Print PageThe commercial catches of largemouth bronze gudgeon (Coreius guichenoti Sauvage et Dabry), an important commercial fish in the upper reaches of the Yangtze River, China, declines dramatically in the last decade due to over fishing and detrimental effects of the hydropower projects in the middle and lower reaches of Jinsha River and Yalong River. However, the basic life history parameters and population dynamics are still poorly understood for this population, which would greatly impair its efficient management. In this study, we estimated important life history parameters of this population through the data obtained from fishery dependent surveys and early-history scientific surveys conducted by Institute of Hydrobiology, CAS, in the upper reaches of Yangtze River from 1998 to 2007. Relative biomass index, CPUE, was used to calculate population density in different reaches. Sex ratio and maturation ratios of spawning age classes were estimated by combining fishery data from 4 surveying locations. Virtual population analysis was used to construct population age structure and calculate age specific mortality rates. Early-history survey data of 2006 and 2007 was used to estimate mortality of 1-year-olds (from newly spawned eggs to age class 2). Then a discrete time age-structured matrix population model was constructed based on vital rates derived from 2006-2007.
Results/Conclusions
CPUE from different reaches showed that the population density center moved upstream after the water storage of the Three Gorges Dam. Sex ratio of the population in different reaches and the breeding population correspond to the 1:1 ratio. The percentage of females in age class 4-6 reaching sexual maturity is 7.91%, 19.6%, 100%. Life history parameters, including maturity ratios, age specific fishery mortalities and age structure, were estimated. The mortality rate of 1-year-olds was 0.2024%, and the fertility rates of 4 to 7 year-olds were 249.2, 1 247, 24 230 and 32 660 eggs. The asymptotic population growth rate was 0.8589 per year. Proportional changes in fertility terms generally have a larger impact on population grow than survival rates, and the survival rate of 2-year-olds had a larger elasticity than that of any other age classes. We recommend extending the current no-fishing period to encompass the breeding season of this fish, and strictly banning the use of small hooks in the harvest of juveniles.
