Effect on tricaine methanesulfonate (MS-222) on hematocrit values in rainbow trout (Salmo gairdneri)

1. Anesthesia of rainbow trout (Salmo gairdneri) with 70 ppm tricaine methanesulfonate (MS-222) for 3-9 min resulted in a linear increase in hematocrit.

2. Handling of unanesthetized trout caused a higher and more variable hematocrit reading than did exposure to MS-222 for up to 3 min.

3. The range and standard error of hematocrit readings was smallest in trout treated with MS-222 for 1 min.