Complete tag loss in capture-recapture studies affects abundance estimates: an elephant seal case study

1. In capture-recapture studies, recycled individuals occur when individuals lose all of their tags and are recaptured as though they were new individuals. Typically, the effect of these recycled individuals is assumed negligible. 2. Through a simulation-based study of double tagging experiments, we examined the effect of recycled individuals on parameter estimates in the Jolly-Seber model with tag loss (Cowen & Schwarz, 2006). We validated the simulation framework using long-term census data of elephant seals. 3. Including recycled individuals did not affect estimates of capture, survival, and tag-retention probabilities. However, with low tag-retention rates, high capture rates, and high survival rates, recycled individuals produced over estimates of population size. For the elephant seal case study, we found population size estimates to be between 8 and 53% larger when recycled individuals were ignored. 4. Ignoring the effects of recycled individuals can cause large biases in population size estimates. These results are particularly noticeable in longer studies.1. 在标记重捕（capture-recapture）研究中，当个体丢失全部标记并被当作新个体重新捕获时，便会出现重复计数个体（recycled individuals）。通常这类重复计数个体的影响被认为可忽略不计。 2. 本研究通过针对双重标记实验的模拟分析，探讨了重复计数个体对存在标记脱落情况的乔利-西贝尔模型（Jolly-Seber model）参数估计的影响（Cowen & Schwarz, 2006）。我们利用象海豹的长期普查数据对该模拟框架进行了验证。 3. 纳入重复计数个体并不会对捕获概率、存活概率以及标记保留概率的估计结果产生影响。但在标记保留率较低、捕获率较高且存活率较高的场景下，重复计数个体会导致种群数量的估计值被高估。针对象海豹的案例研究显示，当忽略重复计数个体的影响时，种群数量的估计值会高出8%至53%。 4. 忽略重复计数个体的影响会导致种群数量估计结果出现显著偏差，这一问题在长期研究中尤为突出。