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The views and opinions expressed or implied in this article are those of the author (or authors) and do not necessarily reflect the position of the National Marine Fisheries Service, NOAA. Abstract—Several rockfish stocks off the U.S. west coast are below target biomass and are managed under rebuilding plans that severely limit the allowable harvest. Limited harvest, however, reduces the opportunity to collect fishery-dependent data, which are the primary source of information on changes in abundance for species poorly sampled by fishery-independent methods. A simulation study was conducted by using an operating model to evaluate the effect of reduced data on estimation of spawning biomass and biological parameters during rebuilding of a stock. Decreased availability of data during rebuilding resulted in increased among-simulation variation in estimates of spawning biomass. Additionally, decreased data resulted in reduced average catches and increased interannual variation in catches during rebuilding compared with averages of and variation in catches when data collection was maintained at higher levels. The presence of time-varying parameters in the operating model that were not accounted for within the estimation method resulted in increased amongsimulation variability in spawning biomass than with the time-invariant case, and the largest increase in variability occurred during stock rebuilding when data were reduced or eliminated. Retaining data collections at historical levels allowed improved parameter estimation during rebuilding, resulting in reduced variability in estimated stock size, increased average catches during rebuilding, and in reduced frequency of stocks being prematurely estimated as rebuilt. In the United States, federally managed stocks that fall below a minimum stock size threshold (MSST) are declared overfished and are mandated to be rebuilt to target biomass levels in the shortest amount of time, accounting for present biological and environmental conditions (Sustainable...1996; National...2016). In the absence of an unexpected run of good recruitment, rebuilding overfished stocks requires a reduction in fishing mortality to a level that allows stock biomass to increase and therefore leads to substantial reductions in fishing effort in relation to historical levels. The severity of management restrictions during rebuilding can, for some stocks, lead to a situation where the ability to collect data becomes limited when the stock is under a rebuilding plan, a period when managers are likely most concerned about stock size and trends in biomass. Overfished rockfish species off the U.S. west coast have experienced large reductions in harvest during rebuilding. One example, yelloweye rockfish (Sebastes ruberrimus), was declared overfished in 2002 (Methot and Piner1). Similar to other rockfish species off the U.S. west coast, catches of yelloweye rockfish were unsustainable during the 1980s and early 1990s. Catches of yelloweye rockfish decreased dramatically in relation to historical catches after the overfished declaration, and the allowable catch during the first year of rebuilding fell to approximately 10% of the catch from 4 years earlier (Stewart et al.2). Yelloweye rockfish is one notable example of an overfished west coast rockfish species that has experienced similar large reductions in harvest during rebuilding. Other examples include the cowcod (Sebastes levis; Dick and MacCall3), canary

The effect of reduced data on the ability to monitor rebuilding of overfished fish stocks