I do not think, that anybody can tell you, which parameter is going to change. You have to measure a variety of blood parameters and compare exposed to non-exposed specimen. For blood parameter analysis there is plenty o fliterature. See e.g.
Kunzmann, A. 1991 Blood physiology and ecological consequences in Weddell Sea fishes. Rep. Polar Res. 91: 1-79.
Y should read many research about these subject to determined the parameters and y can take more than one parameters for hematological and compare the treated group with data of control group