Empirical Formula for Determining Freshwater Zooplankton Biomass from Pigs Manures of the Piggeries in Forest Guinea

To identify an ideal dose of pig manure from piggeries in the Forest Guinea for the production of zooplankton in rural fish farms for larval breeding, three doses including a control of 0 (T0), 300 (T1) and 600 (T2) g/m3 were tested for forty-five days. The experimental device of three buckets with a capacity sixty liters per treatment was each filled with 40 liters of demineralized water and immediately fertilized with the different doses. Three days after fertilization, phytoplankton was seeded followed by zooplankton seventy-two hours later. The initial seeding density was 35±7.62 ind/L or (23±1.13 ind/L of copepod nauplii or 1.84±0.13 µg/L (Thermocyclops sp.), 4±0.1 ind/L or 1.88±0.1 µg/L copepod adults (Thermocyclops sp.), 1±0.007 ind/L or 2.7±0.7 µg/L cladocerans (Moina sp. and Daphnia sp.) and 3±1.48 ind/L or 0.21 ± 1.48 of rotifers (Brachionus sp and Asplanchna sp.). The results show that doses of 300 (T1) and 600 (T2) g/m3 of pig slurry gave good primary production, the highest of which was obtained with T2 (4.63±2.48 mg/L) with a strong correlation with zooplankton biomass (r2 between 0.96 and 0.98). Biomasses recorded in T2 were 594.35±24.93 µg/L rotifers, 589.73±18.98 µg/L copepods and 449.95±18.15 µg/L cladocerans. This dose could be considered ideal for rural fish farmers in forested Guinea.