The Fish Stock Sustainability Index (FSSI) is comprised of 175 stocks (down from 199 beginning in FY 2020) selected for their economic, ecological, and social importance, that represent 83% of total catch. Each stock is given a score between 0 and 4 (0=status unknown; 4=meets all sustainable fishing criteria). The index (scored on a 1,000 point scale) increases when NMFS determines that a stock is either no longer subject to overfishing, no longer overfished, or its biomass has rebuilt or increased to at least 80 percent of target.