EXPERIMENTAL TECHNIQUES (cont)
Blood samples may be obtained from the caudal vein or by cardiac puncture.
The lateral line is a good landmark for locating the caudal vein for obtaining a blood sample. The needle is inserted with the bevel up just above the lateral line at a 45 degree angle toward the base of the vertebra. After the needle touches the vertebra a small amount of suction is applied to the syringe and the blood is collected. The needle size used should be smaller than the diameter of the vessel - for example a 25 gauge needle is adequate on smaller fish such as a blue gill.
Collecting blood from the caudal vein