EFFECT OF THREE DIFFERENT ORGANIC FERTILIZERS ON THE GROWTH OF FINGERLINGS OF Heterobranchus longifilis (VALENCIENNES, 1840).

Abstract

The effect of poultry droppings, cattle dung, and pig excreta, as organic fertilizers on the growth of fingerlings of Heterbranchus longifilis was investigated using the concrete fish ponds in the premises of Department of Zoology’s Garden, Nnamdi Azikiwe University Awka. A pond without any manure was set up as the control and the investigation lasted for eight months. An application rate of 0.8kg/m2 for dry weights of the organic fertilizers was used. Each of the ponds which measured 3.08 m x 2.27 m x 0.9 m was stocked at a density of 7 fingerlings per m3. The average weight of the fingerlings was 3 g with total length of 5.6 cm. Results showed that there were variations in the percentage content of some important chemical elements and minerals like phosphorous, potassium, calcium, magnesium, sodium and nitrogen in these organic fertilizers/manures. These variations reflected on the physico-chemical parameters of ponds’ water particularly pH, temperature, transparency, and dissolved oxygen but all were within the normal range for aquaculture in the tropics. The variations also reflected in the distribution of various plankton which was investigated with the aid of plankton net and microscope and seventeen different plankton identified. Pond II which was treated with cattle dung contained the highest density of most of these plankton. Growth measurements of the fingerlings showed that pond II supported the highest biomass of fish at the end of the investigation, and control pond, although contained no organic manure supported the third high biomass of fish. Statistical analysis of the growth measurements confirmed that the effect of pond treatment with cattle manure was significantly different (P<0.05) from the other treatments. This indicates that the chemical and mineral contents of the cattle dung might have favoured the optimum generation of plankton as energy base more than in other ponds, and this in turn reflected in the support of the highest biomass of fish by pond II.