Distinct types of fish species experience variation in somatic growth rates over their life span; however, growth has historically been assumed to be invariant across time and space in integrated analysis-based stock assessment. A few previous studies have reported biased and imprecise assessment model outcomes when variability in somatic growth was ignored. In this study, we used a simulation-estimation framework to expand previous analyses and to examine the consequences of ignoring or incorporating spatial and temporal (year- and cohort-specific) variability in somatic growth in stock assessment models. The study included three life history types: small pelagic (e.g. sardine), gadids (e.g. cod), and long-lived (e.g. rockfish). In general, ignoring any type of variability in somatic growth led to biased and imprecise estimates of stock spawning biomass and management quantities. Unequal distribution of fishing mortality across space had large impacts on the performance of estimation models as well. Conversely, accounting for somatic growth variability, either by including an environmental index, estimating annual deviates, or implementing a spatially explicit model, produced unbiased and precise results. This study shows that somatic growth variability might produce large effects in stock assessments when ignored and provides pertinent information for stock assessment best practice guidelines.

中文翻译：

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渔业资源评估模型中体细胞生长的时空变异性：评估错误指定的后果

不同类型的鱼类在其生命周期内的体细胞生长速度有所不同；然而，在基于综合分析的存量评估中，历来假定增长在时间和空间上是不变的。一些先前的研究报告了当忽略体细胞生长的变异性时，评估模型的结果存在偏差和不精确。在这项研究中，我们使用模拟估计框架来扩展先前的分析，并检查在种群评估模型中忽略或合并空间和时间（特定于年份和特定队列）变异性的后果。该研究包括三种生活史类型：小型远洋类（例如沙丁鱼）、gadids（例如鳕鱼）和长寿类（例如岩鱼）。一般来说，忽略体细胞生长的任何类型的可变性都会导致对种群产卵生物量和管理数量的有偏见和不准确的估计。不同空间的捕捞死亡率分布不均对估计模型的性能也有很大影响。相反，考虑体细胞生长变异性，无论是通过包括环境指数，估计年度偏差，还是实施空间明确的模型，都会产生无偏见和精确的结果。本研究表明，如果忽略体细胞生长变异性，可能会对种群评估产生巨大影响，并为种群评估最佳实践指南提供相关信息。通过包括环境指数、估计年度偏差或实施空间明确的模型来考虑体细胞生长变异性，产生了无偏见和精确的结果。本研究表明，如果忽略体细胞生长变异性，可能会对种群评估产生巨大影响，并为种群评估最佳实践指南提供相关信息。通过包括环境指数、估计年度偏差或实施空间明确的模型来考虑体细胞生长变异性，产生了无偏见和精确的结果。本研究表明，如果忽略体细胞生长变异性，可能会对种群评估产生巨大影响，并为种群评估最佳实践指南提供相关信息。