ABSTRACT: Tagging studies are often used to measure survival and growth in wild populations. However, issues such as low returns of tagged animals, tag loss, and handling mortality can affect the precision and accuracy of demographic estimates if not accounted for. We conducted a mark-recapture study to measure the survival and growth of juvenile and adult wavy turban snails Megastraea undosa. Our study highlights several methodological advances, including a method for estimating a single growth function by analyzing the joint changes in length and weight of tagged animals; a simple method for estimating rates of tag loss when some animals are double tagged; and a way to estimate handling mortality by comparing encounter histories of animals immediately after tagging and after several weeks in the field. Tag loss was moderate (≈15% over a 100 d period) and handling mortality was substantial during the fall (≈55%), but negligible during the spring. If we did not account for tag loss and handling mortality, our estimate of survival would have been severely underestimated (≈46% lower over a 100 d period). After accounting for such effects, our study revealed that survival probably increased sharply with body size, but survival did not differ among seasons. These snails are slow-growing, mature after approximately 6 yr, and can routinely grow to >10 yr old. There is an emerging fishery for this species, and because our results suggest that the oldest snails have a very high reproductive value, measures that protect these large individuals are likely to be beneficial for the resilience of these populations.

中文翻译：

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在标记回收研究中估算生长，尺寸依赖性死亡率和标签丢失：美国南加州的波浪状头巾蜗牛的人口统计学

摘要：标签研究通常用于衡量野生种群的生存和生长。但是，如果不加以考虑，诸如带标签动物的低回报，标签丢失和处理死亡率之类的问题可能会影响人口统计估计的准确性和准确性。我们进行了标记重捕研究，衡量的生存和少年和成年波浪头巾的增长蜗牛Megastraea undosa。我们的研究突出了几种方法学的进展，包括通过分析被标记动物的体长和体重的联合变化来估计单一生长功能的方法。一种简单的方法来估计某些动物被双重标记时的标记丢失率；以及通过比较标记后立即和田间几周后动物的遭遇历史来估算处理死亡率的方法。标签丢失程度适中（在100 d期间≈15％），秋天的处理死亡率很高（≈55％），而在春季可以忽略不计。如果我们不考虑标签丢失和处理死亡率，那么我们对生存的估计将被严重低估（在100 d内降低约46％）。考虑到此类影响后，我们的研究表明，生存率可能会随着体型的增加而急剧增加，但是生存率在各个季节之间没有差异。这些蜗牛生长缓慢，大约需要6年才能成熟，并且通常可以长到10岁以上。该物种正在出现渔业，并且由于我们的研究结果表明，最古老的蜗牛具有很高的繁殖价值，因此保护这些大个体的措施可能有益于这些种群的复原力。