Sampling the testes Milt can usually be stripped from males of most species when they are ready for spawning by applying gentle pressure to the abdomen between the pelvic fins and the vent. Number of sperm in a volumeof milt is extremely variable, ranging from millions to billions of sperm per milliliter. The male is turned belly up, and the vent area is dried by blotting with a towel. The area just behind the pelvic fins is gently massaged to-ward the vent to strip the milt. The first few drops of milt are wiped away.
Suction is applied while stripping to draw milt into the eye-dropper.
Care must be taken to in-sure that water, urine, intestinal contents, slime, or blood are not mixed with the milt. A drop of milt is placed on a cover slip, and a drop of water is placed on a glass slide. The cover slip with the milt is placed on the drop of water, gently pressed over the slide, and immediately observed under the microscope. The sperm remain active in water for a veryshort period of time, usually less than 1 to 5 minutes, depending on the species of fish and the tempera-ture of the water. Males with milt that have no or low motility should be discarded.