Population dynamics models used to provide management advice for harvested natural resources often estimate population processes that can be mutually confounded. These processes (e.g., natural mortality (M) and catchability (q)) are often assumed to be time-invariant, but this assumption can be violated in real populations. Not allowing for time-variation in these processes can result in retrospective patterns in estimated biomass, which can result in errors in management advice. Allowing for time-variation in these processes can also result in errors in management advice if the estimated time-variation does not reflect the true underlying variation. Here I present a population dynamics model for snow crab in the eastern Bering Sea that tests different combinations of implementation of time-variation in M and q. The North Pacific Fisheries Management Council did not adopt any of the models with time-variation in M or q for management because the estimated variability in M and q was difficult to explain with any known mechanism and management advice differed by nearly an order of magnitude among models. Large differences in management advice underscore the importance of evidence-based approaches to incorporating time-variation in population processes into stock assessment models.

用于为采伐的自然资源提供管理建议的种群动态模型通常会估计可能相互混淆的种群过程。这些过程（例如，自然死亡率 ( M ) 和可捕获性 ( q ))) 通常被假定为时间不变的，但在实际人群中可能违反此假设。不允许在这些过程中随时间变化可能会导致估计的生物量出现追溯模式，这可能会导致管理建议中的错误。如果估计的时间变化不能反映真正的潜在变化，那么在这些过程中考虑时间变化也可能导致管理建议中的错误。在这里，我提出了白令海东部雪蟹的种群动态模型，该模型测试了M和q时变实施的不同组合。北太平洋渔业管理委员会没有采用任何具有M或q时变的模型对于管理来说，因为M和q的估计可变性很难用任何已知的机制来解释，并且管理建议在模型之间相差近一个数量级。管理建议的巨大差异强调了基于证据的方法将种群过程中的时间变化纳入种群评估模型的重要性。