Sweet shrimp is tastiest during late winter. As the name implies it has a very sweet aftertaste.
They are classified as deep sea creatures and live at 3000 ft below sea level at the most.
For the first five years of their lives, they are male, and then after they spawn, their bodies become female.
They are used for sushi or sashimi when they are small or during the male stage of their life.
The female are larger,and carry eggs for about 10 months before they lay them, therefore many of them are caught carrying them.
Sometimes sushi restaurants use the older females with the eggs, so they can garnish the sushi with the beautiful blue colored roe, but the male, or younger stage is considered sweeter, and concentrated in flavors.
Sweet shrimp is the only shrimp (or group of shrimp) that taste better raw. Sweet shrimp is not meant to be cooked, since it looses most of its flavors due to the heat. The flesh becomes soggy and brittle as well, and there is no point in heating it. The only time it may be cooked is when it is carrying eggs. The shrimp are either fried with the shells on, or cooked with rice, since the eggs add extra rich flavor.