Spawning-biomass-per-recruit proxies for fisheries reference points under multiple axes of uncertainty

Biological reference points provide metrics against which the effects of fisheries management can be measured and have been integral in fisheries management reform globally. Some of these reference points are predicated on the idea that a relationship exists between spawning biomass and recruitment, but this relationship has not been observed for a majority of stocks for which there are stock assessments. Proxies for target fishing mortalities and biomasses were developed to address this issue that identify reference points that perform well across a range of stock-recruit relationships using spawning-biomass-per-recruit (SBPR). These proxies are used widely but they only address the uncertainty in the stock-recruit relationship. We present a methodology for identifying SBPR proxies under multiple axes of uncertainty using eastern Bering Sea snow crab (Chionoecetes opilio) as an example. Incorporating uncertainty around the size at which mature crab become reproductively active in addition to stock-recruit uncertainty into the calculation of reference points tripled the spawning-biomass-per-recruit target relative to the status quo. This methodology could be extended to other species and sources of uncertainty, but care must be taken to define plausible realities to be considered in the axes of uncertainty because the most extreme scenarios considered can play a large role in determining reference points.