Relationship between the size of the parental (mature or spawning) biomass and the number of recruits it generates. This is often a key determinant of stock productivity, but is difficult to estimate. In the absence of direct estimates of biomass and recruitment (such as might be obtained from fishery independent surveys), these are usually estimated within stock assessments. S-R relationships can be highly variable, particularly at intermediate to larger stock sizes, with a wide range of recruitment possible for a given stock size. Climate induced changes in S-R productivity can result in substantial changes in estimates of sustainable harvest rates.