Institute of Fisheries and Aquaculture, Varna, Branch Plovdiv, BG - 4003 Plovdiv, Bulgaria
NIKOLOVA, L., 2006. Application of the assessment method for loading the fishponds with ducks under the conditions of complete integration. Bulg. J. Agric. Sci., 12: 236-246
After a 5 -year study on the integration offish and ducks in warm water fishponds (n=32) under the conditions of Bulgaria, carried out at the Institute of Fisheries and Aquaculture -Plovdiv, an analysis was made about the possibilities of applying the methods of complex assessment of the fishponds with ducks under the conditions of complete integration. The method developed by the author (Nikolova, 2003) suggests that for conducting the complex assessment of the effect of waterfowls on the fishpond it is advisable to use the Coefficient of fishpond loading with ducklings (Kd), calculated by the formula: , where: Σ is the sum of the rotations for the vegetation period; N - mean number of ducklings in the rotation; t - the duration of rotation in days; W - average live weight of the ducklings for the period of raising, kg; P -pond area, dka; T - duration of the vegetation period, days; k- coefficient about the evenness of loading ; r - coefficient about the time the ducklings spent in water. The latter coefficient was determined on the basis of the relative stay of the ducks in the water out of the time of the active part of the day. For the ducks of Peking breed r was 0.535 and for the mule ducks - 0.315 (Nikolova, 2001). The method offered makes it possible to determine the annual (Kdy) and the total (Kdt) loading of the fishpond with ducks during the years it is used as integrated. On the basis of the correlation and dispersion analyses it was shown that the coefficient of pond loading with ducks highly correlated with the number of the duck rotations in the pond (R = 0.833), with the duration of the rotations (R = 0.849) and the number of ducks in a rotation (R = 0.862), but it did not depend on the average weight of the ducklings during the period of their stay in the pond. The separate elements of the formula for calculating Kd exerted a specific effect on the fish production indices, which often did not correspond to the effect and even to the tendency of influence of the coefficient. The effect of the ducks on the fish production indices could be more logically explained by the coefficient of pond loading with ducks rather than by the effect of the separate factors included as elements of the formula for calculating the former. Out of that reason it is recommended to use it as a complex index about the duck influence on the fishpond.