Space for WHAM: a multi-region, multi-stock generalization of the Woods Hole Assessment Model with an application to black sea bass Canadian Journal of Fisheries and Aquatic Sciences

The Woods Hole Assessment Model is a general state-space age-structured assessment model that is used to assess and manage many stocks in the Northeast US. We first describe an extension of the model allowing any number of stocks (or stock components) and regions with movement among regions as well as seasonal variation in stock and fleet dynamics. Movement rates can be functions of time- and age-varying random effects and environmental covariates. We then illustrate the model by applying it to data for the northern and southern components of the Northeast United States black sea bass stock and evaluate alternative hypotheses of bottom temperature and time-varying random effects on recruitment and natural mortality. We show strong evidence for temperature effects on recruitment, primarily for the northern stock component, and no evidence for including random effects or temperature effects on age 1 natural mortality.

伍兹霍尔评估模型（Woods Hole Assessment Model）是一款通用的状态空间年龄结构评估模型（state-space age-structured assessment model），被用于评估和管理美国东北部海域的诸多渔业种群。我们首先对该模型进行扩展，使其可支持任意数量的种群（或种群组分）与区域，并可模拟区域间的种群移动，以及种群与捕捞船队动态的季节变化。区域间的移动速率可作为时间、年龄可变的随机效应与环境协变量的函数进行建模。随后，我们通过将该模型应用于美国东北部海域黑海鲈（black sea bass）种群的北部与南部组分的相关数据，完成了实例演示，并针对底温与随时间变化的随机效应对补充量和自然死亡率的影响，评估了多种备选假说。研究结果显示，补充量受温度影响的证据显著，该效应主要体现在北部种群组分中；未发现有证据表明需纳入随机效应，或底温对1龄鱼的自然死亡率存在影响。