ACUTE TOXICITY OF N.P.K 15.15.15 FERTILIZER TO AFRICAN CATFISH (Clariasgariepinus)(Burchell,1822)Juveniles

Abstract

Nitrate: Phosphate and Potassium (N:P:K) 15:15:15 fertilizer is used in aquaculture for pond fertilization but sometimes this quantity is increased by run-off from cultivated agricultural land. The present study investigated the acute toxicity of N.P.K 15.15.15 fertilizer to Clariasgariepinus fingerlings (mean weight 4.84±0.15g) with varying concentrations of N.P.K 15.15.15 fertilizer (0.0, 4.2, 4.4, 4.6 and 4.8g/l) using a static bio- assay test. The 96hr LC50 value was 4.74g/l. Fish exposed to different N:P:K 15:15:15 fertilizer showed alterations in their behavioral pattern such as erratic swimming, restlessness, discoloration of the skin and hyperactivities. These effect increased with increase in concentration of N:P:K 15:15:15 fertilizer. Water quality parameters determined during the experiment showed (p<0.05) in dissolved oxygen and conductivities, while pH and temperature remained the same (p>0.05). The mortality rate was concentration dependent. Liver enzymes of C. gariepinusfingerlings were determined. Activities of AST, ALT, ALP, and GGT increased with increase in N:P:K 15:15:15 fertilizer. The least AST activities was recorded in the control treatment (232.33±2.08μ/L), the ALT had the highest value in 4.8g/l concentration (33.43±2.20μ/L), the highest value for ALP activities was recorded in 4.2g/l concentration (57.85±0.92 μ/L) and the highest value for GGT was recorded in 4.8g/l concentration (33.43±2.20 μ/L). The result of hematological parameters indicated that RBC, HB, PCV, MCV, MCH and MCHC decreased with increase in NPK concentrations, while the WBC increased with increase in NPK concentration over the control. Histological examination revealed alterations in gill architecture, mild to severe erosion of gill lamellae. The liver showed severe vacuolation of the liver cells, macrophages that are prominent and necrosis.