Construction Of Nutritional And Spatial Carrying Capacity Of Young Procypris Rabaudi (Tchang) Under Test Conditions

Based on the food consumption and minimum habitat space of young Procypris rabaudi (Tchang) under test conditions being evaluated in the present study, we preliminarily constructed the models of nutritional and spatial carrying capacity of the young rock carp. By using these predictive models, we estimated the carrying capacity of young rock carp in the Nanxi reach of the upper Yangtze River which based on the data of food resources and surface area in wild from the published references.The gastric evacuation rate and daily food consumption of young rock carp were determined in laboratory by using stomach content method. To calculate the weight of empty digestive tract (EDW) on the basis of body weight (BW) and body length (BL), the empirical formula of EDW-BW-BL were employed. During the experiment, rock carp were fed on Limnodrilus sp. Suitability index curves about substrate, light intensity, water depth for young rock carp in microhabitat were drawn based on the environmental data in laboratory. Four methods (Continued product, Minimum, Arithmetic mean and Geometric mean) were then used to establish the multi-factor habitat suitability index (HSI) model. The minimum habitat area of young rock carp were also experimentally manipulated.The main results in the present study were as follows:1. The feeding intensity of young rock carp had obvious circadian rhythms, with a typical single-peak distribution characteristics and the peak time from0:30to6:30. We directly calculated the daily food consumption of artificial reared young rock carp as24.91g wet/100g wet/d. According to the Elliott-Persson (1978) model, the food consumption of young rock carp under natural environment was presumed as Cd=14.31g wet/100g wet/d.2. The gastric evacuation rate of juvenile rock carp weighing3.30±0.94g was determined at18.6℃in laboratory. The Linear, Exponential and Square root models were fitted to the gastric evacuation data of rock carp. All the three models fitted well to the data (df=18, P<0.001), while the Exponential model (St=0.139e-0.169t) was the best one (r2=0.952, P<0.001). Based on the Exponential model, the gastric evacuation rate of rock carp was calculated as0.169g wet/100g wet/h.3. To simplify the quantification of the digestive tract contents of young rock carp, an empirical formula were employed:EDW=0.24(BW/BL)1.547-0.139(n=83, r2=0.89) to calculate the weight of empty digestive tract (EDW) of young rock carp on the basis of body weight (BW) and body length (BL).4. Through the rearing experiment in laboratory, we found that the young rock carp preferred the habitat with gravel diameter from10to15cm, light intensity from0.2to1.8Ix, water depth from0to15cm. Three suitability index models of substrate, light intensity, water depth for young rock carp in microhabitat expression were YS=1.7338e-0.997x (r2=0.892, P<0.001), YL=3.0121e-1.339x (r2=0.930, P<0.001) and YW=2.4055e-1.245x (r2=0.975, P<0.001), respectively. Based on the data of these three environmental variables, the Habitat Suitability Index (HSI) of young rock carp was estimated using the AMM, i.e., HSI=(SIS+SIL+SIW)/3.5. Seven groups of young rock carp that establish and maintain a relatively stable habitat area range were found. The habitat area ranges from628to2015cm2, with an average of1113.7cm2. And the body length of these seven groups of young rock carp is from6.92to7.53cm, with an average of7.21±0.23cm; fork length from7.62to8.33cm, with an average of7.89±0.26cm; body weight from5.51to6.15g, with an average of5.82±0.24g.6. Based on the above-mentioned studies, the models of both the nutritional and spatial carrying capacity of young rock carp were established. The nutrition model was and the space model was By using these two predictive models, we preliminary assessed the nutritional and spatial carrying capacity of young rock carp in Nanxi reach of the upper Yangtze River. The results showed that, when the resource utilization of young rock carp in Nanxi reach were from10%to100%, the nutritional carrying capacity of young rock carp in Nanxi reach of the upper Yangtze River was575～5745thousand, and the spatial carrying capacity was4864～48645thousand.