It Doesn't Have to Be Hard If We Monitor the Right Things: Vital Rate Variation as a First Step in EBFM

We spend too much time trying to estimate the number of fish in the sea, now and at some mythical static carrying capacity of the past. This was a logical approach when Beverton, Holt and Ricker were working out harvest equations with paper and pencil, relying on theory and calculus rather than simulation and RAM. There have been amazing advances in assessment modeling as computers have gotten faster and more powerful, but we continue to use antiquated assumptions about population dynamics for many stocks. Most critically, natural mortality rates, maturation, and productivity are assumed to be constant in many models, despite increasing evidence of climate- and food web-induced changes to these rates. Ecosystem-based management can break us out of this rut by emphasizing the dynamics of fish life histories, but only if monitoring programs shift some attention from estimation of biomass to estimation of vital rate variance in space and time. As we stumble through this age of “no-analog conditions” with climate change, it is essential to focus more attention on models that link ecosystem conditions to stock vital rates, and consider reference points for management that reflect the changing conditions of fish populations instead of hypothetical carrying capacities.