Effects of direct transfer to fresh water on the haematological parameters of Tilapia guineensis Bleeker, 1862

Changes in blood parameters of Tilapia guineensis transferred directly from brackish water (salinity 14.5 ‰) to fresh water (0.12 ‰) was investigated to assess the effect of sudden change in environment on fish blood characteristics. The results obtained indicated significant reduction (p < 0.05) in mean values of haemoglobin (Hb) from 5.50 . 0.61 to 3.65 . 0.66 dl-1, packed cell volume (PCV) 20.31 . 2.14 to 17.18 . 2.58%, red blood cell (RBC) 2.59 . 0.72 to 1.58 . 0.86 x 106, mean corpuscular haemoglobin concentration (MCHC) 27.03 . 3.66 to 20.99 . 3.75 pg, mean corpuscular volume (MCV) 78.82 . 6.12 to 70.92 . 4.27 fL and platelets (PLT) 175.19 . 12.32 to 144.46 . 9.22 103uL-1. However, increases were observed in the values of erythrocyte sedimentation rate (ESR) from 3.06 . 0.16 to 9.71 . 1.66 mm/hr, white blood cell (WBC) 27.18 . 2.96 to 29.69 . 3.75 x 109L-1, neutrophils (NEUT) 41.64 . 3.76 to 50.76 . 7.27 %, lympphocytes (LYMP) 55.30 . 3.24 to 59.30 . 11.26 % and monocytes (MON) 3.06 . 1.12 to 3.96 . 1.21 %. These alterations in the blood parameter were more noticeable in adult than juvenile fish. Results from this study therefore suggest that direct transfer of fish to area of lower salinity may have negative impact on the physiology of T. guineensis