Canadian Journal of Fisheries and Aquatic Sciences, Ahead of Print.
The body condition of Lake Constance pelagic spawning whitefish (Coregonus wartmanni) has changed substantially during the past century and altered the length-based selectivity of gillnets. Linked hierarchical models using Bayesian inference and error propagation were used to estimate the monthly body condition of whitefish from 1932 to 2018 and condition-dependent gillnet selectivity from 1964 to 2018. As expected, body condition followed past trends in nutrient dynamics and was highest in summer months. Body condition was clearly linked to gillnet selectivity, with a weight increase of a 300 mm whitefish from 205 to 260 g predicted to reduce the mean (from 374 to 330 mm) and standard deviation (from 30.8 to 25.1 mm) of lengths selected by a 38 mm mesh gillnet. Simulations demonstrate that such changes can reduce the mean age in harvest by over 1 year and greatly bias population age distribution estimates if selectivity changes are ignored. Similar variation in gillnet selectivity is expected where trophic conditions or other factors cause body condition differences, and accounting for these changes could reduce biases to inform fishery management.

中文翻译：

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康斯坦茨湖远洋产卵白鱼（Coregonus wartmanni）身体状况和刺网选择性的长期变化

加拿大渔业和水产科学杂志，提前印刷。
在过去的一个世纪里，康斯坦茨湖远洋产卵白鱼 (Coregonus wartmanni) 的身体状况发生了重大变化，并改变了刺网基于长度的选择性。使用贝叶斯推理和误差传播的关联层次模型用于估计 1932 年至 2018 年白鲑的每月身体状况和 1964 年至 2018 年的条件依赖性刺网选择性。 正如预期的那样，身体状况遵循营养动态的过去趋势，并在夏季最高个月。身体状况与刺网选择性明显相关，预计将 300 毫米白鱼的重量从 205 克增加到 260 克，会降低由专家选择的长度的平均值（从 374 到 330 毫米）和标准偏差（从 30.8 到 25.1 毫米）。 38 毫米网眼刺网。模拟表明，如果忽略选择性变化，这种变化可以使收获的平均年龄减少 1 年以上，并且极大地偏差人口年龄分布估计。在营养条件或其他因素导致身体状况差异的情况下，刺网选择性的类似变化预计会发生，考虑到这些变化可以减少为渔业管理提供信息的偏差。