Evaluating harvest control rules for lake whitefish in the Great Lakes: Accounting for variable life-history traits

Few studies have evaluated the performance of harvest control rules while considering uncertainties in life history traits and the management process. We conducted such a study using an age-structured simulation based on lake whitefish in the Great Lakes. The control rules compared were a constant fishing mortality (constantF), conditional constant catch (CCC), biomass-based (BB), and constantF and BB with a 15% limit on the interannual change in the target catch (constantF-lim, BB-lim, respectively). Our application of the CCC and BB rules was conditioned on having reliable estimates of some reference point (e.g., unfished biomass). With appropriate policy parameters, the BB and constantF rules attained higher average yield and spawning stock biomass than other control rules. At yields that could be achieved by all rules, the CCC, constantF-lim, and BB-lim rules had the lowest yearly variability in yield, but at the cost of more frequent low biomass. The relative performance of the control rules was generally consistent with previous research that did not include the variation in life history traits unique to our simulations, which suggested that these variable traits did not affect relative control rule performance. The BB rule achieved more yield and less risk of low biomass than the constantF rule currently used for lake whitefish, with only a modest increase in yield variability. Given that the BB rule requires a stock-specific estimate of unfished biomass, and the constantF rule does not, this result suggests that reliable estimates of unfished biomass could provide substantial value.