Department of Biological Sciences, Macquarie University, Sydney NSW 2109, Australia.
Fisheries NSW, Sydney Institute of Marine Science, 19 Chowder Bay Road, Mosman NSW 2088, Australia.
Sci Rep. 2016 Jul 18;6:29698. doi: 10.1038/srep29698.
Determining the age of sharks using vertebral banding is a vital component of management, but the causes of banding are not fully understood. Traditional shark ageing is based on fish otolith ageing methods where growth bands are assumed to result from varied seasonal calcification rates. Here we investigate these assumptions by mapping elemental distribution within the growth bands of vertebrae from six species of sharks representing four different taxonomic orders using scanning x-ray fluorescence microscopy. Traditional visual growth bands, determined with light microscopy, were more closely correlated to strontium than calcium in all species tested. Elemental distributions suggest that vertebral strontium bands may be related to environmental variations in salinity. These results highlight the requirement for a better understanding of shark movements, and their influence on vertebral development, if confidence in age estimates is to be improved. Analysis of shark vertebrae using similar strontium-focused elemental techniques, once validated for a given species, may allow more successful estimations of age on individuals with few or no visible vertebral bands.
利用脊椎带纹来确定鲨鱼的年龄是管理的重要组成部分，但带纹的成因尚未完全了解。传统的鲨鱼年龄鉴定基于鱼类耳石的年龄鉴定方法，假设生长带是由不同的季节性钙化率产生的。在这里，我们使用扫描 X 射线荧光显微镜，研究了六种鲨鱼的脊椎生长带内的元素分布，这些鲨鱼代表了四个不同的分类阶元，以验证这些假设。在所有测试的物种中，传统的光镜下确定的可视生长带与锶的相关性都高于钙。元素分布表明，脊椎锶带可能与盐度的环境变化有关。这些结果强调，如果要提高对年龄估计的信心，就需要更好地了解鲨鱼的运动及其对脊椎发育的影响。如果对给定物种进行了验证，那么使用类似的锶聚焦元素技术对鲨鱼的脊椎进行分析，可能会使那些带有少量或没有可见脊椎带的个体的年龄估计更加成功。
