The type of harvest is also influenced by whether the crop consists of one cohort, or multiple cohorts; and whether the farmer uses a strategy of "thinning"" or periodic selective harvesting of the crop. Most shrimp crops are reared as a batch process, where the PL's or juveniles are all stocked at one time, the crop grows to some point, and then all are harvested at about the same time. Alternative strategies to this one include:

• stocking at a high density, but all at one time. As the crop approaches carrying capacity of the pond, begin partial harvest to reduce the biomass below the sustainable maximum. Continue partial harvest on a regular basis until the biomass and numbers and greatly reduced, and then drain harvest
• stock repeatedly over some time period, such as once or twice a month for 3 or 4 months, and then begin partial harvest, selecting for the largest shrimp as the first cohort reaches marketable size (Fast, 1992).