Abstract Tagging-induced mortality experiments are an important component of mark-recapture studies, as they can be used to assess the appropriateness of the tagging methodology, and to improve the reliability of estimates of recapture rates used for calculations of mortality rates and population size. Here, short-term tagging mortality of Baltic cod was estimated through containment experiments in the southern Baltic Sea. Experimental cod were selected from trawl catches, and approximately half were tagged externally with T-bar tags and received an intraperitoneal injection of tetracycline-hydrochloride. The rest of the experimental cod formed the control group, and received neither tag nor injection. The tagged and control cod were mixed evenly within submersible cages, and held for 5−8 days. The experiments were conducted in different regions and during different months by different tagging teams. Overall mortality rate was 16 % (n = 324), with the mortality rate of the tagged group 19 %, and the mortality rate of the control group 13 %. A general linear mixed model was fit to assess the effect of tagging, month, experiment duration, fish length and tagging site (i.e. the combined effect of region and tagging team) on mortality. Tagging had no effect on mortality, indicating that mortality can be attributed mainly to the capture and handling procedure. There was a significantly negative relationship between fish length (range: 20−55 cm) and mortality. Mortality did not differ between the months tested, but there was a significant effect of tagging site on mortality. Tagging-related mortality should be accounted for in analyses of data from mark-recapture studies of Baltic cod, and some variability in mortality between tagging sites can be expected.

中文翻译：

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波罗的海鳕鱼 (Gadus morhua) 的短期标记死亡率

摘要 标记诱导死亡率实验是标记再捕获研究的重要组成部分，因为它们可用于评估标记方法的适当性，并提高用于计算死亡率和人口规模的再捕获率估计值的可靠性。在这里，通过波罗的海南部的围堵实验估计了波罗的海鳕鱼的短期标记死亡率。实验鳕鱼是从拖网渔获物中挑选出来的，大约一半的鳕鱼在外部贴上 T 形标签，并接受了盐酸四环素的腹腔注射。其余的实验鳕鱼形成对照组，既不接受标签也不接受注射。标记鳕鱼和对照鳕鱼在潜水笼内均匀混合，并保持 5-8 天。实验由不同的标记团队在不同的地区和不同的月份进行。总死亡率为 16 % (n = 324)，标记组的死亡率为 19 %，对照组的死亡率为 13 %。拟合一般线性混合模型来评估标记、月份、实验持续时间、鱼长度和标记位置（即区域和标记团队的综合影响）对死亡率的影响。标记对死亡率没有影响，表明死亡率可主要归因于捕获和处理程序。鱼的长度（范围：20-55 厘米）和死亡率之间存在显着的负相关关系。测试月份之间的死亡率没有差异，但标记位点对死亡率有显着影响。