The criteria for Class A Wild Trout Waters vary by species. For
brook trout, a biomass of 30 kilograms per hectare (27 lb/acre), including at least 0.1 kilograms per hectare (0.089 lb/acre) of brook trout less than 15 centimeters (5.9 in) long. Additionally, brook trout may not make up less than 75 percent of the total wild trout biomass. The requirements are the same for
brown trout except that the minimum brown trout biomass is 40 kilograms per hectare (36 lb/acre).
For a stream to be Class A Wild Trout Waters for both brook trout and brown trout, the combined biomass of both species must be at least 40 kilograms per hectare (36 lb/acre) and the biomass of each species must include at least 0.1 kilograms per hectare (0.089 lb/acre) of trout less than 15 centimeters (5.9 in) long. Neither species may make up more than 75 percent of the total wild trout biomass.
The criteria for
rainbow trout are considerably simpler: the only requirement is that the biomass of wild rainbow trout less than 15 centimeters (5.9 in) long must be at least 2 kilograms per hectare (1.8 lb/acre).