Patagonian toothfish occurs in the Southern Ocean and on the South American Plateau. Several stock identification methods suggest the existence of at least four biological stock units within the wide Patagonian toothfish’s distribution (Appleyard et al., 2002; CCAMLR, 2004; Laptikhovsky et al., 2006; Ashford et al., 2012): a South American stock; a South Georgia Islands stock, a Macquarie Islands stock, and a Southern Indian Ocean Islands stock.

Within the Southern Indian Ocean Islands stock there are independent assessments units for Heard and McDonaldIslands, Kerguelen Islands and Crozet Islands (CCAMLR, 2015).