基于EPMA的耳石Sr：Ca比分析及其在鱼类生活履历反演中的应用实例研究

摘要

In this study, the migratory histories of four fish species （tapertail anchovy Coilia nasus and C. mystus, hairtail Trichiurus haumela and longsnout catfish Leiocassis longirostris） in the Yangtze River Estuary, China, were investigated using the otolith Sr ： Ca ratios and Sr intensity maps by X-ray electron probe microanalyzer （EPMA）. Results showed that, in the C. nasus stock, both river origin anadromous individuals and estuarine origin non-anadromous ones occurred in this area. The otolith Sr ： Ca ratios along the life history transects showed 3 general categories of migratory history： 〈2.0×10-3 for river residence, （3.5-6.0） ×10-3 for estuarine residence and 〉6.0×10-3 for sea residence. In the C. mystus stock, the otolith Sr ： Ca ratios also indicated two types of migratory histories： estuary origin and residence in the whole life history （4.8 × 10-3） and shifting periodically between estuarine residence and sea residence （〉7.8 × 10-3） after birth in either water. The otolith Sr ： Ca ratios of the hairtail consistently maintained at a high level （4.9×10-3） throughout the life history transects, indicating their whole seawater life. Meanwhile, the low Sr levels in the otoliths of the longsnout catfish suggested that the individuals had freshwater residence all their life stages. These findings confirmed that the oto- lith Sr levels of the four fish species followed an order of seawater residence 〉 brackish residence 〉 freshwater residence. Due to the influences of the varied environmental histories and the physiology of the fish, the interor intra-species differences in the otolith Sr level are remarkable, which is helpful for elementally fingerprinting the migratory history and reconstructing the life history of fish.%利用基于电子探针（EPMA）的耳石Sr：Ca比和Sr含量分析方法研究了长江口水域刀鲚、凤鲚、带鱼和长吻鲍的生活履历及生活史型。结果发现，刀鲚中除存在淡海水洄游性个体生活史型外。还存在出生并生活于河口或近海的非洄游性个体生活史型，其平均耳石Sr：Ca比在不同水环境履历的基准值为：淡水〈2．0×10^-3、河口（3．5—6．0）×10^-3、海水〉6．0×10^-3。凤鲚中也有出生并生活于河口水域的个体（4．8×10-3）和出生于河口或近海水域（〉7．8×10-3）、周期性地迁徙于二者之间的个体两种生活史型。带鱼（4．9×10q）和长吻鲍则分别表现出其个体均一的近海和淡水生活史履历。研究结果证实了鱼类耳石内Sr含量水平遵从海水〉河口〉淡水生活履历这一特征。但受鱼类所经历的水温、盐度等环境史变化及鱼类自身的生理发育状况等因素的影响，耳石内Sr的沉积量水平存在显著的种间或种内差异。这些差异显著的独特元素标识是识别鱼类个体生活履历和重新构建鱼类生活史的重要元素指纹。