Abstract: Haematological profiles have been frequently used to assess the
health status of fish subject to metallic stress. The present study examined
potential alterations that may arise in the haematological profile of the
Mozambique Tilapia (Oreochromis mossambicus) due to exposure to cadmium (Cd).
Adult female fish collected from an aquarium were housed in glass tanks and
exposed to three concentrations (0.2, 2 and 10 mg l^{-1}) of
CdCl_2 for five days. At the end of the trial, fish were
sacrificed to obtain blood to record five primary (erythrocyte count - RBC,
lymphocyte count - WBC, haemoglobin concentration - Hb, packed cell volume -
PCV and clotting time) and three secondary (mean cell haemoglobin - MCH, mean
corpuscular haemoglobin concentration - MCHC and mean cell volume - MCV)
haematological parameters. Results revealed that the observed patterns were
erratic and significant changes were observed only at the low (0.2 mg
l^{-1}) and high (10 mg l^{-1}) levels of
exposure. Significant increases were noted in RBC and WBC counts, Hb, PCV, MCH,
MCHC and MCV, while the clotting time was significantly reduced (2.2 minutes in
the control and 0.8 at the highest concentration). These results are of
particular concern since the lowest test concentration (0.2 mg
l^{-1}), which was capable of inducing changes in some of
the blood parameters, falls within the ranges recorded in some of the water
bodies of Sri Lanka.
Keywords: Blood parameters, cadmium, heavy metals, haematology, Tilapia
