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popular in stock assessments for 2 reasons. First, data 
requirements are low relative to other age-structured 
assessment approaches; for example, computation does 
not depend on a spawner-recruit relationship. Second, 
the spawning potential ratio can provide biological 
reference points for fishery management (Caddy and 
Mahon, 1995), in particular for a target fishing rate 
F x% . The fishing rate F x% is defined as the F that 
provides X% of reproductive output per recruit relative 
to the unfished output level (i.e., spawning potential 
ratio expressed as a percentage). In many cases, F x% 
is used as a proxy for the F associated with maximum 
sustainable yield (F MSY ). Mace (1994) suggested a de- 
fault proxy of F i0% when the spawner-recruit relation- 
ship is unknown; however, the appropriate level of X% 
will depend on life-history and fishery characteristics 
(Clark, 2002; Williams and Shertzer, 2003; Brooks et 
al., 2009). 
Reproductive value Reproductive value (V a ) measures 
the age-dependent contribution to population growth by 
combining survivorship and fecundity, the 2 life-history 
elements crucial to fitness. The concept of reproductive 
value has been applied most commonly to examine life- 
history evolution (Goodman, 1982; Stearns, 1992), but 
it also has been suggested as useful in the context of 
fishery management (MacArthur, 1960; Ware, 1985; Xu 
et ah, 2012). For example, MacArthur (1960) argued that 
