Estimation of fish productivity in Tangxun Lake under ecological fishery culture model and its impact on endogenous pollution

The biomass of natural bait in Tangxun Lake was investigated to evaluate the fish productivity of Tangxun Lake under the condition of neither fertilizer nor bait. The pollution load generated by excretion and defecation and the amount of nutrients stored in fish body by growth gain in ecological fishery culture were evaluated according to the main fish productivity growth metabolic parameters. The results showed that, in Tangxun Lake, the natural fish productivity was around 2 975.49 t/a, and the ecological fishery stocking density could be controlled around 29 g/m³; nitrogen and phosphorus from the sources of excretion and defecation was 309.28 and 13.06 t/a, respectively; in which nitrogen was higher than the weight gained from the nutrition metabolism in fish bodies (73.10 t/a); and phosphorus was lower than the weight gained from the nutrition metabolism in fish bodies (15.90 t/a). Ecological fishery culture produced a certain amount of endogenous pollutant nitrogen, but it could reduce the endogenous pollutant phosphorus in water, which could be used as one of the measures to control lake eutrophication.