Assessment of differences in population resources of Protosalanx chinensis in Dalong Lake and Yuebingpao Lake

Clearhead icefish Protosalanx chinensis, is a typical r-strategy small commercial fish with a life span about 1 year, whose population is susceptible to environmental change and fishing and the yield fluctuates dramatically. To investigate the growth performance and the current status of resource utilization of P. chinensis in two important fish farming grounds (Dalong Lake and Yuebingpao Lake) in Daqing, northeast China, serving for sustainable high quality fisheries, we determined the two population densities in April and collected 1 400 P. chinensis samples from April through October 2023 monthly for measuring the characteristics of population structure dynamics. The parameters of population growth, death, exploitation and utilization were estimated using von Bertalanffy growth equation, Pauly empirical formula and Bayesian biomass estimation method based on body length. The results showed that the population recruitments density of Dalong Lake and Yuebingpao Lake were 109.65 ind./100 m³ and 9.8 ind./100 m³, respectively, the growth equations of the two populations were L_t=141.75×1−e^{−3.1(t+0.05)} and L_t=183.75×1−e^{−2.9(t+0.05)}, respectively, the age (t_tp) at growth inflection were 0.34 a and 0.35 a, respectively. Exploitation rates (E) were 0.41 and 0.44, respectively, and the population survival rate (S) were 0.22% and 0.33%, respectively. The relative catch per unit replenishments (Y'/R) were 0.059 and 0.067, respectively. The differences of population density between Dalong Lake and Yuebingpao Lake were manifested in the parameters related to growth characteristics. Based on this assessment and the parameters of Sustainable High Yield Technique, fishing should be enhanced to reduce the reproductive population size in Dalong Lake, while fishing should be weakened to increase the reproductive population size in Yuebingpao Lake.