POs primarily apply individual limits to the larger sole producers, usually the largest sole gillnetters. This system is very limited for some POs owing to the absence of a global monitoring system. For example, the smallest producers for which sole is a by-catch are not concerned with individual limits but receive a global allocation. The criteria adopted for sole sub-quota management vary between POs. A few of them determine limits in proportion to the reference track records (2001–2003 production average); some POs allocate quotas according to more recent track record keys, and other POs use maximal production over the last 10 years or a fixed package.