Based on the grading system that I outlined in my previous post, Grade #1, sometimes called sushi grade tuna is as high as it gets. The ideal scenario is quite simple: the fish is caught, drained of blood and treated and chilled immediately. If there are no complications the fish should be in perfect, undamaged condition with no internal sicknesses. Deviations from this ideal scenario are common and fish that was once in pristine condition can be physically damaged in shipping, temperature abused, or can begin to decompose. These sources of degredation need to be minimized in order to save the fish from being down-graded from a #1.