutrient sources and large nutrient levels,and the trophic levels were C.nasus>P.parva>H.bleekeri in order.Comparative analysis of?¹³C and?¹⁵N values revealed that there were highly significant differences(P<0.01)in?¹³C,?¹⁵N values and trophic levels of the dominant small-scale fishes in Zhushan Lake.Meanwhile,there were significant seasonal differences(P<0.05)in?¹⁵N values and trophic levels of C.nasus and P.parva,while the seasonal variations of?¹³C values of all three species of fish were not significant.There was no significant seasonal characteristic change in trophic level length(NR),basal food source(CR)and trophic diversity level(CD)for the three species.The overall community density(NND)and trophic niche distribution range values(SDNND)of C.nasus and P.parva gradually decreased except for autumn 2019,and the nutrient redundancy was gradually increasing.3.Trophic niche analysis showed that H.bleekeri had the largest total area of trophic niche(TA value of 43.26)and C.nasus and P.parva had similar total area of niche.The trophic niche of the three dominant small-scale fishes overlapped to a high degree and there was competition for food use,with the largest area of trophic niche in autumn(TA value of 55.02)and the largest width of trophic niche in summer(CR value of 8.64).4.Spatial niche analysis showed that the spatial niche widths of H.bleekeri(2.22)and P.parva(2.15)were similar and significantly smaller than that of C.nasus(3.58);the niche overlap between C.nasus and P.parva was high(0.71),and there was greater competition in the spatial dimension.The temporal niche analysis showed that the niche width of C.nasus(1.33)was greater than that of H.bleekeri(0.99)and P.parva(0.98),and the temporal niche overlap of all three species exceeded 0.6,with a high degree of overlap,and the competition for resources among the three species in the temporal dimension was more intense.The temporal-spatial niche analysis revealed that the ecological niche width of C.nasus(4.76)dominated significantly and had a high overlap with P.parva,with an overlap value of 0.62.