Abstract
Steepness, a parameter derived from the stock‐recruit relationship, is widely used in fishery stock assessments to scale the productivity of a population. Steepness is a highly influential parameter, but it is often unknown a priori and is typically difficult to estimate. Attempts to statistically estimate steepness, either within stock assessments or through meta‐analyses, can lead to implausible results. We move beyond steepness as a statistical concept to emphasize that steepness is determined by life history traits and the early life survival of offspring of a population. We return to the original derivation of the Beverton‐Holt stock‐recruit relationship, and model recruitment to the population as a function of total egg production, rather than using spawning biomass as a proxy. We then demonstrate how to calculate steepness based on biology through a case study of rockfishes ( Sebastes spp., Scorpaenidae) in the California Current, where steepness has been notoriously difficult to estimate. We leverage a wealth of reproductive ecology and early life history information (empirical data and associated life history parameters) to compute steepness values for four species of rockfishes, in order to illustrate how steepness varies by species based on differences in their life histories. We also show the sensitivity of steepness to the different life history traits. We conclude that steepness of a stock‐recruit relationship is a real biological parameter and can be meaningfully informed with life history parameters including early life survival.